sqlite3/callback.c

   1 /*
   2 ** 2005 May 23
   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 functions used to access the internal hash tables
  14 ** of user defined functions and collation sequences.
  15 **
  16 ** $Id$
  17 */
  18
  19 #include "sqliteInt.h"
  20
  21 /*
  22 ** Invoke the 'collation needed' callback to request a collation sequence
  23 ** in the database text encoding of name zName, length nName.
  24 ** If the collation sequence
  25 */
  26 static void callCollNeeded(sqlite3 *db, const char *zName, int nName){
  27   assert( !db->xCollNeeded || !db->xCollNeeded16 );
  28   if( nName<0 ) nName = strlen(zName);
  29   if( db->xCollNeeded ){
  30     char *zExternal = sqliteStrNDup(zName, nName);
  31     if( !zExternal ) return;
  32     db->xCollNeeded(db->pCollNeededArg, db, (int)db->enc, zExternal);
  33     sqliteFree(zExternal);
  34   }
  35 #ifndef SQLITE_OMIT_UTF16
  36   if( db->xCollNeeded16 ){
  37     char const *zExternal;
  38     sqlite3_value *pTmp = sqlite3GetTransientValue(db);
  39     sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);
  40     zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);
  41     if( !zExternal ) return;
  42     db->xCollNeeded16(db->pCollNeededArg, db, (int)db->enc, zExternal);
  43   }
  44 #endif
  45 }
  46
  47 /*
  48 ** This routine is called if the collation factory fails to deliver a
  49 ** collation function in the best encoding but there may be other versions
  50 ** of this collation function (for other text encodings) available. Use one
  51 ** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if
  52 ** possible.
  53 */
  54 static int synthCollSeq(sqlite3 *db, CollSeq *pColl){
  55   CollSeq *pColl2;
  56   char *z = pColl->zName;
  57   int n = strlen(z);
  58   int i;
  59   static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
  60   for(i=0; i<3; i++){
  61     pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, n, 0);
  62     if( pColl2->xCmp!=0 ){
  63       memcpy(pColl, pColl2, sizeof(CollSeq));
  64       return SQLITE_OK;
  65     }
  66   }
  67   return SQLITE_ERROR;
  68 }
  69
  70 /*
  71 ** This function is responsible for invoking the collation factory callback
  72 ** or substituting a collation sequence of a different encoding when the
  73 ** requested collation sequence is not available in the database native
  74 ** encoding.
  75 **
  76 ** If it is not NULL, then pColl must point to the database native encoding
  77 ** collation sequence with name zName, length nName.
  78 **
  79 ** The return value is either the collation sequence to be used in database
  80 ** db for collation type name zName, length nName, or NULL, if no collation
  81 ** sequence can be found.
  82 */
  83 CollSeq *sqlite3GetCollSeq(
  84   sqlite3* db,
  85   CollSeq *pColl,
  86   const char *zName,
  87   int nName
  88 ){
  89   CollSeq *p;
  90
  91   p = pColl;
  92   if( !p ){
  93     p = sqlite3FindCollSeq(db, db->enc, zName, nName, 0);
  94   }
  95   if( !p || !p->xCmp ){
  96     /* No collation sequence of this type for this encoding is registered.
  97     ** Call the collation factory to see if it can supply us with one.
  98     */
  99     callCollNeeded(db, zName, nName);
 100     p = sqlite3FindCollSeq(db, db->enc, zName, nName, 0);
 101   }
 102   if( p && !p->xCmp && synthCollSeq(db, p) ){
 103     p = 0;
 104   }
 105   assert( !p || p->xCmp );
 106   return p;
 107 }
 108
 109 /*
 110 ** This routine is called on a collation sequence before it is used to
 111 ** check that it is defined. An undefined collation sequence exists when
 112 ** a database is loaded that contains references to collation sequences
 113 ** that have not been defined by sqlite3_create_collation() etc.
 114 **
 115 ** If required, this routine calls the 'collation needed' callback to
 116 ** request a definition of the collating sequence. If this doesn't work,
 117 ** an equivalent collating sequence that uses a text encoding different
 118 ** from the main database is substituted, if one is available.
 119 */
 120 int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
 121   if( pColl ){
 122     const char *zName = pColl->zName;
 123     CollSeq *p = sqlite3GetCollSeq(pParse->db, pColl, zName, -1);
 124     if( !p ){
 125       if( pParse->nErr==0 ){
 126         sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
 127       }
 128       pParse->nErr++;
 129       return SQLITE_ERROR;
 130     }
 131   }
 132   return SQLITE_OK;
 133 }
 134
 135
 136
 137 /*
 138 ** Locate and return an entry from the db.aCollSeq hash table. If the entry
 139 ** specified by zName and nName is not found and parameter 'create' is
 140 ** true, then create a new entry. Otherwise return NULL.
 141 **
 142 ** Each pointer stored in the sqlite3.aCollSeq hash table contains an
 143 ** array of three CollSeq structures. The first is the collation sequence
 144 ** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.
 145 **
 146 ** Stored immediately after the three collation sequences is a copy of
 147 ** the collation sequence name. A pointer to this string is stored in
 148 ** each collation sequence structure.
 149 */
 150 static CollSeq * findCollSeqEntry(
 151   sqlite3 *db,
 152   const char *zName,
 153   int nName,
 154   int create
 155 ){
 156   CollSeq *pColl;
 157   if( nName<0 ) nName = strlen(zName);
 158   pColl = sqlite3HashFind(&db->aCollSeq, zName, nName);
 159
 160   if( 0==pColl && create ){
 161     pColl = sqliteMalloc( 3*sizeof(*pColl) + nName + 1 );
 162     if( pColl ){
 163       CollSeq *pDel = 0;
 164       pColl[0].zName = (char*)&pColl[3];
 165       pColl[0].enc = SQLITE_UTF8;
 166       pColl[1].zName = (char*)&pColl[3];
 167       pColl[1].enc = SQLITE_UTF16LE;
 168       pColl[2].zName = (char*)&pColl[3];
 169       pColl[2].enc = SQLITE_UTF16BE;
 170       memcpy(pColl[0].zName, zName, nName);
 171       pColl[0].zName[nName] = 0;
 172       pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);
 173
 174       /* If a malloc() failure occured in sqlite3HashInsert(), it will
 175       ** return the pColl pointer to be deleted (because it wasn't added
 176       ** to the hash table).
 177       */
 178       assert( !pDel || (sqlite3_malloc_failed && pDel==pColl) );
 179       sqliteFree(pDel);
 180     }
 181   }
 182   return pColl;
 183 }
 184
 185 /*
 186 ** Parameter zName points to a UTF-8 encoded string nName bytes long.
 187 ** Return the CollSeq* pointer for the collation sequence named zName
 188 ** for the encoding 'enc' from the database 'db'.
 189 **
 190 ** If the entry specified is not found and 'create' is true, then create a
 191 ** new entry.  Otherwise return NULL.
 192 */
 193 CollSeq *sqlite3FindCollSeq(
 194   sqlite3 *db,
 195   u8 enc,
 196   const char *zName,
 197   int nName,
 198   int create
 199 ){
 200   CollSeq *pColl = findCollSeqEntry(db, zName, nName, create);
 201   assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
 202   assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
 203   if( pColl ) pColl += enc-1;
 204   return pColl;
 205 }
 206
 207 /*
 208 ** Locate a user function given a name, a number of arguments and a flag
 209 ** indicating whether the function prefers UTF-16 over UTF-8.  Return a
 210 ** pointer to the FuncDef structure that defines that function, or return
 211 ** NULL if the function does not exist.
 212 **
 213 ** If the createFlag argument is true, then a new (blank) FuncDef
 214 ** structure is created and liked into the "db" structure if a
 215 ** no matching function previously existed.  When createFlag is true
 216 ** and the nArg parameter is -1, then only a function that accepts
 217 ** any number of arguments will be returned.
 218 **
 219 ** If createFlag is false and nArg is -1, then the first valid
 220 ** function found is returned.  A function is valid if either xFunc
 221 ** or xStep is non-zero.
 222 **
 223 ** If createFlag is false, then a function with the required name and
 224 ** number of arguments may be returned even if the eTextRep flag does not
 225 ** match that requested.
 226 */
 227 FuncDef *sqlite3FindFunction(
 228   sqlite3 *db,       /* An open database */
 229   const char *zName, /* Name of the function.  Not null-terminated */
 230   int nName,         /* Number of characters in the name */
 231   int nArg,          /* Number of arguments.  -1 means any number */
 232   u8 enc,            /* Preferred text encoding */
 233   int createFlag     /* Create new entry if true and does not otherwise exist */
 234 ){
 235   FuncDef *p;         /* Iterator variable */
 236   FuncDef *pFirst;    /* First function with this name */
 237   FuncDef *pBest = 0; /* Best match found so far */
 238   int bestmatch = 0;
 239
 240
 241   assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
 242   if( nArg<-1 ) nArg = -1;
 243
 244   pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);
 245   for(p=pFirst; p; p=p->pNext){
 246     /* During the search for the best function definition, bestmatch is set
 247     ** as follows to indicate the quality of the match with the definition
 248     ** pointed to by pBest:
 249     **
 250     ** 0: pBest is NULL. No match has been found.
 251     ** 1: A variable arguments function that prefers UTF-8 when a UTF-16
 252     **    encoding is requested, or vice versa.
 253     ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
 254     **    requested, or vice versa.
 255     ** 3: A variable arguments function using the same text encoding.
 256     ** 4: A function with the exact number of arguments requested that
 257     **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
 258     ** 5: A function with the exact number of arguments requested that
 259     **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
 260     ** 6: An exact match.
 261     **
 262     ** A larger value of 'matchqual' indicates a more desirable match.
 263     */
 264     if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){
 265       int match = 1;          /* Quality of this match */
 266       if( p->nArg==nArg || nArg==-1 ){
 267         match = 4;
 268       }
 269       if( enc==p->iPrefEnc ){
 270         match += 2;
 271       }
 272       else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||
 273                (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){
 274         match += 1;
 275       }
 276
 277       if( match>bestmatch ){
 278         pBest = p;
 279         bestmatch = match;
 280       }
 281     }
 282   }
 283
 284   /* If the createFlag parameter is true, and the seach did not reveal an
 285   ** exact match for the name, number of arguments and encoding, then add a
 286   ** new entry to the hash table and return it.
 287   */
 288   if( createFlag && bestmatch<6 &&
 289       (pBest = sqliteMalloc(sizeof(*pBest)+nName+1)) ){
 290     pBest->nArg = nArg;
 291     pBest->pNext = pFirst;
 292     pBest->zName = (char*)&pBest[1];
 293     pBest->iPrefEnc = enc;
 294     memcpy(pBest->zName, zName, nName);
 295     pBest->zName[nName] = 0;
 296     if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){
 297       sqliteFree(pBest);
 298       return 0;
 299     }
 300   }
 301
 302   if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){
 303     return pBest;
 304   }
 305   return 0;
 306 }