/*** 2005 May 23 **** 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 functions used to access the internal hash tables** of user defined functions and collation sequences.**** $Id: callback.c,v 1.3 2005/08/14 01:20:38 drh Exp $*/#include "sqliteInt.h"/*** Invoke the 'collation needed' callback to request a collation sequence** in the database text encoding of name zName, length nName.** If the collation sequence*/static void callCollNeeded(sqlite3 *db, const char *zName, int nName){  assert( !db->xCollNeeded || !db->xCollNeeded16 );  if( nName<0 ) nName = strlen(zName);  if( db->xCollNeeded ){    char *zExternal = sqliteStrNDup(zName, nName);    if( !zExternal ) return;    db->xCollNeeded(db->pCollNeededArg, db, (int)db->enc, zExternal);    sqliteFree(zExternal);  }#ifndef SQLITE_OMIT_UTF16  if( db->xCollNeeded16 ){    char const *zExternal;    sqlite3_value *pTmp = sqlite3GetTransientValue(db);    sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);    zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);    if( !zExternal ) return;    db->xCollNeeded16(db->pCollNeededArg, db, (int)db->enc, zExternal);  }#endif}/*** This routine is called if the collation factory fails to deliver a** collation function in the best encoding but there may be other versions** of this collation function (for other text encodings) available. Use one** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if** possible.*/static int synthCollSeq(sqlite3 *db, CollSeq *pColl){  CollSeq *pColl2;  char *z = pColl->zName;  int n = strlen(z);  int i;  static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };  for(i=0; i<3; i++){    pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, n, 0);    if( pColl2->xCmp!=0 ){      memcpy(pColl, pColl2, sizeof(CollSeq));      return SQLITE_OK;    }  }  return SQLITE_ERROR;}/*** This function is responsible for invoking the collation factory callback** or substituting a collation sequence of a different encoding when the** requested collation sequence is not available in the database native** encoding.** ** If it is not NULL, then pColl must point to the database native encoding ** collation sequence with name zName, length nName.**** The return value is either the collation sequence to be used in database** db for collation type name zName, length nName, or NULL, if no collation** sequence can be found.*/CollSeq *sqlite3GetCollSeq(  sqlite3* db,   CollSeq *pColl,   const char *zName,   int nName){  CollSeq *p;  p = pColl;  if( !p ){    p = sqlite3FindCollSeq(db, db->enc, zName, nName, 0);  }  if( !p || !p->xCmp ){    /* No collation sequence of this type for this encoding is registered.    ** Call the collation factory to see if it can supply us with one.    */    callCollNeeded(db, zName, nName);    p = sqlite3FindCollSeq(db, db->enc, zName, nName, 0);  }  if( p && !p->xCmp && synthCollSeq(db, p) ){    p = 0;  }  assert( !p || p->xCmp );  return p;}/*** This routine is called on a collation sequence before it is used to** check that it is defined. An undefined collation sequence exists when** a database is loaded that contains references to collation sequences** that have not been defined by sqlite3_create_collation() etc.**** If required, this routine calls the 'collation needed' callback to** request a definition of the collating sequence. If this doesn't work, ** an equivalent collating sequence that uses a text encoding different** from the main database is substituted, if one is available.*/int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){  if( pColl ){    const char *zName = pColl->zName;    CollSeq *p = sqlite3GetCollSeq(pParse->db, pColl, zName, -1);    if( !p ){      if( pParse->nErr==0 ){        sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);      }      pParse->nErr++;      return SQLITE_ERROR;    }  }  return SQLITE_OK;}/*** Locate and return an entry from the db.aCollSeq hash table. If the entry** specified by zName and nName is not found and parameter 'create' is** true, then create a new entry. Otherwise return NULL.**** Each pointer stored in the sqlite3.aCollSeq hash table contains an** array of three CollSeq structures. The first is the collation sequence** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.**** Stored immediately after the three collation sequences is a copy of** the collation sequence name. A pointer to this string is stored in** each collation sequence structure.*/static CollSeq *findCollSeqEntry(  sqlite3 *db,  const char *zName,  int nName,  int create){  CollSeq *pColl;  if( nName<0 ) nName = strlen(zName);  pColl = sqlite3HashFind(&db->aCollSeq, zName, nName);  if( 0==pColl && create ){    pColl = sqliteMalloc( 3*sizeof(*pColl) + nName + 1 );    if( pColl ){      CollSeq *pDel = 0;      pColl[0].zName = (char*)&pColl[3];      pColl[0].enc = SQLITE_UTF8;      pColl[1].zName = (char*)&pColl[3];      pColl[1].enc = SQLITE_UTF16LE;      pColl[2].zName = (char*)&pColl[3];      pColl[2].enc = SQLITE_UTF16BE;      memcpy(pColl[0].zName, zName, nName);      pColl[0].zName[nName] = 0;      pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);      /* If a malloc() failure occured in sqlite3HashInsert(), it will       ** return the pColl pointer to be deleted (because it wasn't added      ** to the hash table).      */      assert( !pDel || (sqlite3_malloc_failed && pDel==pColl) );      sqliteFree(pDel);    }  }  return pColl;}/*** Parameter zName points to a UTF-8 encoded string nName bytes long.** Return the CollSeq* pointer for the collation sequence named zName** for the encoding 'enc' from the database 'db'.**** If the entry specified is not found and 'create' is true, then create a** new entry.  Otherwise return NULL.*/CollSeq *sqlite3FindCollSeq(  sqlite3 *db,  u8 enc,  const char *zName,  int nName,  int create){  CollSeq *pColl = findCollSeqEntry(db, zName, nName, create);  assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );  assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );  if( pColl ) pColl += enc-1;  return pColl;}/*** Locate a user function given a name, a number of arguments and a flag** indicating whether the function prefers UTF-16 over UTF-8.  Return a** pointer to the FuncDef structure that defines that function, or return** NULL if the function does not exist.**** If the createFlag argument is true, then a new (blank) FuncDef** structure is created and liked into the "db" structure if a** no matching function previously existed.  When createFlag is true** and the nArg parameter is -1, then only a function that accepts** any number of arguments will be returned.**** If createFlag is false and nArg is -1, then the first valid** function found is returned.  A function is valid if either xFunc** or xStep is non-zero.**** If createFlag is false, then a function with the required name and** number of arguments may be returned even if the eTextRep flag does not** match that requested.*/FuncDef *sqlite3FindFunction(  sqlite3 *db,       /* An open database */  const char *zName, /* Name of the function.  Not null-terminated */  int nName,         /* Number of characters in the name */  int nArg,          /* Number of arguments.  -1 means any number */  u8 enc,            /* Preferred text encoding */  int createFlag     /* Create new entry if true and does not otherwise exist */){  FuncDef *p;         /* Iterator variable */  FuncDef *pFirst;    /* First function with this name */  FuncDef *pBest = 0; /* Best match found so far */  int bestmatch = 0;    assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );  if( nArg<-1 ) nArg = -1;  pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);  for(p=pFirst; p; p=p->pNext){    /* During the search for the best function definition, bestmatch is set    ** as follows to indicate the quality of the match with the definition    ** pointed to by pBest:    **    ** 0: pBest is NULL. No match has been found.    ** 1: A variable arguments function that prefers UTF-8 when a UTF-16    **    encoding is requested, or vice versa.    ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is    **    requested, or vice versa.    ** 3: A variable arguments function using the same text encoding.    ** 4: A function with the exact number of arguments requested that    **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.    ** 5: A function with the exact number of arguments requested that    **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.    ** 6: An exact match.    **    ** A larger value of 'matchqual' indicates a more desirable match.    */    if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){      int match = 1;          /* Quality of this match */      if( p->nArg==nArg || nArg==-1 ){        match = 4;      }      if( enc==p->iPrefEnc ){        match += 2;      }      else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||               (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){        match += 1;      }      if( match>bestmatch ){        pBest = p;        bestmatch = match;      }    }  }  /* If the createFlag parameter is true, and the seach did not reveal an  ** exact match for the name, number of arguments and encoding, then add a  ** new entry to the hash table and return it.  */  if( createFlag && bestmatch<6 &&       (pBest = sqliteMalloc(sizeof(*pBest)+nName)) ){    pBest->nArg = nArg;    pBest->pNext = pFirst;    pBest->iPrefEnc = enc;    memcpy(pBest->zName, zName, nName);    pBest->zName[nName] = 0;    if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){      sqliteFree(pBest);      return 0;    }  }  if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){    return pBest;  }  return 0;}