src/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
  17 #include "sqliteInt.h"
  18
  19 /*
  20 ** Invoke the 'collation needed' callback to request a collation sequence
  21 ** in the encoding enc of name zName, length nName.
  22 */
  23 static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
  24   assert( !db->xCollNeeded || !db->xCollNeeded16 );
  25   if( db->xCollNeeded ){
  26     char *zExternal = sqlite3DbStrDup(db, zName);
  27     if( !zExternal ) return;
  28     db->xCollNeeded(db->pCollNeededArg, db, enc, zExternal);
  29     sqlite3DbFree(db, zExternal);
  30   }
  31 #ifndef SQLITE_OMIT_UTF16
  32   if( db->xCollNeeded16 ){
  33     char const *zExternal;
  34     sqlite3_value *pTmp = sqlite3ValueNew(db);
  35     sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);
  36     zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);
  37     if( zExternal ){
  38       db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);
  39     }
  40     sqlite3ValueFree(pTmp);
  41   }
  42 #endif
  43 }
  44
  45 /*
  46 ** This routine is called if the collation factory fails to deliver a
  47 ** collation function in the best encoding but there may be other versions
  48 ** of this collation function (for other text encodings) available. Use one
  49 ** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if
  50 ** possible.
  51 */
  52 static int synthCollSeq(sqlite3 *db, CollSeq *pColl){
  53   CollSeq *pColl2;
  54   char *z = pColl->zName;
  55   int i;
  56   static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
  57   for(i=0; i<3; i++){
  58     pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, 0);
  59     if( pColl2->xCmp!=0 ){
  60       memcpy(pColl, pColl2, sizeof(CollSeq));
  61       pColl->xDel = 0;         /* Do not copy the destructor */
  62       return SQLITE_OK;
  63     }
  64   }
  65   return SQLITE_ERROR;
  66 }
  67
  68 /*
  69 ** This routine is called on a collation sequence before it is used to
  70 ** check that it is defined. An undefined collation sequence exists when
  71 ** a database is loaded that contains references to collation sequences
  72 ** that have not been defined by sqlite3_create_collation() etc.
  73 **
  74 ** If required, this routine calls the 'collation needed' callback to
  75 ** request a definition of the collating sequence. If this doesn't work,
  76 ** an equivalent collating sequence that uses a text encoding different
  77 ** from the main database is substituted, if one is available.
  78 */
  79 int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
  80   if( pColl && pColl->xCmp==0 ){
  81     const char *zName = pColl->zName;
  82     sqlite3 *db = pParse->db;
  83     CollSeq *p = sqlite3GetCollSeq(pParse, ENC(db), pColl, zName);
  84     if( !p ){
  85       return SQLITE_ERROR;
  86     }
  87     assert( p==pColl );
  88   }
  89   return SQLITE_OK;
  90 }
  91
  92
  93
  94 /*
  95 ** Locate and return an entry from the db.aCollSeq hash table. If the entry
  96 ** specified by zName and nName is not found and parameter 'create' is
  97 ** true, then create a new entry. Otherwise return NULL.
  98 **
  99 ** Each pointer stored in the sqlite3.aCollSeq hash table contains an
 100 ** array of three CollSeq structures. The first is the collation sequence
 101 ** preferred for UTF-8, the second UTF-16le, and the third UTF-16be.
 102 **
 103 ** Stored immediately after the three collation sequences is a copy of
 104 ** the collation sequence name. A pointer to this string is stored in
 105 ** each collation sequence structure.
 106 */
 107 static CollSeq *findCollSeqEntry(
 108   sqlite3 *db,          /* Database connection */
 109   const char *zName,    /* Name of the collating sequence */
 110   int create            /* Create a new entry if true */
 111 ){
 112   CollSeq *pColl;
 113   pColl = sqlite3HashFind(&db->aCollSeq, zName);
 114
 115   if( 0==pColl && create ){
 116     int nName = sqlite3Strlen30(zName) + 1;
 117     pColl = sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName);
 118     if( pColl ){
 119       CollSeq *pDel = 0;
 120       pColl[0].zName = (char*)&pColl[3];
 121       pColl[0].enc = SQLITE_UTF8;
 122       pColl[1].zName = (char*)&pColl[3];
 123       pColl[1].enc = SQLITE_UTF16LE;
 124       pColl[2].zName = (char*)&pColl[3];
 125       pColl[2].enc = SQLITE_UTF16BE;
 126       memcpy(pColl[0].zName, zName, nName);
 127       pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, pColl);
 128
 129       /* If a malloc() failure occurred in sqlite3HashInsert(), it will
 130       ** return the pColl pointer to be deleted (because it wasn't added
 131       ** to the hash table).
 132       */
 133       assert( pDel==0 || pDel==pColl );
 134       if( pDel!=0 ){
 135         sqlite3OomFault(db);
 136         sqlite3DbFree(db, pDel);
 137         pColl = 0;
 138       }
 139     }
 140   }
 141   return pColl;
 142 }
 143
 144 /*
 145 ** Parameter zName points to a UTF-8 encoded string nName bytes long.
 146 ** Return the CollSeq* pointer for the collation sequence named zName
 147 ** for the encoding 'enc' from the database 'db'.
 148 **
 149 ** If the entry specified is not found and 'create' is true, then create a
 150 ** new entry.  Otherwise return NULL.
 151 **
 152 ** A separate function sqlite3LocateCollSeq() is a wrapper around
 153 ** this routine.  sqlite3LocateCollSeq() invokes the collation factory
 154 ** if necessary and generates an error message if the collating sequence
 155 ** cannot be found.
 156 **
 157 ** See also: sqlite3LocateCollSeq(), sqlite3GetCollSeq()
 158 */
 159 CollSeq *sqlite3FindCollSeq(
 160   sqlite3 *db,          /* Database connection to search */
 161   u8 enc,               /* Desired text encoding */
 162   const char *zName,    /* Name of the collating sequence.  Might be NULL */
 163   int create            /* True to create CollSeq if doesn't already exist */
 164 ){
 165   CollSeq *pColl;
 166   assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
 167   assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
 168   if( zName ){
 169     pColl = findCollSeqEntry(db, zName, create);
 170     if( pColl ) pColl += enc-1;
 171   }else{
 172     pColl = db->pDfltColl;
 173   }
 174   return pColl;
 175 }
 176
 177 /*
 178 ** Change the text encoding for a database connection. This means that
 179 ** the pDfltColl must change as well.
 180 */
 181 void sqlite3SetTextEncoding(sqlite3 *db, u8 enc){
 182   assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
 183   db->enc = enc;
 184   /* EVIDENCE-OF: R-08308-17224 The default collating function for all
 185   ** strings is BINARY.
 186   */
 187   db->pDfltColl = sqlite3FindCollSeq(db, enc, sqlite3StrBINARY, 0);
 188   sqlite3ExpirePreparedStatements(db, 1);
 189 }
 190
 191 /*
 192 ** This function is responsible for invoking the collation factory callback
 193 ** or substituting a collation sequence of a different encoding when the
 194 ** requested collation sequence is not available in the desired encoding.
 195 **
 196 ** If it is not NULL, then pColl must point to the database native encoding
 197 ** collation sequence with name zName, length nName.
 198 **
 199 ** The return value is either the collation sequence to be used in database
 200 ** db for collation type name zName, length nName, or NULL, if no collation
 201 ** sequence can be found.  If no collation is found, leave an error message.
 202 **
 203 ** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
 204 */
 205 CollSeq *sqlite3GetCollSeq(
 206   Parse *pParse,        /* Parsing context */
 207   u8 enc,               /* The desired encoding for the collating sequence */
 208   CollSeq *pColl,       /* Collating sequence with native encoding, or NULL */
 209   const char *zName     /* Collating sequence name */
 210 ){
 211   CollSeq *p;
 212   sqlite3 *db = pParse->db;
 213
 214   p = pColl;
 215   if( !p ){
 216     p = sqlite3FindCollSeq(db, enc, zName, 0);
 217   }
 218   if( !p || !p->xCmp ){
 219     /* No collation sequence of this type for this encoding is registered.
 220     ** Call the collation factory to see if it can supply us with one.
 221     */
 222     callCollNeeded(db, enc, zName);
 223     p = sqlite3FindCollSeq(db, enc, zName, 0);
 224   }
 225   if( p && !p->xCmp && synthCollSeq(db, p) ){
 226     p = 0;
 227   }
 228   assert( !p || p->xCmp );
 229   if( p==0 ){
 230     sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
 231     pParse->rc = SQLITE_ERROR_MISSING_COLLSEQ;
 232   }
 233   return p;
 234 }
 235
 236 /*
 237 ** This function returns the collation sequence for database native text
 238 ** encoding identified by the string zName.
 239 **
 240 ** If the requested collation sequence is not available, or not available
 241 ** in the database native encoding, the collation factory is invoked to
 242 ** request it. If the collation factory does not supply such a sequence,
 243 ** and the sequence is available in another text encoding, then that is
 244 ** returned instead.
 245 **
 246 ** If no versions of the requested collations sequence are available, or
 247 ** another error occurs, NULL is returned and an error message written into
 248 ** pParse.
 249 **
 250 ** This routine is a wrapper around sqlite3FindCollSeq().  This routine
 251 ** invokes the collation factory if the named collation cannot be found
 252 ** and generates an error message.
 253 **
 254 ** See also: sqlite3FindCollSeq(), sqlite3GetCollSeq()
 255 */
 256 CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char *zName){
 257   sqlite3 *db = pParse->db;
 258   u8 enc = ENC(db);
 259   u8 initbusy = db->init.busy;
 260   CollSeq *pColl;
 261
 262   pColl = sqlite3FindCollSeq(db, enc, zName, initbusy);
 263   if( !initbusy && (!pColl || !pColl->xCmp) ){
 264     pColl = sqlite3GetCollSeq(pParse, enc, pColl, zName);
 265   }
 266
 267   return pColl;
 268 }
 269
 270 /* During the search for the best function definition, this procedure
 271 ** is called to test how well the function passed as the first argument
 272 ** matches the request for a function with nArg arguments in a system
 273 ** that uses encoding enc. The value returned indicates how well the
 274 ** request is matched. A higher value indicates a better match.
 275 **
 276 ** If nArg is -1 that means to only return a match (non-zero) if p->nArg
 277 ** is also -1.  In other words, we are searching for a function that
 278 ** takes a variable number of arguments.
 279 **
 280 ** If nArg is -2 that means that we are searching for any function
 281 ** regardless of the number of arguments it uses, so return a positive
 282 ** match score for any
 283 **
 284 ** The returned value is always between 0 and 6, as follows:
 285 **
 286 ** 0: Not a match.
 287 ** 1: UTF8/16 conversion required and function takes any number of arguments.
 288 ** 2: UTF16 byte order change required and function takes any number of args.
 289 ** 3: encoding matches and function takes any number of arguments
 290 ** 4: UTF8/16 conversion required - argument count matches exactly
 291 ** 5: UTF16 byte order conversion required - argument count matches exactly
 292 ** 6: Perfect match:  encoding and argument count match exactly.
 293 **
 294 ** If nArg==(-2) then any function with a non-null xSFunc is
 295 ** a perfect match and any function with xSFunc NULL is
 296 ** a non-match.
 297 */
 298 #define FUNC_PERFECT_MATCH 6  /* The score for a perfect match */
 299 static int matchQuality(
 300   FuncDef *p,     /* The function we are evaluating for match quality */
 301   int nArg,       /* Desired number of arguments.  (-1)==any */
 302   u8 enc          /* Desired text encoding */
 303 ){
 304   int match;
 305   assert( p->nArg>=-1 );
 306
 307   /* Wrong number of arguments means "no match" */
 308   if( p->nArg!=nArg ){
 309     if( nArg==(-2) ) return (p->xSFunc==0) ? 0 : FUNC_PERFECT_MATCH;
 310     if( p->nArg>=0 ) return 0;
 311   }
 312
 313   /* Give a better score to a function with a specific number of arguments
 314   ** than to function that accepts any number of arguments. */
 315   if( p->nArg==nArg ){
 316     match = 4;
 317   }else{
 318     match = 1;
 319   }
 320
 321   /* Bonus points if the text encoding matches */
 322   if( enc==(p->funcFlags & SQLITE_FUNC_ENCMASK) ){
 323     match += 2;  /* Exact encoding match */
 324   }else if( (enc & p->funcFlags & 2)!=0 ){
 325     match += 1;  /* Both are UTF16, but with different byte orders */
 326   }
 327
 328   return match;
 329 }
 330
 331 /*
 332 ** Search a FuncDefHash for a function with the given name.  Return
 333 ** a pointer to the matching FuncDef if found, or 0 if there is no match.
 334 */
 335 FuncDef *sqlite3FunctionSearch(
 336   int h,               /* Hash of the name */
 337   const char *zFunc    /* Name of function */
 338 ){
 339   FuncDef *p;
 340   for(p=sqlite3BuiltinFunctions.a[h]; p; p=p->u.pHash){
 341     assert( p->funcFlags & SQLITE_FUNC_BUILTIN );
 342     if( sqlite3StrICmp(p->zName, zFunc)==0 ){
 343       return p;
 344     }
 345   }
 346   return 0;
 347 }
 348
 349 /*
 350 ** Insert a new FuncDef into a FuncDefHash hash table.
 351 */
 352 void sqlite3InsertBuiltinFuncs(
 353   FuncDef *aDef,      /* List of global functions to be inserted */
 354   int nDef            /* Length of the apDef[] list */
 355 ){
 356   int i;
 357   for(i=0; i<nDef; i++){
 358     FuncDef *pOther;
 359     const char *zName = aDef[i].zName;
 360     int nName = sqlite3Strlen30(zName);
 361     int h = SQLITE_FUNC_HASH(zName[0], nName);
 362     assert( aDef[i].funcFlags & SQLITE_FUNC_BUILTIN );
 363     pOther = sqlite3FunctionSearch(h, zName);
 364     if( pOther ){
 365       assert( pOther!=&aDef[i] && pOther->pNext!=&aDef[i] );
 366       aDef[i].pNext = pOther->pNext;
 367       pOther->pNext = &aDef[i];
 368     }else{
 369       aDef[i].pNext = 0;
 370       aDef[i].u.pHash = sqlite3BuiltinFunctions.a[h];
 371       sqlite3BuiltinFunctions.a[h] = &aDef[i];
 372     }
 373   }
 374 }
 375
 376
 377
 378 /*
 379 ** Locate a user function given a name, a number of arguments and a flag
 380 ** indicating whether the function prefers UTF-16 over UTF-8.  Return a
 381 ** pointer to the FuncDef structure that defines that function, or return
 382 ** NULL if the function does not exist.
 383 **
 384 ** If the createFlag argument is true, then a new (blank) FuncDef
 385 ** structure is created and liked into the "db" structure if a
 386 ** no matching function previously existed.
 387 **
 388 ** If nArg is -2, then the first valid function found is returned.  A
 389 ** function is valid if xSFunc is non-zero.  The nArg==(-2)
 390 ** case is used to see if zName is a valid function name for some number
 391 ** of arguments.  If nArg is -2, then createFlag must be 0.
 392 **
 393 ** If createFlag is false, then a function with the required name and
 394 ** number of arguments may be returned even if the eTextRep flag does not
 395 ** match that requested.
 396 */
 397 FuncDef *sqlite3FindFunction(
 398   sqlite3 *db,       /* An open database */
 399   const char *zName, /* Name of the function.  zero-terminated */
 400   int nArg,          /* Number of arguments.  -1 means any number */
 401   u8 enc,            /* Preferred text encoding */
 402   u8 createFlag      /* Create new entry if true and does not otherwise exist */
 403 ){
 404   FuncDef *p;         /* Iterator variable */
 405   FuncDef *pBest = 0; /* Best match found so far */
 406   int bestScore = 0;  /* Score of best match */
 407   int h;              /* Hash value */
 408   int nName;          /* Length of the name */
 409
 410   assert( nArg>=(-2) );
 411   assert( nArg>=(-1) || createFlag==0 );
 412   nName = sqlite3Strlen30(zName);
 413
 414   /* First search for a match amongst the application-defined functions.
 415   */
 416   p = (FuncDef*)sqlite3HashFind(&db->aFunc, zName);
 417   while( p ){
 418     int score = matchQuality(p, nArg, enc);
 419     if( score>bestScore ){
 420       pBest = p;
 421       bestScore = score;
 422     }
 423     p = p->pNext;
 424   }
 425
 426   /* If no match is found, search the built-in functions.
 427   **
 428   ** If the DBFLAG_PreferBuiltin flag is set, then search the built-in
 429   ** functions even if a prior app-defined function was found.  And give
 430   ** priority to built-in functions.
 431   **
 432   ** Except, if createFlag is true, that means that we are trying to
 433   ** install a new function.  Whatever FuncDef structure is returned it will
 434   ** have fields overwritten with new information appropriate for the
 435   ** new function.  But the FuncDefs for built-in functions are read-only.
 436   ** So we must not search for built-ins when creating a new function.
 437   */
 438   if( !createFlag && (pBest==0 || (db->mDbFlags & DBFLAG_PreferBuiltin)!=0) ){
 439     bestScore = 0;
 440     h = SQLITE_FUNC_HASH(sqlite3UpperToLower[(u8)zName[0]], nName);
 441     p = sqlite3FunctionSearch(h, zName);
 442     while( p ){
 443       int score = matchQuality(p, nArg, enc);
 444       if( score>bestScore ){
 445         pBest = p;
 446         bestScore = score;
 447       }
 448       p = p->pNext;
 449     }
 450   }
 451
 452   /* If the createFlag parameter is true and the search did not reveal an
 453   ** exact match for the name, number of arguments and encoding, then add a
 454   ** new entry to the hash table and return it.
 455   */
 456   if( createFlag && bestScore<FUNC_PERFECT_MATCH &&
 457       (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
 458     FuncDef *pOther;
 459     u8 *z;
 460     pBest->zName = (const char*)&pBest[1];
 461     pBest->nArg = (u16)nArg;
 462     pBest->funcFlags = enc;
 463     memcpy((char*)&pBest[1], zName, nName+1);
 464     for(z=(u8*)pBest->zName; *z; z++) *z = sqlite3UpperToLower[*z];
 465     pOther = (FuncDef*)sqlite3HashInsert(&db->aFunc, pBest->zName, pBest);
 466     if( pOther==pBest ){
 467       sqlite3DbFree(db, pBest);
 468       sqlite3OomFault(db);
 469       return 0;
 470     }else{
 471       pBest->pNext = pOther;
 472     }
 473   }
 474
 475   if( pBest && (pBest->xSFunc || createFlag) ){
 476     return pBest;
 477   }
 478   return 0;
 479 }
 480
 481 /*
 482 ** Free all resources held by the schema structure. The void* argument points
 483 ** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the
 484 ** pointer itself, it just cleans up subsidiary resources (i.e. the contents
 485 ** of the schema hash tables).
 486 **
 487 ** The Schema.cache_size variable is not cleared.
 488 */
 489 void sqlite3SchemaClear(void *p){
 490   Hash temp1;
 491   Hash temp2;
 492   HashElem *pElem;
 493   Schema *pSchema = (Schema *)p;
 494   sqlite3 xdb;
 495
 496   memset(&xdb, 0, sizeof(xdb));
 497   temp1 = pSchema->tblHash;
 498   temp2 = pSchema->trigHash;
 499   sqlite3HashInit(&pSchema->trigHash);
 500   sqlite3HashClear(&pSchema->idxHash);
 501   for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
 502     sqlite3DeleteTrigger(&xdb, (Trigger*)sqliteHashData(pElem));
 503   }
 504   sqlite3HashClear(&temp2);
 505   sqlite3HashInit(&pSchema->tblHash);
 506   for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){
 507     Table *pTab = sqliteHashData(pElem);
 508     sqlite3DeleteTable(&xdb, pTab);
 509   }
 510   sqlite3HashClear(&temp1);
 511   sqlite3HashClear(&pSchema->fkeyHash);
 512   pSchema->pSeqTab = 0;
 513   if( pSchema->schemaFlags & DB_SchemaLoaded ){
 514     pSchema->iGeneration++;
 515   }
 516   pSchema->schemaFlags &= ~(DB_SchemaLoaded|DB_ResetWanted);
 517 }
 518
 519 /*
 520 ** Find and return the schema associated with a BTree.  Create
 521 ** a new one if necessary.
 522 */
 523 Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
 524   Schema * p;
 525   if( pBt ){
 526     p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
 527   }else{
 528     p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
 529   }
 530   if( !p ){
 531     sqlite3OomFault(db);
 532   }else if ( 0==p->file_format ){
 533     sqlite3HashInit(&p->tblHash);
 534     sqlite3HashInit(&p->idxHash);
 535     sqlite3HashInit(&p->trigHash);
 536     sqlite3HashInit(&p->fkeyHash);
 537     p->enc = SQLITE_UTF8;
 538   }
 539   return p;
 540 }