/*

 ** 2005 May 25

 **

 ** The author disclaims copyright to this source code.  In place of

 ** a legal notice, here is a blessing:

 **

 **    May you do good and not evil.

 **    May you find forgiveness for yourself and forgive others.

 **    May you share freely, never taking more than you give.

 **

 *************************************************************************

 ** This file contains the implementation of the sqlite3_prepare()

 ** interface, and routines that contribute to loading the database schema

 ** from disk.

 **

 ** $Id: prepare.c,v 1.97 2008/09/08 09:06:19 danielk1977 Exp $

 */

 #include "sqliteInt.h"

 #include <ctype.h>

 /*

 ** Fill the InitData structure with an error message that indicates

 ** that the database is corrupt.

 */

 static void corruptSchema(

   InitData *pData,     /* Initialization context */

   const char *zObj,    /* Object being parsed at the point of error */

   const char *zExtra   /* Error information */

 ){

   sqlite3 *db = pData->db;

   if( !db->mallocFailed && (db->flags & SQLITE_RecoveryMode)==0 ){

     if( zObj==0 ) zObj = "?";

     sqlite3SetString(pData->pzErrMsg, pData->db,

        "malformed database schema (%s)", zObj);

     if( zExtra && zExtra[0] ){

       *pData->pzErrMsg = sqlite3MAppendf(pData->db, *pData->pzErrMsg, "%s - %s",

                                   *pData->pzErrMsg, zExtra);

     }

   }

   pData->rc = SQLITE_CORRUPT;

 }

 /*

 ** This is the callback routine for the code that initializes the

 ** database.  See sqlite3Init() below for additional information.

 ** This routine is also called from the OP_ParseSchema opcode of the VDBE.

 **

 ** Each callback contains the following information:

 **

 **     argv[0] = name of thing being created

 **     argv[1] = root page number for table or index. 0 for trigger or view.

 **     argv[2] = SQL text for the CREATE statement.

 **

 */

 int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){

   InitData *pData = (InitData*)pInit;

   sqlite3 *db = pData->db;

   int iDb = pData->iDb;

   assert( sqlite3_mutex_held(db->mutex) );

   DbClearProperty(db, iDb, DB_Empty);

   if( db->mallocFailed ){

     corruptSchema(pData, argv[0], 0);

     return SQLITE_NOMEM;

   }

   assert( argc==3 );

   assert( iDb>=0 && iDb<db->nDb );

   if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */

   if( argv[1]==0 ){

     corruptSchema(pData, argv[0], 0);

   }else if( argv[2] && argv[2][0] ){

     /* Call the parser to process a CREATE TABLE, INDEX or VIEW.

     ** But because db->init.busy is set to 1, no VDBE code is generated

     ** or executed.  All the parser does is build the internal data

     ** structures that describe the table, index, or view.

     */

     char *zErr;

     int rc;

     u8 lookasideEnabled;

     assert( db->init.busy );

     db->init.iDb = iDb;

     db->init.newTnum = atoi(argv[1]);

     lookasideEnabled = db->lookaside.bEnabled;

     db->lookaside.bEnabled = 0;

     rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);

     db->init.iDb = 0;

     db->lookaside.bEnabled = lookasideEnabled;

     assert( rc!=SQLITE_OK || zErr==0 );

     if( SQLITE_OK!=rc ){

       pData->rc = rc;

       if( rc==SQLITE_NOMEM ){

         db->mallocFailed = 1;

       }else if( rc!=SQLITE_INTERRUPT ){

         corruptSchema(pData, argv[0], zErr);

       }

       sqlite3DbFree(db, zErr);

     }

   }else if( argv[0]==0 ){

     corruptSchema(pData, 0, 0);

   }else{

     /* If the SQL column is blank it means this is an index that

     ** was created to be the PRIMARY KEY or to fulfill a UNIQUE

     ** constraint for a CREATE TABLE.  The index should have already

     ** been created when we processed the CREATE TABLE.  All we have

     ** to do here is record the root page number for that index.

     */

     Index *pIndex;

     pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zName);

     if( pIndex==0 || pIndex->tnum!=0 ){

       /* This can occur if there exists an index on a TEMP table which

       ** has the same name as another index on a permanent index.  Since

       ** the permanent table is hidden by the TEMP table, we can also

       ** safely ignore the index on the permanent table.

       */

       /* Do Nothing */;

     }else{

       pIndex->tnum = atoi(argv[1]);

     }

   }

   return 0;

 }

 /*

 ** Attempt to read the database schema and initialize internal

 ** data structures for a single database file.  The index of the

 ** database file is given by iDb.  iDb==0 is used for the main

 ** database.  iDb==1 should never be used.  iDb>=2 is used for

 ** auxiliary databases.  Return one of the SQLITE_ error codes to

 ** indicate success or failure.

 */

 static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){

   int rc;

   BtCursor *curMain;

   int size;

   Table *pTab;

   Db *pDb;

   char const *azArg[4];

   int meta[10];

   InitData initData;

   char const *zMasterSchema;

   char const *zMasterName = SCHEMA_TABLE(iDb);

   /*

   ** The master database table has a structure like this

   */

   static const char master_schema[] = 

      "CREATE TABLE sqlite_master(\n"

      "  type text,\n"

      "  name text,\n"

      "  tbl_name text,\n"

      "  rootpage integer,\n"

      "  sql text\n"

      ")"

   ;

 #ifndef SQLITE_OMIT_TEMPDB

   static const char temp_master_schema[] = 

      "CREATE TEMP TABLE sqlite_temp_master(\n"

      "  type text,\n"

      "  name text,\n"

      "  tbl_name text,\n"

      "  rootpage integer,\n"

      "  sql text\n"

      ")"

   ;

 #else

   #define temp_master_schema 0

 #endif

   assert( iDb>=0 && iDb<db->nDb );

   assert( db->aDb[iDb].pSchema );

   assert( sqlite3_mutex_held(db->mutex) );

   assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );

   /* zMasterSchema and zInitScript are set to point at the master schema

   ** and initialisation script appropriate for the database being

   ** initialised. zMasterName is the name of the master table.

   */

   if( !OMIT_TEMPDB && iDb==1 ){

     zMasterSchema = temp_master_schema;

   }else{

     zMasterSchema = master_schema;

   }

   zMasterName = SCHEMA_TABLE(iDb);

   /* Construct the schema tables.  */

   azArg[0] = zMasterName;

   azArg[1] = "1";

   azArg[2] = zMasterSchema;

   azArg[3] = 0;

   initData.db = db;

   initData.iDb = iDb;

   initData.rc = SQLITE_OK;

   initData.pzErrMsg = pzErrMsg;

   (void)sqlite3SafetyOff(db);

   sqlite3InitCallback(&initData, 3, (char **)azArg, 0);

   (void)sqlite3SafetyOn(db);

   if( initData.rc ){

     rc = initData.rc;

     goto error_out;

   }

   pTab = sqlite3FindTable(db, zMasterName, db->aDb[iDb].zName);

   if( pTab ){

     pTab->tabFlags |= TF_Readonly;

   }

   /* Create a cursor to hold the database open

   */

   pDb = &db->aDb[iDb];

   if( pDb->pBt==0 ){

     if( !OMIT_TEMPDB && iDb==1 ){

       DbSetProperty(db, 1, DB_SchemaLoaded);

     }

     return SQLITE_OK;

   }

   curMain = sqlite3MallocZero(sqlite3BtreeCursorSize());

   if( !curMain ){

     rc = SQLITE_NOMEM;

     goto error_out;

   }

   sqlite3BtreeEnter(pDb->pBt);

   rc = sqlite3BtreeCursor(pDb->pBt, MASTER_ROOT, 0, 0, curMain);

   if( rc!=SQLITE_OK && rc!=SQLITE_EMPTY ){

     sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));

     goto initone_error_out;

   }

   /* Get the database meta information.

   **

   ** Meta values are as follows:

   **    meta[0]   Schema cookie.  Changes with each schema change.

   **    meta[1]   File format of schema layer.

   **    meta[2]   Size of the page cache.

   **    meta[3]   Use freelist if 0.  Autovacuum if greater than zero.

   **    meta[4]   Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE

   **    meta[5]   The user cookie. Used by the application.

   **    meta[6]   Incremental-vacuum flag.

   **    meta[7]

   **    meta[8]

   **    meta[9]

   **

   ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to

   ** the possible values of meta[4].

   */

   if( rc==SQLITE_OK ){

     int i;

     for(i=0; i<sizeof(meta)/sizeof(meta[0]); i++){

       rc = sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);

       if( rc ){

         sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));

         goto initone_error_out;

       }

     }

   }else{

     memset(meta, 0, sizeof(meta));

   }

   pDb->pSchema->schema_cookie = meta[0];

   /* If opening a non-empty database, check the text encoding. For the

   ** main database, set sqlite3.enc to the encoding of the main database.

   ** For an attached db, it is an error if the encoding is not the same

   ** as sqlite3.enc.

   */

   if( meta[4] ){  /* text encoding */

     if( iDb==0 ){

       /* If opening the main database, set ENC(db). */

       ENC(db) = (u8)meta[4];

       db->pDfltColl = sqlite3FindCollSeq(db, SQLITE_UTF8, "BINARY", 6, 0);

     }else{

       /* If opening an attached database, the encoding much match ENC(db) */

       if( meta[4]!=ENC(db) ){

         sqlite3SetString(pzErrMsg, db, "attached databases must use the same"

             " text encoding as main database");

         rc = SQLITE_ERROR;

         goto initone_error_out;

       }

     }

   }else{

     DbSetProperty(db, iDb, DB_Empty);

   }

   pDb->pSchema->enc = ENC(db);

   if( pDb->pSchema->cache_size==0 ){

     size = meta[2];

     if( size==0 ){ size = SQLITE_DEFAULT_CACHE_SIZE; }

     if( size<0 ) size = -size;

     pDb->pSchema->cache_size = size;

     sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);

   }

   /*

   ** file_format==1    Version 3.0.0.

   ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN

   ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults

   ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants

   */

   pDb->pSchema->file_format = meta[1];

   if( pDb->pSchema->file_format==0 ){

     pDb->pSchema->file_format = 1;

   }

   if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){

     sqlite3SetString(pzErrMsg, db, "unsupported file format");

     rc = SQLITE_ERROR;

     goto initone_error_out;

   }

   /* Ticket #2804:  When we open a database in the newer file format,

   ** clear the legacy_file_format pragma flag so that a VACUUM will

   ** not downgrade the database and thus invalidate any descending

   ** indices that the user might have created.

   */

   if( iDb==0 && meta[1]>=4 ){

     db->flags &= ~SQLITE_LegacyFileFmt;

   }

   /* Read the schema information out of the schema tables

   */

   assert( db->init.busy );

   if( rc==SQLITE_EMPTY ){

     /* For an empty database, there is nothing to read */

     rc = SQLITE_OK;

   }else{

     char *zSql;

     zSql = sqlite3MPrintf(db, 

         "SELECT name, rootpage, sql FROM '%q'.%s",

         db->aDb[iDb].zName, zMasterName);

     (void)sqlite3SafetyOff(db);

 #ifndef SQLITE_OMIT_AUTHORIZATION

     {

       int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);

       xAuth = db->xAuth;

       db->xAuth = 0;

 #endif

       rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);

 #ifndef SQLITE_OMIT_AUTHORIZATION

       db->xAuth = xAuth;

     }

 #endif

     if( rc==SQLITE_OK ) rc = initData.rc;

     (void)sqlite3SafetyOn(db);

     sqlite3DbFree(db, zSql);

 #ifndef SQLITE_OMIT_ANALYZE

     if( rc==SQLITE_OK ){

       sqlite3AnalysisLoad(db, iDb);

     }

 #endif

   }

   if( db->mallocFailed ){

     rc = SQLITE_NOMEM;

     sqlite3ResetInternalSchema(db, 0);

   }

   if( rc==SQLITE_OK || (db->flags&SQLITE_RecoveryMode)){

     /* Black magic: If the SQLITE_RecoveryMode flag is set, then consider

     ** the schema loaded, even if errors occured. In this situation the 

     ** current sqlite3_prepare() operation will fail, but the following one

     ** will attempt to compile the supplied statement against whatever subset

     ** of the schema was loaded before the error occured. The primary

     ** purpose of this is to allow access to the sqlite_master table

     ** even when its contents have been corrupted.

     */

     DbSetProperty(db, iDb, DB_SchemaLoaded);

     rc = SQLITE_OK;

   }

   /* Jump here for an error that occurs after successfully allocating

   ** curMain and calling sqlite3BtreeEnter(). For an error that occurs

   ** before that point, jump to error_out.

   */

 initone_error_out:

   sqlite3BtreeCloseCursor(curMain);

   sqlite3_free(curMain);

   sqlite3BtreeLeave(pDb->pBt);

 error_out:

   if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){

     db->mallocFailed = 1;

   }

   return rc;

 }

 /*

 ** Initialize all database files - the main database file, the file

 ** used to store temporary tables, and any additional database files

 ** created using ATTACH statements.  Return a success code.  If an

 ** error occurs, write an error message into *pzErrMsg.

 **

 ** After a database is initialized, the DB_SchemaLoaded bit is set

 ** bit is set in the flags field of the Db structure. If the database

 ** file was of zero-length, then the DB_Empty flag is also set.

 */

 int sqlite3Init(sqlite3 *db, char **pzErrMsg){

   int i, rc;

   int commit_internal = !(db->flags&SQLITE_InternChanges);

   assert( sqlite3_mutex_held(db->mutex) );

   if( db->init.busy ) return SQLITE_OK;

   rc = SQLITE_OK;

   db->init.busy = 1;

   for(i=0; rc==SQLITE_OK && i<db->nDb; i++){

     if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;

     rc = sqlite3InitOne(db, i, pzErrMsg);

     if( rc ){

       sqlite3ResetInternalSchema(db, i);

     }

   }

   /* Once all the other databases have been initialised, load the schema

   ** for the TEMP database. This is loaded last, as the TEMP database

   ** schema may contain references to objects in other databases.

   */

 #ifndef SQLITE_OMIT_TEMPDB

   if( rc==SQLITE_OK && db->nDb>1 && !DbHasProperty(db, 1, DB_SchemaLoaded) ){

     rc = sqlite3InitOne(db, 1, pzErrMsg);

     if( rc ){

       sqlite3ResetInternalSchema(db, 1);

     }

   }

 #endif

   db->init.busy = 0;

   if( rc==SQLITE_OK && commit_internal ){

     sqlite3CommitInternalChanges(db);

   }

   return rc; 

 }

 /*

 ** This routine is a no-op if the database schema is already initialised.

 ** Otherwise, the schema is loaded. An error code is returned.

 */

 int sqlite3ReadSchema(Parse *pParse){

   int rc = SQLITE_OK;

   sqlite3 *db = pParse->db;

   assert( sqlite3_mutex_held(db->mutex) );

   if( !db->init.busy ){

     rc = sqlite3Init(db, &pParse->zErrMsg);

   }

   if( rc!=SQLITE_OK ){

     pParse->rc = rc;

     pParse->nErr++;

   }

   return rc;

 }

 /*

 ** Check schema cookies in all databases.  If any cookie is out

 ** of date, return 0.  If all schema cookies are current, return 1.

 */

 static int schemaIsValid(sqlite3 *db){

   int iDb;

   int rc;

   BtCursor *curTemp;

   int cookie;

   int allOk = 1;

   curTemp = (BtCursor *)sqlite3Malloc(sqlite3BtreeCursorSize());

   if( curTemp ){

     assert( sqlite3_mutex_held(db->mutex) );

     for(iDb=0; allOk && iDb<db->nDb; iDb++){

       Btree *pBt;

       pBt = db->aDb[iDb].pBt;

       if( pBt==0 ) continue;

       memset(curTemp, 0, sqlite3BtreeCursorSize());

       rc = sqlite3BtreeCursor(pBt, MASTER_ROOT, 0, 0, curTemp);

       if( rc==SQLITE_OK ){

         rc = sqlite3BtreeGetMeta(pBt, 1, (u32 *)&cookie);

         if( rc==SQLITE_OK && cookie!=db->aDb[iDb].pSchema->schema_cookie ){

           allOk = 0;

         }

         sqlite3BtreeCloseCursor(curTemp);

       }

       if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){

         db->mallocFailed = 1;

       }

     }

     sqlite3_free(curTemp);

   }else{

     allOk = 0;

     db->mallocFailed = 1;

   }

   return allOk;

 }

 /*

 ** Convert a schema pointer into the iDb index that indicates

 ** which database file in db->aDb[] the schema refers to.

 **

 ** If the same database is attached more than once, the first

 ** attached database is returned.

 */

 int sqlite3SchemaToIndex(sqlite3 *db, Schema *pSchema){

   int i = -1000000;

   /* If pSchema is NULL, then return -1000000. This happens when code in 

   ** expr.c is trying to resolve a reference to a transient table (i.e. one

   ** created by a sub-select). In this case the return value of this 

   ** function should never be used.

   **

   ** We return -1000000 instead of the more usual -1 simply because using

   ** -1000000 as incorrectly using -1000000 index into db->aDb[] is much 

   ** more likely to cause a segfault than -1 (of course there are assert()

   ** statements too, but it never hurts to play the odds).

   */

   assert( sqlite3_mutex_held(db->mutex) );

   if( pSchema ){

     for(i=0; i<db->nDb; i++){

       if( db->aDb[i].pSchema==pSchema ){

         break;

       }

     }

     assert( i>=0 &&i>=0 &&  i<db->nDb );

   }

   return i;

 }

 /*

 ** Compile the UTF-8 encoded SQL statement zSql into a statement handle.

 */

 static int sqlite3Prepare(

   sqlite3 *db,              /* Database handle. */

   const char *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const char **pzTail       /* OUT: End of parsed string */

 ){

   Parse sParse;

   char *zErrMsg = 0;

   int rc = SQLITE_OK;

   int i;

   assert( ppStmt );

   *ppStmt = 0;

   if( sqlite3SafetyOn(db) ){

     return SQLITE_MISUSE;

   }

   assert( !db->mallocFailed );

   assert( sqlite3_mutex_held(db->mutex) );

   /* If any attached database schemas are locked, do not proceed with

   ** compilation. Instead return SQLITE_LOCKED immediately.

   */

   for(i=0; i<db->nDb; i++) {

     Btree *pBt = db->aDb[i].pBt;

     if( pBt ){

       int rc;

       rc = sqlite3BtreeSchemaLocked(pBt);

       if( rc ){

         const char *zDb = db->aDb[i].zName;

         sqlite3Error(db, SQLITE_LOCKED, "database schema is locked: %s", zDb);

         (void)sqlite3SafetyOff(db);

         return sqlite3ApiExit(db, SQLITE_LOCKED);

       }

     }

   }

   memset(&sParse, 0, sizeof(sParse));

   sParse.db = db;

   if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){

     char *zSqlCopy;

     int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];

     if( nBytes>mxLen ){

       sqlite3Error(db, SQLITE_TOOBIG, "statement too long");

       (void)sqlite3SafetyOff(db);

       return sqlite3ApiExit(db, SQLITE_TOOBIG);

     }

     zSqlCopy = sqlite3DbStrNDup(db, zSql, nBytes);

     if( zSqlCopy ){

       sqlite3RunParser(&sParse, zSqlCopy, &zErrMsg);

       sqlite3DbFree(db, zSqlCopy);

       sParse.zTail = &zSql[sParse.zTail-zSqlCopy];

     }else{

       sParse.zTail = &zSql[nBytes];

     }

   }else{

     sqlite3RunParser(&sParse, zSql, &zErrMsg);

   }

   if( db->mallocFailed ){

     sParse.rc = SQLITE_NOMEM;

   }

   if( sParse.rc==SQLITE_DONE ) sParse.rc = SQLITE_OK;

   if( sParse.checkSchema && !schemaIsValid(db) ){

     sParse.rc = SQLITE_SCHEMA;

   }

   if( sParse.rc==SQLITE_SCHEMA ){

     sqlite3ResetInternalSchema(db, 0);

   }

   if( db->mallocFailed ){

     sParse.rc = SQLITE_NOMEM;

   }

   if( pzTail ){

     *pzTail = sParse.zTail;

   }

   rc = sParse.rc;

 #ifndef SQLITE_OMIT_EXPLAIN

   if( rc==SQLITE_OK && sParse.pVdbe && sParse.explain ){

     if( sParse.explain==2 ){

       sqlite3VdbeSetNumCols(sParse.pVdbe, 3);

       sqlite3VdbeSetColName(sParse.pVdbe, 0, COLNAME_NAME, "order", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 1, COLNAME_NAME, "from", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 2, COLNAME_NAME, "detail", P4_STATIC);

     }else{

       sqlite3VdbeSetNumCols(sParse.pVdbe, 8);

       sqlite3VdbeSetColName(sParse.pVdbe, 0, COLNAME_NAME, "addr", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 1, COLNAME_NAME, "opcode", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 2, COLNAME_NAME, "p1", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 3, COLNAME_NAME, "p2", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 4, COLNAME_NAME, "p3", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 5, COLNAME_NAME, "p4", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 6, COLNAME_NAME, "p5", P4_STATIC);

       sqlite3VdbeSetColName(sParse.pVdbe, 7, COLNAME_NAME, "comment",P4_STATIC);

     }

   }

 #endif

   if( sqlite3SafetyOff(db) ){

     rc = SQLITE_MISUSE;

   }

   if( saveSqlFlag ){

     sqlite3VdbeSetSql(sParse.pVdbe, zSql, sParse.zTail - zSql);

   }

   if( rc!=SQLITE_OK || db->mallocFailed ){

     sqlite3_finalize((sqlite3_stmt*)sParse.pVdbe);

     assert(!(*ppStmt));

   }else{

     *ppStmt = (sqlite3_stmt*)sParse.pVdbe;

   }

   if( zErrMsg ){

     sqlite3Error(db, rc, "%s", zErrMsg);

     sqlite3DbFree(db, zErrMsg);

   }else{

     sqlite3Error(db, rc, 0);

   }

   rc = sqlite3ApiExit(db, rc);

   assert( (rc&db->errMask)==rc );

   return rc;

 }

 static int sqlite3LockAndPrepare(

   sqlite3 *db,              /* Database handle. */

   const char *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   int saveSqlFlag,          /* True to copy SQL text into the sqlite3_stmt */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const char **pzTail       /* OUT: End of parsed string */

 ){

   int rc;

   if( !sqlite3SafetyCheckOk(db) ){

     return SQLITE_MISUSE;

   }

   sqlite3_mutex_enter(db->mutex);

   sqlite3BtreeEnterAll(db);

   rc = sqlite3Prepare(db, zSql, nBytes, saveSqlFlag, ppStmt, pzTail);

   sqlite3BtreeLeaveAll(db);

   sqlite3_mutex_leave(db->mutex);

   return rc;

 }

 /*

 ** Rerun the compilation of a statement after a schema change.

 ** Return true if the statement was recompiled successfully.

 ** Return false if there is an error of some kind.

 */

 int sqlite3Reprepare(Vdbe *p){

   int rc;

   sqlite3_stmt *pNew;

   const char *zSql;

   sqlite3 *db;

   assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );

   zSql = sqlite3_sql((sqlite3_stmt *)p);

   assert( zSql!=0 );  /* Reprepare only called for prepare_v2() statements */

   db = sqlite3VdbeDb(p);

   assert( sqlite3_mutex_held(db->mutex) );

   rc = sqlite3LockAndPrepare(db, zSql, -1, 0, &pNew, 0);

   if( rc ){

     if( rc==SQLITE_NOMEM ){

       db->mallocFailed = 1;

     }

     assert( pNew==0 );

     return 0;

   }else{

     assert( pNew!=0 );

   }

   sqlite3VdbeSwap((Vdbe*)pNew, p);

   sqlite3TransferBindings(pNew, (sqlite3_stmt*)p);

   sqlite3VdbeResetStepResult((Vdbe*)pNew);

   sqlite3VdbeFinalize((Vdbe*)pNew);

   return 1;

 }

 /*

 ** Two versions of the official API.  Legacy and new use.  In the legacy

 ** version, the original SQL text is not saved in the prepared statement

 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by

 ** sqlite3_step().  In the new version, the original SQL text is retained

 ** and the statement is automatically recompiled if an schema change

 ** occurs.

 */

 int sqlite3_prepare(

   sqlite3 *db,              /* Database handle. */

   const char *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const char **pzTail       /* OUT: End of parsed string */

 ){

   int rc;

   rc = sqlite3LockAndPrepare(db,zSql,nBytes,0,ppStmt,pzTail);

   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */

   return rc;

 }

 int sqlite3_prepare_v2(

   sqlite3 *db,              /* Database handle. */

   const char *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const char **pzTail       /* OUT: End of parsed string */

 ){

   int rc;

   rc = sqlite3LockAndPrepare(db,zSql,nBytes,1,ppStmt,pzTail);

   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */

   return rc;

 }

 #ifndef SQLITE_OMIT_UTF16

 /*

 ** Compile the UTF-16 encoded SQL statement zSql into a statement handle.

 */

 static int sqlite3Prepare16(

   sqlite3 *db,              /* Database handle. */ 

   const void *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   int saveSqlFlag,          /* True to save SQL text into the sqlite3_stmt */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const void **pzTail       /* OUT: End of parsed string */

 ){

   /* This function currently works by first transforming the UTF-16

   ** encoded string to UTF-8, then invoking sqlite3_prepare(). The

   ** tricky bit is figuring out the pointer to return in *pzTail.

   */

   char *zSql8;

   const char *zTail8 = 0;

   int rc = SQLITE_OK;

   if( !sqlite3SafetyCheckOk(db) ){

     return SQLITE_MISUSE;

   }

   sqlite3_mutex_enter(db->mutex);

   zSql8 = sqlite3Utf16to8(db, zSql, nBytes);

   if( zSql8 ){

     rc = sqlite3LockAndPrepare(db, zSql8, -1, saveSqlFlag, ppStmt, &zTail8);

   }

   if( zTail8 && pzTail ){

     /* If sqlite3_prepare returns a tail pointer, we calculate the

     ** equivalent pointer into the UTF-16 string by counting the unicode

     ** characters between zSql8 and zTail8, and then returning a pointer

     ** the same number of characters into the UTF-16 string.

     */

     int chars_parsed = sqlite3Utf8CharLen(zSql8, zTail8-zSql8);

     *pzTail = (u8 *)zSql + sqlite3Utf16ByteLen(zSql, chars_parsed);

   }

   sqlite3DbFree(db, zSql8); 

   rc = sqlite3ApiExit(db, rc);

   sqlite3_mutex_leave(db->mutex);

   return rc;

 }

 /*

 ** Two versions of the official API.  Legacy and new use.  In the legacy

 ** version, the original SQL text is not saved in the prepared statement

 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by

 ** sqlite3_step().  In the new version, the original SQL text is retained

 ** and the statement is automatically recompiled if an schema change

 ** occurs.

 */

 int sqlite3_prepare16(

   sqlite3 *db,              /* Database handle. */ 

   const void *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const void **pzTail       /* OUT: End of parsed string */

 ){

   int rc;

   rc = sqlite3Prepare16(db,zSql,nBytes,0,ppStmt,pzTail);

   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */

   return rc;

 }

 int sqlite3_prepare16_v2(

   sqlite3 *db,              /* Database handle. */ 

   const void *zSql,         /* UTF-8 encoded SQL statement. */

   int nBytes,               /* Length of zSql in bytes. */

   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */

   const void **pzTail       /* OUT: End of parsed string */

 ){

   int rc;

   rc = sqlite3Prepare16(db,zSql,nBytes,1,ppStmt,pzTail);

   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */

   return rc;

 }

 #endif /* SQLITE_OMIT_UTF16 */