/*+
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** 2005 May 23 +
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**+
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** The author disclaims copyright to this source code.  In place of+
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** a legal notice, here is a blessing:+
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**+
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**    May you do good and not evil.+
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**    May you find forgiveness for yourself and forgive others.+
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**    May you share freely, never taking more than you give.+
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**+
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*************************************************************************+
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**+
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** This file contains functions used to access the internal hash tables+
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** of user defined functions and collation sequences.+
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**+
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** $Id: callback.cpp 1282 2008-11-13 09:31:33Z LarsPson $+
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*/+
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+
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#include "sqliteInt.h"+
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+
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/*+
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** Invoke the 'collation needed' callback to request a collation sequence+
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** in the database text encoding of name zName, length nName.+
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** If the collation sequence+
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*/+
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static void callCollNeeded(sqlite3 *db, const char *zName, int nName){+
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  assert( !db->xCollNeeded || !db->xCollNeeded16 );+
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  if( nName<0 ) nName = strlen(zName);+
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  if( db->xCollNeeded ){+
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    char *zExternal = sqlite3DbStrNDup(db, zName, nName);+
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    if( !zExternal ) return;+
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    db->xCollNeeded(db->pCollNeededArg, db, (int)ENC(db), zExternal);+
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    sqlite3_free(zExternal);+
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  }+
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#ifndef SQLITE_OMIT_UTF16+
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  if( db->xCollNeeded16 ){+
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    char const *zExternal;+
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    sqlite3_value *pTmp = sqlite3ValueNew(db);+
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    sqlite3ValueSetStr(pTmp, nName, zName, SQLITE_UTF8, SQLITE_STATIC);+
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    zExternal = (const char*)sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);+
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    if( zExternal ){+
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      db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);+
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    }+
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    sqlite3ValueFree(pTmp);+
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  }+
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#endif+
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}+
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+
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/*+
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** This routine is called if the collation factory fails to deliver a+
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** collation function in the best encoding but there may be other versions+
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** of this collation function (for other text encodings) available. Use one+
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** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if+
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** possible.+
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*/+
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static int synthCollSeq(sqlite3 *db, CollSeq *pColl){+
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  CollSeq *pColl2;+
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  char *z = pColl->zName;+
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  int n = strlen(z);+
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  int i;+
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  static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };+
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  for(i=0; i<3; i++){+
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    pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, n, 0);+
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    if( pColl2->xCmp!=0 ){+
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      memcpy(pColl, pColl2, sizeof(CollSeq));+
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      pColl->xDel = 0;         /* Do not copy the destructor */+
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      return SQLITE_OK;+
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    }+
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  }+
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  return SQLITE_ERROR;+
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}+
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+
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/*+
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** This function is responsible for invoking the collation factory callback+
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** or substituting a collation sequence of a different encoding when the+
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** requested collation sequence is not available in the database native+
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** encoding.+
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** +
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** If it is not NULL, then pColl must point to the database native encoding +
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** collation sequence with name zName, length nName.+
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**+
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** The return value is either the collation sequence to be used in database+
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** db for collation type name zName, length nName, or NULL, if no collation+
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** sequence can be found.+
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*/+
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CollSeq *sqlite3GetCollSeq(+
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  sqlite3* db, +
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  CollSeq *pColl, +
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  const char *zName, +
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  int nName+
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){+
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  CollSeq *p;+
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+
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  p = pColl;+
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  if( !p ){+
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    p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);+
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  }+
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  if( !p || !p->xCmp ){+
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    /* No collation sequence of this type for this encoding is registered.+
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    ** Call the collation factory to see if it can supply us with one.+
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    */+
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    callCollNeeded(db, zName, nName);+
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    p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);+
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  }+
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  if( p && !p->xCmp && synthCollSeq(db, p) ){+
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    p = 0;+
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  }+
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  assert( !p || p->xCmp );+
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  return p;+
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}+
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+
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/*+
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** This routine is called on a collation sequence before it is used to+
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** check that it is defined. An undefined collation sequence exists when+
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** a database is loaded that contains references to collation sequences+
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** that have not been defined by sqlite3_create_collation() etc.+
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**+
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** If required, this routine calls the 'collation needed' callback to+
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** request a definition of the collating sequence. If this doesn't work, +
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** an equivalent collating sequence that uses a text encoding different+
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** from the main database is substituted, if one is available.+
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*/+
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int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){+
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  if( pColl ){+
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    const char *zName = pColl->zName;+
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    CollSeq *p = sqlite3GetCollSeq(pParse->db, pColl, zName, -1);+
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    if( !p ){+
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      if( pParse->nErr==0 ){+
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        sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);+
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      }+
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      pParse->nErr++;+
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      return SQLITE_ERROR;+
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    }+
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    assert( p==pColl );+
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  }+
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  return SQLITE_OK;+
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}+
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+
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+
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+
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/*+
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** Locate and return an entry from the db.aCollSeq hash table. If the entry+
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** specified by zName and nName is not found and parameter 'create' is+
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** true, then create a new entry. Otherwise return NULL.+
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**+
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** Each pointer stored in the sqlite3.aCollSeq hash table contains an+
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** array of three CollSeq structures. The first is the collation sequence+
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** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.+
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**+
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** Stored immediately after the three collation sequences is a copy of+
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** the collation sequence name. A pointer to this string is stored in+
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** each collation sequence structure.+
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*/+
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static CollSeq *findCollSeqEntry(+
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  sqlite3 *db,+
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  const char *zName,+
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  int nName,+
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  int create+
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){+
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  CollSeq *pColl;+
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  if( nName<0 ) nName = strlen(zName);+
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  pColl = (CollSeq*)sqlite3HashFind(&db->aCollSeq, zName, nName);+
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+
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  if( 0==pColl && create ){+
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    pColl = (CollSeq*)sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName + 1 );+
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    if( pColl ){+
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      CollSeq *pDel = 0;+
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      pColl[0].zName = (char*)&pColl[3];+
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      pColl[0].enc = SQLITE_UTF8;+
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      pColl[1].zName = (char*)&pColl[3];+
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      pColl[1].enc = SQLITE_UTF16LE;+
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      pColl[2].zName = (char*)&pColl[3];+
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      pColl[2].enc = SQLITE_UTF16BE;+
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      memcpy(pColl[0].zName, zName, nName);+
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      pColl[0].zName[nName] = 0;+
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      pDel = (CollSeq*)sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);+
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+
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      /* If a malloc() failure occured in sqlite3HashInsert(), it will +
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      ** return the pColl pointer to be deleted (because it wasn't added+
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      ** to the hash table).+
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      */+
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      assert( pDel==0 || pDel==pColl );+
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      if( pDel!=0 ){+
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        db->mallocFailed = 1;+
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        sqlite3_free(pDel);+
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        pColl = 0;+
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      }+
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    }+
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  }+
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  return pColl;+
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}+
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+
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/*+
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** Parameter zName points to a UTF-8 encoded string nName bytes long.+
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** Return the CollSeq* pointer for the collation sequence named zName+
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** for the encoding 'enc' from the database 'db'.+
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**+
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** If the entry specified is not found and 'create' is true, then create a+
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** new entry.  Otherwise return NULL.+
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**+
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** A separate function sqlite3LocateCollSeq() is a wrapper around+
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** this routine.  sqlite3LocateCollSeq() invokes the collation factory+
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** if necessary and generates an error message if the collating sequence+
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** cannot be found.+
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*/+
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CollSeq *sqlite3FindCollSeq(+
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  sqlite3 *db,+
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  u8 enc,+
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  const char *zName,+
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  int nName,+
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  int create+
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){+
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  CollSeq *pColl;+
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  if( zName ){+
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    pColl = findCollSeqEntry(db, zName, nName, create);+
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  }else{+
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    pColl = db->pDfltColl;+
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  }+
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  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );+
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  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );+
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  if( pColl ) pColl += enc-1;+
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  return pColl;+
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}+
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+
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/*+
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** Locate a user function given a name, a number of arguments and a flag+
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** indicating whether the function prefers UTF-16 over UTF-8.  Return a+
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** pointer to the FuncDef structure that defines that function, or return+
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** NULL if the function does not exist.+
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**+
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** If the createFlag argument is true, then a new (blank) FuncDef+
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** structure is created and liked into the "db" structure if a+
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** no matching function previously existed.  When createFlag is true+
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** and the nArg parameter is -1, then only a function that accepts+
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** any number of arguments will be returned.+
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**+
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** If createFlag is false and nArg is -1, then the first valid+
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** function found is returned.  A function is valid if either xFunc+
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** or xStep is non-zero.+
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**+
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** If createFlag is false, then a function with the required name and+
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** number of arguments may be returned even if the eTextRep flag does not+
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** match that requested.+
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*/+
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FuncDef *sqlite3FindFunction(+
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  sqlite3 *db,       /* An open database */+
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  const char *zName, /* Name of the function.  Not null-terminated */+
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  int nName,         /* Number of characters in the name */+
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  int nArg,          /* Number of arguments.  -1 means any number */+
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  u8 enc,            /* Preferred text encoding */+
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  int createFlag     /* Create new entry if true and does not otherwise exist */+
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){+
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  FuncDef *p;         /* Iterator variable */+
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  FuncDef *pFirst;    /* First function with this name */+
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  FuncDef *pBest = 0; /* Best match found so far */+
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  int bestmatch = 0;  +
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+
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+
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  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );+
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  if( nArg<-1 ) nArg = -1;+
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+
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  pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);+
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  for(p=pFirst; p; p=p->pNext){+
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    /* During the search for the best function definition, bestmatch is set+
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    ** as follows to indicate the quality of the match with the definition+
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    ** pointed to by pBest:+
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    **+
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    ** 0: pBest is NULL. No match has been found.+
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    ** 1: A variable arguments function that prefers UTF-8 when a UTF-16+
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    **    encoding is requested, or vice versa.+
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    ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is+
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    **    requested, or vice versa.+
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    ** 3: A variable arguments function using the same text encoding.+
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    ** 4: A function with the exact number of arguments requested that+
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    **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.+
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    ** 5: A function with the exact number of arguments requested that+
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    **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.+
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    ** 6: An exact match.+
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    **+
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    ** A larger value of 'matchqual' indicates a more desirable match.+
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    */+
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    if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){+
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      int match = 1;          /* Quality of this match */+
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      if( p->nArg==nArg || nArg==-1 ){+
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        match = 4;+
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      }+
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      if( enc==p->iPrefEnc ){+
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        match += 2;+
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      }+
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      else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||+
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               (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){+
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        match += 1;+
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      }+
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+
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      if( match>bestmatch ){+
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        pBest = p;+
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        bestmatch = match;+
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      }+
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    }+
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  }+
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+
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  /* If the createFlag parameter is true, and the seach did not reveal an+
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  ** exact match for the name, number of arguments and encoding, then add a+
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  ** new entry to the hash table and return it.+
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  */+
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  if( createFlag && bestmatch<6 && +
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      (pBest = (FuncDef*)sqlite3DbMallocZero(db, sizeof(*pBest)+nName))!=0 ){+
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    pBest->nArg = nArg;+
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    pBest->pNext = pFirst;+
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    pBest->iPrefEnc = enc;+
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    memcpy(pBest->zName, zName, nName);+
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    pBest->zName[nName] = 0;+
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    if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){+
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      db->mallocFailed = 1;+
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      sqlite3_free(pBest);+
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      return 0;+
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    }+
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  }+
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+
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  if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){+
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    return pBest;+
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  }+
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  return 0;+
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}+
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+
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/*+
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** Free all resources held by the schema structure. The void* argument points+
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** at a Schema struct. This function does not call sqlite3_free() on the +
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** pointer itself, it just cleans up subsiduary resources (i.e. the contents+
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** of the schema hash tables).+
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*/+
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void sqlite3SchemaFree(void *p){+
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  Hash temp1;+
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  Hash temp2;+
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  HashElem *pElem;+
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  Schema *pSchema = (Schema *)p;+
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+
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  temp1 = pSchema->tblHash;+
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  temp2 = pSchema->trigHash;+
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  sqlite3HashInit(&pSchema->trigHash, SQLITE_HASH_STRING, 0);+
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  sqlite3HashClear(&pSchema->aFKey);+
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  sqlite3HashClear(&pSchema->idxHash);+
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  for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){+
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    sqlite3DeleteTrigger((Trigger*)sqliteHashData(pElem));+
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  }+
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  sqlite3HashClear(&temp2);+
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  sqlite3HashInit(&pSchema->tblHash, SQLITE_HASH_STRING, 0);+
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  for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){+
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    Table *pTab = (Table*)sqliteHashData(pElem);+
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    sqlite3DeleteTable(pTab);+
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  }+
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  sqlite3HashClear(&temp1);+
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  pSchema->pSeqTab = 0;+
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  pSchema->flags &= ~DB_SchemaLoaded;+
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}+
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+
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/*+
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** Find and return the schema associated with a BTree.  Create+
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** a new one if necessary.+
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*/+
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Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){+
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  Schema * p;+
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  if( pBt ){+
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    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaFree);+
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  }else{+
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    p = (Schema *)sqlite3MallocZero(sizeof(Schema));+
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  }+
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  if( !p ){+
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    db->mallocFailed = 1;+
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  }else if ( 0==p->file_format ){+
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    sqlite3HashInit(&p->tblHash, SQLITE_HASH_STRING, 0);+
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    sqlite3HashInit(&p->idxHash, SQLITE_HASH_STRING, 0);+
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    sqlite3HashInit(&p->trigHash, SQLITE_HASH_STRING, 0);+
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    sqlite3HashInit(&p->aFKey, SQLITE_HASH_STRING, 1);+
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    p->enc = SQLITE_UTF8;+
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  }+
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  return p;+
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}+
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