xref: /sqlite-3.40.0/src/vdbeapi.c (revision a3f06598)
1 /*
2 ** 2004 May 26
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 **
13 ** This file contains code use to implement APIs that are part of the
14 ** VDBE.
15 **
16 ** $Id: vdbeapi.c,v 1.163 2009/04/14 12:58:20 drh Exp $
17 */
18 #include "sqliteInt.h"
19 #include "vdbeInt.h"
20 
21 #if 0 && defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
22 /*
23 ** The following structure contains pointers to the end points of a
24 ** doubly-linked list of all compiled SQL statements that may be holding
25 ** buffers eligible for release when the sqlite3_release_memory() interface is
26 ** invoked. Access to this list is protected by the SQLITE_MUTEX_STATIC_LRU2
27 ** mutex.
28 **
29 ** Statements are added to the end of this list when sqlite3_reset() is
30 ** called. They are removed either when sqlite3_step() or sqlite3_finalize()
31 ** is called. When statements are added to this list, the associated
32 ** register array (p->aMem[1..p->nMem]) may contain dynamic buffers that
33 ** can be freed using sqlite3VdbeReleaseMemory().
34 **
35 ** When statements are added or removed from this list, the mutex
36 ** associated with the Vdbe being added or removed (Vdbe.db->mutex) is
37 ** already held. The LRU2 mutex is then obtained, blocking if necessary,
38 ** the linked-list pointers manipulated and the LRU2 mutex relinquished.
39 */
40 struct StatementLruList {
41   Vdbe *pFirst;
42   Vdbe *pLast;
43 };
44 static struct StatementLruList sqlite3LruStatements;
45 
46 /*
47 ** Check that the list looks to be internally consistent. This is used
48 ** as part of an assert() statement as follows:
49 **
50 **   assert( stmtLruCheck() );
51 */
52 #ifndef NDEBUG
53 static int stmtLruCheck(){
54   Vdbe *p;
55   for(p=sqlite3LruStatements.pFirst; p; p=p->pLruNext){
56     assert(p->pLruNext || p==sqlite3LruStatements.pLast);
57     assert(!p->pLruNext || p->pLruNext->pLruPrev==p);
58     assert(p->pLruPrev || p==sqlite3LruStatements.pFirst);
59     assert(!p->pLruPrev || p->pLruPrev->pLruNext==p);
60   }
61   return 1;
62 }
63 #endif
64 
65 /*
66 ** Add vdbe p to the end of the statement lru list. It is assumed that
67 ** p is not already part of the list when this is called. The lru list
68 ** is protected by the SQLITE_MUTEX_STATIC_LRU mutex.
69 */
70 static void stmtLruAdd(Vdbe *p){
71   sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
72 
73   if( p->pLruPrev || p->pLruNext || sqlite3LruStatements.pFirst==p ){
74     sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
75     return;
76   }
77 
78   assert( stmtLruCheck() );
79 
80   if( !sqlite3LruStatements.pFirst ){
81     assert( !sqlite3LruStatements.pLast );
82     sqlite3LruStatements.pFirst = p;
83     sqlite3LruStatements.pLast = p;
84   }else{
85     assert( !sqlite3LruStatements.pLast->pLruNext );
86     p->pLruPrev = sqlite3LruStatements.pLast;
87     sqlite3LruStatements.pLast->pLruNext = p;
88     sqlite3LruStatements.pLast = p;
89   }
90 
91   assert( stmtLruCheck() );
92 
93   sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
94 }
95 
96 /*
97 ** Assuming the SQLITE_MUTEX_STATIC_LRU2 mutext is already held, remove
98 ** statement p from the least-recently-used statement list. If the
99 ** statement is not currently part of the list, this call is a no-op.
100 */
101 static void stmtLruRemoveNomutex(Vdbe *p){
102   if( p->pLruPrev || p->pLruNext || p==sqlite3LruStatements.pFirst ){
103     assert( stmtLruCheck() );
104     if( p->pLruNext ){
105       p->pLruNext->pLruPrev = p->pLruPrev;
106     }else{
107       sqlite3LruStatements.pLast = p->pLruPrev;
108     }
109     if( p->pLruPrev ){
110       p->pLruPrev->pLruNext = p->pLruNext;
111     }else{
112       sqlite3LruStatements.pFirst = p->pLruNext;
113     }
114     p->pLruNext = 0;
115     p->pLruPrev = 0;
116     assert( stmtLruCheck() );
117   }
118 }
119 
120 /*
121 ** Assuming the SQLITE_MUTEX_STATIC_LRU2 mutext is not held, remove
122 ** statement p from the least-recently-used statement list. If the
123 ** statement is not currently part of the list, this call is a no-op.
124 */
125 static void stmtLruRemove(Vdbe *p){
126   sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
127   stmtLruRemoveNomutex(p);
128   sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
129 }
130 
131 /*
132 ** Try to release n bytes of memory by freeing buffers associated
133 ** with the memory registers of currently unused vdbes.
134 */
135 int sqlite3VdbeReleaseMemory(int n){
136   Vdbe *p;
137   Vdbe *pNext;
138   int nFree = 0;
139 
140   sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
141   for(p=sqlite3LruStatements.pFirst; p && nFree<n; p=pNext){
142     pNext = p->pLruNext;
143 
144     /* For each statement handle in the lru list, attempt to obtain the
145     ** associated database mutex. If it cannot be obtained, continue
146     ** to the next statement handle. It is not possible to block on
147     ** the database mutex - that could cause deadlock.
148     */
149     if( SQLITE_OK==sqlite3_mutex_try(p->db->mutex) ){
150       nFree += sqlite3VdbeReleaseBuffers(p);
151       stmtLruRemoveNomutex(p);
152       sqlite3_mutex_leave(p->db->mutex);
153     }
154   }
155   sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_LRU2));
156 
157   return nFree;
158 }
159 
160 /*
161 ** Call sqlite3Reprepare() on the statement. Remove it from the
162 ** lru list before doing so, as Reprepare() will free all the
163 ** memory register buffers anyway.
164 */
165 int vdbeReprepare(Vdbe *p){
166   stmtLruRemove(p);
167   return sqlite3Reprepare(p);
168 }
169 
170 #else       /* !SQLITE_ENABLE_MEMORY_MANAGEMENT */
171   #define stmtLruRemove(x)
172   #define stmtLruAdd(x)
173   #define vdbeReprepare(x) sqlite3Reprepare(x)
174 #endif
175 
176 
177 #ifndef SQLITE_OMIT_DEPRECATED
178 /*
179 ** Return TRUE (non-zero) of the statement supplied as an argument needs
180 ** to be recompiled.  A statement needs to be recompiled whenever the
181 ** execution environment changes in a way that would alter the program
182 ** that sqlite3_prepare() generates.  For example, if new functions or
183 ** collating sequences are registered or if an authorizer function is
184 ** added or changed.
185 */
186 int sqlite3_expired(sqlite3_stmt *pStmt){
187   Vdbe *p = (Vdbe*)pStmt;
188   return p==0 || p->expired;
189 }
190 #endif
191 
192 /*
193 ** The following routine destroys a virtual machine that is created by
194 ** the sqlite3_compile() routine. The integer returned is an SQLITE_
195 ** success/failure code that describes the result of executing the virtual
196 ** machine.
197 **
198 ** This routine sets the error code and string returned by
199 ** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
200 */
201 int sqlite3_finalize(sqlite3_stmt *pStmt){
202   int rc;
203   if( pStmt==0 ){
204     rc = SQLITE_OK;
205   }else{
206     Vdbe *v = (Vdbe*)pStmt;
207     sqlite3 *db = v->db;
208 #if SQLITE_THREADSAFE
209     sqlite3_mutex *mutex = v->db->mutex;
210 #endif
211     sqlite3_mutex_enter(mutex);
212     stmtLruRemove(v);
213     rc = sqlite3VdbeFinalize(v);
214     rc = sqlite3ApiExit(db, rc);
215     sqlite3_mutex_leave(mutex);
216   }
217   return rc;
218 }
219 
220 /*
221 ** Terminate the current execution of an SQL statement and reset it
222 ** back to its starting state so that it can be reused. A success code from
223 ** the prior execution is returned.
224 **
225 ** This routine sets the error code and string returned by
226 ** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16().
227 */
228 int sqlite3_reset(sqlite3_stmt *pStmt){
229   int rc;
230   if( pStmt==0 ){
231     rc = SQLITE_OK;
232   }else{
233     Vdbe *v = (Vdbe*)pStmt;
234     sqlite3_mutex_enter(v->db->mutex);
235     rc = sqlite3VdbeReset(v);
236     stmtLruAdd(v);
237     sqlite3VdbeMakeReady(v, -1, 0, 0, 0);
238     assert( (rc & (v->db->errMask))==rc );
239     rc = sqlite3ApiExit(v->db, rc);
240     sqlite3_mutex_leave(v->db->mutex);
241   }
242   return rc;
243 }
244 
245 /*
246 ** Set all the parameters in the compiled SQL statement to NULL.
247 */
248 int sqlite3_clear_bindings(sqlite3_stmt *pStmt){
249   int i;
250   int rc = SQLITE_OK;
251   Vdbe *p = (Vdbe*)pStmt;
252 #if SQLITE_THREADSAFE
253   sqlite3_mutex *mutex = ((Vdbe*)pStmt)->db->mutex;
254 #endif
255   sqlite3_mutex_enter(mutex);
256   for(i=0; i<p->nVar; i++){
257     sqlite3VdbeMemRelease(&p->aVar[i]);
258     p->aVar[i].flags = MEM_Null;
259   }
260   sqlite3_mutex_leave(mutex);
261   return rc;
262 }
263 
264 
265 /**************************** sqlite3_value_  *******************************
266 ** The following routines extract information from a Mem or sqlite3_value
267 ** structure.
268 */
269 const void *sqlite3_value_blob(sqlite3_value *pVal){
270   Mem *p = (Mem*)pVal;
271   if( p->flags & (MEM_Blob|MEM_Str) ){
272     sqlite3VdbeMemExpandBlob(p);
273     p->flags &= ~MEM_Str;
274     p->flags |= MEM_Blob;
275     return p->z;
276   }else{
277     return sqlite3_value_text(pVal);
278   }
279 }
280 int sqlite3_value_bytes(sqlite3_value *pVal){
281   return sqlite3ValueBytes(pVal, SQLITE_UTF8);
282 }
283 int sqlite3_value_bytes16(sqlite3_value *pVal){
284   return sqlite3ValueBytes(pVal, SQLITE_UTF16NATIVE);
285 }
286 double sqlite3_value_double(sqlite3_value *pVal){
287   return sqlite3VdbeRealValue((Mem*)pVal);
288 }
289 int sqlite3_value_int(sqlite3_value *pVal){
290   return (int)sqlite3VdbeIntValue((Mem*)pVal);
291 }
292 sqlite_int64 sqlite3_value_int64(sqlite3_value *pVal){
293   return sqlite3VdbeIntValue((Mem*)pVal);
294 }
295 const unsigned char *sqlite3_value_text(sqlite3_value *pVal){
296   return (const unsigned char *)sqlite3ValueText(pVal, SQLITE_UTF8);
297 }
298 #ifndef SQLITE_OMIT_UTF16
299 const void *sqlite3_value_text16(sqlite3_value* pVal){
300   return sqlite3ValueText(pVal, SQLITE_UTF16NATIVE);
301 }
302 const void *sqlite3_value_text16be(sqlite3_value *pVal){
303   return sqlite3ValueText(pVal, SQLITE_UTF16BE);
304 }
305 const void *sqlite3_value_text16le(sqlite3_value *pVal){
306   return sqlite3ValueText(pVal, SQLITE_UTF16LE);
307 }
308 #endif /* SQLITE_OMIT_UTF16 */
309 int sqlite3_value_type(sqlite3_value* pVal){
310   return pVal->type;
311 }
312 
313 /**************************** sqlite3_result_  *******************************
314 ** The following routines are used by user-defined functions to specify
315 ** the function result.
316 */
317 void sqlite3_result_blob(
318   sqlite3_context *pCtx,
319   const void *z,
320   int n,
321   void (*xDel)(void *)
322 ){
323   assert( n>=0 );
324   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
325   sqlite3VdbeMemSetStr(&pCtx->s, z, n, 0, xDel);
326 }
327 void sqlite3_result_double(sqlite3_context *pCtx, double rVal){
328   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
329   sqlite3VdbeMemSetDouble(&pCtx->s, rVal);
330 }
331 void sqlite3_result_error(sqlite3_context *pCtx, const char *z, int n){
332   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
333   pCtx->isError = SQLITE_ERROR;
334   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, SQLITE_TRANSIENT);
335 }
336 #ifndef SQLITE_OMIT_UTF16
337 void sqlite3_result_error16(sqlite3_context *pCtx, const void *z, int n){
338   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
339   pCtx->isError = SQLITE_ERROR;
340   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, SQLITE_TRANSIENT);
341 }
342 #endif
343 void sqlite3_result_int(sqlite3_context *pCtx, int iVal){
344   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
345   sqlite3VdbeMemSetInt64(&pCtx->s, (i64)iVal);
346 }
347 void sqlite3_result_int64(sqlite3_context *pCtx, i64 iVal){
348   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
349   sqlite3VdbeMemSetInt64(&pCtx->s, iVal);
350 }
351 void sqlite3_result_null(sqlite3_context *pCtx){
352   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
353   sqlite3VdbeMemSetNull(&pCtx->s);
354 }
355 void sqlite3_result_text(
356   sqlite3_context *pCtx,
357   const char *z,
358   int n,
359   void (*xDel)(void *)
360 ){
361   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
362   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF8, xDel);
363 }
364 #ifndef SQLITE_OMIT_UTF16
365 void sqlite3_result_text16(
366   sqlite3_context *pCtx,
367   const void *z,
368   int n,
369   void (*xDel)(void *)
370 ){
371   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
372   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16NATIVE, xDel);
373 }
374 void sqlite3_result_text16be(
375   sqlite3_context *pCtx,
376   const void *z,
377   int n,
378   void (*xDel)(void *)
379 ){
380   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
381   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16BE, xDel);
382 }
383 void sqlite3_result_text16le(
384   sqlite3_context *pCtx,
385   const void *z,
386   int n,
387   void (*xDel)(void *)
388 ){
389   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
390   sqlite3VdbeMemSetStr(&pCtx->s, z, n, SQLITE_UTF16LE, xDel);
391 }
392 #endif /* SQLITE_OMIT_UTF16 */
393 void sqlite3_result_value(sqlite3_context *pCtx, sqlite3_value *pValue){
394   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
395   sqlite3VdbeMemCopy(&pCtx->s, pValue);
396 }
397 void sqlite3_result_zeroblob(sqlite3_context *pCtx, int n){
398   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
399   sqlite3VdbeMemSetZeroBlob(&pCtx->s, n);
400 }
401 void sqlite3_result_error_code(sqlite3_context *pCtx, int errCode){
402   pCtx->isError = errCode;
403 }
404 
405 /* Force an SQLITE_TOOBIG error. */
406 void sqlite3_result_error_toobig(sqlite3_context *pCtx){
407   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
408   pCtx->isError = SQLITE_TOOBIG;
409   sqlite3VdbeMemSetStr(&pCtx->s, "string or blob too big", -1,
410                        SQLITE_UTF8, SQLITE_STATIC);
411 }
412 
413 /* An SQLITE_NOMEM error. */
414 void sqlite3_result_error_nomem(sqlite3_context *pCtx){
415   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
416   sqlite3VdbeMemSetNull(&pCtx->s);
417   pCtx->isError = SQLITE_NOMEM;
418   pCtx->s.db->mallocFailed = 1;
419 }
420 
421 /*
422 ** Execute the statement pStmt, either until a row of data is ready, the
423 ** statement is completely executed or an error occurs.
424 **
425 ** This routine implements the bulk of the logic behind the sqlite_step()
426 ** API.  The only thing omitted is the automatic recompile if a
427 ** schema change has occurred.  That detail is handled by the
428 ** outer sqlite3_step() wrapper procedure.
429 */
430 static int sqlite3Step(Vdbe *p){
431   sqlite3 *db;
432   int rc;
433 
434   assert(p);
435   if( p->magic!=VDBE_MAGIC_RUN ){
436     return SQLITE_MISUSE;
437   }
438 
439   /* Assert that malloc() has not failed */
440   db = p->db;
441   if( db->mallocFailed ){
442     return SQLITE_NOMEM;
443   }
444 
445   if( p->pc<=0 && p->expired ){
446     if( ALWAYS(p->rc==SQLITE_OK) ){
447       p->rc = SQLITE_SCHEMA;
448     }
449     rc = SQLITE_ERROR;
450     goto end_of_step;
451   }
452   if( sqlite3SafetyOn(db) ){
453     p->rc = SQLITE_MISUSE;
454     return SQLITE_MISUSE;
455   }
456   if( p->pc<0 ){
457     /* If there are no other statements currently running, then
458     ** reset the interrupt flag.  This prevents a call to sqlite3_interrupt
459     ** from interrupting a statement that has not yet started.
460     */
461     if( db->activeVdbeCnt==0 ){
462       db->u1.isInterrupted = 0;
463     }
464 
465 #ifndef SQLITE_OMIT_TRACE
466     if( db->xProfile && !db->init.busy ){
467       double rNow;
468       sqlite3OsCurrentTime(db->pVfs, &rNow);
469       p->startTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
470     }
471 #endif
472 
473     db->activeVdbeCnt++;
474     if( p->readOnly==0 ) db->writeVdbeCnt++;
475     p->pc = 0;
476     stmtLruRemove(p);
477   }
478 #ifndef SQLITE_OMIT_EXPLAIN
479   if( p->explain ){
480     rc = sqlite3VdbeList(p);
481   }else
482 #endif /* SQLITE_OMIT_EXPLAIN */
483   {
484     rc = sqlite3VdbeExec(p);
485   }
486 
487   if( sqlite3SafetyOff(db) ){
488     rc = SQLITE_MISUSE;
489   }
490 
491 #ifndef SQLITE_OMIT_TRACE
492   /* Invoke the profile callback if there is one
493   */
494   if( rc!=SQLITE_ROW && db->xProfile && !db->init.busy && p->zSql ){
495     double rNow;
496     u64 elapseTime;
497 
498     sqlite3OsCurrentTime(db->pVfs, &rNow);
499     elapseTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
500     elapseTime -= p->startTime;
501     db->xProfile(db->pProfileArg, p->zSql, elapseTime);
502   }
503 #endif
504 
505   db->errCode = rc;
506   if( SQLITE_NOMEM==sqlite3ApiExit(p->db, p->rc) ){
507     p->rc = SQLITE_NOMEM;
508   }
509 end_of_step:
510   /* At this point local variable rc holds the value that should be
511   ** returned if this statement was compiled using the legacy
512   ** sqlite3_prepare() interface. According to the docs, this can only
513   ** be one of the values in the first assert() below. Variable p->rc
514   ** contains the value that would be returned if sqlite3_finalize()
515   ** were called on statement p.
516   */
517   assert( rc==SQLITE_ROW  || rc==SQLITE_DONE   || rc==SQLITE_ERROR
518        || rc==SQLITE_BUSY || rc==SQLITE_MISUSE
519   );
520   assert( p->rc!=SQLITE_ROW && p->rc!=SQLITE_DONE );
521   if( p->isPrepareV2 && rc!=SQLITE_ROW && rc!=SQLITE_DONE ){
522     /* If this statement was prepared using sqlite3_prepare_v2(), and an
523     ** error has occured, then return the error code in p->rc to the
524     ** caller. Set the error code in the database handle to the same value.
525     */
526     rc = db->errCode = p->rc;
527   }
528   return (rc&db->errMask);
529 }
530 
531 /*
532 ** This is the top-level implementation of sqlite3_step().  Call
533 ** sqlite3Step() to do most of the work.  If a schema error occurs,
534 ** call sqlite3Reprepare() and try again.
535 */
536 #ifdef SQLITE_OMIT_PARSER
537 int sqlite3_step(sqlite3_stmt *pStmt){
538   int rc = SQLITE_MISUSE;
539   if( pStmt ){
540     Vdbe *v;
541     v = (Vdbe*)pStmt;
542     sqlite3_mutex_enter(v->db->mutex);
543     rc = sqlite3Step(v);
544     sqlite3_mutex_leave(v->db->mutex);
545   }
546   return rc;
547 }
548 #else
549 int sqlite3_step(sqlite3_stmt *pStmt){
550   int rc = SQLITE_MISUSE;
551   if( pStmt ){
552     int cnt = 0;
553     Vdbe *v = (Vdbe*)pStmt;
554     sqlite3 *db = v->db;
555     sqlite3_mutex_enter(db->mutex);
556     while( (rc = sqlite3Step(v))==SQLITE_SCHEMA
557            && cnt++ < 5
558            && (rc = vdbeReprepare(v))==SQLITE_OK ){
559       sqlite3_reset(pStmt);
560       v->expired = 0;
561     }
562     if( rc==SQLITE_SCHEMA && ALWAYS(v->isPrepareV2) && ALWAYS(db->pErr) ){
563       /* This case occurs after failing to recompile an sql statement.
564       ** The error message from the SQL compiler has already been loaded
565       ** into the database handle. This block copies the error message
566       ** from the database handle into the statement and sets the statement
567       ** program counter to 0 to ensure that when the statement is
568       ** finalized or reset the parser error message is available via
569       ** sqlite3_errmsg() and sqlite3_errcode().
570       */
571       const char *zErr = (const char *)sqlite3_value_text(db->pErr);
572       sqlite3DbFree(db, v->zErrMsg);
573       if( !db->mallocFailed ){
574         v->zErrMsg = sqlite3DbStrDup(db, zErr);
575       } else {
576         v->zErrMsg = 0;
577         v->rc = SQLITE_NOMEM;
578       }
579     }
580     rc = sqlite3ApiExit(db, rc);
581     sqlite3_mutex_leave(db->mutex);
582   }
583   return rc;
584 }
585 #endif
586 
587 /*
588 ** Extract the user data from a sqlite3_context structure and return a
589 ** pointer to it.
590 */
591 void *sqlite3_user_data(sqlite3_context *p){
592   assert( p && p->pFunc );
593   return p->pFunc->pUserData;
594 }
595 
596 /*
597 ** Extract the user data from a sqlite3_context structure and return a
598 ** pointer to it.
599 */
600 sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
601   assert( p && p->pFunc );
602   return p->s.db;
603 }
604 
605 /*
606 ** The following is the implementation of an SQL function that always
607 ** fails with an error message stating that the function is used in the
608 ** wrong context.  The sqlite3_overload_function() API might construct
609 ** SQL function that use this routine so that the functions will exist
610 ** for name resolution but are actually overloaded by the xFindFunction
611 ** method of virtual tables.
612 */
613 void sqlite3InvalidFunction(
614   sqlite3_context *context,  /* The function calling context */
615   int NotUsed,               /* Number of arguments to the function */
616   sqlite3_value **NotUsed2   /* Value of each argument */
617 ){
618   const char *zName = context->pFunc->zName;
619   char *zErr;
620   UNUSED_PARAMETER2(NotUsed, NotUsed2);
621   zErr = sqlite3_mprintf(
622       "unable to use function %s in the requested context", zName);
623   sqlite3_result_error(context, zErr, -1);
624   sqlite3_free(zErr);
625 }
626 
627 /*
628 ** Allocate or return the aggregate context for a user function.  A new
629 ** context is allocated on the first call.  Subsequent calls return the
630 ** same context that was returned on prior calls.
631 */
632 void *sqlite3_aggregate_context(sqlite3_context *p, int nByte){
633   Mem *pMem;
634   assert( p && p->pFunc && p->pFunc->xStep );
635   assert( sqlite3_mutex_held(p->s.db->mutex) );
636   pMem = p->pMem;
637   if( (pMem->flags & MEM_Agg)==0 ){
638     if( nByte==0 ){
639       sqlite3VdbeMemReleaseExternal(pMem);
640       pMem->flags = MEM_Null;
641       pMem->z = 0;
642     }else{
643       sqlite3VdbeMemGrow(pMem, nByte, 0);
644       pMem->flags = MEM_Agg;
645       pMem->u.pDef = p->pFunc;
646       if( pMem->z ){
647         memset(pMem->z, 0, nByte);
648       }
649     }
650   }
651   return (void*)pMem->z;
652 }
653 
654 /*
655 ** Return the auxilary data pointer, if any, for the iArg'th argument to
656 ** the user-function defined by pCtx.
657 */
658 void *sqlite3_get_auxdata(sqlite3_context *pCtx, int iArg){
659   VdbeFunc *pVdbeFunc;
660 
661   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
662   pVdbeFunc = pCtx->pVdbeFunc;
663   if( !pVdbeFunc || iArg>=pVdbeFunc->nAux || iArg<0 ){
664     return 0;
665   }
666   return pVdbeFunc->apAux[iArg].pAux;
667 }
668 
669 /*
670 ** Set the auxilary data pointer and delete function, for the iArg'th
671 ** argument to the user-function defined by pCtx. Any previous value is
672 ** deleted by calling the delete function specified when it was set.
673 */
674 void sqlite3_set_auxdata(
675   sqlite3_context *pCtx,
676   int iArg,
677   void *pAux,
678   void (*xDelete)(void*)
679 ){
680   struct AuxData *pAuxData;
681   VdbeFunc *pVdbeFunc;
682   if( iArg<0 ) goto failed;
683 
684   assert( sqlite3_mutex_held(pCtx->s.db->mutex) );
685   pVdbeFunc = pCtx->pVdbeFunc;
686   if( !pVdbeFunc || pVdbeFunc->nAux<=iArg ){
687     int nAux = (pVdbeFunc ? pVdbeFunc->nAux : 0);
688     int nMalloc = sizeof(VdbeFunc) + sizeof(struct AuxData)*iArg;
689     pVdbeFunc = sqlite3DbRealloc(pCtx->s.db, pVdbeFunc, nMalloc);
690     if( !pVdbeFunc ){
691       goto failed;
692     }
693     pCtx->pVdbeFunc = pVdbeFunc;
694     memset(&pVdbeFunc->apAux[nAux], 0, sizeof(struct AuxData)*(iArg+1-nAux));
695     pVdbeFunc->nAux = iArg+1;
696     pVdbeFunc->pFunc = pCtx->pFunc;
697   }
698 
699   pAuxData = &pVdbeFunc->apAux[iArg];
700   if( pAuxData->pAux && pAuxData->xDelete ){
701     pAuxData->xDelete(pAuxData->pAux);
702   }
703   pAuxData->pAux = pAux;
704   pAuxData->xDelete = xDelete;
705   return;
706 
707 failed:
708   if( xDelete ){
709     xDelete(pAux);
710   }
711 }
712 
713 #ifndef SQLITE_OMIT_DEPRECATED
714 /*
715 ** Return the number of times the Step function of a aggregate has been
716 ** called.
717 **
718 ** This function is deprecated.  Do not use it for new code.  It is
719 ** provide only to avoid breaking legacy code.  New aggregate function
720 ** implementations should keep their own counts within their aggregate
721 ** context.
722 */
723 int sqlite3_aggregate_count(sqlite3_context *p){
724   assert( p && p->pMem && p->pFunc && p->pFunc->xStep );
725   return p->pMem->n;
726 }
727 #endif
728 
729 /*
730 ** Return the number of columns in the result set for the statement pStmt.
731 */
732 int sqlite3_column_count(sqlite3_stmt *pStmt){
733   Vdbe *pVm = (Vdbe *)pStmt;
734   return pVm ? pVm->nResColumn : 0;
735 }
736 
737 /*
738 ** Return the number of values available from the current row of the
739 ** currently executing statement pStmt.
740 */
741 int sqlite3_data_count(sqlite3_stmt *pStmt){
742   Vdbe *pVm = (Vdbe *)pStmt;
743   if( pVm==0 || pVm->pResultSet==0 ) return 0;
744   return pVm->nResColumn;
745 }
746 
747 
748 /*
749 ** Check to see if column iCol of the given statement is valid.  If
750 ** it is, return a pointer to the Mem for the value of that column.
751 ** If iCol is not valid, return a pointer to a Mem which has a value
752 ** of NULL.
753 */
754 static Mem *columnMem(sqlite3_stmt *pStmt, int i){
755   Vdbe *pVm;
756   int vals;
757   Mem *pOut;
758 
759   pVm = (Vdbe *)pStmt;
760   if( pVm && pVm->pResultSet!=0 && i<pVm->nResColumn && i>=0 ){
761     sqlite3_mutex_enter(pVm->db->mutex);
762     vals = sqlite3_data_count(pStmt);
763     pOut = &pVm->pResultSet[i];
764   }else{
765     /* ((double)0) In case of SQLITE_OMIT_FLOATING_POINT... */
766     static const Mem nullMem = {{0}, (double)0, 0, "", 0, MEM_Null, SQLITE_NULL, 0, 0, 0 };
767     if( pVm && ALWAYS(pVm->db) ){
768       sqlite3_mutex_enter(pVm->db->mutex);
769       sqlite3Error(pVm->db, SQLITE_RANGE, 0);
770     }
771     pOut = (Mem*)&nullMem;
772   }
773   return pOut;
774 }
775 
776 /*
777 ** This function is called after invoking an sqlite3_value_XXX function on a
778 ** column value (i.e. a value returned by evaluating an SQL expression in the
779 ** select list of a SELECT statement) that may cause a malloc() failure. If
780 ** malloc() has failed, the threads mallocFailed flag is cleared and the result
781 ** code of statement pStmt set to SQLITE_NOMEM.
782 **
783 ** Specifically, this is called from within:
784 **
785 **     sqlite3_column_int()
786 **     sqlite3_column_int64()
787 **     sqlite3_column_text()
788 **     sqlite3_column_text16()
789 **     sqlite3_column_real()
790 **     sqlite3_column_bytes()
791 **     sqlite3_column_bytes16()
792 **
793 ** But not for sqlite3_column_blob(), which never calls malloc().
794 */
795 static void columnMallocFailure(sqlite3_stmt *pStmt)
796 {
797   /* If malloc() failed during an encoding conversion within an
798   ** sqlite3_column_XXX API, then set the return code of the statement to
799   ** SQLITE_NOMEM. The next call to _step() (if any) will return SQLITE_ERROR
800   ** and _finalize() will return NOMEM.
801   */
802   Vdbe *p = (Vdbe *)pStmt;
803   if( p ){
804     p->rc = sqlite3ApiExit(p->db, p->rc);
805     sqlite3_mutex_leave(p->db->mutex);
806   }
807 }
808 
809 /**************************** sqlite3_column_  *******************************
810 ** The following routines are used to access elements of the current row
811 ** in the result set.
812 */
813 const void *sqlite3_column_blob(sqlite3_stmt *pStmt, int i){
814   const void *val;
815   val = sqlite3_value_blob( columnMem(pStmt,i) );
816   /* Even though there is no encoding conversion, value_blob() might
817   ** need to call malloc() to expand the result of a zeroblob()
818   ** expression.
819   */
820   columnMallocFailure(pStmt);
821   return val;
822 }
823 int sqlite3_column_bytes(sqlite3_stmt *pStmt, int i){
824   int val = sqlite3_value_bytes( columnMem(pStmt,i) );
825   columnMallocFailure(pStmt);
826   return val;
827 }
828 int sqlite3_column_bytes16(sqlite3_stmt *pStmt, int i){
829   int val = sqlite3_value_bytes16( columnMem(pStmt,i) );
830   columnMallocFailure(pStmt);
831   return val;
832 }
833 double sqlite3_column_double(sqlite3_stmt *pStmt, int i){
834   double val = sqlite3_value_double( columnMem(pStmt,i) );
835   columnMallocFailure(pStmt);
836   return val;
837 }
838 int sqlite3_column_int(sqlite3_stmt *pStmt, int i){
839   int val = sqlite3_value_int( columnMem(pStmt,i) );
840   columnMallocFailure(pStmt);
841   return val;
842 }
843 sqlite_int64 sqlite3_column_int64(sqlite3_stmt *pStmt, int i){
844   sqlite_int64 val = sqlite3_value_int64( columnMem(pStmt,i) );
845   columnMallocFailure(pStmt);
846   return val;
847 }
848 const unsigned char *sqlite3_column_text(sqlite3_stmt *pStmt, int i){
849   const unsigned char *val = sqlite3_value_text( columnMem(pStmt,i) );
850   columnMallocFailure(pStmt);
851   return val;
852 }
853 sqlite3_value *sqlite3_column_value(sqlite3_stmt *pStmt, int i){
854   Mem *pOut = columnMem(pStmt, i);
855   if( pOut->flags&MEM_Static ){
856     pOut->flags &= ~MEM_Static;
857     pOut->flags |= MEM_Ephem;
858   }
859   columnMallocFailure(pStmt);
860   return (sqlite3_value *)pOut;
861 }
862 #ifndef SQLITE_OMIT_UTF16
863 const void *sqlite3_column_text16(sqlite3_stmt *pStmt, int i){
864   const void *val = sqlite3_value_text16( columnMem(pStmt,i) );
865   columnMallocFailure(pStmt);
866   return val;
867 }
868 #endif /* SQLITE_OMIT_UTF16 */
869 int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
870   int iType = sqlite3_value_type( columnMem(pStmt,i) );
871   columnMallocFailure(pStmt);
872   return iType;
873 }
874 
875 /* The following function is experimental and subject to change or
876 ** removal */
877 /*int sqlite3_column_numeric_type(sqlite3_stmt *pStmt, int i){
878 **  return sqlite3_value_numeric_type( columnMem(pStmt,i) );
879 **}
880 */
881 
882 /*
883 ** Convert the N-th element of pStmt->pColName[] into a string using
884 ** xFunc() then return that string.  If N is out of range, return 0.
885 **
886 ** There are up to 5 names for each column.  useType determines which
887 ** name is returned.  Here are the names:
888 **
889 **    0      The column name as it should be displayed for output
890 **    1      The datatype name for the column
891 **    2      The name of the database that the column derives from
892 **    3      The name of the table that the column derives from
893 **    4      The name of the table column that the result column derives from
894 **
895 ** If the result is not a simple column reference (if it is an expression
896 ** or a constant) then useTypes 2, 3, and 4 return NULL.
897 */
898 static const void *columnName(
899   sqlite3_stmt *pStmt,
900   int N,
901   const void *(*xFunc)(Mem*),
902   int useType
903 ){
904   const void *ret = 0;
905   Vdbe *p = (Vdbe *)pStmt;
906   int n;
907   sqlite3 *db = p->db;
908 
909   assert( db!=0 );
910   n = sqlite3_column_count(pStmt);
911   if( N<n && N>=0 ){
912     N += useType*n;
913     sqlite3_mutex_enter(db->mutex);
914     assert( db->mallocFailed==0 );
915     ret = xFunc(&p->aColName[N]);
916      /* A malloc may have failed inside of the xFunc() call. If this
917     ** is the case, clear the mallocFailed flag and return NULL.
918     */
919     if( db->mallocFailed ){
920       db->mallocFailed = 0;
921       ret = 0;
922     }
923     sqlite3_mutex_leave(db->mutex);
924   }
925   return ret;
926 }
927 
928 /*
929 ** Return the name of the Nth column of the result set returned by SQL
930 ** statement pStmt.
931 */
932 const char *sqlite3_column_name(sqlite3_stmt *pStmt, int N){
933   return columnName(
934       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_NAME);
935 }
936 #ifndef SQLITE_OMIT_UTF16
937 const void *sqlite3_column_name16(sqlite3_stmt *pStmt, int N){
938   return columnName(
939       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_NAME);
940 }
941 #endif
942 
943 /*
944 ** Constraint:  If you have ENABLE_COLUMN_METADATA then you must
945 ** not define OMIT_DECLTYPE.
946 */
947 #if defined(SQLITE_OMIT_DECLTYPE) && defined(SQLITE_ENABLE_COLUMN_METADATA)
948 # error "Must not define both SQLITE_OMIT_DECLTYPE \
949          and SQLITE_ENABLE_COLUMN_METADATA"
950 #endif
951 
952 #ifndef SQLITE_OMIT_DECLTYPE
953 /*
954 ** Return the column declaration type (if applicable) of the 'i'th column
955 ** of the result set of SQL statement pStmt.
956 */
957 const char *sqlite3_column_decltype(sqlite3_stmt *pStmt, int N){
958   return columnName(
959       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_DECLTYPE);
960 }
961 #ifndef SQLITE_OMIT_UTF16
962 const void *sqlite3_column_decltype16(sqlite3_stmt *pStmt, int N){
963   return columnName(
964       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_DECLTYPE);
965 }
966 #endif /* SQLITE_OMIT_UTF16 */
967 #endif /* SQLITE_OMIT_DECLTYPE */
968 
969 #ifdef SQLITE_ENABLE_COLUMN_METADATA
970 /*
971 ** Return the name of the database from which a result column derives.
972 ** NULL is returned if the result column is an expression or constant or
973 ** anything else which is not an unabiguous reference to a database column.
974 */
975 const char *sqlite3_column_database_name(sqlite3_stmt *pStmt, int N){
976   return columnName(
977       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_DATABASE);
978 }
979 #ifndef SQLITE_OMIT_UTF16
980 const void *sqlite3_column_database_name16(sqlite3_stmt *pStmt, int N){
981   return columnName(
982       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_DATABASE);
983 }
984 #endif /* SQLITE_OMIT_UTF16 */
985 
986 /*
987 ** Return the name of the table from which a result column derives.
988 ** NULL is returned if the result column is an expression or constant or
989 ** anything else which is not an unabiguous reference to a database column.
990 */
991 const char *sqlite3_column_table_name(sqlite3_stmt *pStmt, int N){
992   return columnName(
993       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_TABLE);
994 }
995 #ifndef SQLITE_OMIT_UTF16
996 const void *sqlite3_column_table_name16(sqlite3_stmt *pStmt, int N){
997   return columnName(
998       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_TABLE);
999 }
1000 #endif /* SQLITE_OMIT_UTF16 */
1001 
1002 /*
1003 ** Return the name of the table column from which a result column derives.
1004 ** NULL is returned if the result column is an expression or constant or
1005 ** anything else which is not an unabiguous reference to a database column.
1006 */
1007 const char *sqlite3_column_origin_name(sqlite3_stmt *pStmt, int N){
1008   return columnName(
1009       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text, COLNAME_COLUMN);
1010 }
1011 #ifndef SQLITE_OMIT_UTF16
1012 const void *sqlite3_column_origin_name16(sqlite3_stmt *pStmt, int N){
1013   return columnName(
1014       pStmt, N, (const void*(*)(Mem*))sqlite3_value_text16, COLNAME_COLUMN);
1015 }
1016 #endif /* SQLITE_OMIT_UTF16 */
1017 #endif /* SQLITE_ENABLE_COLUMN_METADATA */
1018 
1019 
1020 /******************************* sqlite3_bind_  ***************************
1021 **
1022 ** Routines used to attach values to wildcards in a compiled SQL statement.
1023 */
1024 /*
1025 ** Unbind the value bound to variable i in virtual machine p. This is the
1026 ** the same as binding a NULL value to the column. If the "i" parameter is
1027 ** out of range, then SQLITE_RANGE is returned. Othewise SQLITE_OK.
1028 **
1029 ** A successful evaluation of this routine acquires the mutex on p.
1030 ** the mutex is released if any kind of error occurs.
1031 **
1032 ** The error code stored in database p->db is overwritten with the return
1033 ** value in any case.
1034 */
1035 static int vdbeUnbind(Vdbe *p, int i){
1036   Mem *pVar;
1037   if( p==0 ) return SQLITE_MISUSE;
1038   sqlite3_mutex_enter(p->db->mutex);
1039   if( p->magic!=VDBE_MAGIC_RUN || p->pc>=0 ){
1040     sqlite3Error(p->db, SQLITE_MISUSE, 0);
1041     sqlite3_mutex_leave(p->db->mutex);
1042     return SQLITE_MISUSE;
1043   }
1044   if( i<1 || i>p->nVar ){
1045     sqlite3Error(p->db, SQLITE_RANGE, 0);
1046     sqlite3_mutex_leave(p->db->mutex);
1047     return SQLITE_RANGE;
1048   }
1049   i--;
1050   pVar = &p->aVar[i];
1051   sqlite3VdbeMemRelease(pVar);
1052   pVar->flags = MEM_Null;
1053   sqlite3Error(p->db, SQLITE_OK, 0);
1054   return SQLITE_OK;
1055 }
1056 
1057 /*
1058 ** Bind a text or BLOB value.
1059 */
1060 static int bindText(
1061   sqlite3_stmt *pStmt,   /* The statement to bind against */
1062   int i,                 /* Index of the parameter to bind */
1063   const void *zData,     /* Pointer to the data to be bound */
1064   int nData,             /* Number of bytes of data to be bound */
1065   void (*xDel)(void*),   /* Destructor for the data */
1066   u8 encoding            /* Encoding for the data */
1067 ){
1068   Vdbe *p = (Vdbe *)pStmt;
1069   Mem *pVar;
1070   int rc;
1071 
1072   rc = vdbeUnbind(p, i);
1073   if( rc==SQLITE_OK ){
1074     if( zData!=0 ){
1075       pVar = &p->aVar[i-1];
1076       rc = sqlite3VdbeMemSetStr(pVar, zData, nData, encoding, xDel);
1077       if( rc==SQLITE_OK && encoding!=0 ){
1078         rc = sqlite3VdbeChangeEncoding(pVar, ENC(p->db));
1079       }
1080       sqlite3Error(p->db, rc, 0);
1081       rc = sqlite3ApiExit(p->db, rc);
1082     }
1083     sqlite3_mutex_leave(p->db->mutex);
1084   }
1085   return rc;
1086 }
1087 
1088 
1089 /*
1090 ** Bind a blob value to an SQL statement variable.
1091 */
1092 int sqlite3_bind_blob(
1093   sqlite3_stmt *pStmt,
1094   int i,
1095   const void *zData,
1096   int nData,
1097   void (*xDel)(void*)
1098 ){
1099   return bindText(pStmt, i, zData, nData, xDel, 0);
1100 }
1101 int sqlite3_bind_double(sqlite3_stmt *pStmt, int i, double rValue){
1102   int rc;
1103   Vdbe *p = (Vdbe *)pStmt;
1104   rc = vdbeUnbind(p, i);
1105   if( rc==SQLITE_OK ){
1106     sqlite3VdbeMemSetDouble(&p->aVar[i-1], rValue);
1107     sqlite3_mutex_leave(p->db->mutex);
1108   }
1109   return rc;
1110 }
1111 int sqlite3_bind_int(sqlite3_stmt *p, int i, int iValue){
1112   return sqlite3_bind_int64(p, i, (i64)iValue);
1113 }
1114 int sqlite3_bind_int64(sqlite3_stmt *pStmt, int i, sqlite_int64 iValue){
1115   int rc;
1116   Vdbe *p = (Vdbe *)pStmt;
1117   rc = vdbeUnbind(p, i);
1118   if( rc==SQLITE_OK ){
1119     sqlite3VdbeMemSetInt64(&p->aVar[i-1], iValue);
1120     sqlite3_mutex_leave(p->db->mutex);
1121   }
1122   return rc;
1123 }
1124 int sqlite3_bind_null(sqlite3_stmt *pStmt, int i){
1125   int rc;
1126   Vdbe *p = (Vdbe*)pStmt;
1127   rc = vdbeUnbind(p, i);
1128   if( rc==SQLITE_OK ){
1129     sqlite3_mutex_leave(p->db->mutex);
1130   }
1131   return rc;
1132 }
1133 int sqlite3_bind_text(
1134   sqlite3_stmt *pStmt,
1135   int i,
1136   const char *zData,
1137   int nData,
1138   void (*xDel)(void*)
1139 ){
1140   return bindText(pStmt, i, zData, nData, xDel, SQLITE_UTF8);
1141 }
1142 #ifndef SQLITE_OMIT_UTF16
1143 int sqlite3_bind_text16(
1144   sqlite3_stmt *pStmt,
1145   int i,
1146   const void *zData,
1147   int nData,
1148   void (*xDel)(void*)
1149 ){
1150   return bindText(pStmt, i, zData, nData, xDel, SQLITE_UTF16NATIVE);
1151 }
1152 #endif /* SQLITE_OMIT_UTF16 */
1153 int sqlite3_bind_value(sqlite3_stmt *pStmt, int i, const sqlite3_value *pValue){
1154   int rc;
1155   switch( pValue->type ){
1156     case SQLITE_INTEGER: {
1157       rc = sqlite3_bind_int64(pStmt, i, pValue->u.i);
1158       break;
1159     }
1160     case SQLITE_FLOAT: {
1161       rc = sqlite3_bind_double(pStmt, i, pValue->r);
1162       break;
1163     }
1164     case SQLITE_BLOB: {
1165       if( pValue->flags & MEM_Zero ){
1166         rc = sqlite3_bind_zeroblob(pStmt, i, pValue->u.nZero);
1167       }else{
1168         rc = sqlite3_bind_blob(pStmt, i, pValue->z, pValue->n,SQLITE_TRANSIENT);
1169       }
1170       break;
1171     }
1172     case SQLITE_TEXT: {
1173       rc = bindText(pStmt,i,  pValue->z, pValue->n, SQLITE_TRANSIENT,
1174                               pValue->enc);
1175       break;
1176     }
1177     default: {
1178       rc = sqlite3_bind_null(pStmt, i);
1179       break;
1180     }
1181   }
1182   return rc;
1183 }
1184 int sqlite3_bind_zeroblob(sqlite3_stmt *pStmt, int i, int n){
1185   int rc;
1186   Vdbe *p = (Vdbe *)pStmt;
1187   rc = vdbeUnbind(p, i);
1188   if( rc==SQLITE_OK ){
1189     sqlite3VdbeMemSetZeroBlob(&p->aVar[i-1], n);
1190     sqlite3_mutex_leave(p->db->mutex);
1191   }
1192   return rc;
1193 }
1194 
1195 /*
1196 ** Return the number of wildcards that can be potentially bound to.
1197 ** This routine is added to support DBD::SQLite.
1198 */
1199 int sqlite3_bind_parameter_count(sqlite3_stmt *pStmt){
1200   Vdbe *p = (Vdbe*)pStmt;
1201   return p ? p->nVar : 0;
1202 }
1203 
1204 /*
1205 ** Create a mapping from variable numbers to variable names
1206 ** in the Vdbe.azVar[] array, if such a mapping does not already
1207 ** exist.
1208 */
1209 static void createVarMap(Vdbe *p){
1210   if( !p->okVar ){
1211     int j;
1212     Op *pOp;
1213     sqlite3_mutex_enter(p->db->mutex);
1214     /* The race condition here is harmless.  If two threads call this
1215     ** routine on the same Vdbe at the same time, they both might end
1216     ** up initializing the Vdbe.azVar[] array.  That is a little extra
1217     ** work but it results in the same answer.
1218     */
1219     for(j=0, pOp=p->aOp; j<p->nOp; j++, pOp++){
1220       if( pOp->opcode==OP_Variable ){
1221         assert( pOp->p1>0 && pOp->p1<=p->nVar );
1222         p->azVar[pOp->p1-1] = pOp->p4.z;
1223       }
1224     }
1225     p->okVar = 1;
1226     sqlite3_mutex_leave(p->db->mutex);
1227   }
1228 }
1229 
1230 /*
1231 ** Return the name of a wildcard parameter.  Return NULL if the index
1232 ** is out of range or if the wildcard is unnamed.
1233 **
1234 ** The result is always UTF-8.
1235 */
1236 const char *sqlite3_bind_parameter_name(sqlite3_stmt *pStmt, int i){
1237   Vdbe *p = (Vdbe*)pStmt;
1238   if( p==0 || i<1 || i>p->nVar ){
1239     return 0;
1240   }
1241   createVarMap(p);
1242   return p->azVar[i-1];
1243 }
1244 
1245 /*
1246 ** Given a wildcard parameter name, return the index of the variable
1247 ** with that name.  If there is no variable with the given name,
1248 ** return 0.
1249 */
1250 int sqlite3_bind_parameter_index(sqlite3_stmt *pStmt, const char *zName){
1251   Vdbe *p = (Vdbe*)pStmt;
1252   int i;
1253   if( p==0 ){
1254     return 0;
1255   }
1256   createVarMap(p);
1257   if( zName ){
1258     for(i=0; i<p->nVar; i++){
1259       const char *z = p->azVar[i];
1260       if( z && strcmp(z,zName)==0 ){
1261         return i+1;
1262       }
1263     }
1264   }
1265   return 0;
1266 }
1267 
1268 /*
1269 ** Transfer all bindings from the first statement over to the second.
1270 */
1271 int sqlite3TransferBindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
1272   Vdbe *pFrom = (Vdbe*)pFromStmt;
1273   Vdbe *pTo = (Vdbe*)pToStmt;
1274   int i;
1275   assert( pTo->db==pFrom->db );
1276   assert( pTo->nVar==pFrom->nVar );
1277   sqlite3_mutex_enter(pTo->db->mutex);
1278   for(i=0; i<pFrom->nVar; i++){
1279     sqlite3VdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
1280   }
1281   sqlite3_mutex_leave(pTo->db->mutex);
1282   return SQLITE_OK;
1283 }
1284 
1285 #ifndef SQLITE_OMIT_DEPRECATED
1286 /*
1287 ** Deprecated external interface.  Internal/core SQLite code
1288 ** should call sqlite3TransferBindings.
1289 **
1290 ** Is is misuse to call this routine with statements from different
1291 ** database connections.  But as this is a deprecated interface, we
1292 ** will not bother to check for that condition.
1293 **
1294 ** If the two statements contain a different number of bindings, then
1295 ** an SQLITE_ERROR is returned.  Nothing else can go wrong, so otherwise
1296 ** SQLITE_OK is returned.
1297 */
1298 int sqlite3_transfer_bindings(sqlite3_stmt *pFromStmt, sqlite3_stmt *pToStmt){
1299   Vdbe *pFrom = (Vdbe*)pFromStmt;
1300   Vdbe *pTo = (Vdbe*)pToStmt;
1301   if( pFrom->nVar!=pTo->nVar ){
1302     return SQLITE_ERROR;
1303   }
1304   return sqlite3TransferBindings(pFromStmt, pToStmt);
1305 }
1306 #endif
1307 
1308 /*
1309 ** Return the sqlite3* database handle to which the prepared statement given
1310 ** in the argument belongs.  This is the same database handle that was
1311 ** the first argument to the sqlite3_prepare() that was used to create
1312 ** the statement in the first place.
1313 */
1314 sqlite3 *sqlite3_db_handle(sqlite3_stmt *pStmt){
1315   return pStmt ? ((Vdbe*)pStmt)->db : 0;
1316 }
1317 
1318 /*
1319 ** Return a pointer to the next prepared statement after pStmt associated
1320 ** with database connection pDb.  If pStmt is NULL, return the first
1321 ** prepared statement for the database connection.  Return NULL if there
1322 ** are no more.
1323 */
1324 sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt){
1325   sqlite3_stmt *pNext;
1326   sqlite3_mutex_enter(pDb->mutex);
1327   if( pStmt==0 ){
1328     pNext = (sqlite3_stmt*)pDb->pVdbe;
1329   }else{
1330     pNext = (sqlite3_stmt*)((Vdbe*)pStmt)->pNext;
1331   }
1332   sqlite3_mutex_leave(pDb->mutex);
1333   return pNext;
1334 }
1335 
1336 /*
1337 ** Return the value of a status counter for a prepared statement
1338 */
1339 int sqlite3_stmt_status(sqlite3_stmt *pStmt, int op, int resetFlag){
1340   Vdbe *pVdbe = (Vdbe*)pStmt;
1341   int v = pVdbe->aCounter[op-1];
1342   if( resetFlag ) pVdbe->aCounter[op-1] = 0;
1343   return v;
1344 }
1345