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4*22ce4affSfengbojiang<title>zstd 1.4.8 Manual</title>
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7*22ce4affSfengbojiang<h1>zstd 1.4.8 Manual</h1>
8*22ce4affSfengbojiang<hr>
9*22ce4affSfengbojiang<a name="Contents"></a><h2>Contents</h2>
10*22ce4affSfengbojiang<ol>
11*22ce4affSfengbojiang<li><a href="#Chapter1">Introduction</a></li>
12*22ce4affSfengbojiang<li><a href="#Chapter2">Version</a></li>
13*22ce4affSfengbojiang<li><a href="#Chapter3">Simple API</a></li>
14*22ce4affSfengbojiang<li><a href="#Chapter4">Explicit context</a></li>
15*22ce4affSfengbojiang<li><a href="#Chapter5">Advanced compression API</a></li>
16*22ce4affSfengbojiang<li><a href="#Chapter6">Advanced decompression API</a></li>
17*22ce4affSfengbojiang<li><a href="#Chapter7">Streaming</a></li>
18*22ce4affSfengbojiang<li><a href="#Chapter8">Streaming compression - HowTo</a></li>
19*22ce4affSfengbojiang<li><a href="#Chapter9">Streaming decompression - HowTo</a></li>
20*22ce4affSfengbojiang<li><a href="#Chapter10">Simple dictionary API</a></li>
21*22ce4affSfengbojiang<li><a href="#Chapter11">Bulk processing dictionary API</a></li>
22*22ce4affSfengbojiang<li><a href="#Chapter12">Dictionary helper functions</a></li>
23*22ce4affSfengbojiang<li><a href="#Chapter13">Advanced dictionary and prefix API</a></li>
24*22ce4affSfengbojiang<li><a href="#Chapter14">experimental API (static linking only)</a></li>
25*22ce4affSfengbojiang<li><a href="#Chapter15">Frame size functions</a></li>
26*22ce4affSfengbojiang<li><a href="#Chapter16">Memory management</a></li>
27*22ce4affSfengbojiang<li><a href="#Chapter17">Advanced compression functions</a></li>
28*22ce4affSfengbojiang<li><a href="#Chapter18">Advanced decompression functions</a></li>
29*22ce4affSfengbojiang<li><a href="#Chapter19">Advanced streaming functions</a></li>
30*22ce4affSfengbojiang<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions</a></li>
31*22ce4affSfengbojiang<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
32*22ce4affSfengbojiang<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
33*22ce4affSfengbojiang<li><a href="#Chapter23">Block level API</a></li>
34*22ce4affSfengbojiang</ol>
35*22ce4affSfengbojiang<hr>
36*22ce4affSfengbojiang<a name="Chapter1"></a><h2>Introduction</h2><pre>
37*22ce4affSfengbojiang  zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
38*22ce4affSfengbojiang  real-time compression scenarios at zlib-level and better compression ratios.
39*22ce4affSfengbojiang  The zstd compression library provides in-memory compression and decompression
40*22ce4affSfengbojiang  functions.
41*22ce4affSfengbojiang
42*22ce4affSfengbojiang  The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
43*22ce4affSfengbojiang  which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
44*22ce4affSfengbojiang  caution, as they require more memory. The library also offers negative
45*22ce4affSfengbojiang  compression levels, which extend the range of speed vs. ratio preferences.
46*22ce4affSfengbojiang  The lower the level, the faster the speed (at the cost of compression).
47*22ce4affSfengbojiang
48*22ce4affSfengbojiang  Compression can be done in:
49*22ce4affSfengbojiang    - a single step (described as Simple API)
50*22ce4affSfengbojiang    - a single step, reusing a context (described as Explicit context)
51*22ce4affSfengbojiang    - unbounded multiple steps (described as Streaming compression)
52*22ce4affSfengbojiang
53*22ce4affSfengbojiang  The compression ratio achievable on small data can be highly improved using
54*22ce4affSfengbojiang  a dictionary. Dictionary compression can be performed in:
55*22ce4affSfengbojiang    - a single step (described as Simple dictionary API)
56*22ce4affSfengbojiang    - a single step, reusing a dictionary (described as Bulk-processing
57*22ce4affSfengbojiang      dictionary API)
58*22ce4affSfengbojiang
59*22ce4affSfengbojiang  Advanced experimental functions can be accessed using
60*22ce4affSfengbojiang  `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
61*22ce4affSfengbojiang
62*22ce4affSfengbojiang  Advanced experimental APIs should never be used with a dynamically-linked
63*22ce4affSfengbojiang  library. They are not "stable"; their definitions or signatures may change in
64*22ce4affSfengbojiang  the future. Only static linking is allowed.
65*22ce4affSfengbojiang<BR></pre>
66*22ce4affSfengbojiang
67*22ce4affSfengbojiang<a name="Chapter2"></a><h2>Version</h2><pre></pre>
68*22ce4affSfengbojiang
69*22ce4affSfengbojiang<pre><b>unsigned ZSTD_versionNumber(void);
70*22ce4affSfengbojiang</b><p>  Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
71*22ce4affSfengbojiang</p></pre><BR>
72*22ce4affSfengbojiang
73*22ce4affSfengbojiang<pre><b>const char* ZSTD_versionString(void);
74*22ce4affSfengbojiang</b><p>  Return runtime library version, like "1.4.5". Requires v1.3.0+.
75*22ce4affSfengbojiang</p></pre><BR>
76*22ce4affSfengbojiang
77*22ce4affSfengbojiang<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
78*22ce4affSfengbojiang
79*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
80*22ce4affSfengbojiang                const void* src, size_t srcSize,
81*22ce4affSfengbojiang                      int compressionLevel);
82*22ce4affSfengbojiang</b><p>  Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
83*22ce4affSfengbojiang  Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
84*22ce4affSfengbojiang  @return : compressed size written into `dst` (<= `dstCapacity),
85*22ce4affSfengbojiang            or an error code if it fails (which can be tested using ZSTD_isError()).
86*22ce4affSfengbojiang</p></pre><BR>
87*22ce4affSfengbojiang
88*22ce4affSfengbojiang<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
89*22ce4affSfengbojiang                  const void* src, size_t compressedSize);
90*22ce4affSfengbojiang</b><p>  `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
91*22ce4affSfengbojiang  `dstCapacity` is an upper bound of originalSize to regenerate.
92*22ce4affSfengbojiang  If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
93*22ce4affSfengbojiang  @return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
94*22ce4affSfengbojiang            or an errorCode if it fails (which can be tested using ZSTD_isError()).
95*22ce4affSfengbojiang</p></pre><BR>
96*22ce4affSfengbojiang
97*22ce4affSfengbojiang<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
98*22ce4affSfengbojiang#define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)
99*22ce4affSfengbojiangunsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
100*22ce4affSfengbojiang</b><p>  `src` should point to the start of a ZSTD encoded frame.
101*22ce4affSfengbojiang  `srcSize` must be at least as large as the frame header.
102*22ce4affSfengbojiang            hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
103*22ce4affSfengbojiang  @return : - decompressed size of `src` frame content, if known
104*22ce4affSfengbojiang            - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
105*22ce4affSfengbojiang            - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
106*22ce4affSfengbojiang   note 1 : a 0 return value means the frame is valid but "empty".
107*22ce4affSfengbojiang   note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
108*22ce4affSfengbojiang            When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
109*22ce4affSfengbojiang            In which case, it's necessary to use streaming mode to decompress data.
110*22ce4affSfengbojiang            Optionally, application can rely on some implicit limit,
111*22ce4affSfengbojiang            as ZSTD_decompress() only needs an upper bound of decompressed size.
112*22ce4affSfengbojiang            (For example, data could be necessarily cut into blocks <= 16 KB).
113*22ce4affSfengbojiang   note 3 : decompressed size is always present when compression is completed using single-pass functions,
114*22ce4affSfengbojiang            such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
115*22ce4affSfengbojiang   note 4 : decompressed size can be very large (64-bits value),
116*22ce4affSfengbojiang            potentially larger than what local system can handle as a single memory segment.
117*22ce4affSfengbojiang            In which case, it's necessary to use streaming mode to decompress data.
118*22ce4affSfengbojiang   note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
119*22ce4affSfengbojiang            Always ensure return value fits within application's authorized limits.
120*22ce4affSfengbojiang            Each application can set its own limits.
121*22ce4affSfengbojiang   note 6 : This function replaces ZSTD_getDecompressedSize()
122*22ce4affSfengbojiang</p></pre><BR>
123*22ce4affSfengbojiang
124*22ce4affSfengbojiang<pre><b>unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
125*22ce4affSfengbojiang</b><p>  NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
126*22ce4affSfengbojiang  Both functions work the same way, but ZSTD_getDecompressedSize() blends
127*22ce4affSfengbojiang  "empty", "unknown" and "error" results to the same return value (0),
128*22ce4affSfengbojiang  while ZSTD_getFrameContentSize() gives them separate return values.
129*22ce4affSfengbojiang @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise.
130*22ce4affSfengbojiang</p></pre><BR>
131*22ce4affSfengbojiang
132*22ce4affSfengbojiang<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
133*22ce4affSfengbojiang</b><p> `src` should point to the start of a ZSTD frame or skippable frame.
134*22ce4affSfengbojiang `srcSize` must be >= first frame size
135*22ce4affSfengbojiang @return : the compressed size of the first frame starting at `src`,
136*22ce4affSfengbojiang           suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
137*22ce4affSfengbojiang        or an error code if input is invalid
138*22ce4affSfengbojiang</p></pre><BR>
139*22ce4affSfengbojiang
140*22ce4affSfengbojiang<h3>Helper functions</h3><pre></pre><b><pre>#define ZSTD_COMPRESSBOUND(srcSize)   ((srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0))  /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
141*22ce4affSfengbojiangsize_t      ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
142*22ce4affSfengbojiangunsigned    ZSTD_isError(size_t code);          </b>/*!< tells if a `size_t` function result is an error code */<b>
143*22ce4affSfengbojiangconst char* ZSTD_getErrorName(size_t code);     </b>/*!< provides readable string from an error code */<b>
144*22ce4affSfengbojiangint         ZSTD_minCLevel(void);               </b>/*!< minimum negative compression level allowed */<b>
145*22ce4affSfengbojiangint         ZSTD_maxCLevel(void);               </b>/*!< maximum compression level available */<b>
146*22ce4affSfengbojiang</pre></b><BR>
147*22ce4affSfengbojiang<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
148*22ce4affSfengbojiang
149*22ce4affSfengbojiang<h3>Compression context</h3><pre>  When compressing many times,
150*22ce4affSfengbojiang  it is recommended to allocate a context just once,
151*22ce4affSfengbojiang  and re-use it for each successive compression operation.
152*22ce4affSfengbojiang  This will make workload friendlier for system's memory.
153*22ce4affSfengbojiang  Note : re-using context is just a speed / resource optimization.
154*22ce4affSfengbojiang         It doesn't change the compression ratio, which remains identical.
155*22ce4affSfengbojiang  Note 2 : In multi-threaded environments,
156*22ce4affSfengbojiang         use one different context per thread for parallel execution.
157*22ce4affSfengbojiang
158*22ce4affSfengbojiang</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
159*22ce4affSfengbojiangZSTD_CCtx* ZSTD_createCCtx(void);
160*22ce4affSfengbojiangsize_t     ZSTD_freeCCtx(ZSTD_CCtx* cctx);
161*22ce4affSfengbojiang</pre></b><BR>
162*22ce4affSfengbojiang<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
163*22ce4affSfengbojiang                         void* dst, size_t dstCapacity,
164*22ce4affSfengbojiang                   const void* src, size_t srcSize,
165*22ce4affSfengbojiang                         int compressionLevel);
166*22ce4affSfengbojiang</b><p>  Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
167*22ce4affSfengbojiang  Important : in order to behave similarly to `ZSTD_compress()`,
168*22ce4affSfengbojiang  this function compresses at requested compression level,
169*22ce4affSfengbojiang  __ignoring any other parameter__ .
170*22ce4affSfengbojiang  If any advanced parameter was set using the advanced API,
171*22ce4affSfengbojiang  they will all be reset. Only `compressionLevel` remains.
172*22ce4affSfengbojiang
173*22ce4affSfengbojiang</p></pre><BR>
174*22ce4affSfengbojiang
175*22ce4affSfengbojiang<h3>Decompression context</h3><pre>  When decompressing many times,
176*22ce4affSfengbojiang  it is recommended to allocate a context only once,
177*22ce4affSfengbojiang  and re-use it for each successive compression operation.
178*22ce4affSfengbojiang  This will make workload friendlier for system's memory.
179*22ce4affSfengbojiang  Use one context per thread for parallel execution.
180*22ce4affSfengbojiang</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
181*22ce4affSfengbojiangZSTD_DCtx* ZSTD_createDCtx(void);
182*22ce4affSfengbojiangsize_t     ZSTD_freeDCtx(ZSTD_DCtx* dctx);
183*22ce4affSfengbojiang</pre></b><BR>
184*22ce4affSfengbojiang<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
185*22ce4affSfengbojiang                           void* dst, size_t dstCapacity,
186*22ce4affSfengbojiang                     const void* src, size_t srcSize);
187*22ce4affSfengbojiang</b><p>  Same as ZSTD_decompress(),
188*22ce4affSfengbojiang  requires an allocated ZSTD_DCtx.
189*22ce4affSfengbojiang  Compatible with sticky parameters.
190*22ce4affSfengbojiang
191*22ce4affSfengbojiang</p></pre><BR>
192*22ce4affSfengbojiang
193*22ce4affSfengbojiang<a name="Chapter5"></a><h2>Advanced compression API</h2><pre></pre>
194*22ce4affSfengbojiang
195*22ce4affSfengbojiang<pre><b>typedef enum { ZSTD_fast=1,
196*22ce4affSfengbojiang               ZSTD_dfast=2,
197*22ce4affSfengbojiang               ZSTD_greedy=3,
198*22ce4affSfengbojiang               ZSTD_lazy=4,
199*22ce4affSfengbojiang               ZSTD_lazy2=5,
200*22ce4affSfengbojiang               ZSTD_btlazy2=6,
201*22ce4affSfengbojiang               ZSTD_btopt=7,
202*22ce4affSfengbojiang               ZSTD_btultra=8,
203*22ce4affSfengbojiang               ZSTD_btultra2=9
204*22ce4affSfengbojiang               </b>/* note : new strategies _might_ be added in the future.<b>
205*22ce4affSfengbojiang                         Only the order (from fast to strong) is guaranteed */
206*22ce4affSfengbojiang} ZSTD_strategy;
207*22ce4affSfengbojiang</b></pre><BR>
208*22ce4affSfengbojiang<pre><b>typedef enum {
209*22ce4affSfengbojiang
210*22ce4affSfengbojiang    </b>/* compression parameters<b>
211*22ce4affSfengbojiang     * Note: When compressing with a ZSTD_CDict these parameters are superseded
212*22ce4affSfengbojiang     * by the parameters used to construct the ZSTD_CDict.
213*22ce4affSfengbojiang     * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
214*22ce4affSfengbojiang    ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
215*22ce4affSfengbojiang                              * Note that exact compression parameters are dynamically determined,
216*22ce4affSfengbojiang                              * depending on both compression level and srcSize (when known).
217*22ce4affSfengbojiang                              * Default level is ZSTD_CLEVEL_DEFAULT==3.
218*22ce4affSfengbojiang                              * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
219*22ce4affSfengbojiang                              * Note 1 : it's possible to pass a negative compression level.
220*22ce4affSfengbojiang                              * Note 2 : setting a level does not automatically set all other compression parameters
221*22ce4affSfengbojiang                              *   to default. Setting this will however eventually dynamically impact the compression
222*22ce4affSfengbojiang                              *   parameters which have not been manually set. The manually set
223*22ce4affSfengbojiang                              *   ones will 'stick'. */
224*22ce4affSfengbojiang    </b>/* Advanced compression parameters :<b>
225*22ce4affSfengbojiang     * It's possible to pin down compression parameters to some specific values.
226*22ce4affSfengbojiang     * In which case, these values are no longer dynamically selected by the compressor */
227*22ce4affSfengbojiang    ZSTD_c_windowLog=101,    </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
228*22ce4affSfengbojiang                              * This will set a memory budget for streaming decompression,
229*22ce4affSfengbojiang                              * with larger values requiring more memory
230*22ce4affSfengbojiang                              * and typically compressing more.
231*22ce4affSfengbojiang                              * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
232*22ce4affSfengbojiang                              * Special: value 0 means "use default windowLog".
233*22ce4affSfengbojiang                              * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
234*22ce4affSfengbojiang                              *       requires explicitly allowing such size at streaming decompression stage. */
235*22ce4affSfengbojiang    ZSTD_c_hashLog=102,      </b>/* Size of the initial probe table, as a power of 2.<b>
236*22ce4affSfengbojiang                              * Resulting memory usage is (1 << (hashLog+2)).
237*22ce4affSfengbojiang                              * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
238*22ce4affSfengbojiang                              * Larger tables improve compression ratio of strategies <= dFast,
239*22ce4affSfengbojiang                              * and improve speed of strategies > dFast.
240*22ce4affSfengbojiang                              * Special: value 0 means "use default hashLog". */
241*22ce4affSfengbojiang    ZSTD_c_chainLog=103,     </b>/* Size of the multi-probe search table, as a power of 2.<b>
242*22ce4affSfengbojiang                              * Resulting memory usage is (1 << (chainLog+2)).
243*22ce4affSfengbojiang                              * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
244*22ce4affSfengbojiang                              * Larger tables result in better and slower compression.
245*22ce4affSfengbojiang                              * This parameter is useless for "fast" strategy.
246*22ce4affSfengbojiang                              * It's still useful when using "dfast" strategy,
247*22ce4affSfengbojiang                              * in which case it defines a secondary probe table.
248*22ce4affSfengbojiang                              * Special: value 0 means "use default chainLog". */
249*22ce4affSfengbojiang    ZSTD_c_searchLog=104,    </b>/* Number of search attempts, as a power of 2.<b>
250*22ce4affSfengbojiang                              * More attempts result in better and slower compression.
251*22ce4affSfengbojiang                              * This parameter is useless for "fast" and "dFast" strategies.
252*22ce4affSfengbojiang                              * Special: value 0 means "use default searchLog". */
253*22ce4affSfengbojiang    ZSTD_c_minMatch=105,     </b>/* Minimum size of searched matches.<b>
254*22ce4affSfengbojiang                              * Note that Zstandard can still find matches of smaller size,
255*22ce4affSfengbojiang                              * it just tweaks its search algorithm to look for this size and larger.
256*22ce4affSfengbojiang                              * Larger values increase compression and decompression speed, but decrease ratio.
257*22ce4affSfengbojiang                              * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
258*22ce4affSfengbojiang                              * Note that currently, for all strategies < btopt, effective minimum is 4.
259*22ce4affSfengbojiang                              *                    , for all strategies > fast, effective maximum is 6.
260*22ce4affSfengbojiang                              * Special: value 0 means "use default minMatchLength". */
261*22ce4affSfengbojiang    ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
262*22ce4affSfengbojiang                              * For strategies btopt, btultra & btultra2:
263*22ce4affSfengbojiang                              *     Length of Match considered "good enough" to stop search.
264*22ce4affSfengbojiang                              *     Larger values make compression stronger, and slower.
265*22ce4affSfengbojiang                              * For strategy fast:
266*22ce4affSfengbojiang                              *     Distance between match sampling.
267*22ce4affSfengbojiang                              *     Larger values make compression faster, and weaker.
268*22ce4affSfengbojiang                              * Special: value 0 means "use default targetLength". */
269*22ce4affSfengbojiang    ZSTD_c_strategy=107,     </b>/* See ZSTD_strategy enum definition.<b>
270*22ce4affSfengbojiang                              * The higher the value of selected strategy, the more complex it is,
271*22ce4affSfengbojiang                              * resulting in stronger and slower compression.
272*22ce4affSfengbojiang                              * Special: value 0 means "use default strategy". */
273*22ce4affSfengbojiang
274*22ce4affSfengbojiang    </b>/* LDM mode parameters */<b>
275*22ce4affSfengbojiang    ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
276*22ce4affSfengbojiang                                     * This parameter is designed to improve compression ratio
277*22ce4affSfengbojiang                                     * for large inputs, by finding large matches at long distance.
278*22ce4affSfengbojiang                                     * It increases memory usage and window size.
279*22ce4affSfengbojiang                                     * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
280*22ce4affSfengbojiang                                     * except when expressly set to a different value.
281*22ce4affSfengbojiang                                     * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
282*22ce4affSfengbojiang                                     * compression strategy >= ZSTD_btopt (== compression level 16+) */
283*22ce4affSfengbojiang    ZSTD_c_ldmHashLog=161,   </b>/* Size of the table for long distance matching, as a power of 2.<b>
284*22ce4affSfengbojiang                              * Larger values increase memory usage and compression ratio,
285*22ce4affSfengbojiang                              * but decrease compression speed.
286*22ce4affSfengbojiang                              * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
287*22ce4affSfengbojiang                              * default: windowlog - 7.
288*22ce4affSfengbojiang                              * Special: value 0 means "automatically determine hashlog". */
289*22ce4affSfengbojiang    ZSTD_c_ldmMinMatch=162,  </b>/* Minimum match size for long distance matcher.<b>
290*22ce4affSfengbojiang                              * Larger/too small values usually decrease compression ratio.
291*22ce4affSfengbojiang                              * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
292*22ce4affSfengbojiang                              * Special: value 0 means "use default value" (default: 64). */
293*22ce4affSfengbojiang    ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
294*22ce4affSfengbojiang                              * Larger values improve collision resolution but decrease compression speed.
295*22ce4affSfengbojiang                              * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
296*22ce4affSfengbojiang                              * Special: value 0 means "use default value" (default: 3). */
297*22ce4affSfengbojiang    ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
298*22ce4affSfengbojiang                              * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
299*22ce4affSfengbojiang                              * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
300*22ce4affSfengbojiang                              * Larger values improve compression speed.
301*22ce4affSfengbojiang                              * Deviating far from default value will likely result in a compression ratio decrease.
302*22ce4affSfengbojiang                              * Special: value 0 means "automatically determine hashRateLog". */
303*22ce4affSfengbojiang
304*22ce4affSfengbojiang    </b>/* frame parameters */<b>
305*22ce4affSfengbojiang    ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
306*22ce4affSfengbojiang                              * Content size must be known at the beginning of compression.
307*22ce4affSfengbojiang                              * This is automatically the case when using ZSTD_compress2(),
308*22ce4affSfengbojiang                              * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
309*22ce4affSfengbojiang    ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
310*22ce4affSfengbojiang    ZSTD_c_dictIDFlag=202,   </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
311*22ce4affSfengbojiang
312*22ce4affSfengbojiang    </b>/* multi-threading parameters */<b>
313*22ce4affSfengbojiang    </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
314*22ce4affSfengbojiang     * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
315*22ce4affSfengbojiang     * In a situation where it's unknown if the linked library supports multi-threading or not,
316*22ce4affSfengbojiang     * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
317*22ce4affSfengbojiang     */
318*22ce4affSfengbojiang    ZSTD_c_nbWorkers=400,    </b>/* Select how many threads will be spawned to compress in parallel.<b>
319*22ce4affSfengbojiang                              * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
320*22ce4affSfengbojiang                              * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
321*22ce4affSfengbojiang                              * while compression is performed in parallel, within worker thread(s).
322*22ce4affSfengbojiang                              * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
323*22ce4affSfengbojiang                              *  in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
324*22ce4affSfengbojiang                              * More workers improve speed, but also increase memory usage.
325*22ce4affSfengbojiang                              * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
326*22ce4affSfengbojiang                              * compression is performed inside Caller's thread, and all invocations are blocking */
327*22ce4affSfengbojiang    ZSTD_c_jobSize=401,      </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
328*22ce4affSfengbojiang                              * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
329*22ce4affSfengbojiang                              * 0 means default, which is dynamically determined based on compression parameters.
330*22ce4affSfengbojiang                              * Job size must be a minimum of overlap size, or 1 MB, whichever is largest.
331*22ce4affSfengbojiang                              * The minimum size is automatically and transparently enforced. */
332*22ce4affSfengbojiang    ZSTD_c_overlapLog=402,   </b>/* Control the overlap size, as a fraction of window size.<b>
333*22ce4affSfengbojiang                              * The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
334*22ce4affSfengbojiang                              * It helps preserve compression ratio, while each job is compressed in parallel.
335*22ce4affSfengbojiang                              * This value is enforced only when nbWorkers >= 1.
336*22ce4affSfengbojiang                              * Larger values increase compression ratio, but decrease speed.
337*22ce4affSfengbojiang                              * Possible values range from 0 to 9 :
338*22ce4affSfengbojiang                              * - 0 means "default" : value will be determined by the library, depending on strategy
339*22ce4affSfengbojiang                              * - 1 means "no overlap"
340*22ce4affSfengbojiang                              * - 9 means "full overlap", using a full window size.
341*22ce4affSfengbojiang                              * Each intermediate rank increases/decreases load size by a factor 2 :
342*22ce4affSfengbojiang                              * 9: full window;  8: w/2;  7: w/4;  6: w/8;  5:w/16;  4: w/32;  3:w/64;  2:w/128;  1:no overlap;  0:default
343*22ce4affSfengbojiang                              * default value varies between 6 and 9, depending on strategy */
344*22ce4affSfengbojiang
345*22ce4affSfengbojiang    </b>/* note : additional experimental parameters are also available<b>
346*22ce4affSfengbojiang     * within the experimental section of the API.
347*22ce4affSfengbojiang     * At the time of this writing, they include :
348*22ce4affSfengbojiang     * ZSTD_c_rsyncable
349*22ce4affSfengbojiang     * ZSTD_c_format
350*22ce4affSfengbojiang     * ZSTD_c_forceMaxWindow
351*22ce4affSfengbojiang     * ZSTD_c_forceAttachDict
352*22ce4affSfengbojiang     * ZSTD_c_literalCompressionMode
353*22ce4affSfengbojiang     * ZSTD_c_targetCBlockSize
354*22ce4affSfengbojiang     * ZSTD_c_srcSizeHint
355*22ce4affSfengbojiang     * ZSTD_c_enableDedicatedDictSearch
356*22ce4affSfengbojiang     * ZSTD_c_stableInBuffer
357*22ce4affSfengbojiang     * ZSTD_c_stableOutBuffer
358*22ce4affSfengbojiang     * ZSTD_c_blockDelimiters
359*22ce4affSfengbojiang     * ZSTD_c_validateSequences
360*22ce4affSfengbojiang     * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
361*22ce4affSfengbojiang     * note : never ever use experimentalParam? names directly;
362*22ce4affSfengbojiang     *        also, the enums values themselves are unstable and can still change.
363*22ce4affSfengbojiang     */
364*22ce4affSfengbojiang     ZSTD_c_experimentalParam1=500,
365*22ce4affSfengbojiang     ZSTD_c_experimentalParam2=10,
366*22ce4affSfengbojiang     ZSTD_c_experimentalParam3=1000,
367*22ce4affSfengbojiang     ZSTD_c_experimentalParam4=1001,
368*22ce4affSfengbojiang     ZSTD_c_experimentalParam5=1002,
369*22ce4affSfengbojiang     ZSTD_c_experimentalParam6=1003,
370*22ce4affSfengbojiang     ZSTD_c_experimentalParam7=1004,
371*22ce4affSfengbojiang     ZSTD_c_experimentalParam8=1005,
372*22ce4affSfengbojiang     ZSTD_c_experimentalParam9=1006,
373*22ce4affSfengbojiang     ZSTD_c_experimentalParam10=1007,
374*22ce4affSfengbojiang     ZSTD_c_experimentalParam11=1008,
375*22ce4affSfengbojiang     ZSTD_c_experimentalParam12=1009
376*22ce4affSfengbojiang} ZSTD_cParameter;
377*22ce4affSfengbojiang</b></pre><BR>
378*22ce4affSfengbojiang<pre><b>typedef struct {
379*22ce4affSfengbojiang    size_t error;
380*22ce4affSfengbojiang    int lowerBound;
381*22ce4affSfengbojiang    int upperBound;
382*22ce4affSfengbojiang} ZSTD_bounds;
383*22ce4affSfengbojiang</b></pre><BR>
384*22ce4affSfengbojiang<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
385*22ce4affSfengbojiang</b><p>  All parameters must belong to an interval with lower and upper bounds,
386*22ce4affSfengbojiang  otherwise they will either trigger an error or be automatically clamped.
387*22ce4affSfengbojiang @return : a structure, ZSTD_bounds, which contains
388*22ce4affSfengbojiang         - an error status field, which must be tested using ZSTD_isError()
389*22ce4affSfengbojiang         - lower and upper bounds, both inclusive
390*22ce4affSfengbojiang
391*22ce4affSfengbojiang</p></pre><BR>
392*22ce4affSfengbojiang
393*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
394*22ce4affSfengbojiang</b><p>  Set one compression parameter, selected by enum ZSTD_cParameter.
395*22ce4affSfengbojiang  All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
396*22ce4affSfengbojiang  Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
397*22ce4affSfengbojiang  Setting a parameter is generally only possible during frame initialization (before starting compression).
398*22ce4affSfengbojiang  Exception : when using multi-threading mode (nbWorkers >= 1),
399*22ce4affSfengbojiang              the following parameters can be updated _during_ compression (within same frame):
400*22ce4affSfengbojiang              => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
401*22ce4affSfengbojiang              new parameters will be active for next job only (after a flush()).
402*22ce4affSfengbojiang @return : an error code (which can be tested using ZSTD_isError()).
403*22ce4affSfengbojiang
404*22ce4affSfengbojiang</p></pre><BR>
405*22ce4affSfengbojiang
406*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
407*22ce4affSfengbojiang</b><p>  Total input data size to be compressed as a single frame.
408*22ce4affSfengbojiang  Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
409*22ce4affSfengbojiang  This value will also be controlled at end of frame, and trigger an error if not respected.
410*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
411*22ce4affSfengbojiang  Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
412*22ce4affSfengbojiang           In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
413*22ce4affSfengbojiang           ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
414*22ce4affSfengbojiang  Note 2 : pledgedSrcSize is only valid once, for the next frame.
415*22ce4affSfengbojiang           It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
416*22ce4affSfengbojiang  Note 3 : Whenever all input data is provided and consumed in a single round,
417*22ce4affSfengbojiang           for example with ZSTD_compress2(),
418*22ce4affSfengbojiang           or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
419*22ce4affSfengbojiang           this value is automatically overridden by srcSize instead.
420*22ce4affSfengbojiang
421*22ce4affSfengbojiang</p></pre><BR>
422*22ce4affSfengbojiang
423*22ce4affSfengbojiang<pre><b>typedef enum {
424*22ce4affSfengbojiang    ZSTD_reset_session_only = 1,
425*22ce4affSfengbojiang    ZSTD_reset_parameters = 2,
426*22ce4affSfengbojiang    ZSTD_reset_session_and_parameters = 3
427*22ce4affSfengbojiang} ZSTD_ResetDirective;
428*22ce4affSfengbojiang</b></pre><BR>
429*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
430*22ce4affSfengbojiang</b><p>  There are 2 different things that can be reset, independently or jointly :
431*22ce4affSfengbojiang  - The session : will stop compressing current frame, and make CCtx ready to start a new one.
432*22ce4affSfengbojiang                  Useful after an error, or to interrupt any ongoing compression.
433*22ce4affSfengbojiang                  Any internal data not yet flushed is cancelled.
434*22ce4affSfengbojiang                  Compression parameters and dictionary remain unchanged.
435*22ce4affSfengbojiang                  They will be used to compress next frame.
436*22ce4affSfengbojiang                  Resetting session never fails.
437*22ce4affSfengbojiang  - The parameters : changes all parameters back to "default".
438*22ce4affSfengbojiang                  This removes any reference to any dictionary too.
439*22ce4affSfengbojiang                  Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
440*22ce4affSfengbojiang                  otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
441*22ce4affSfengbojiang  - Both : similar to resetting the session, followed by resetting parameters.
442*22ce4affSfengbojiang
443*22ce4affSfengbojiang</p></pre><BR>
444*22ce4affSfengbojiang
445*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
446*22ce4affSfengbojiang                       void* dst, size_t dstCapacity,
447*22ce4affSfengbojiang                 const void* src, size_t srcSize);
448*22ce4affSfengbojiang</b><p>  Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
449*22ce4affSfengbojiang  ZSTD_compress2() always starts a new frame.
450*22ce4affSfengbojiang  Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
451*22ce4affSfengbojiang  - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
452*22ce4affSfengbojiang  - The function is always blocking, returns when compression is completed.
453*22ce4affSfengbojiang  Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
454*22ce4affSfengbojiang @return : compressed size written into `dst` (<= `dstCapacity),
455*22ce4affSfengbojiang           or an error code if it fails (which can be tested using ZSTD_isError()).
456*22ce4affSfengbojiang
457*22ce4affSfengbojiang</p></pre><BR>
458*22ce4affSfengbojiang
459*22ce4affSfengbojiang<a name="Chapter6"></a><h2>Advanced decompression API</h2><pre></pre>
460*22ce4affSfengbojiang
461*22ce4affSfengbojiang<pre><b>typedef enum {
462*22ce4affSfengbojiang
463*22ce4affSfengbojiang    ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
464*22ce4affSfengbojiang                              * the streaming API will refuse to allocate memory buffer
465*22ce4affSfengbojiang                              * in order to protect the host from unreasonable memory requirements.
466*22ce4affSfengbojiang                              * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
467*22ce4affSfengbojiang                              * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
468*22ce4affSfengbojiang                              * Special: value 0 means "use default maximum windowLog". */
469*22ce4affSfengbojiang
470*22ce4affSfengbojiang    </b>/* note : additional experimental parameters are also available<b>
471*22ce4affSfengbojiang     * within the experimental section of the API.
472*22ce4affSfengbojiang     * At the time of this writing, they include :
473*22ce4affSfengbojiang     * ZSTD_d_format
474*22ce4affSfengbojiang     * ZSTD_d_stableOutBuffer
475*22ce4affSfengbojiang     * ZSTD_d_forceIgnoreChecksum
476*22ce4affSfengbojiang     * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
477*22ce4affSfengbojiang     * note : never ever use experimentalParam? names directly
478*22ce4affSfengbojiang     */
479*22ce4affSfengbojiang     ZSTD_d_experimentalParam1=1000,
480*22ce4affSfengbojiang     ZSTD_d_experimentalParam2=1001,
481*22ce4affSfengbojiang     ZSTD_d_experimentalParam3=1002
482*22ce4affSfengbojiang
483*22ce4affSfengbojiang} ZSTD_dParameter;
484*22ce4affSfengbojiang</b></pre><BR>
485*22ce4affSfengbojiang<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
486*22ce4affSfengbojiang</b><p>  All parameters must belong to an interval with lower and upper bounds,
487*22ce4affSfengbojiang  otherwise they will either trigger an error or be automatically clamped.
488*22ce4affSfengbojiang @return : a structure, ZSTD_bounds, which contains
489*22ce4affSfengbojiang         - an error status field, which must be tested using ZSTD_isError()
490*22ce4affSfengbojiang         - both lower and upper bounds, inclusive
491*22ce4affSfengbojiang
492*22ce4affSfengbojiang</p></pre><BR>
493*22ce4affSfengbojiang
494*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
495*22ce4affSfengbojiang</b><p>  Set one compression parameter, selected by enum ZSTD_dParameter.
496*22ce4affSfengbojiang  All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
497*22ce4affSfengbojiang  Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
498*22ce4affSfengbojiang  Setting a parameter is only possible during frame initialization (before starting decompression).
499*22ce4affSfengbojiang @return : 0, or an error code (which can be tested using ZSTD_isError()).
500*22ce4affSfengbojiang
501*22ce4affSfengbojiang</p></pre><BR>
502*22ce4affSfengbojiang
503*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
504*22ce4affSfengbojiang</b><p>  Return a DCtx to clean state.
505*22ce4affSfengbojiang  Session and parameters can be reset jointly or separately.
506*22ce4affSfengbojiang  Parameters can only be reset when no active frame is being decompressed.
507*22ce4affSfengbojiang @return : 0, or an error code, which can be tested with ZSTD_isError()
508*22ce4affSfengbojiang
509*22ce4affSfengbojiang</p></pre><BR>
510*22ce4affSfengbojiang
511*22ce4affSfengbojiang<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
512*22ce4affSfengbojiang
513*22ce4affSfengbojiang<pre><b>typedef struct ZSTD_inBuffer_s {
514*22ce4affSfengbojiang  const void* src;    </b>/**< start of input buffer */<b>
515*22ce4affSfengbojiang  size_t size;        </b>/**< size of input buffer */<b>
516*22ce4affSfengbojiang  size_t pos;         </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
517*22ce4affSfengbojiang} ZSTD_inBuffer;
518*22ce4affSfengbojiang</b></pre><BR>
519*22ce4affSfengbojiang<pre><b>typedef struct ZSTD_outBuffer_s {
520*22ce4affSfengbojiang  void*  dst;         </b>/**< start of output buffer */<b>
521*22ce4affSfengbojiang  size_t size;        </b>/**< size of output buffer */<b>
522*22ce4affSfengbojiang  size_t pos;         </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
523*22ce4affSfengbojiang} ZSTD_outBuffer;
524*22ce4affSfengbojiang</b></pre><BR>
525*22ce4affSfengbojiang<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
526*22ce4affSfengbojiang  A ZSTD_CStream object is required to track streaming operation.
527*22ce4affSfengbojiang  Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
528*22ce4affSfengbojiang  ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
529*22ce4affSfengbojiang  It is recommended to re-use ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
530*22ce4affSfengbojiang
531*22ce4affSfengbojiang  For parallel execution, use one separate ZSTD_CStream per thread.
532*22ce4affSfengbojiang
533*22ce4affSfengbojiang  note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
534*22ce4affSfengbojiang
535*22ce4affSfengbojiang  Parameters are sticky : when starting a new compression on the same context,
536*22ce4affSfengbojiang  it will re-use the same sticky parameters as previous compression session.
537*22ce4affSfengbojiang  When in doubt, it's recommended to fully initialize the context before usage.
538*22ce4affSfengbojiang  Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
539*22ce4affSfengbojiang  ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
540*22ce4affSfengbojiang  set more specific parameters, the pledged source size, or load a dictionary.
541*22ce4affSfengbojiang
542*22ce4affSfengbojiang  Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
543*22ce4affSfengbojiang  consume input stream. The function will automatically update both `pos`
544*22ce4affSfengbojiang  fields within `input` and `output`.
545*22ce4affSfengbojiang  Note that the function may not consume the entire input, for example, because
546*22ce4affSfengbojiang  the output buffer is already full, in which case `input.pos < input.size`.
547*22ce4affSfengbojiang  The caller must check if input has been entirely consumed.
548*22ce4affSfengbojiang  If not, the caller must make some room to receive more compressed data,
549*22ce4affSfengbojiang  and then present again remaining input data.
550*22ce4affSfengbojiang  note: ZSTD_e_continue is guaranteed to make some forward progress when called,
551*22ce4affSfengbojiang        but doesn't guarantee maximal forward progress. This is especially relevant
552*22ce4affSfengbojiang        when compressing with multiple threads. The call won't block if it can
553*22ce4affSfengbojiang        consume some input, but if it can't it will wait for some, but not all,
554*22ce4affSfengbojiang        output to be flushed.
555*22ce4affSfengbojiang @return : provides a minimum amount of data remaining to be flushed from internal buffers
556*22ce4affSfengbojiang           or an error code, which can be tested using ZSTD_isError().
557*22ce4affSfengbojiang
558*22ce4affSfengbojiang  At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
559*22ce4affSfengbojiang  using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
560*22ce4affSfengbojiang  Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
561*22ce4affSfengbojiang  In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
562*22ce4affSfengbojiang  You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
563*22ce4affSfengbojiang  operation.
564*22ce4affSfengbojiang  note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
565*22ce4affSfengbojiang        block until the flush is complete or the output buffer is full.
566*22ce4affSfengbojiang  @return : 0 if internal buffers are entirely flushed,
567*22ce4affSfengbojiang            >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
568*22ce4affSfengbojiang            or an error code, which can be tested using ZSTD_isError().
569*22ce4affSfengbojiang
570*22ce4affSfengbojiang  Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
571*22ce4affSfengbojiang  It will perform a flush and write frame epilogue.
572*22ce4affSfengbojiang  The epilogue is required for decoders to consider a frame completed.
573*22ce4affSfengbojiang  flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
574*22ce4affSfengbojiang  You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
575*22ce4affSfengbojiang  start a new frame.
576*22ce4affSfengbojiang  note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
577*22ce4affSfengbojiang        block until the flush is complete or the output buffer is full.
578*22ce4affSfengbojiang  @return : 0 if frame fully completed and fully flushed,
579*22ce4affSfengbojiang            >0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
580*22ce4affSfengbojiang            or an error code, which can be tested using ZSTD_isError().
581*22ce4affSfengbojiang
582*22ce4affSfengbojiang
583*22ce4affSfengbojiang<BR></pre>
584*22ce4affSfengbojiang
585*22ce4affSfengbojiang<pre><b>typedef ZSTD_CCtx ZSTD_CStream;  </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
586*22ce4affSfengbojiang</b></pre><BR>
587*22ce4affSfengbojiang<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
588*22ce4affSfengbojiangsize_t ZSTD_freeCStream(ZSTD_CStream* zcs);
589*22ce4affSfengbojiang</pre></b><BR>
590*22ce4affSfengbojiang<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
591*22ce4affSfengbojiang    ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
592*22ce4affSfengbojiang    ZSTD_e_flush=1,    </b>/* flush any data provided so far,<b>
593*22ce4affSfengbojiang                        * it creates (at least) one new block, that can be decoded immediately on reception;
594*22ce4affSfengbojiang                        * frame will continue: any future data can still reference previously compressed data, improving compression.
595*22ce4affSfengbojiang                        * note : multithreaded compression will block to flush as much output as possible. */
596*22ce4affSfengbojiang    ZSTD_e_end=2       </b>/* flush any remaining data _and_ close current frame.<b>
597*22ce4affSfengbojiang                        * note that frame is only closed after compressed data is fully flushed (return value == 0).
598*22ce4affSfengbojiang                        * After that point, any additional data starts a new frame.
599*22ce4affSfengbojiang                        * note : each frame is independent (does not reference any content from previous frame).
600*22ce4affSfengbojiang                        : note : multithreaded compression will block to flush as much output as possible. */
601*22ce4affSfengbojiang} ZSTD_EndDirective;
602*22ce4affSfengbojiang</pre></b><BR>
603*22ce4affSfengbojiang<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
604*22ce4affSfengbojiang                             ZSTD_outBuffer* output,
605*22ce4affSfengbojiang                             ZSTD_inBuffer* input,
606*22ce4affSfengbojiang                             ZSTD_EndDirective endOp);
607*22ce4affSfengbojiang</b><p>  Behaves about the same as ZSTD_compressStream, with additional control on end directive.
608*22ce4affSfengbojiang  - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
609*22ce4affSfengbojiang  - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
610*22ce4affSfengbojiang  - output->pos must be <= dstCapacity, input->pos must be <= srcSize
611*22ce4affSfengbojiang  - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
612*22ce4affSfengbojiang  - endOp must be a valid directive
613*22ce4affSfengbojiang  - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
614*22ce4affSfengbojiang  - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available,
615*22ce4affSfengbojiang                                                  and then immediately returns, just indicating that there is some data remaining to be flushed.
616*22ce4affSfengbojiang                                                  The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
617*22ce4affSfengbojiang  - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking.
618*22ce4affSfengbojiang  - @return provides a minimum amount of data remaining to be flushed from internal buffers
619*22ce4affSfengbojiang            or an error code, which can be tested using ZSTD_isError().
620*22ce4affSfengbojiang            if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
621*22ce4affSfengbojiang            This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
622*22ce4affSfengbojiang            For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
623*22ce4affSfengbojiang  - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
624*22ce4affSfengbojiang            only ZSTD_e_end or ZSTD_e_flush operations are allowed.
625*22ce4affSfengbojiang            Before starting a new compression job, or changing compression parameters,
626*22ce4affSfengbojiang            it is required to fully flush internal buffers.
627*22ce4affSfengbojiang
628*22ce4affSfengbojiang</p></pre><BR>
629*22ce4affSfengbojiang
630*22ce4affSfengbojiang<pre><b>size_t ZSTD_CStreamInSize(void);    </b>/**< recommended size for input buffer */<b>
631*22ce4affSfengbojiang</b></pre><BR>
632*22ce4affSfengbojiang<pre><b>size_t ZSTD_CStreamOutSize(void);   </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
633*22ce4affSfengbojiang</b></pre><BR>
634*22ce4affSfengbojiang<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
635*22ce4affSfengbojiang</b>/*!<b>
636*22ce4affSfengbojiang * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
637*22ce4affSfengbojiang * NOTE: The return value is different. ZSTD_compressStream() returns a hint for
638*22ce4affSfengbojiang * the next read size (if non-zero and not an error). ZSTD_compressStream2()
639*22ce4affSfengbojiang * returns the minimum nb of bytes left to flush (if non-zero and not an error).
640*22ce4affSfengbojiang */
641*22ce4affSfengbojiangsize_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
642*22ce4affSfengbojiang</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
643*22ce4affSfengbojiangsize_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
644*22ce4affSfengbojiang</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
645*22ce4affSfengbojiangsize_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
646*22ce4affSfengbojiang</b><p>
647*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
648*22ce4affSfengbojiang     ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
649*22ce4affSfengbojiang     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
650*22ce4affSfengbojiang
651*22ce4affSfengbojiang</p></pre><BR>
652*22ce4affSfengbojiang
653*22ce4affSfengbojiang<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
654*22ce4affSfengbojiang  A ZSTD_DStream object is required to track streaming operations.
655*22ce4affSfengbojiang  Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
656*22ce4affSfengbojiang  ZSTD_DStream objects can be re-used multiple times.
657*22ce4affSfengbojiang
658*22ce4affSfengbojiang  Use ZSTD_initDStream() to start a new decompression operation.
659*22ce4affSfengbojiang @return : recommended first input size
660*22ce4affSfengbojiang  Alternatively, use advanced API to set specific properties.
661*22ce4affSfengbojiang
662*22ce4affSfengbojiang  Use ZSTD_decompressStream() repetitively to consume your input.
663*22ce4affSfengbojiang  The function will update both `pos` fields.
664*22ce4affSfengbojiang  If `input.pos < input.size`, some input has not been consumed.
665*22ce4affSfengbojiang  It's up to the caller to present again remaining data.
666*22ce4affSfengbojiang  The function tries to flush all data decoded immediately, respecting output buffer size.
667*22ce4affSfengbojiang  If `output.pos < output.size`, decoder has flushed everything it could.
668*22ce4affSfengbojiang  But if `output.pos == output.size`, there might be some data left within internal buffers.,
669*22ce4affSfengbojiang  In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
670*22ce4affSfengbojiang  Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
671*22ce4affSfengbojiang @return : 0 when a frame is completely decoded and fully flushed,
672*22ce4affSfengbojiang        or an error code, which can be tested using ZSTD_isError(),
673*22ce4affSfengbojiang        or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
674*22ce4affSfengbojiang                                the return value is a suggested next input size (just a hint for better latency)
675*22ce4affSfengbojiang                                that will never request more than the remaining frame size.
676*22ce4affSfengbojiang
677*22ce4affSfengbojiang<BR></pre>
678*22ce4affSfengbojiang
679*22ce4affSfengbojiang<pre><b>typedef ZSTD_DCtx ZSTD_DStream;  </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
680*22ce4affSfengbojiang</b></pre><BR>
681*22ce4affSfengbojiang<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
682*22ce4affSfengbojiangsize_t ZSTD_freeDStream(ZSTD_DStream* zds);
683*22ce4affSfengbojiang</pre></b><BR>
684*22ce4affSfengbojiang<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
685*22ce4affSfengbojiang<pre><b>size_t ZSTD_DStreamInSize(void);    </b>/*!< recommended size for input buffer */<b>
686*22ce4affSfengbojiang</b></pre><BR>
687*22ce4affSfengbojiang<pre><b>size_t ZSTD_DStreamOutSize(void);   </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b>
688*22ce4affSfengbojiang</b></pre><BR>
689*22ce4affSfengbojiang<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
690*22ce4affSfengbojiang
691*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
692*22ce4affSfengbojiang                               void* dst, size_t dstCapacity,
693*22ce4affSfengbojiang                         const void* src, size_t srcSize,
694*22ce4affSfengbojiang                         const void* dict,size_t dictSize,
695*22ce4affSfengbojiang                               int compressionLevel);
696*22ce4affSfengbojiang</b><p>  Compression at an explicit compression level using a Dictionary.
697*22ce4affSfengbojiang  A dictionary can be any arbitrary data segment (also called a prefix),
698*22ce4affSfengbojiang  or a buffer with specified information (see dictBuilder/zdict.h).
699*22ce4affSfengbojiang  Note : This function loads the dictionary, resulting in significant startup delay.
700*22ce4affSfengbojiang         It's intended for a dictionary used only once.
701*22ce4affSfengbojiang  Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
702*22ce4affSfengbojiang</p></pre><BR>
703*22ce4affSfengbojiang
704*22ce4affSfengbojiang<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
705*22ce4affSfengbojiang                                 void* dst, size_t dstCapacity,
706*22ce4affSfengbojiang                           const void* src, size_t srcSize,
707*22ce4affSfengbojiang                           const void* dict,size_t dictSize);
708*22ce4affSfengbojiang</b><p>  Decompression using a known Dictionary.
709*22ce4affSfengbojiang  Dictionary must be identical to the one used during compression.
710*22ce4affSfengbojiang  Note : This function loads the dictionary, resulting in significant startup delay.
711*22ce4affSfengbojiang         It's intended for a dictionary used only once.
712*22ce4affSfengbojiang  Note : When `dict == NULL || dictSize < 8` no dictionary is used.
713*22ce4affSfengbojiang</p></pre><BR>
714*22ce4affSfengbojiang
715*22ce4affSfengbojiang<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
716*22ce4affSfengbojiang
717*22ce4affSfengbojiang<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
718*22ce4affSfengbojiang                             int compressionLevel);
719*22ce4affSfengbojiang</b><p>  When compressing multiple messages or blocks using the same dictionary,
720*22ce4affSfengbojiang  it's recommended to digest the dictionary only once, since it's a costly operation.
721*22ce4affSfengbojiang  ZSTD_createCDict() will create a state from digesting a dictionary.
722*22ce4affSfengbojiang  The resulting state can be used for future compression operations with very limited startup cost.
723*22ce4affSfengbojiang  ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
724*22ce4affSfengbojiang @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
725*22ce4affSfengbojiang  Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
726*22ce4affSfengbojiang  Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
727*22ce4affSfengbojiang      in which case the only thing that it transports is the @compressionLevel.
728*22ce4affSfengbojiang      This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
729*22ce4affSfengbojiang      expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
730*22ce4affSfengbojiang</p></pre><BR>
731*22ce4affSfengbojiang
732*22ce4affSfengbojiang<pre><b>size_t      ZSTD_freeCDict(ZSTD_CDict* CDict);
733*22ce4affSfengbojiang</b><p>  Function frees memory allocated by ZSTD_createCDict().
734*22ce4affSfengbojiang</p></pre><BR>
735*22ce4affSfengbojiang
736*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
737*22ce4affSfengbojiang                                void* dst, size_t dstCapacity,
738*22ce4affSfengbojiang                          const void* src, size_t srcSize,
739*22ce4affSfengbojiang                          const ZSTD_CDict* cdict);
740*22ce4affSfengbojiang</b><p>  Compression using a digested Dictionary.
741*22ce4affSfengbojiang  Recommended when same dictionary is used multiple times.
742*22ce4affSfengbojiang  Note : compression level is _decided at dictionary creation time_,
743*22ce4affSfengbojiang     and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
744*22ce4affSfengbojiang</p></pre><BR>
745*22ce4affSfengbojiang
746*22ce4affSfengbojiang<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
747*22ce4affSfengbojiang</b><p>  Create a digested dictionary, ready to start decompression operation without startup delay.
748*22ce4affSfengbojiang  dictBuffer can be released after DDict creation, as its content is copied inside DDict.
749*22ce4affSfengbojiang</p></pre><BR>
750*22ce4affSfengbojiang
751*22ce4affSfengbojiang<pre><b>size_t      ZSTD_freeDDict(ZSTD_DDict* ddict);
752*22ce4affSfengbojiang</b><p>  Function frees memory allocated with ZSTD_createDDict()
753*22ce4affSfengbojiang</p></pre><BR>
754*22ce4affSfengbojiang
755*22ce4affSfengbojiang<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
756*22ce4affSfengbojiang                                  void* dst, size_t dstCapacity,
757*22ce4affSfengbojiang                            const void* src, size_t srcSize,
758*22ce4affSfengbojiang                            const ZSTD_DDict* ddict);
759*22ce4affSfengbojiang</b><p>  Decompression using a digested Dictionary.
760*22ce4affSfengbojiang  Recommended when same dictionary is used multiple times.
761*22ce4affSfengbojiang</p></pre><BR>
762*22ce4affSfengbojiang
763*22ce4affSfengbojiang<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
764*22ce4affSfengbojiang
765*22ce4affSfengbojiang<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
766*22ce4affSfengbojiang</b><p>  Provides the dictID stored within dictionary.
767*22ce4affSfengbojiang  if @return == 0, the dictionary is not conformant with Zstandard specification.
768*22ce4affSfengbojiang  It can still be loaded, but as a content-only dictionary.
769*22ce4affSfengbojiang</p></pre><BR>
770*22ce4affSfengbojiang
771*22ce4affSfengbojiang<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
772*22ce4affSfengbojiang</b><p>  Provides the dictID of the dictionary loaded into `ddict`.
773*22ce4affSfengbojiang  If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
774*22ce4affSfengbojiang  Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
775*22ce4affSfengbojiang</p></pre><BR>
776*22ce4affSfengbojiang
777*22ce4affSfengbojiang<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
778*22ce4affSfengbojiang</b><p>  Provides the dictID required to decompressed the frame stored within `src`.
779*22ce4affSfengbojiang  If @return == 0, the dictID could not be decoded.
780*22ce4affSfengbojiang  This could for one of the following reasons :
781*22ce4affSfengbojiang  - The frame does not require a dictionary to be decoded (most common case).
782*22ce4affSfengbojiang  - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
783*22ce4affSfengbojiang    Note : this use case also happens when using a non-conformant dictionary.
784*22ce4affSfengbojiang  - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
785*22ce4affSfengbojiang  - This is not a Zstandard frame.
786*22ce4affSfengbojiang  When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
787*22ce4affSfengbojiang</p></pre><BR>
788*22ce4affSfengbojiang
789*22ce4affSfengbojiang<a name="Chapter13"></a><h2>Advanced dictionary and prefix API</h2><pre>
790*22ce4affSfengbojiang This API allows dictionaries to be used with ZSTD_compress2(),
791*22ce4affSfengbojiang ZSTD_compressStream2(), and ZSTD_decompress(). Dictionaries are sticky, and
792*22ce4affSfengbojiang only reset with the context is reset with ZSTD_reset_parameters or
793*22ce4affSfengbojiang ZSTD_reset_session_and_parameters. Prefixes are single-use.
794*22ce4affSfengbojiang<BR></pre>
795*22ce4affSfengbojiang
796*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
797*22ce4affSfengbojiang</b><p>  Create an internal CDict from `dict` buffer.
798*22ce4affSfengbojiang  Decompression will have to use same dictionary.
799*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
800*22ce4affSfengbojiang  Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
801*22ce4affSfengbojiang           meaning "return to no-dictionary mode".
802*22ce4affSfengbojiang  Note 1 : Dictionary is sticky, it will be used for all future compressed frames.
803*22ce4affSfengbojiang           To return to "no-dictionary" situation, load a NULL dictionary (or reset parameters).
804*22ce4affSfengbojiang  Note 2 : Loading a dictionary involves building tables.
805*22ce4affSfengbojiang           It's also a CPU consuming operation, with non-negligible impact on latency.
806*22ce4affSfengbojiang           Tables are dependent on compression parameters, and for this reason,
807*22ce4affSfengbojiang           compression parameters can no longer be changed after loading a dictionary.
808*22ce4affSfengbojiang  Note 3 :`dict` content will be copied internally.
809*22ce4affSfengbojiang           Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
810*22ce4affSfengbojiang           In such a case, dictionary buffer must outlive its users.
811*22ce4affSfengbojiang  Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
812*22ce4affSfengbojiang           to precisely select how dictionary content must be interpreted.
813*22ce4affSfengbojiang</p></pre><BR>
814*22ce4affSfengbojiang
815*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
816*22ce4affSfengbojiang</b><p>  Reference a prepared dictionary, to be used for all next compressed frames.
817*22ce4affSfengbojiang  Note that compression parameters are enforced from within CDict,
818*22ce4affSfengbojiang  and supersede any compression parameter previously set within CCtx.
819*22ce4affSfengbojiang  The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
820*22ce4affSfengbojiang  The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
821*22ce4affSfengbojiang  The dictionary will remain valid for future compressed frames using same CCtx.
822*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
823*22ce4affSfengbojiang  Special : Referencing a NULL CDict means "return to no-dictionary mode".
824*22ce4affSfengbojiang  Note 1 : Currently, only one dictionary can be managed.
825*22ce4affSfengbojiang           Referencing a new dictionary effectively "discards" any previous one.
826*22ce4affSfengbojiang  Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
827*22ce4affSfengbojiang</p></pre><BR>
828*22ce4affSfengbojiang
829*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
830*22ce4affSfengbojiang                     const void* prefix, size_t prefixSize);
831*22ce4affSfengbojiang</b><p>  Reference a prefix (single-usage dictionary) for next compressed frame.
832*22ce4affSfengbojiang  A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
833*22ce4affSfengbojiang  Decompression will need same prefix to properly regenerate data.
834*22ce4affSfengbojiang  Compressing with a prefix is similar in outcome as performing a diff and compressing it,
835*22ce4affSfengbojiang  but performs much faster, especially during decompression (compression speed is tunable with compression level).
836*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
837*22ce4affSfengbojiang  Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
838*22ce4affSfengbojiang  Note 1 : Prefix buffer is referenced. It **must** outlive compression.
839*22ce4affSfengbojiang           Its content must remain unmodified during compression.
840*22ce4affSfengbojiang  Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
841*22ce4affSfengbojiang           ensure that the window size is large enough to contain the entire source.
842*22ce4affSfengbojiang           See ZSTD_c_windowLog.
843*22ce4affSfengbojiang  Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
844*22ce4affSfengbojiang           It's a CPU consuming operation, with non-negligible impact on latency.
845*22ce4affSfengbojiang           If there is a need to use the same prefix multiple times, consider loadDictionary instead.
846*22ce4affSfengbojiang  Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
847*22ce4affSfengbojiang           Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
848*22ce4affSfengbojiang</p></pre><BR>
849*22ce4affSfengbojiang
850*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
851*22ce4affSfengbojiang</b><p>  Create an internal DDict from dict buffer,
852*22ce4affSfengbojiang  to be used to decompress next frames.
853*22ce4affSfengbojiang  The dictionary remains valid for all future frames, until explicitly invalidated.
854*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
855*22ce4affSfengbojiang  Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
856*22ce4affSfengbojiang            meaning "return to no-dictionary mode".
857*22ce4affSfengbojiang  Note 1 : Loading a dictionary involves building tables,
858*22ce4affSfengbojiang           which has a non-negligible impact on CPU usage and latency.
859*22ce4affSfengbojiang           It's recommended to "load once, use many times", to amortize the cost
860*22ce4affSfengbojiang  Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
861*22ce4affSfengbojiang           Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
862*22ce4affSfengbojiang  Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
863*22ce4affSfengbojiang           how dictionary content is loaded and interpreted.
864*22ce4affSfengbojiang
865*22ce4affSfengbojiang</p></pre><BR>
866*22ce4affSfengbojiang
867*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
868*22ce4affSfengbojiang</b><p>  Reference a prepared dictionary, to be used to decompress next frames.
869*22ce4affSfengbojiang  The dictionary remains active for decompression of future frames using same DCtx.
870*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
871*22ce4affSfengbojiang  Note 1 : Currently, only one dictionary can be managed.
872*22ce4affSfengbojiang           Referencing a new dictionary effectively "discards" any previous one.
873*22ce4affSfengbojiang  Special: referencing a NULL DDict means "return to no-dictionary mode".
874*22ce4affSfengbojiang  Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
875*22ce4affSfengbojiang
876*22ce4affSfengbojiang</p></pre><BR>
877*22ce4affSfengbojiang
878*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
879*22ce4affSfengbojiang                     const void* prefix, size_t prefixSize);
880*22ce4affSfengbojiang</b><p>  Reference a prefix (single-usage dictionary) to decompress next frame.
881*22ce4affSfengbojiang  This is the reverse operation of ZSTD_CCtx_refPrefix(),
882*22ce4affSfengbojiang  and must use the same prefix as the one used during compression.
883*22ce4affSfengbojiang  Prefix is **only used once**. Reference is discarded at end of frame.
884*22ce4affSfengbojiang  End of frame is reached when ZSTD_decompressStream() returns 0.
885*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
886*22ce4affSfengbojiang  Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
887*22ce4affSfengbojiang  Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
888*22ce4affSfengbojiang           Prefix buffer must remain unmodified up to the end of frame,
889*22ce4affSfengbojiang           reached when ZSTD_decompressStream() returns 0.
890*22ce4affSfengbojiang  Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
891*22ce4affSfengbojiang           Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
892*22ce4affSfengbojiang  Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
893*22ce4affSfengbojiang           A full dictionary is more costly, as it requires building tables.
894*22ce4affSfengbojiang
895*22ce4affSfengbojiang</p></pre><BR>
896*22ce4affSfengbojiang
897*22ce4affSfengbojiang<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
898*22ce4affSfengbojiangsize_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
899*22ce4affSfengbojiangsize_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
900*22ce4affSfengbojiangsize_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
901*22ce4affSfengbojiangsize_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
902*22ce4affSfengbojiangsize_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
903*22ce4affSfengbojiang</b><p>  These functions give the _current_ memory usage of selected object.
904*22ce4affSfengbojiang  Note that object memory usage can evolve (increase or decrease) over time.
905*22ce4affSfengbojiang</p></pre><BR>
906*22ce4affSfengbojiang
907*22ce4affSfengbojiang<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
908*22ce4affSfengbojiang The following symbols and constants
909*22ce4affSfengbojiang are not planned to join "stable API" status in the near future.
910*22ce4affSfengbojiang They can still change in future versions.
911*22ce4affSfengbojiang Some of them are planned to remain in the static_only section indefinitely.
912*22ce4affSfengbojiang Some of them might be removed in the future (especially when redundant with existing stable functions)
913*22ce4affSfengbojiang
914*22ce4affSfengbojiang<BR></pre>
915*22ce4affSfengbojiang
916*22ce4affSfengbojiang<pre><b>typedef struct {
917*22ce4affSfengbojiang    unsigned int offset;      </b>/* The offset of the match. (NOT the same as the offset code)<b>
918*22ce4affSfengbojiang                               * If offset == 0 and matchLength == 0, this sequence represents the last
919*22ce4affSfengbojiang                               * literals in the block of litLength size.
920*22ce4affSfengbojiang                               */
921*22ce4affSfengbojiang
922*22ce4affSfengbojiang    unsigned int litLength;   </b>/* Literal length of the sequence. */<b>
923*22ce4affSfengbojiang    unsigned int matchLength; </b>/* Match length of the sequence. */<b>
924*22ce4affSfengbojiang
925*22ce4affSfengbojiang                              </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
926*22ce4affSfengbojiang                               * In this case, we will treat the sequence as a marker for a block boundary.
927*22ce4affSfengbojiang                               */
928*22ce4affSfengbojiang
929*22ce4affSfengbojiang    unsigned int rep;         </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
930*22ce4affSfengbojiang                               * Ranges from [0, 3].
931*22ce4affSfengbojiang                               *
932*22ce4affSfengbojiang                               * Repeat offsets are essentially previous offsets from previous sequences sorted in
933*22ce4affSfengbojiang                               * recency order. For more detail, see doc/zstd_compression_format.md
934*22ce4affSfengbojiang                               *
935*22ce4affSfengbojiang                               * If rep == 0, then 'offset' does not contain a repeat offset.
936*22ce4affSfengbojiang                               * If rep > 0:
937*22ce4affSfengbojiang                               *  If litLength != 0:
938*22ce4affSfengbojiang                               *      rep == 1 --> offset == repeat_offset_1
939*22ce4affSfengbojiang                               *      rep == 2 --> offset == repeat_offset_2
940*22ce4affSfengbojiang                               *      rep == 3 --> offset == repeat_offset_3
941*22ce4affSfengbojiang                               *  If litLength == 0:
942*22ce4affSfengbojiang                               *      rep == 1 --> offset == repeat_offset_2
943*22ce4affSfengbojiang                               *      rep == 2 --> offset == repeat_offset_3
944*22ce4affSfengbojiang                               *      rep == 3 --> offset == repeat_offset_1 - 1
945*22ce4affSfengbojiang                               *
946*22ce4affSfengbojiang                               * Note: This field is optional. ZSTD_generateSequences() will calculate the value of
947*22ce4affSfengbojiang                               * 'rep', but repeat offsets do not necessarily need to be calculated from an external
948*22ce4affSfengbojiang                               * sequence provider's perspective. For example, ZSTD_compressSequences() does not
949*22ce4affSfengbojiang                               * use this 'rep' field at all (as of now).
950*22ce4affSfengbojiang                               */
951*22ce4affSfengbojiang} ZSTD_Sequence;
952*22ce4affSfengbojiang</b></pre><BR>
953*22ce4affSfengbojiang<pre><b>typedef struct {
954*22ce4affSfengbojiang    unsigned windowLog;       </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
955*22ce4affSfengbojiang    unsigned chainLog;        </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
956*22ce4affSfengbojiang    unsigned hashLog;         </b>/**< dispatch table : larger == faster, more memory */<b>
957*22ce4affSfengbojiang    unsigned searchLog;       </b>/**< nb of searches : larger == more compression, slower */<b>
958*22ce4affSfengbojiang    unsigned minMatch;        </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
959*22ce4affSfengbojiang    unsigned targetLength;    </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
960*22ce4affSfengbojiang    ZSTD_strategy strategy;   </b>/**< see ZSTD_strategy definition above */<b>
961*22ce4affSfengbojiang} ZSTD_compressionParameters;
962*22ce4affSfengbojiang</b></pre><BR>
963*22ce4affSfengbojiang<pre><b>typedef struct {
964*22ce4affSfengbojiang    int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
965*22ce4affSfengbojiang    int checksumFlag;    </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
966*22ce4affSfengbojiang    int noDictIDFlag;    </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
967*22ce4affSfengbojiang} ZSTD_frameParameters;
968*22ce4affSfengbojiang</b></pre><BR>
969*22ce4affSfengbojiang<pre><b>typedef struct {
970*22ce4affSfengbojiang    ZSTD_compressionParameters cParams;
971*22ce4affSfengbojiang    ZSTD_frameParameters fParams;
972*22ce4affSfengbojiang} ZSTD_parameters;
973*22ce4affSfengbojiang</b></pre><BR>
974*22ce4affSfengbojiang<pre><b>typedef enum {
975*22ce4affSfengbojiang    ZSTD_dct_auto = 0,       </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
976*22ce4affSfengbojiang    ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
977*22ce4affSfengbojiang    ZSTD_dct_fullDict = 2    </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
978*22ce4affSfengbojiang} ZSTD_dictContentType_e;
979*22ce4affSfengbojiang</b></pre><BR>
980*22ce4affSfengbojiang<pre><b>typedef enum {
981*22ce4affSfengbojiang    ZSTD_dlm_byCopy = 0,  </b>/**< Copy dictionary content internally */<b>
982*22ce4affSfengbojiang    ZSTD_dlm_byRef = 1    </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
983*22ce4affSfengbojiang} ZSTD_dictLoadMethod_e;
984*22ce4affSfengbojiang</b></pre><BR>
985*22ce4affSfengbojiang<pre><b>typedef enum {
986*22ce4affSfengbojiang    ZSTD_f_zstd1 = 0,           </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
987*22ce4affSfengbojiang    ZSTD_f_zstd1_magicless = 1  </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
988*22ce4affSfengbojiang                                 * Useful to save 4 bytes per generated frame.
989*22ce4affSfengbojiang                                 * Decoder cannot recognise automatically this format, requiring this instruction. */
990*22ce4affSfengbojiang} ZSTD_format_e;
991*22ce4affSfengbojiang</b></pre><BR>
992*22ce4affSfengbojiang<pre><b>typedef enum {
993*22ce4affSfengbojiang    </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
994*22ce4affSfengbojiang    ZSTD_d_validateChecksum = 0,
995*22ce4affSfengbojiang    ZSTD_d_ignoreChecksum = 1
996*22ce4affSfengbojiang} ZSTD_forceIgnoreChecksum_e;
997*22ce4affSfengbojiang</b></pre><BR>
998*22ce4affSfengbojiang<pre><b>typedef enum {
999*22ce4affSfengbojiang    </b>/* Note: this enum and the behavior it controls are effectively internal<b>
1000*22ce4affSfengbojiang     * implementation details of the compressor. They are expected to continue
1001*22ce4affSfengbojiang     * to evolve and should be considered only in the context of extremely
1002*22ce4affSfengbojiang     * advanced performance tuning.
1003*22ce4affSfengbojiang     *
1004*22ce4affSfengbojiang     * Zstd currently supports the use of a CDict in three ways:
1005*22ce4affSfengbojiang     *
1006*22ce4affSfengbojiang     * - The contents of the CDict can be copied into the working context. This
1007*22ce4affSfengbojiang     *   means that the compression can search both the dictionary and input
1008*22ce4affSfengbojiang     *   while operating on a single set of internal tables. This makes
1009*22ce4affSfengbojiang     *   the compression faster per-byte of input. However, the initial copy of
1010*22ce4affSfengbojiang     *   the CDict's tables incurs a fixed cost at the beginning of the
1011*22ce4affSfengbojiang     *   compression. For small compressions (< 8 KB), that copy can dominate
1012*22ce4affSfengbojiang     *   the cost of the compression.
1013*22ce4affSfengbojiang     *
1014*22ce4affSfengbojiang     * - The CDict's tables can be used in-place. In this model, compression is
1015*22ce4affSfengbojiang     *   slower per input byte, because the compressor has to search two sets of
1016*22ce4affSfengbojiang     *   tables. However, this model incurs no start-up cost (as long as the
1017*22ce4affSfengbojiang     *   working context's tables can be reused). For small inputs, this can be
1018*22ce4affSfengbojiang     *   faster than copying the CDict's tables.
1019*22ce4affSfengbojiang     *
1020*22ce4affSfengbojiang     * - The CDict's tables are not used at all, and instead we use the working
1021*22ce4affSfengbojiang     *   context alone to reload the dictionary and use params based on the source
1022*22ce4affSfengbojiang     *   size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
1023*22ce4affSfengbojiang     *   This method is effective when the dictionary sizes are very small relative
1024*22ce4affSfengbojiang     *   to the input size, and the input size is fairly large to begin with.
1025*22ce4affSfengbojiang     *
1026*22ce4affSfengbojiang     * Zstd has a simple internal heuristic that selects which strategy to use
1027*22ce4affSfengbojiang     * at the beginning of a compression. However, if experimentation shows that
1028*22ce4affSfengbojiang     * Zstd is making poor choices, it is possible to override that choice with
1029*22ce4affSfengbojiang     * this enum.
1030*22ce4affSfengbojiang     */
1031*22ce4affSfengbojiang    ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
1032*22ce4affSfengbojiang    ZSTD_dictForceAttach   = 1, </b>/* Never copy the dictionary. */<b>
1033*22ce4affSfengbojiang    ZSTD_dictForceCopy     = 2, </b>/* Always copy the dictionary. */<b>
1034*22ce4affSfengbojiang    ZSTD_dictForceLoad     = 3  </b>/* Always reload the dictionary */<b>
1035*22ce4affSfengbojiang} ZSTD_dictAttachPref_e;
1036*22ce4affSfengbojiang</b></pre><BR>
1037*22ce4affSfengbojiang<pre><b>typedef enum {
1038*22ce4affSfengbojiang  ZSTD_lcm_auto = 0,          </b>/**< Automatically determine the compression mode based on the compression level.<b>
1039*22ce4affSfengbojiang                               *   Negative compression levels will be uncompressed, and positive compression
1040*22ce4affSfengbojiang                               *   levels will be compressed. */
1041*22ce4affSfengbojiang  ZSTD_lcm_huffman = 1,       </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
1042*22ce4affSfengbojiang                               *   emitted if Huffman compression is not profitable. */
1043*22ce4affSfengbojiang  ZSTD_lcm_uncompressed = 2   </b>/**< Always emit uncompressed literals. */<b>
1044*22ce4affSfengbojiang} ZSTD_literalCompressionMode_e;
1045*22ce4affSfengbojiang</b></pre><BR>
1046*22ce4affSfengbojiang<a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre>
1047*22ce4affSfengbojiang
1048*22ce4affSfengbojiang<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
1049*22ce4affSfengbojiang</b><p>  `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1050*22ce4affSfengbojiang  `srcSize` must be the _exact_ size of this series
1051*22ce4affSfengbojiang       (i.e. there should be a frame boundary at `src + srcSize`)
1052*22ce4affSfengbojiang  @return : - decompressed size of all data in all successive frames
1053*22ce4affSfengbojiang            - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
1054*22ce4affSfengbojiang            - if an error occurred: ZSTD_CONTENTSIZE_ERROR
1055*22ce4affSfengbojiang
1056*22ce4affSfengbojiang   note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
1057*22ce4affSfengbojiang            When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
1058*22ce4affSfengbojiang            In which case, it's necessary to use streaming mode to decompress data.
1059*22ce4affSfengbojiang   note 2 : decompressed size is always present when compression is done with ZSTD_compress()
1060*22ce4affSfengbojiang   note 3 : decompressed size can be very large (64-bits value),
1061*22ce4affSfengbojiang            potentially larger than what local system can handle as a single memory segment.
1062*22ce4affSfengbojiang            In which case, it's necessary to use streaming mode to decompress data.
1063*22ce4affSfengbojiang   note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
1064*22ce4affSfengbojiang            Always ensure result fits within application's authorized limits.
1065*22ce4affSfengbojiang            Each application can set its own limits.
1066*22ce4affSfengbojiang   note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
1067*22ce4affSfengbojiang            read each contained frame header.  This is fast as most of the data is skipped,
1068*22ce4affSfengbojiang            however it does mean that all frame data must be present and valid.
1069*22ce4affSfengbojiang</p></pre><BR>
1070*22ce4affSfengbojiang
1071*22ce4affSfengbojiang<pre><b>unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
1072*22ce4affSfengbojiang</b><p>  `src` should point to the start of a series of ZSTD encoded and/or skippable frames
1073*22ce4affSfengbojiang  `srcSize` must be the _exact_ size of this series
1074*22ce4affSfengbojiang       (i.e. there should be a frame boundary at `src + srcSize`)
1075*22ce4affSfengbojiang  @return : - upper-bound for the decompressed size of all data in all successive frames
1076*22ce4affSfengbojiang            - if an error occured: ZSTD_CONTENTSIZE_ERROR
1077*22ce4affSfengbojiang
1078*22ce4affSfengbojiang  note 1  : an error can occur if `src` contains an invalid or incorrectly formatted frame.
1079*22ce4affSfengbojiang  note 2  : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
1080*22ce4affSfengbojiang            in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
1081*22ce4affSfengbojiang  note 3  : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
1082*22ce4affSfengbojiang              upper-bound = # blocks * min(128 KB, Window_Size)
1083*22ce4affSfengbojiang
1084*22ce4affSfengbojiang</p></pre><BR>
1085*22ce4affSfengbojiang
1086*22ce4affSfengbojiang<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
1087*22ce4affSfengbojiang</b><p>  srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
1088*22ce4affSfengbojiang @return : size of the Frame Header,
1089*22ce4affSfengbojiang           or an error code (if srcSize is too small)
1090*22ce4affSfengbojiang</p></pre><BR>
1091*22ce4affSfengbojiang
1092*22ce4affSfengbojiang<pre><b>typedef enum {
1093*22ce4affSfengbojiang  ZSTD_sf_noBlockDelimiters = 0,         </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
1094*22ce4affSfengbojiang  ZSTD_sf_explicitBlockDelimiters = 1    </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
1095*22ce4affSfengbojiang} ZSTD_sequenceFormat_e;
1096*22ce4affSfengbojiang</b></pre><BR>
1097*22ce4affSfengbojiang<pre><b></b><p> Generate sequences using ZSTD_compress2, given a source buffer.
1098*22ce4affSfengbojiang
1099*22ce4affSfengbojiang Each block will end with a dummy sequence
1100*22ce4affSfengbojiang with offset == 0, matchLength == 0, and litLength == length of last literals.
1101*22ce4affSfengbojiang litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
1102*22ce4affSfengbojiang simply acts as a block delimiter.
1103*22ce4affSfengbojiang
1104*22ce4affSfengbojiang zc can be used to insert custom compression params.
1105*22ce4affSfengbojiang This function invokes ZSTD_compress2
1106*22ce4affSfengbojiang
1107*22ce4affSfengbojiang The output of this function can be fed into ZSTD_compressSequences() with CCtx
1108*22ce4affSfengbojiang setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
1109*22ce4affSfengbojiang @return : number of sequences generated
1110*22ce4affSfengbojiang
1111*22ce4affSfengbojiang</p></pre><BR>
1112*22ce4affSfengbojiang
1113*22ce4affSfengbojiang<pre><b>size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
1114*22ce4affSfengbojiang</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
1115*22ce4affSfengbojiang by merging them into into the literals of the next sequence.
1116*22ce4affSfengbojiang
1117*22ce4affSfengbojiang As such, the final generated result has no explicit representation of block boundaries,
1118*22ce4affSfengbojiang and the final last literals segment is not represented in the sequences.
1119*22ce4affSfengbojiang
1120*22ce4affSfengbojiang The output of this function can be fed into ZSTD_compressSequences() with CCtx
1121*22ce4affSfengbojiang setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
1122*22ce4affSfengbojiang @return : number of sequences left after merging
1123*22ce4affSfengbojiang
1124*22ce4affSfengbojiang</p></pre><BR>
1125*22ce4affSfengbojiang
1126*22ce4affSfengbojiang<pre><b>size_t ZSTD_compressSequences(ZSTD_CCtx* const cctx, void* dst, size_t dstSize,
1127*22ce4affSfengbojiang                      const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
1128*22ce4affSfengbojiang                      const void* src, size_t srcSize);
1129*22ce4affSfengbojiang</b><p> Compress an array of ZSTD_Sequence, generated from the original source buffer, into dst.
1130*22ce4affSfengbojiang If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
1131*22ce4affSfengbojiang The entire source is compressed into a single frame.
1132*22ce4affSfengbojiang
1133*22ce4affSfengbojiang The compression behavior changes based on cctx params. In particular:
1134*22ce4affSfengbojiang    If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1135*22ce4affSfengbojiang    no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
1136*22ce4affSfengbojiang    the block size derived from the cctx, and sequences may be split. This is the default setting.
1137*22ce4affSfengbojiang
1138*22ce4affSfengbojiang    If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
1139*22ce4affSfengbojiang    block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
1140*22ce4affSfengbojiang
1141*22ce4affSfengbojiang    If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
1142*22ce4affSfengbojiang    behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
1143*22ce4affSfengbojiang    specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
1144*22ce4affSfengbojiang
1145*22ce4affSfengbojiang    In addition to the two adjustable experimental params, there are other important cctx params.
1146*22ce4affSfengbojiang    - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN.
1147*22ce4affSfengbojiang    - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
1148*22ce4affSfengbojiang    - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
1149*22ce4affSfengbojiang      is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
1150*22ce4affSfengbojiang
1151*22ce4affSfengbojiang Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
1152*22ce4affSfengbojiang Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
1153*22ce4affSfengbojiang         and cannot emit an RLE block that disagrees with the repcode history
1154*22ce4affSfengbojiang @return : final compressed size or a ZSTD error.
1155*22ce4affSfengbojiang
1156*22ce4affSfengbojiang</p></pre><BR>
1157*22ce4affSfengbojiang
1158*22ce4affSfengbojiang<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
1159*22ce4affSfengbojiang
1160*22ce4affSfengbojiang<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
1161*22ce4affSfengbojiangsize_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
1162*22ce4affSfengbojiangsize_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1163*22ce4affSfengbojiangsize_t ZSTD_estimateDCtxSize(void);
1164*22ce4affSfengbojiang</b><p>  These functions make it possible to estimate memory usage
1165*22ce4affSfengbojiang  of a future {D,C}Ctx, before its creation.
1166*22ce4affSfengbojiang
1167*22ce4affSfengbojiang  ZSTD_estimateCCtxSize() will provide a memory budget large enough
1168*22ce4affSfengbojiang  for any compression level up to selected one.
1169*22ce4affSfengbojiang  Note : Unlike ZSTD_estimateCStreamSize*(), this estimate
1170*22ce4affSfengbojiang         does not include space for a window buffer.
1171*22ce4affSfengbojiang         Therefore, the estimation is only guaranteed for single-shot compressions, not streaming.
1172*22ce4affSfengbojiang  The estimate will assume the input may be arbitrarily large,
1173*22ce4affSfengbojiang  which is the worst case.
1174*22ce4affSfengbojiang
1175*22ce4affSfengbojiang  When srcSize can be bound by a known and rather "small" value,
1176*22ce4affSfengbojiang  this fact can be used to provide a tighter estimation
1177*22ce4affSfengbojiang  because the CCtx compression context will need less memory.
1178*22ce4affSfengbojiang  This tighter estimation can be provided by more advanced functions
1179*22ce4affSfengbojiang  ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
1180*22ce4affSfengbojiang  and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
1181*22ce4affSfengbojiang  Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
1182*22ce4affSfengbojiang
1183*22ce4affSfengbojiang  Note 2 : only single-threaded compression is supported.
1184*22ce4affSfengbojiang  ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
1185*22ce4affSfengbojiang
1186*22ce4affSfengbojiang</p></pre><BR>
1187*22ce4affSfengbojiang
1188*22ce4affSfengbojiang<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
1189*22ce4affSfengbojiangsize_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
1190*22ce4affSfengbojiangsize_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
1191*22ce4affSfengbojiangsize_t ZSTD_estimateDStreamSize(size_t windowSize);
1192*22ce4affSfengbojiangsize_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
1193*22ce4affSfengbojiang</b><p>  ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
1194*22ce4affSfengbojiang  It will also consider src size to be arbitrarily "large", which is worst case.
1195*22ce4affSfengbojiang  If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
1196*22ce4affSfengbojiang  ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
1197*22ce4affSfengbojiang  ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
1198*22ce4affSfengbojiang  Note : CStream size estimation is only correct for single-threaded compression.
1199*22ce4affSfengbojiang  ZSTD_DStream memory budget depends on window Size.
1200*22ce4affSfengbojiang  This information can be passed manually, using ZSTD_estimateDStreamSize,
1201*22ce4affSfengbojiang  or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
1202*22ce4affSfengbojiang  Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
1203*22ce4affSfengbojiang         an internal ?Dict will be created, which additional size is not estimated here.
1204*22ce4affSfengbojiang         In this case, get total size by adding ZSTD_estimate?DictSize
1205*22ce4affSfengbojiang</p></pre><BR>
1206*22ce4affSfengbojiang
1207*22ce4affSfengbojiang<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
1208*22ce4affSfengbojiangsize_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
1209*22ce4affSfengbojiangsize_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
1210*22ce4affSfengbojiang</b><p>  ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
1211*22ce4affSfengbojiang  ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
1212*22ce4affSfengbojiang  Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
1213*22ce4affSfengbojiang
1214*22ce4affSfengbojiang</p></pre><BR>
1215*22ce4affSfengbojiang
1216*22ce4affSfengbojiang<pre><b>ZSTD_CCtx*    ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
1217*22ce4affSfengbojiangZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize);    </b>/**< same as ZSTD_initStaticCCtx() */<b>
1218*22ce4affSfengbojiang</b><p>  Initialize an object using a pre-allocated fixed-size buffer.
1219*22ce4affSfengbojiang  workspace: The memory area to emplace the object into.
1220*22ce4affSfengbojiang             Provided pointer *must be 8-bytes aligned*.
1221*22ce4affSfengbojiang             Buffer must outlive object.
1222*22ce4affSfengbojiang  workspaceSize: Use ZSTD_estimate*Size() to determine
1223*22ce4affSfengbojiang                 how large workspace must be to support target scenario.
1224*22ce4affSfengbojiang @return : pointer to object (same address as workspace, just different type),
1225*22ce4affSfengbojiang           or NULL if error (size too small, incorrect alignment, etc.)
1226*22ce4affSfengbojiang  Note : zstd will never resize nor malloc() when using a static buffer.
1227*22ce4affSfengbojiang         If the object requires more memory than available,
1228*22ce4affSfengbojiang         zstd will just error out (typically ZSTD_error_memory_allocation).
1229*22ce4affSfengbojiang  Note 2 : there is no corresponding "free" function.
1230*22ce4affSfengbojiang           Since workspace is allocated externally, it must be freed externally too.
1231*22ce4affSfengbojiang  Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
1232*22ce4affSfengbojiang           into its associated cParams.
1233*22ce4affSfengbojiang  Limitation 1 : currently not compatible with internal dictionary creation, triggered by
1234*22ce4affSfengbojiang                 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
1235*22ce4affSfengbojiang  Limitation 2 : static cctx currently not compatible with multi-threading.
1236*22ce4affSfengbojiang  Limitation 3 : static dctx is incompatible with legacy support.
1237*22ce4affSfengbojiang
1238*22ce4affSfengbojiang</p></pre><BR>
1239*22ce4affSfengbojiang
1240*22ce4affSfengbojiang<pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize);    </b>/**< same as ZSTD_initStaticDCtx() */<b>
1241*22ce4affSfengbojiang</b></pre><BR>
1242*22ce4affSfengbojiang<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
1243*22ce4affSfengbojiangtypedef void  (*ZSTD_freeFunction) (void* opaque, void* address);
1244*22ce4affSfengbojiangtypedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
1245*22ce4affSfengbojiangstatic
1246*22ce4affSfengbojiang#ifdef __GNUC__
1247*22ce4affSfengbojiang__attribute__((__unused__))
1248*22ce4affSfengbojiang#endif
1249*22ce4affSfengbojiangZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL };  </b>/**< this constant defers to stdlib's functions */<b>
1250*22ce4affSfengbojiang</b><p>  These prototypes make it possible to pass your own allocation/free functions.
1251*22ce4affSfengbojiang  ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
1252*22ce4affSfengbojiang  All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
1253*22ce4affSfengbojiang
1254*22ce4affSfengbojiang</p></pre><BR>
1255*22ce4affSfengbojiang
1256*22ce4affSfengbojiang<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
1257*22ce4affSfengbojiang
1258*22ce4affSfengbojiang<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
1259*22ce4affSfengbojiang</b><p>  Create a digested dictionary for compression
1260*22ce4affSfengbojiang  Dictionary content is just referenced, not duplicated.
1261*22ce4affSfengbojiang  As a consequence, `dictBuffer` **must** outlive CDict,
1262*22ce4affSfengbojiang  and its content must remain unmodified throughout the lifetime of CDict.
1263*22ce4affSfengbojiang  note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
1264*22ce4affSfengbojiang</p></pre><BR>
1265*22ce4affSfengbojiang
1266*22ce4affSfengbojiang<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
1267*22ce4affSfengbojiang</b><p>  Provides the dictID of the dictionary loaded into `cdict`.
1268*22ce4affSfengbojiang  If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
1269*22ce4affSfengbojiang  Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
1270*22ce4affSfengbojiang</p></pre><BR>
1271*22ce4affSfengbojiang
1272*22ce4affSfengbojiang<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1273*22ce4affSfengbojiang</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
1274*22ce4affSfengbojiang `estimatedSrcSize` value is optional, select 0 if not known
1275*22ce4affSfengbojiang</p></pre><BR>
1276*22ce4affSfengbojiang
1277*22ce4affSfengbojiang<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
1278*22ce4affSfengbojiang</b><p>  same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
1279*22ce4affSfengbojiang  All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
1280*22ce4affSfengbojiang</p></pre><BR>
1281*22ce4affSfengbojiang
1282*22ce4affSfengbojiang<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
1283*22ce4affSfengbojiang</b><p>  Ensure param values remain within authorized range.
1284*22ce4affSfengbojiang @return 0 on success, or an error code (can be checked with ZSTD_isError())
1285*22ce4affSfengbojiang</p></pre><BR>
1286*22ce4affSfengbojiang
1287*22ce4affSfengbojiang<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
1288*22ce4affSfengbojiang</b><p>  optimize params for a given `srcSize` and `dictSize`.
1289*22ce4affSfengbojiang `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
1290*22ce4affSfengbojiang `dictSize` must be `0` when there is no dictionary.
1291*22ce4affSfengbojiang  cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
1292*22ce4affSfengbojiang  This function never fails (wide contract)
1293*22ce4affSfengbojiang</p></pre><BR>
1294*22ce4affSfengbojiang
1295*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
1296*22ce4affSfengbojiang                              void* dst, size_t dstCapacity,
1297*22ce4affSfengbojiang                        const void* src, size_t srcSize,
1298*22ce4affSfengbojiang                        const void* dict,size_t dictSize,
1299*22ce4affSfengbojiang                              ZSTD_parameters params);
1300*22ce4affSfengbojiang</b><p>  Note : this function is now DEPRECATED.
1301*22ce4affSfengbojiang         It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
1302*22ce4affSfengbojiang  This prototype will be marked as deprecated and generate compilation warning on reaching v1.5.x
1303*22ce4affSfengbojiang</p></pre><BR>
1304*22ce4affSfengbojiang
1305*22ce4affSfengbojiang<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
1306*22ce4affSfengbojiang                                  void* dst, size_t dstCapacity,
1307*22ce4affSfengbojiang                            const void* src, size_t srcSize,
1308*22ce4affSfengbojiang                            const ZSTD_CDict* cdict,
1309*22ce4affSfengbojiang                                  ZSTD_frameParameters fParams);
1310*22ce4affSfengbojiang</b><p>  Note : this function is now REDUNDANT.
1311*22ce4affSfengbojiang         It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
1312*22ce4affSfengbojiang  This prototype will be marked as deprecated and generate compilation warning in some future version
1313*22ce4affSfengbojiang</p></pre><BR>
1314*22ce4affSfengbojiang
1315*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
1316*22ce4affSfengbojiang</b><p>  Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
1317*22ce4affSfengbojiang  It saves some memory, but also requires that `dict` outlives its usage within `cctx`
1318*22ce4affSfengbojiang</p></pre><BR>
1319*22ce4affSfengbojiang
1320*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1321*22ce4affSfengbojiang</b><p>  Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
1322*22ce4affSfengbojiang  how to load the dictionary (by copy ? by reference ?)
1323*22ce4affSfengbojiang  and how to interpret it (automatic ? force raw mode ? full mode only ?)
1324*22ce4affSfengbojiang</p></pre><BR>
1325*22ce4affSfengbojiang
1326*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1327*22ce4affSfengbojiang</b><p>  Same as ZSTD_CCtx_refPrefix(), but gives finer control over
1328*22ce4affSfengbojiang  how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1329*22ce4affSfengbojiang</p></pre><BR>
1330*22ce4affSfengbojiang
1331*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_getParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
1332*22ce4affSfengbojiang</b><p>  Get the requested compression parameter value, selected by enum ZSTD_cParameter,
1333*22ce4affSfengbojiang  and store it into int* value.
1334*22ce4affSfengbojiang @return : 0, or an error code (which can be tested with ZSTD_isError()).
1335*22ce4affSfengbojiang
1336*22ce4affSfengbojiang</p></pre><BR>
1337*22ce4affSfengbojiang
1338*22ce4affSfengbojiang<pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
1339*22ce4affSfengbojiangsize_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params);
1340*22ce4affSfengbojiang</b><p>  Quick howto :
1341*22ce4affSfengbojiang  - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
1342*22ce4affSfengbojiang  - ZSTD_CCtxParams_setParameter() : Push parameters one by one into
1343*22ce4affSfengbojiang                                     an existing ZSTD_CCtx_params structure.
1344*22ce4affSfengbojiang                                     This is similar to
1345*22ce4affSfengbojiang                                     ZSTD_CCtx_setParameter().
1346*22ce4affSfengbojiang  - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
1347*22ce4affSfengbojiang                                    an existing CCtx.
1348*22ce4affSfengbojiang                                    These parameters will be applied to
1349*22ce4affSfengbojiang                                    all subsequent frames.
1350*22ce4affSfengbojiang  - ZSTD_compressStream2() : Do compression using the CCtx.
1351*22ce4affSfengbojiang  - ZSTD_freeCCtxParams() : Free the memory.
1352*22ce4affSfengbojiang
1353*22ce4affSfengbojiang  This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
1354*22ce4affSfengbojiang  for static allocation of CCtx for single-threaded compression.
1355*22ce4affSfengbojiang
1356*22ce4affSfengbojiang</p></pre><BR>
1357*22ce4affSfengbojiang
1358*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
1359*22ce4affSfengbojiang</b><p>  Reset params to default values.
1360*22ce4affSfengbojiang
1361*22ce4affSfengbojiang</p></pre><BR>
1362*22ce4affSfengbojiang
1363*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
1364*22ce4affSfengbojiang</b><p>  Initializes the compression parameters of cctxParams according to
1365*22ce4affSfengbojiang  compression level. All other parameters are reset to their default values.
1366*22ce4affSfengbojiang
1367*22ce4affSfengbojiang</p></pre><BR>
1368*22ce4affSfengbojiang
1369*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
1370*22ce4affSfengbojiang</b><p>  Initializes the compression and frame parameters of cctxParams according to
1371*22ce4affSfengbojiang  params. All other parameters are reset to their default values.
1372*22ce4affSfengbojiang
1373*22ce4affSfengbojiang</p></pre><BR>
1374*22ce4affSfengbojiang
1375*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
1376*22ce4affSfengbojiang</b><p>  Similar to ZSTD_CCtx_setParameter.
1377*22ce4affSfengbojiang  Set one compression parameter, selected by enum ZSTD_cParameter.
1378*22ce4affSfengbojiang  Parameters must be applied to a ZSTD_CCtx using
1379*22ce4affSfengbojiang  ZSTD_CCtx_setParametersUsingCCtxParams().
1380*22ce4affSfengbojiang @result : a code representing success or failure (which can be tested with
1381*22ce4affSfengbojiang           ZSTD_isError()).
1382*22ce4affSfengbojiang
1383*22ce4affSfengbojiang</p></pre><BR>
1384*22ce4affSfengbojiang
1385*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtxParams_getParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
1386*22ce4affSfengbojiang</b><p> Similar to ZSTD_CCtx_getParameter.
1387*22ce4affSfengbojiang Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
1388*22ce4affSfengbojiang @result : 0, or an error code (which can be tested with ZSTD_isError()).
1389*22ce4affSfengbojiang
1390*22ce4affSfengbojiang</p></pre><BR>
1391*22ce4affSfengbojiang
1392*22ce4affSfengbojiang<pre><b>size_t ZSTD_CCtx_setParametersUsingCCtxParams(
1393*22ce4affSfengbojiang        ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
1394*22ce4affSfengbojiang</b><p>  Apply a set of ZSTD_CCtx_params to the compression context.
1395*22ce4affSfengbojiang  This can be done even after compression is started,
1396*22ce4affSfengbojiang    if nbWorkers==0, this will have no impact until a new compression is started.
1397*22ce4affSfengbojiang    if nbWorkers>=1, new parameters will be picked up at next job,
1398*22ce4affSfengbojiang       with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
1399*22ce4affSfengbojiang
1400*22ce4affSfengbojiang</p></pre><BR>
1401*22ce4affSfengbojiang
1402*22ce4affSfengbojiang<pre><b>size_t ZSTD_compressStream2_simpleArgs (
1403*22ce4affSfengbojiang                ZSTD_CCtx* cctx,
1404*22ce4affSfengbojiang                void* dst, size_t dstCapacity, size_t* dstPos,
1405*22ce4affSfengbojiang          const void* src, size_t srcSize, size_t* srcPos,
1406*22ce4affSfengbojiang                ZSTD_EndDirective endOp);
1407*22ce4affSfengbojiang</b><p>  Same as ZSTD_compressStream2(),
1408*22ce4affSfengbojiang  but using only integral types as arguments.
1409*22ce4affSfengbojiang  This variant might be helpful for binders from dynamic languages
1410*22ce4affSfengbojiang  which have troubles handling structures containing memory pointers.
1411*22ce4affSfengbojiang
1412*22ce4affSfengbojiang</p></pre><BR>
1413*22ce4affSfengbojiang
1414*22ce4affSfengbojiang<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
1415*22ce4affSfengbojiang
1416*22ce4affSfengbojiang<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
1417*22ce4affSfengbojiang</b><p>  Tells if the content of `buffer` starts with a valid Frame Identifier.
1418*22ce4affSfengbojiang  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
1419*22ce4affSfengbojiang  Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
1420*22ce4affSfengbojiang  Note 3 : Skippable Frame Identifiers are considered valid.
1421*22ce4affSfengbojiang</p></pre><BR>
1422*22ce4affSfengbojiang
1423*22ce4affSfengbojiang<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
1424*22ce4affSfengbojiang</b><p>  Create a digested dictionary, ready to start decompression operation without startup delay.
1425*22ce4affSfengbojiang  Dictionary content is referenced, and therefore stays in dictBuffer.
1426*22ce4affSfengbojiang  It is important that dictBuffer outlives DDict,
1427*22ce4affSfengbojiang  it must remain read accessible throughout the lifetime of DDict
1428*22ce4affSfengbojiang</p></pre><BR>
1429*22ce4affSfengbojiang
1430*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
1431*22ce4affSfengbojiang</b><p>  Same as ZSTD_DCtx_loadDictionary(),
1432*22ce4affSfengbojiang  but references `dict` content instead of copying it into `dctx`.
1433*22ce4affSfengbojiang  This saves memory if `dict` remains around.,
1434*22ce4affSfengbojiang  However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
1435*22ce4affSfengbojiang</p></pre><BR>
1436*22ce4affSfengbojiang
1437*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
1438*22ce4affSfengbojiang</b><p>  Same as ZSTD_DCtx_loadDictionary(),
1439*22ce4affSfengbojiang  but gives direct control over
1440*22ce4affSfengbojiang  how to load the dictionary (by copy ? by reference ?)
1441*22ce4affSfengbojiang  and how to interpret it (automatic ? force raw mode ? full mode only ?).
1442*22ce4affSfengbojiang</p></pre><BR>
1443*22ce4affSfengbojiang
1444*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
1445*22ce4affSfengbojiang</b><p>  Same as ZSTD_DCtx_refPrefix(), but gives finer control over
1446*22ce4affSfengbojiang  how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
1447*22ce4affSfengbojiang</p></pre><BR>
1448*22ce4affSfengbojiang
1449*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
1450*22ce4affSfengbojiang</b><p>  Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
1451*22ce4affSfengbojiang  This protects a decoder context from reserving too much memory for itself (potential attack scenario).
1452*22ce4affSfengbojiang  This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
1453*22ce4affSfengbojiang  By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
1454*22ce4affSfengbojiang @return : 0, or an error code (which can be tested using ZSTD_isError()).
1455*22ce4affSfengbojiang
1456*22ce4affSfengbojiang</p></pre><BR>
1457*22ce4affSfengbojiang
1458*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
1459*22ce4affSfengbojiang</b><p>  Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
1460*22ce4affSfengbojiang  and store it into int* value.
1461*22ce4affSfengbojiang @return : 0, or an error code (which can be tested with ZSTD_isError()).
1462*22ce4affSfengbojiang
1463*22ce4affSfengbojiang</p></pre><BR>
1464*22ce4affSfengbojiang
1465*22ce4affSfengbojiang<pre><b>size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
1466*22ce4affSfengbojiang</b><p>  Instruct the decoder context about what kind of data to decode next.
1467*22ce4affSfengbojiang  This instruction is mandatory to decode data without a fully-formed header,
1468*22ce4affSfengbojiang  such ZSTD_f_zstd1_magicless for example.
1469*22ce4affSfengbojiang @return : 0, or an error code (which can be tested using ZSTD_isError()).
1470*22ce4affSfengbojiang</p></pre><BR>
1471*22ce4affSfengbojiang
1472*22ce4affSfengbojiang<pre><b>size_t ZSTD_decompressStream_simpleArgs (
1473*22ce4affSfengbojiang                ZSTD_DCtx* dctx,
1474*22ce4affSfengbojiang                void* dst, size_t dstCapacity, size_t* dstPos,
1475*22ce4affSfengbojiang          const void* src, size_t srcSize, size_t* srcPos);
1476*22ce4affSfengbojiang</b><p>  Same as ZSTD_decompressStream(),
1477*22ce4affSfengbojiang  but using only integral types as arguments.
1478*22ce4affSfengbojiang  This can be helpful for binders from dynamic languages
1479*22ce4affSfengbojiang  which have troubles handling structures containing memory pointers.
1480*22ce4affSfengbojiang
1481*22ce4affSfengbojiang</p></pre><BR>
1482*22ce4affSfengbojiang
1483*22ce4affSfengbojiang<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre>  Warning : most of these functions are now redundant with the Advanced API.
1484*22ce4affSfengbojiang  Once Advanced API reaches "stable" status,
1485*22ce4affSfengbojiang  redundant functions will be deprecated, and then at some point removed.
1486*22ce4affSfengbojiang<BR></pre>
1487*22ce4affSfengbojiang
1488*22ce4affSfengbojiang<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
1489*22ce4affSfengbojiang<pre><b>size_t
1490*22ce4affSfengbojiangZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
1491*22ce4affSfengbojiang             int compressionLevel,
1492*22ce4affSfengbojiang             unsigned long long pledgedSrcSize);
1493*22ce4affSfengbojiang</b><p> This function is deprecated, and equivalent to:
1494*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1495*22ce4affSfengbojiang     ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
1496*22ce4affSfengbojiang     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1497*22ce4affSfengbojiang     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1498*22ce4affSfengbojiang
1499*22ce4affSfengbojiang pledgedSrcSize must be correct. If it is not known at init time, use
1500*22ce4affSfengbojiang ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
1501*22ce4affSfengbojiang "0" also disables frame content size field. It may be enabled in the future.
1502*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1503*22ce4affSfengbojiang
1504*22ce4affSfengbojiang</p></pre><BR>
1505*22ce4affSfengbojiang
1506*22ce4affSfengbojiang<pre><b>size_t
1507*22ce4affSfengbojiangZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
1508*22ce4affSfengbojiang         const void* dict, size_t dictSize,
1509*22ce4affSfengbojiang               int compressionLevel);
1510*22ce4affSfengbojiang</b><p> This function is deprecated, and is equivalent to:
1511*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1512*22ce4affSfengbojiang     ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
1513*22ce4affSfengbojiang     ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1514*22ce4affSfengbojiang
1515*22ce4affSfengbojiang Creates of an internal CDict (incompatible with static CCtx), except if
1516*22ce4affSfengbojiang dict == NULL or dictSize < 8, in which case no dict is used.
1517*22ce4affSfengbojiang Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
1518*22ce4affSfengbojiang it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
1519*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1520*22ce4affSfengbojiang
1521*22ce4affSfengbojiang</p></pre><BR>
1522*22ce4affSfengbojiang
1523*22ce4affSfengbojiang<pre><b>size_t
1524*22ce4affSfengbojiangZSTD_initCStream_advanced(ZSTD_CStream* zcs,
1525*22ce4affSfengbojiang        const void* dict, size_t dictSize,
1526*22ce4affSfengbojiang              ZSTD_parameters params,
1527*22ce4affSfengbojiang              unsigned long long pledgedSrcSize);
1528*22ce4affSfengbojiang</b><p> This function is deprecated, and is approximately equivalent to:
1529*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1530*22ce4affSfengbojiang     // Pseudocode: Set each zstd parameter and leave the rest as-is.
1531*22ce4affSfengbojiang     for ((param, value) : params) {
1532*22ce4affSfengbojiang         ZSTD_CCtx_setParameter(zcs, param, value);
1533*22ce4affSfengbojiang     }
1534*22ce4affSfengbojiang     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1535*22ce4affSfengbojiang     ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
1536*22ce4affSfengbojiang
1537*22ce4affSfengbojiang dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
1538*22ce4affSfengbojiang pledgedSrcSize must be correct.
1539*22ce4affSfengbojiang If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
1540*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1541*22ce4affSfengbojiang
1542*22ce4affSfengbojiang</p></pre><BR>
1543*22ce4affSfengbojiang
1544*22ce4affSfengbojiang<pre><b>size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
1545*22ce4affSfengbojiang</b><p> This function is deprecated, and equivalent to:
1546*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1547*22ce4affSfengbojiang     ZSTD_CCtx_refCDict(zcs, cdict);
1548*22ce4affSfengbojiang
1549*22ce4affSfengbojiang note : cdict will just be referenced, and must outlive compression session
1550*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1551*22ce4affSfengbojiang
1552*22ce4affSfengbojiang</p></pre><BR>
1553*22ce4affSfengbojiang
1554*22ce4affSfengbojiang<pre><b>size_t
1555*22ce4affSfengbojiangZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
1556*22ce4affSfengbojiang                   const ZSTD_CDict* cdict,
1557*22ce4affSfengbojiang                         ZSTD_frameParameters fParams,
1558*22ce4affSfengbojiang                         unsigned long long pledgedSrcSize);
1559*22ce4affSfengbojiang</b><p>   This function is DEPRECATED, and is approximately equivalent to:
1560*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1561*22ce4affSfengbojiang     // Pseudocode: Set each zstd frame parameter and leave the rest as-is.
1562*22ce4affSfengbojiang     for ((fParam, value) : fParams) {
1563*22ce4affSfengbojiang         ZSTD_CCtx_setParameter(zcs, fParam, value);
1564*22ce4affSfengbojiang     }
1565*22ce4affSfengbojiang     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1566*22ce4affSfengbojiang     ZSTD_CCtx_refCDict(zcs, cdict);
1567*22ce4affSfengbojiang
1568*22ce4affSfengbojiang same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
1569*22ce4affSfengbojiang pledgedSrcSize must be correct. If srcSize is not known at init time, use
1570*22ce4affSfengbojiang value ZSTD_CONTENTSIZE_UNKNOWN.
1571*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1572*22ce4affSfengbojiang
1573*22ce4affSfengbojiang</p></pre><BR>
1574*22ce4affSfengbojiang
1575*22ce4affSfengbojiang<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
1576*22ce4affSfengbojiang</b><p> This function is deprecated, and is equivalent to:
1577*22ce4affSfengbojiang     ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
1578*22ce4affSfengbojiang     ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
1579*22ce4affSfengbojiang
1580*22ce4affSfengbojiang  start a new frame, using same parameters from previous frame.
1581*22ce4affSfengbojiang  This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
1582*22ce4affSfengbojiang  Note that zcs must be init at least once before using ZSTD_resetCStream().
1583*22ce4affSfengbojiang  If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
1584*22ce4affSfengbojiang  If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
1585*22ce4affSfengbojiang  For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
1586*22ce4affSfengbojiang  but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
1587*22ce4affSfengbojiang @return : 0, or an error code (which can be tested using ZSTD_isError())
1588*22ce4affSfengbojiang  Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1589*22ce4affSfengbojiang
1590*22ce4affSfengbojiang</p></pre><BR>
1591*22ce4affSfengbojiang
1592*22ce4affSfengbojiang<pre><b>typedef struct {
1593*22ce4affSfengbojiang    unsigned long long ingested;   </b>/* nb input bytes read and buffered */<b>
1594*22ce4affSfengbojiang    unsigned long long consumed;   </b>/* nb input bytes actually compressed */<b>
1595*22ce4affSfengbojiang    unsigned long long produced;   </b>/* nb of compressed bytes generated and buffered */<b>
1596*22ce4affSfengbojiang    unsigned long long flushed;    </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
1597*22ce4affSfengbojiang    unsigned currentJobID;         </b>/* MT only : latest started job nb */<b>
1598*22ce4affSfengbojiang    unsigned nbActiveWorkers;      </b>/* MT only : nb of workers actively compressing at probe time */<b>
1599*22ce4affSfengbojiang} ZSTD_frameProgression;
1600*22ce4affSfengbojiang</b></pre><BR>
1601*22ce4affSfengbojiang<pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
1602*22ce4affSfengbojiang</b><p>  Tell how many bytes are ready to be flushed immediately.
1603*22ce4affSfengbojiang  Useful for multithreading scenarios (nbWorkers >= 1).
1604*22ce4affSfengbojiang  Probe the oldest active job, defined as oldest job not yet entirely flushed,
1605*22ce4affSfengbojiang  and check its output buffer.
1606*22ce4affSfengbojiang @return : amount of data stored in oldest job and ready to be flushed immediately.
1607*22ce4affSfengbojiang  if @return == 0, it means either :
1608*22ce4affSfengbojiang  + there is no active job (could be checked with ZSTD_frameProgression()), or
1609*22ce4affSfengbojiang  + oldest job is still actively compressing data,
1610*22ce4affSfengbojiang    but everything it has produced has also been flushed so far,
1611*22ce4affSfengbojiang    therefore flush speed is limited by production speed of oldest job
1612*22ce4affSfengbojiang    irrespective of the speed of concurrent (and newer) jobs.
1613*22ce4affSfengbojiang
1614*22ce4affSfengbojiang</p></pre><BR>
1615*22ce4affSfengbojiang
1616*22ce4affSfengbojiang<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
1617*22ce4affSfengbojiang<pre><b>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
1618*22ce4affSfengbojiang</b><p>
1619*22ce4affSfengbojiang     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1620*22ce4affSfengbojiang     ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
1621*22ce4affSfengbojiang
1622*22ce4affSfengbojiang note: no dictionary will be used if dict == NULL or dictSize < 8
1623*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1624*22ce4affSfengbojiang
1625*22ce4affSfengbojiang</p></pre><BR>
1626*22ce4affSfengbojiang
1627*22ce4affSfengbojiang<pre><b>size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
1628*22ce4affSfengbojiang</b><p>
1629*22ce4affSfengbojiang     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1630*22ce4affSfengbojiang     ZSTD_DCtx_refDDict(zds, ddict);
1631*22ce4affSfengbojiang
1632*22ce4affSfengbojiang note : ddict is referenced, it must outlive decompression session
1633*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1634*22ce4affSfengbojiang
1635*22ce4affSfengbojiang</p></pre><BR>
1636*22ce4affSfengbojiang
1637*22ce4affSfengbojiang<pre><b>size_t ZSTD_resetDStream(ZSTD_DStream* zds);
1638*22ce4affSfengbojiang</b><p>
1639*22ce4affSfengbojiang     ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
1640*22ce4affSfengbojiang
1641*22ce4affSfengbojiang re-use decompression parameters from previous init; saves dictionary loading
1642*22ce4affSfengbojiang Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
1643*22ce4affSfengbojiang
1644*22ce4affSfengbojiang</p></pre><BR>
1645*22ce4affSfengbojiang
1646*22ce4affSfengbojiang<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
1647*22ce4affSfengbojiang  This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
1648*22ce4affSfengbojiang  But it's also a complex one, with several restrictions, documented below.
1649*22ce4affSfengbojiang  Prefer normal streaming API for an easier experience.
1650*22ce4affSfengbojiang
1651*22ce4affSfengbojiang<BR></pre>
1652*22ce4affSfengbojiang
1653*22ce4affSfengbojiang<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
1654*22ce4affSfengbojiang  A ZSTD_CCtx object is required to track streaming operations.
1655*22ce4affSfengbojiang  Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
1656*22ce4affSfengbojiang  ZSTD_CCtx object can be re-used multiple times within successive compression operations.
1657*22ce4affSfengbojiang
1658*22ce4affSfengbojiang  Start by initializing a context.
1659*22ce4affSfengbojiang  Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
1660*22ce4affSfengbojiang  or ZSTD_compressBegin_advanced(), for finer parameter control.
1661*22ce4affSfengbojiang  It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
1662*22ce4affSfengbojiang
1663*22ce4affSfengbojiang  Then, consume your input using ZSTD_compressContinue().
1664*22ce4affSfengbojiang  There are some important considerations to keep in mind when using this advanced function :
1665*22ce4affSfengbojiang  - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
1666*22ce4affSfengbojiang  - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
1667*22ce4affSfengbojiang  - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
1668*22ce4affSfengbojiang    Worst case evaluation is provided by ZSTD_compressBound().
1669*22ce4affSfengbojiang    ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
1670*22ce4affSfengbojiang  - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
1671*22ce4affSfengbojiang    It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
1672*22ce4affSfengbojiang  - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
1673*22ce4affSfengbojiang    In which case, it will "discard" the relevant memory section from its history.
1674*22ce4affSfengbojiang
1675*22ce4affSfengbojiang  Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
1676*22ce4affSfengbojiang  It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
1677*22ce4affSfengbojiang  Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
1678*22ce4affSfengbojiang
1679*22ce4affSfengbojiang  `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
1680*22ce4affSfengbojiang<BR></pre>
1681*22ce4affSfengbojiang
1682*22ce4affSfengbojiang<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
1683*22ce4affSfengbojiangsize_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
1684*22ce4affSfengbojiangsize_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
1685*22ce4affSfengbojiangsize_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
1686*22ce4affSfengbojiangsize_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize);   </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b>
1687*22ce4affSfengbojiangsize_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**<  note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
1688*22ce4affSfengbojiang</pre></b><BR>
1689*22ce4affSfengbojiang<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
1690*22ce4affSfengbojiang  A ZSTD_DCtx object is required to track streaming operations.
1691*22ce4affSfengbojiang  Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
1692*22ce4affSfengbojiang  A ZSTD_DCtx object can be re-used multiple times.
1693*22ce4affSfengbojiang
1694*22ce4affSfengbojiang  First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
1695*22ce4affSfengbojiang  Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
1696*22ce4affSfengbojiang  Data fragment must be large enough to ensure successful decoding.
1697*22ce4affSfengbojiang `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
1698*22ce4affSfengbojiang  @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
1699*22ce4affSfengbojiang           >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
1700*22ce4affSfengbojiang           errorCode, which can be tested using ZSTD_isError().
1701*22ce4affSfengbojiang
1702*22ce4affSfengbojiang  It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
1703*22ce4affSfengbojiang  such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
1704*22ce4affSfengbojiang  Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
1705*22ce4affSfengbojiang  As a consequence, check that values remain within valid application range.
1706*22ce4affSfengbojiang  For example, do not allocate memory blindly, check that `windowSize` is within expectation.
1707*22ce4affSfengbojiang  Each application can set its own limits, depending on local restrictions.
1708*22ce4affSfengbojiang  For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
1709*22ce4affSfengbojiang
1710*22ce4affSfengbojiang  ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
1711*22ce4affSfengbojiang  ZSTD_decompressContinue() is very sensitive to contiguity,
1712*22ce4affSfengbojiang  if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
1713*22ce4affSfengbojiang  or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
1714*22ce4affSfengbojiang  There are multiple ways to guarantee this condition.
1715*22ce4affSfengbojiang
1716*22ce4affSfengbojiang  The most memory efficient way is to use a round buffer of sufficient size.
1717*22ce4affSfengbojiang  Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
1718*22ce4affSfengbojiang  which can @return an error code if required value is too large for current system (in 32-bits mode).
1719*22ce4affSfengbojiang  In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
1720*22ce4affSfengbojiang  up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
1721*22ce4affSfengbojiang  which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
1722*22ce4affSfengbojiang  At which point, decoding can resume from the beginning of the buffer.
1723*22ce4affSfengbojiang  Note that already decoded data stored in the buffer should be flushed before being overwritten.
1724*22ce4affSfengbojiang
1725*22ce4affSfengbojiang  There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
1726*22ce4affSfengbojiang
1727*22ce4affSfengbojiang  Finally, if you control the compression process, you can also ignore all buffer size rules,
1728*22ce4affSfengbojiang  as long as the encoder and decoder progress in "lock-step",
1729*22ce4affSfengbojiang  aka use exactly the same buffer sizes, break contiguity at the same place, etc.
1730*22ce4affSfengbojiang
1731*22ce4affSfengbojiang  Once buffers are setup, start decompression, with ZSTD_decompressBegin().
1732*22ce4affSfengbojiang  If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
1733*22ce4affSfengbojiang
1734*22ce4affSfengbojiang  Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
1735*22ce4affSfengbojiang  ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
1736*22ce4affSfengbojiang  ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
1737*22ce4affSfengbojiang
1738*22ce4affSfengbojiang @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
1739*22ce4affSfengbojiang  It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
1740*22ce4affSfengbojiang  It can also be an error code, which can be tested with ZSTD_isError().
1741*22ce4affSfengbojiang
1742*22ce4affSfengbojiang  A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
1743*22ce4affSfengbojiang  Context can then be reset to start a new decompression.
1744*22ce4affSfengbojiang
1745*22ce4affSfengbojiang  Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
1746*22ce4affSfengbojiang  This information is not required to properly decode a frame.
1747*22ce4affSfengbojiang
1748*22ce4affSfengbojiang  == Special case : skippable frames
1749*22ce4affSfengbojiang
1750*22ce4affSfengbojiang  Skippable frames allow integration of user-defined data into a flow of concatenated frames.
1751*22ce4affSfengbojiang  Skippable frames will be ignored (skipped) by decompressor.
1752*22ce4affSfengbojiang  The format of skippable frames is as follows :
1753*22ce4affSfengbojiang  a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
1754*22ce4affSfengbojiang  b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
1755*22ce4affSfengbojiang  c) Frame Content - any content (User Data) of length equal to Frame Size
1756*22ce4affSfengbojiang  For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
1757*22ce4affSfengbojiang  For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
1758*22ce4affSfengbojiang<BR></pre>
1759*22ce4affSfengbojiang
1760*22ce4affSfengbojiang<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
1761*22ce4affSfengbojiangtypedef struct {
1762*22ce4affSfengbojiang    unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
1763*22ce4affSfengbojiang    unsigned long long windowSize;       </b>/* can be very large, up to <= frameContentSize */<b>
1764*22ce4affSfengbojiang    unsigned blockSizeMax;
1765*22ce4affSfengbojiang    ZSTD_frameType_e frameType;          </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
1766*22ce4affSfengbojiang    unsigned headerSize;
1767*22ce4affSfengbojiang    unsigned dictID;
1768*22ce4affSfengbojiang    unsigned checksumFlag;
1769*22ce4affSfengbojiang} ZSTD_frameHeader;
1770*22ce4affSfengbojiang</pre></b><BR>
1771*22ce4affSfengbojiang<pre><b>size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize);   </b>/**< doesn't consume input */<b>
1772*22ce4affSfengbojiang</b>/*! ZSTD_getFrameHeader_advanced() :<b>
1773*22ce4affSfengbojiang *  same as ZSTD_getFrameHeader(),
1774*22ce4affSfengbojiang *  with added capability to select a format (like ZSTD_f_zstd1_magicless) */
1775*22ce4affSfengbojiangsize_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
1776*22ce4affSfengbojiangsize_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize);  </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b>
1777*22ce4affSfengbojiang</b><p>  decode Frame Header, or requires larger `srcSize`.
1778*22ce4affSfengbojiang @return : 0, `zfhPtr` is correctly filled,
1779*22ce4affSfengbojiang          >0, `srcSize` is too small, value is wanted `srcSize` amount,
1780*22ce4affSfengbojiang           or an error code, which can be tested using ZSTD_isError()
1781*22ce4affSfengbojiang</p></pre><BR>
1782*22ce4affSfengbojiang
1783*22ce4affSfengbojiang<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
1784*22ce4affSfengbojiang</b></pre><BR>
1785*22ce4affSfengbojiang<a name="Chapter23"></a><h2>Block level API</h2><pre></pre>
1786*22ce4affSfengbojiang
1787*22ce4affSfengbojiang<pre><b></b><p>    Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
1788*22ce4affSfengbojiang    But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
1789*22ce4affSfengbojiang
1790*22ce4affSfengbojiang    A few rules to respect :
1791*22ce4affSfengbojiang    - Compressing and decompressing require a context structure
1792*22ce4affSfengbojiang      + Use ZSTD_createCCtx() and ZSTD_createDCtx()
1793*22ce4affSfengbojiang    - It is necessary to init context before starting
1794*22ce4affSfengbojiang      + compression : any ZSTD_compressBegin*() variant, including with dictionary
1795*22ce4affSfengbojiang      + decompression : any ZSTD_decompressBegin*() variant, including with dictionary
1796*22ce4affSfengbojiang      + copyCCtx() and copyDCtx() can be used too
1797*22ce4affSfengbojiang    - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
1798*22ce4affSfengbojiang      + If input is larger than a block size, it's necessary to split input data into multiple blocks
1799*22ce4affSfengbojiang      + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
1800*22ce4affSfengbojiang        Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
1801*22ce4affSfengbojiang    - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
1802*22ce4affSfengbojiang      ===> In which case, nothing is produced into `dst` !
1803*22ce4affSfengbojiang      + User __must__ test for such outcome and deal directly with uncompressed data
1804*22ce4affSfengbojiang      + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
1805*22ce4affSfengbojiang        Doing so would mess up with statistics history, leading to potential data corruption.
1806*22ce4affSfengbojiang      + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
1807*22ce4affSfengbojiang      + In case of multiple successive blocks, should some of them be uncompressed,
1808*22ce4affSfengbojiang        decoder must be informed of their existence in order to follow proper history.
1809*22ce4affSfengbojiang        Use ZSTD_insertBlock() for such a case.
1810*22ce4affSfengbojiang</p></pre><BR>
1811*22ce4affSfengbojiang
1812*22ce4affSfengbojiang<h3>Raw zstd block functions</h3><pre></pre><b><pre>size_t ZSTD_getBlockSize   (const ZSTD_CCtx* cctx);
1813*22ce4affSfengbojiangsize_t ZSTD_compressBlock  (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1814*22ce4affSfengbojiangsize_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
1815*22ce4affSfengbojiangsize_t ZSTD_insertBlock    (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize);  </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b>
1816*22ce4affSfengbojiang</pre></b><BR>
1817*22ce4affSfengbojiang</html>
1818*22ce4affSfengbojiang</body>
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