xref: /sqlite-3.40.0/src/prepare.c (revision 545311ee)
1 /*
2 ** 2005 May 25
3 **
4 ** The author disclaims copyright to this source code.  In place of
5 ** a legal notice, here is a blessing:
6 **
7 **    May you do good and not evil.
8 **    May you find forgiveness for yourself and forgive others.
9 **    May you share freely, never taking more than you give.
10 **
11 *************************************************************************
12 ** This file contains the implementation of the sqlite3_prepare()
13 ** interface, and routines that contribute to loading the database schema
14 ** from disk.
15 **
16 ** $Id: prepare.c,v 1.41 2006/11/09 00:24:54 drh Exp $
17 */
18 #include "sqliteInt.h"
19 #include "os.h"
20 #include <ctype.h>
21 
22 /*
23 ** Fill the InitData structure with an error message that indicates
24 ** that the database is corrupt.
25 */
26 static void corruptSchema(InitData *pData, const char *zExtra){
27   if( !sqlite3MallocFailed() ){
28     sqlite3SetString(pData->pzErrMsg, "malformed database schema",
29        zExtra!=0 && zExtra[0]!=0 ? " - " : (char*)0, zExtra, (char*)0);
30   }
31   pData->rc = SQLITE_CORRUPT;
32 }
33 
34 /*
35 ** This is the callback routine for the code that initializes the
36 ** database.  See sqlite3Init() below for additional information.
37 ** This routine is also called from the OP_ParseSchema opcode of the VDBE.
38 **
39 ** Each callback contains the following information:
40 **
41 **     argv[0] = name of thing being created
42 **     argv[1] = root page number for table or index. 0 for trigger or view.
43 **     argv[2] = SQL text for the CREATE statement.
44 **
45 */
46 int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){
47   InitData *pData = (InitData*)pInit;
48   sqlite3 *db = pData->db;
49   int iDb = pData->iDb;
50 
51   pData->rc = SQLITE_OK;
52   DbClearProperty(db, iDb, DB_Empty);
53   if( sqlite3MallocFailed() ){
54     corruptSchema(pData, 0);
55     return SQLITE_NOMEM;
56   }
57 
58   assert( argc==3 );
59   if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
60   if( argv[1]==0 ){
61     corruptSchema(pData, 0);
62     return 1;
63   }
64   assert( iDb>=0 && iDb<db->nDb );
65   if( argv[2] && argv[2][0] ){
66     /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
67     ** But because db->init.busy is set to 1, no VDBE code is generated
68     ** or executed.  All the parser does is build the internal data
69     ** structures that describe the table, index, or view.
70     */
71     char *zErr;
72     int rc;
73     assert( db->init.busy );
74     db->init.iDb = iDb;
75     db->init.newTnum = atoi(argv[1]);
76     rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
77     db->init.iDb = 0;
78     assert( rc!=SQLITE_OK || zErr==0 );
79     if( SQLITE_OK!=rc ){
80       pData->rc = rc;
81       if( rc==SQLITE_NOMEM ){
82         sqlite3FailedMalloc();
83       }else if( rc!=SQLITE_INTERRUPT ){
84         corruptSchema(pData, zErr);
85       }
86       sqlite3_free(zErr);
87       return 1;
88     }
89   }else{
90     /* If the SQL column is blank it means this is an index that
91     ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
92     ** constraint for a CREATE TABLE.  The index should have already
93     ** been created when we processed the CREATE TABLE.  All we have
94     ** to do here is record the root page number for that index.
95     */
96     Index *pIndex;
97     pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zName);
98     if( pIndex==0 || pIndex->tnum!=0 ){
99       /* This can occur if there exists an index on a TEMP table which
100       ** has the same name as another index on a permanent index.  Since
101       ** the permanent table is hidden by the TEMP table, we can also
102       ** safely ignore the index on the permanent table.
103       */
104       /* Do Nothing */;
105     }else{
106       pIndex->tnum = atoi(argv[1]);
107     }
108   }
109   return 0;
110 }
111 
112 /*
113 ** Attempt to read the database schema and initialize internal
114 ** data structures for a single database file.  The index of the
115 ** database file is given by iDb.  iDb==0 is used for the main
116 ** database.  iDb==1 should never be used.  iDb>=2 is used for
117 ** auxiliary databases.  Return one of the SQLITE_ error codes to
118 ** indicate success or failure.
119 */
120 static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
121   int rc;
122   BtCursor *curMain;
123   int size;
124   Table *pTab;
125   Db *pDb;
126   char const *azArg[4];
127   int meta[10];
128   InitData initData;
129   char const *zMasterSchema;
130   char const *zMasterName = SCHEMA_TABLE(iDb);
131 
132   /*
133   ** The master database table has a structure like this
134   */
135   static const char master_schema[] =
136      "CREATE TABLE sqlite_master(\n"
137      "  type text,\n"
138      "  name text,\n"
139      "  tbl_name text,\n"
140      "  rootpage integer,\n"
141      "  sql text\n"
142      ")"
143   ;
144 #ifndef SQLITE_OMIT_TEMPDB
145   static const char temp_master_schema[] =
146      "CREATE TEMP TABLE sqlite_temp_master(\n"
147      "  type text,\n"
148      "  name text,\n"
149      "  tbl_name text,\n"
150      "  rootpage integer,\n"
151      "  sql text\n"
152      ")"
153   ;
154 #else
155   #define temp_master_schema 0
156 #endif
157 
158   assert( iDb>=0 && iDb<db->nDb );
159   assert( db->aDb[iDb].pSchema );
160 
161   /* zMasterSchema and zInitScript are set to point at the master schema
162   ** and initialisation script appropriate for the database being
163   ** initialised. zMasterName is the name of the master table.
164   */
165   if( !OMIT_TEMPDB && iDb==1 ){
166     zMasterSchema = temp_master_schema;
167   }else{
168     zMasterSchema = master_schema;
169   }
170   zMasterName = SCHEMA_TABLE(iDb);
171 
172   /* Construct the schema tables.  */
173   sqlite3SafetyOff(db);
174   azArg[0] = zMasterName;
175   azArg[1] = "1";
176   azArg[2] = zMasterSchema;
177   azArg[3] = 0;
178   initData.db = db;
179   initData.iDb = iDb;
180   initData.pzErrMsg = pzErrMsg;
181   rc = sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
182   if( rc ){
183     sqlite3SafetyOn(db);
184     return initData.rc;
185   }
186   pTab = sqlite3FindTable(db, zMasterName, db->aDb[iDb].zName);
187   if( pTab ){
188     pTab->readOnly = 1;
189   }
190   sqlite3SafetyOn(db);
191 
192   /* Create a cursor to hold the database open
193   */
194   pDb = &db->aDb[iDb];
195   if( pDb->pBt==0 ){
196     if( !OMIT_TEMPDB && iDb==1 ){
197       DbSetProperty(db, 1, DB_SchemaLoaded);
198     }
199     return SQLITE_OK;
200   }
201   rc = sqlite3BtreeCursor(pDb->pBt, MASTER_ROOT, 0, 0, 0, &curMain);
202   if( rc!=SQLITE_OK && rc!=SQLITE_EMPTY ){
203     sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
204     return rc;
205   }
206 
207   /* Get the database meta information.
208   **
209   ** Meta values are as follows:
210   **    meta[0]   Schema cookie.  Changes with each schema change.
211   **    meta[1]   File format of schema layer.
212   **    meta[2]   Size of the page cache.
213   **    meta[3]   Use freelist if 0.  Autovacuum if greater than zero.
214   **    meta[4]   Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE
215   **    meta[5]   The user cookie. Used by the application.
216   **    meta[6]
217   **    meta[7]
218   **    meta[8]
219   **    meta[9]
220   **
221   ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
222   ** the possible values of meta[4].
223   */
224   if( rc==SQLITE_OK ){
225     int i;
226     for(i=0; rc==SQLITE_OK && i<sizeof(meta)/sizeof(meta[0]); i++){
227       rc = sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
228     }
229     if( rc ){
230       sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
231       sqlite3BtreeCloseCursor(curMain);
232       return rc;
233     }
234   }else{
235     memset(meta, 0, sizeof(meta));
236   }
237   pDb->pSchema->schema_cookie = meta[0];
238 
239   /* If opening a non-empty database, check the text encoding. For the
240   ** main database, set sqlite3.enc to the encoding of the main database.
241   ** For an attached db, it is an error if the encoding is not the same
242   ** as sqlite3.enc.
243   */
244   if( meta[4] ){  /* text encoding */
245     if( iDb==0 ){
246       /* If opening the main database, set ENC(db). */
247       ENC(db) = (u8)meta[4];
248       db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 6, 0);
249     }else{
250       /* If opening an attached database, the encoding much match ENC(db) */
251       if( meta[4]!=ENC(db) ){
252         sqlite3BtreeCloseCursor(curMain);
253         sqlite3SetString(pzErrMsg, "attached databases must use the same"
254             " text encoding as main database", (char*)0);
255         return SQLITE_ERROR;
256       }
257     }
258   }else{
259     DbSetProperty(db, iDb, DB_Empty);
260   }
261   pDb->pSchema->enc = ENC(db);
262 
263   size = meta[2];
264   if( size==0 ){ size = MAX_PAGES; }
265   pDb->pSchema->cache_size = size;
266   sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
267 
268   /*
269   ** file_format==1    Version 3.0.0.
270   ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN
271   ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults
272   ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants
273   */
274   pDb->pSchema->file_format = meta[1];
275   if( pDb->pSchema->file_format==0 ){
276     pDb->pSchema->file_format = 1;
277   }
278   if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
279     sqlite3BtreeCloseCursor(curMain);
280     sqlite3SetString(pzErrMsg, "unsupported file format", (char*)0);
281     return SQLITE_ERROR;
282   }
283 
284 
285   /* Read the schema information out of the schema tables
286   */
287   assert( db->init.busy );
288   if( rc==SQLITE_EMPTY ){
289     /* For an empty database, there is nothing to read */
290     rc = SQLITE_OK;
291   }else{
292     char *zSql;
293     zSql = sqlite3MPrintf(
294         "SELECT name, rootpage, sql FROM '%q'.%s",
295         db->aDb[iDb].zName, zMasterName);
296     sqlite3SafetyOff(db);
297     rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
298     if( rc==SQLITE_ABORT ) rc = initData.rc;
299     sqlite3SafetyOn(db);
300     sqliteFree(zSql);
301 #ifndef SQLITE_OMIT_ANALYZE
302     if( rc==SQLITE_OK ){
303       sqlite3AnalysisLoad(db, iDb);
304     }
305 #endif
306     sqlite3BtreeCloseCursor(curMain);
307   }
308   if( sqlite3MallocFailed() ){
309     /* sqlite3SetString(pzErrMsg, "out of memory", (char*)0); */
310     rc = SQLITE_NOMEM;
311     sqlite3ResetInternalSchema(db, 0);
312   }
313   if( rc==SQLITE_OK ){
314     DbSetProperty(db, iDb, DB_SchemaLoaded);
315   }else{
316     sqlite3ResetInternalSchema(db, iDb);
317   }
318   return rc;
319 }
320 
321 /*
322 ** Initialize all database files - the main database file, the file
323 ** used to store temporary tables, and any additional database files
324 ** created using ATTACH statements.  Return a success code.  If an
325 ** error occurs, write an error message into *pzErrMsg.
326 **
327 ** After a database is initialized, the DB_SchemaLoaded bit is set
328 ** bit is set in the flags field of the Db structure. If the database
329 ** file was of zero-length, then the DB_Empty flag is also set.
330 */
331 int sqlite3Init(sqlite3 *db, char **pzErrMsg){
332   int i, rc;
333   int called_initone = 0;
334 
335   if( db->init.busy ) return SQLITE_OK;
336   rc = SQLITE_OK;
337   db->init.busy = 1;
338   for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
339     if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
340     rc = sqlite3InitOne(db, i, pzErrMsg);
341     if( rc ){
342       sqlite3ResetInternalSchema(db, i);
343     }
344     called_initone = 1;
345   }
346 
347   /* Once all the other databases have been initialised, load the schema
348   ** for the TEMP database. This is loaded last, as the TEMP database
349   ** schema may contain references to objects in other databases.
350   */
351 #ifndef SQLITE_OMIT_TEMPDB
352   if( rc==SQLITE_OK && db->nDb>1 && !DbHasProperty(db, 1, DB_SchemaLoaded) ){
353     rc = sqlite3InitOne(db, 1, pzErrMsg);
354     if( rc ){
355       sqlite3ResetInternalSchema(db, 1);
356     }
357     called_initone = 1;
358   }
359 #endif
360 
361   db->init.busy = 0;
362   if( rc==SQLITE_OK && called_initone ){
363     sqlite3CommitInternalChanges(db);
364   }
365 
366   return rc;
367 }
368 
369 /*
370 ** This routine is a no-op if the database schema is already initialised.
371 ** Otherwise, the schema is loaded. An error code is returned.
372 */
373 int sqlite3ReadSchema(Parse *pParse){
374   int rc = SQLITE_OK;
375   sqlite3 *db = pParse->db;
376   if( !db->init.busy ){
377     rc = sqlite3Init(db, &pParse->zErrMsg);
378   }
379   if( rc!=SQLITE_OK ){
380     pParse->rc = rc;
381     pParse->nErr++;
382   }
383   return rc;
384 }
385 
386 
387 /*
388 ** Check schema cookies in all databases.  If any cookie is out
389 ** of date, return 0.  If all schema cookies are current, return 1.
390 */
391 static int schemaIsValid(sqlite3 *db){
392   int iDb;
393   int rc;
394   BtCursor *curTemp;
395   int cookie;
396   int allOk = 1;
397 
398   for(iDb=0; allOk && iDb<db->nDb; iDb++){
399     Btree *pBt;
400     pBt = db->aDb[iDb].pBt;
401     if( pBt==0 ) continue;
402     rc = sqlite3BtreeCursor(pBt, MASTER_ROOT, 0, 0, 0, &curTemp);
403     if( rc==SQLITE_OK ){
404       rc = sqlite3BtreeGetMeta(pBt, 1, (u32 *)&cookie);
405       if( rc==SQLITE_OK && cookie!=db->aDb[iDb].pSchema->schema_cookie ){
406         allOk = 0;
407       }
408       sqlite3BtreeCloseCursor(curTemp);
409     }
410   }
411   return allOk;
412 }
413 
414 /*
415 ** Convert a schema pointer into the iDb index that indicates
416 ** which database file in db->aDb[] the schema refers to.
417 **
418 ** If the same database is attached more than once, the first
419 ** attached database is returned.
420 */
421 int sqlite3SchemaToIndex(sqlite3 *db, Schema *pSchema){
422   int i = -1000000;
423 
424   /* If pSchema is NULL, then return -1000000. This happens when code in
425   ** expr.c is trying to resolve a reference to a transient table (i.e. one
426   ** created by a sub-select). In this case the return value of this
427   ** function should never be used.
428   **
429   ** We return -1000000 instead of the more usual -1 simply because using
430   ** -1000000 as incorrectly using -1000000 index into db->aDb[] is much
431   ** more likely to cause a segfault than -1 (of course there are assert()
432   ** statements too, but it never hurts to play the odds).
433   */
434   if( pSchema ){
435     for(i=0; i<db->nDb; i++){
436       if( db->aDb[i].pSchema==pSchema ){
437         break;
438       }
439     }
440     assert( i>=0 &&i>=0 &&  i<db->nDb );
441   }
442   return i;
443 }
444 
445 /*
446 ** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
447 */
448 int sqlite3Prepare(
449   sqlite3 *db,              /* Database handle. */
450   const char *zSql,         /* UTF-8 encoded SQL statement. */
451   int nBytes,               /* Length of zSql in bytes. */
452   int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */
453   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
454   const char **pzTail       /* OUT: End of parsed string */
455 ){
456   Parse sParse;
457   char *zErrMsg = 0;
458   int rc = SQLITE_OK;
459   int i;
460 
461   /* Assert that malloc() has not failed */
462   assert( !sqlite3MallocFailed() );
463 
464   assert( ppStmt );
465   *ppStmt = 0;
466   if( sqlite3SafetyOn(db) ){
467     return SQLITE_MISUSE;
468   }
469 
470   /* If any attached database schemas are locked, do not proceed with
471   ** compilation. Instead return SQLITE_LOCKED immediately.
472   */
473   for(i=0; i<db->nDb; i++) {
474     Btree *pBt = db->aDb[i].pBt;
475     if( pBt && sqlite3BtreeSchemaLocked(pBt) ){
476       const char *zDb = db->aDb[i].zName;
477       sqlite3Error(db, SQLITE_LOCKED, "database schema is locked: %s", zDb);
478       sqlite3SafetyOff(db);
479       return SQLITE_LOCKED;
480     }
481   }
482 
483   memset(&sParse, 0, sizeof(sParse));
484   sParse.db = db;
485   if( nBytes>=0 && zSql[nBytes]!=0 ){
486     char *zSqlCopy = sqlite3StrNDup(zSql, nBytes);
487     sqlite3RunParser(&sParse, zSqlCopy, &zErrMsg);
488     sParse.zTail += zSql - zSqlCopy;
489     sqliteFree(zSqlCopy);
490   }else{
491     sqlite3RunParser(&sParse, zSql, &zErrMsg);
492   }
493 
494   if( sqlite3MallocFailed() ){
495     sParse.rc = SQLITE_NOMEM;
496   }
497   if( sParse.rc==SQLITE_DONE ) sParse.rc = SQLITE_OK;
498   if( sParse.checkSchema && !schemaIsValid(db) ){
499     sParse.rc = SQLITE_SCHEMA;
500   }
501   if( sParse.rc==SQLITE_SCHEMA ){
502     sqlite3ResetInternalSchema(db, 0);
503   }
504   if( sqlite3MallocFailed() ){
505     sParse.rc = SQLITE_NOMEM;
506   }
507   if( pzTail ){
508     *pzTail = sParse.zTail;
509   }
510   rc = sParse.rc;
511 
512 #ifndef SQLITE_OMIT_EXPLAIN
513   if( rc==SQLITE_OK && sParse.pVdbe && sParse.explain ){
514     if( sParse.explain==2 ){
515       sqlite3VdbeSetNumCols(sParse.pVdbe, 3);
516       sqlite3VdbeSetColName(sParse.pVdbe, 0, COLNAME_NAME, "order", P3_STATIC);
517       sqlite3VdbeSetColName(sParse.pVdbe, 1, COLNAME_NAME, "from", P3_STATIC);
518       sqlite3VdbeSetColName(sParse.pVdbe, 2, COLNAME_NAME, "detail", P3_STATIC);
519     }else{
520       sqlite3VdbeSetNumCols(sParse.pVdbe, 5);
521       sqlite3VdbeSetColName(sParse.pVdbe, 0, COLNAME_NAME, "addr", P3_STATIC);
522       sqlite3VdbeSetColName(sParse.pVdbe, 1, COLNAME_NAME, "opcode", P3_STATIC);
523       sqlite3VdbeSetColName(sParse.pVdbe, 2, COLNAME_NAME, "p1", P3_STATIC);
524       sqlite3VdbeSetColName(sParse.pVdbe, 3, COLNAME_NAME, "p2", P3_STATIC);
525       sqlite3VdbeSetColName(sParse.pVdbe, 4, COLNAME_NAME, "p3", P3_STATIC);
526     }
527   }
528 #endif
529 
530   if( sqlite3SafetyOff(db) ){
531     rc = SQLITE_MISUSE;
532   }
533   if( rc==SQLITE_OK ){
534     if( saveSqlFlag ){
535       sqlite3VdbeSetSql(sParse.pVdbe, zSql, sParse.zTail - zSql);
536     }
537     *ppStmt = (sqlite3_stmt*)sParse.pVdbe;
538   }else if( sParse.pVdbe ){
539     sqlite3_finalize((sqlite3_stmt*)sParse.pVdbe);
540   }
541 
542   if( zErrMsg ){
543     sqlite3Error(db, rc, "%s", zErrMsg);
544     sqliteFree(zErrMsg);
545   }else{
546     sqlite3Error(db, rc, 0);
547   }
548 
549   rc = sqlite3ApiExit(db, rc);
550   sqlite3ReleaseThreadData();
551   assert( (rc&db->errMask)==rc );
552   return rc;
553 }
554 
555 /*
556 ** Rerun the compilation of a statement after a schema change.
557 ** Return true if the statement was recompiled successfully.
558 ** Return false if there is an error of some kind.
559 */
560 int sqlite3Reprepare(Vdbe *p){
561   int rc;
562   Vdbe *pNew;
563   const char *zSql;
564   sqlite3 *db;
565 
566   zSql = sqlite3VdbeGetSql(p);
567   if( zSql==0 ){
568     return 0;
569   }
570   db = sqlite3VdbeDb(p);
571   rc = sqlite3Prepare(db, zSql, -1, 0, (sqlite3_stmt**)&pNew, 0);
572   if( rc ){
573     assert( pNew==0 );
574     return 0;
575   }else{
576     assert( pNew!=0 );
577   }
578   sqlite3VdbeSwapOps(pNew, p);
579   sqlite3_finalize((sqlite3_stmt*)pNew);
580   return 1;
581 }
582 
583 
584 /*
585 ** Two versions of the official API.  Legacy and new use.  In the legacy
586 ** version, the original SQL text is not saved in the prepared statement
587 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by
588 ** sqlite3_step().  In the new version, the original SQL text is retained
589 ** and the statement is automatically recompiled if an schema change
590 ** occurs.
591 */
592 int sqlite3_prepare(
593   sqlite3 *db,              /* Database handle. */
594   const char *zSql,         /* UTF-8 encoded SQL statement. */
595   int nBytes,               /* Length of zSql in bytes. */
596   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
597   const char **pzTail       /* OUT: End of parsed string */
598 ){
599   return sqlite3Prepare(db,zSql,nBytes,0,ppStmt,pzTail);
600 }
601 int sqlite3_prepare_v2(
602   sqlite3 *db,              /* Database handle. */
603   const char *zSql,         /* UTF-8 encoded SQL statement. */
604   int nBytes,               /* Length of zSql in bytes. */
605   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
606   const char **pzTail       /* OUT: End of parsed string */
607 ){
608   return sqlite3Prepare(db,zSql,nBytes,1,ppStmt,pzTail);
609 }
610 
611 
612 #ifndef SQLITE_OMIT_UTF16
613 /*
614 ** Compile the UTF-16 encoded SQL statement zSql into a statement handle.
615 */
616 static int sqlite3Prepare16(
617   sqlite3 *db,              /* Database handle. */
618   const void *zSql,         /* UTF-8 encoded SQL statement. */
619   int nBytes,               /* Length of zSql in bytes. */
620   int saveSqlFlag,          /* True to save SQL text into the sqlite3_stmt */
621   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
622   const void **pzTail       /* OUT: End of parsed string */
623 ){
624   /* This function currently works by first transforming the UTF-16
625   ** encoded string to UTF-8, then invoking sqlite3_prepare(). The
626   ** tricky bit is figuring out the pointer to return in *pzTail.
627   */
628   char *zSql8;
629   const char *zTail8 = 0;
630   int rc = SQLITE_OK;
631 
632   if( sqlite3SafetyCheck(db) ){
633     return SQLITE_MISUSE;
634   }
635   zSql8 = sqlite3utf16to8(zSql, nBytes);
636   if( zSql8 ){
637     rc = sqlite3Prepare(db, zSql8, -1, saveSqlFlag, ppStmt, &zTail8);
638   }
639 
640   if( zTail8 && pzTail ){
641     /* If sqlite3_prepare returns a tail pointer, we calculate the
642     ** equivalent pointer into the UTF-16 string by counting the unicode
643     ** characters between zSql8 and zTail8, and then returning a pointer
644     ** the same number of characters into the UTF-16 string.
645     */
646     int chars_parsed = sqlite3utf8CharLen(zSql8, zTail8-zSql8);
647     *pzTail = (u8 *)zSql + sqlite3utf16ByteLen(zSql, chars_parsed);
648   }
649   sqliteFree(zSql8);
650   return sqlite3ApiExit(db, rc);
651 }
652 
653 /*
654 ** Two versions of the official API.  Legacy and new use.  In the legacy
655 ** version, the original SQL text is not saved in the prepared statement
656 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by
657 ** sqlite3_step().  In the new version, the original SQL text is retained
658 ** and the statement is automatically recompiled if an schema change
659 ** occurs.
660 */
661 int sqlite3_prepare16(
662   sqlite3 *db,              /* Database handle. */
663   const void *zSql,         /* UTF-8 encoded SQL statement. */
664   int nBytes,               /* Length of zSql in bytes. */
665   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
666   const void **pzTail       /* OUT: End of parsed string */
667 ){
668   return sqlite3Prepare16(db,zSql,nBytes,0,ppStmt,pzTail);
669 }
670 int sqlite3_prepare16_v2(
671   sqlite3 *db,              /* Database handle. */
672   const void *zSql,         /* UTF-8 encoded SQL statement. */
673   int nBytes,               /* Length of zSql in bytes. */
674   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
675   const void **pzTail       /* OUT: End of parsed string */
676 ){
677   return sqlite3Prepare16(db,zSql,nBytes,1,ppStmt,pzTail);
678 }
679 
680 #endif /* SQLITE_OMIT_UTF16 */
681