1 /*
2 ** {======================================================
3 ** Library for packing/unpacking structures.
4 ** $Id: struct.c,v 1.7 2018/05/11 22:04:31 roberto Exp $
5 ** See Copyright Notice at the end of this file
6 ** =======================================================
7 */
8 /*
9 ** Valid formats:
10 ** > - big endian
11 ** < - little endian
12 ** ![num] - alignment
13 ** x - pading
14 ** b/B - signed/unsigned byte
15 ** h/H - signed/unsigned short
16 ** l/L - signed/unsigned long
17 ** T - size_t
18 ** i/In - signed/unsigned integer with size 'n' (default is size of int)
19 ** cn - sequence of 'n' chars (from/to a string); when packing, n==0 means
20 the whole string; when unpacking, n==0 means use the previous
21 read number as the string length
22 ** s - zero-terminated string
23 ** f - float
24 ** d - double
25 ** ' ' - ignored
26 */
27
28
29 #include <assert.h>
30 #include <ctype.h>
31 #include <limits.h>
32 #include <stddef.h>
33 #include <string.h>
34
35
36 #include "lua.h"
37 #include "lauxlib.h"
38
39
40 #if (LUA_VERSION_NUM >= 502)
41
42 #define luaL_register(L,n,f) luaL_newlib(L,f)
43
44 #endif
45
46
47 /* basic integer type */
48 #if !defined(STRUCT_INT)
49 #define STRUCT_INT long
50 #endif
51
52 typedef STRUCT_INT Inttype;
53
54 /* corresponding unsigned version */
55 typedef unsigned STRUCT_INT Uinttype;
56
57
58 /* maximum size (in bytes) for integral types */
59 #define MAXINTSIZE 32
60
61 /* is 'x' a power of 2? */
62 #define isp2(x) ((x) > 0 && ((x) & ((x) - 1)) == 0)
63
64 /* dummy structure to get alignment requirements */
65 struct cD {
66 char c;
67 double d;
68 };
69
70
71 #define PADDING (sizeof(struct cD) - sizeof(double))
72 #define MAXALIGN (PADDING > sizeof(int) ? PADDING : sizeof(int))
73
74
75 /* endian options */
76 #define BIG 0
77 #define LITTLE 1
78
79
80 static union {
81 int dummy;
82 char endian;
83 } const native = {1};
84
85
86 typedef struct Header {
87 int endian;
88 int align;
89 } Header;
90
91
getnum(const char ** fmt,int df)92 static int getnum (const char **fmt, int df) {
93 if (!isdigit(**fmt)) /* no number? */
94 return df; /* return default value */
95 else {
96 int a = 0;
97 do {
98 a = a*10 + *((*fmt)++) - '0';
99 } while (isdigit(**fmt));
100 return a;
101 }
102 }
103
104
105 #define defaultoptions(h) ((h)->endian = native.endian, (h)->align = 1)
106
107
108
optsize(lua_State * L,char opt,const char ** fmt)109 static size_t optsize (lua_State *L, char opt, const char **fmt) {
110 switch (opt) {
111 case 'B': case 'b': return sizeof(char);
112 case 'H': case 'h': return sizeof(short);
113 case 'L': case 'l': return sizeof(long);
114 case 'T': return sizeof(size_t);
115 case 'f': return sizeof(float);
116 case 'd': return sizeof(double);
117 case 'x': return 1;
118 case 'c': return getnum(fmt, 1);
119 case 'i': case 'I': {
120 int sz = getnum(fmt, sizeof(int));
121 if (sz > MAXINTSIZE)
122 luaL_error(L, "integral size %d is larger than limit of %d",
123 sz, MAXINTSIZE);
124 return sz;
125 }
126 default: return 0; /* other cases do not need alignment */
127 }
128 }
129
130
131 /*
132 ** return number of bytes needed to align an element of size 'size'
133 ** at current position 'len'
134 */
gettoalign(size_t len,Header * h,int opt,size_t size)135 static int gettoalign (size_t len, Header *h, int opt, size_t size) {
136 if (size == 0 || opt == 'c') return 0;
137 if (size > (size_t)h->align)
138 size = h->align; /* respect max. alignment */
139 return (size - (len & (size - 1))) & (size - 1);
140 }
141
142
143 /*
144 ** options to control endianess and alignment
145 */
controloptions(lua_State * L,int opt,const char ** fmt,Header * h)146 static void controloptions (lua_State *L, int opt, const char **fmt,
147 Header *h) {
148 switch (opt) {
149 case ' ': return; /* ignore white spaces */
150 case '>': h->endian = BIG; return;
151 case '<': h->endian = LITTLE; return;
152 case '!': {
153 int a = getnum(fmt, MAXALIGN);
154 if (!isp2(a))
155 luaL_error(L, "alignment %d is not a power of 2", a);
156 h->align = a;
157 return;
158 }
159 default: {
160 const char *msg = lua_pushfstring(L, "invalid format option '%c'", opt);
161 luaL_argerror(L, 1, msg);
162 }
163 }
164 }
165
166
putinteger(lua_State * L,luaL_Buffer * b,int arg,int endian,int size)167 static void putinteger (lua_State *L, luaL_Buffer *b, int arg, int endian,
168 int size) {
169 lua_Number n = luaL_checknumber(L, arg);
170 Uinttype value;
171 char buff[MAXINTSIZE];
172 if (n < 0)
173 value = (Uinttype)(Inttype)n;
174 else
175 value = (Uinttype)n;
176 if (endian == LITTLE) {
177 int i;
178 for (i = 0; i < size; i++) {
179 buff[i] = (value & 0xff);
180 value >>= 8;
181 }
182 }
183 else {
184 int i;
185 for (i = size - 1; i >= 0; i--) {
186 buff[i] = (value & 0xff);
187 value >>= 8;
188 }
189 }
190 luaL_addlstring(b, buff, size);
191 }
192
193
correctbytes(char * b,int size,int endian)194 static void correctbytes (char *b, int size, int endian) {
195 if (endian != native.endian) {
196 int i = 0;
197 while (i < --size) {
198 char temp = b[i];
199 b[i++] = b[size];
200 b[size] = temp;
201 }
202 }
203 }
204
205
b_pack(lua_State * L)206 static int b_pack (lua_State *L) {
207 luaL_Buffer b;
208 const char *fmt = luaL_checkstring(L, 1);
209 Header h;
210 int arg = 2;
211 size_t totalsize = 0;
212 defaultoptions(&h);
213 lua_pushnil(L); /* mark to separate arguments from string buffer */
214 luaL_buffinit(L, &b);
215 while (*fmt != '\0') {
216 int opt = *fmt++;
217 size_t size = optsize(L, opt, &fmt);
218 int toalign = gettoalign(totalsize, &h, opt, size);
219 totalsize += toalign;
220 while (toalign-- > 0) luaL_addchar(&b, '\0');
221 switch (opt) {
222 case 'b': case 'B': case 'h': case 'H':
223 case 'l': case 'L': case 'T': case 'i': case 'I': { /* integer types */
224 putinteger(L, &b, arg++, h.endian, size);
225 break;
226 }
227 case 'x': {
228 luaL_addchar(&b, '\0');
229 break;
230 }
231 case 'f': {
232 float f = (float)luaL_checknumber(L, arg++);
233 correctbytes((char *)&f, size, h.endian);
234 luaL_addlstring(&b, (char *)&f, size);
235 break;
236 }
237 case 'd': {
238 double d = luaL_checknumber(L, arg++);
239 correctbytes((char *)&d, size, h.endian);
240 luaL_addlstring(&b, (char *)&d, size);
241 break;
242 }
243 case 'c': case 's': {
244 size_t l;
245 const char *s = luaL_checklstring(L, arg++, &l);
246 if (size == 0) size = l;
247 luaL_argcheck(L, l >= (size_t)size, arg, "string too short");
248 luaL_addlstring(&b, s, size);
249 if (opt == 's') {
250 luaL_addchar(&b, '\0'); /* add zero at the end */
251 size++;
252 }
253 break;
254 }
255 default: controloptions(L, opt, &fmt, &h);
256 }
257 totalsize += size;
258 }
259 luaL_pushresult(&b);
260 return 1;
261 }
262
263
getinteger(const char * buff,int endian,int issigned,int size)264 static lua_Number getinteger (const char *buff, int endian,
265 int issigned, int size) {
266 Uinttype l = 0;
267 int i;
268 if (endian == BIG) {
269 for (i = 0; i < size; i++) {
270 l <<= 8;
271 l |= (Uinttype)(unsigned char)buff[i];
272 }
273 }
274 else {
275 for (i = size - 1; i >= 0; i--) {
276 l <<= 8;
277 l |= (Uinttype)(unsigned char)buff[i];
278 }
279 }
280 if (!issigned)
281 return (lua_Number)l;
282 else { /* signed format */
283 Uinttype mask = (Uinttype)(~((Uinttype)0)) << (size*8 - 1);
284 if (l & mask) /* negative value? */
285 l |= mask; /* signal extension */
286 return (lua_Number)(Inttype)l;
287 }
288 }
289
290
b_unpack(lua_State * L)291 static int b_unpack (lua_State *L) {
292 Header h;
293 const char *fmt = luaL_checkstring(L, 1);
294 size_t ld;
295 const char *data = luaL_checklstring(L, 2, &ld);
296 size_t pos = luaL_optinteger(L, 3, 1);
297 luaL_argcheck(L, pos > 0, 3, "offset must be 1 or greater");
298 pos--; /* Lua indexes are 1-based, but here we want 0-based for C
299 * pointer math. */
300 int n = 0; /* number of results */
301 defaultoptions(&h);
302 while (*fmt) {
303 int opt = *fmt++;
304 size_t size = optsize(L, opt, &fmt);
305 pos += gettoalign(pos, &h, opt, size);
306 luaL_argcheck(L, size <= ld && pos <= ld - size,
307 2, "data string too short");
308 /* stack space for item + next position */
309 luaL_checkstack(L, 2, "too many results");
310 switch (opt) {
311 case 'b': case 'B': case 'h': case 'H':
312 case 'l': case 'L': case 'T': case 'i': case 'I': { /* integer types */
313 int issigned = islower(opt);
314 lua_Number res = getinteger(data+pos, h.endian, issigned, size);
315 lua_pushnumber(L, res); n++;
316 break;
317 }
318 case 'x': {
319 break;
320 }
321 case 'f': {
322 float f;
323 memcpy(&f, data+pos, size);
324 correctbytes((char *)&f, sizeof(f), h.endian);
325 lua_pushnumber(L, f); n++;
326 break;
327 }
328 case 'd': {
329 double d;
330 memcpy(&d, data+pos, size);
331 correctbytes((char *)&d, sizeof(d), h.endian);
332 lua_pushnumber(L, d); n++;
333 break;
334 }
335 case 'c': {
336 if (size == 0) {
337 if (n == 0 || !lua_isnumber(L, -1))
338 luaL_error(L, "format 'c0' needs a previous size");
339 size = lua_tonumber(L, -1);
340 lua_pop(L, 1); n--;
341 luaL_argcheck(L, size <= ld && pos <= ld - size,
342 2, "data string too short");
343 }
344 lua_pushlstring(L, data+pos, size); n++;
345 break;
346 }
347 case 's': {
348 const char *e = (const char *)memchr(data+pos, '\0', ld - pos);
349 if (e == NULL)
350 luaL_error(L, "unfinished string in data");
351 size = (e - (data+pos)) + 1;
352 lua_pushlstring(L, data+pos, size - 1); n++;
353 break;
354 }
355 default: controloptions(L, opt, &fmt, &h);
356 }
357 pos += size;
358 }
359 lua_pushinteger(L, pos + 1); /* next position */
360 return n + 1;
361 }
362
363
b_size(lua_State * L)364 static int b_size (lua_State *L) {
365 Header h;
366 const char *fmt = luaL_checkstring(L, 1);
367 size_t pos = 0;
368 defaultoptions(&h);
369 while (*fmt) {
370 int opt = *fmt++;
371 size_t size = optsize(L, opt, &fmt);
372 pos += gettoalign(pos, &h, opt, size);
373 if (opt == 's')
374 luaL_argerror(L, 1, "option 's' has no fixed size");
375 else if (opt == 'c' && size == 0)
376 luaL_argerror(L, 1, "option 'c0' has no fixed size");
377 if (!isalnum(opt))
378 controloptions(L, opt, &fmt, &h);
379 pos += size;
380 }
381 lua_pushinteger(L, pos);
382 return 1;
383 }
384
385 /* }====================================================== */
386
387
388
389 static const struct luaL_Reg thislib[] = {
390 {"pack", b_pack},
391 {"unpack", b_unpack},
392 {"size", b_size},
393 {NULL, NULL}
394 };
395
396
397 LUALIB_API int luaopen_struct (lua_State *L);
398
luaopen_struct(lua_State * L)399 LUALIB_API int luaopen_struct (lua_State *L) {
400 luaL_register(L, "struct", thislib);
401 return 1;
402 }
403
404
405 /******************************************************************************
406 * Copyright (C) 2010-2018 Lua.org, PUC-Rio. All rights reserved.
407 *
408 * Permission is hereby granted, free of charge, to any person obtaining
409 * a copy of this software and associated documentation files (the
410 * "Software"), to deal in the Software without restriction, including
411 * without limitation the rights to use, copy, modify, merge, publish,
412 * distribute, sublicense, and/or sell copies of the Software, and to
413 * permit persons to whom the Software is furnished to do so, subject to
414 * the following conditions:
415 *
416 * The above copyright notice and this permission notice shall be
417 * included in all copies or substantial portions of the Software.
418 *
419 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
420 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
421 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
422 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
423 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
424 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
425 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
426 ******************************************************************************/
427
428