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