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: callback.c,v 1.15 2006/05/24 12:43:27 drh Exp $

    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)ENC(db), zExternal);

    33     sqliteFree(zExternal);

    34   }

    35 #ifndef SQLITE_OMIT_UTF16

    36   if( db->xCollNeeded16 ){

    37     char const *zExternal;

    38     sqlite3_value *pTmp = sqlite3ValueNew();

    39     sqlite3ValueSetStr(pTmp, nName, zName, SQLITE_UTF8, SQLITE_STATIC);

    40     zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);

    41     if( zExternal ){

    42       db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);

    43     }

    44     sqlite3ValueFree(pTmp);

    45   }

    46 #endif

    47 }

    48 

    49 /*

    50 ** This routine is called if the collation factory fails to deliver a

    51 ** collation function in the best encoding but there may be other versions

    52 ** of this collation function (for other text encodings) available. Use one

    53 ** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if

    54 ** possible.

    55 */

    56 static int synthCollSeq(sqlite3 *db, CollSeq *pColl){

    57   CollSeq *pColl2;

    58   char *z = pColl->zName;

    59   int n = strlen(z);

    60   int i;

    61   static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };

    62   for(i=0; i<3; i++){

    63     pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, n, 0);

    64     if( pColl2->xCmp!=0 ){

    65       memcpy(pColl, pColl2, sizeof(CollSeq));

    66       return SQLITE_OK;

    67     }

    68   }

    69   return SQLITE_ERROR;

    70 }

    71 

    72 /*

    73 ** This function is responsible for invoking the collation factory callback

    74 ** or substituting a collation sequence of a different encoding when the

    75 ** requested collation sequence is not available in the database native

    76 ** encoding.

    77 ** 

    78 ** If it is not NULL, then pColl must point to the database native encoding 

    79 ** collation sequence with name zName, length nName.

    80 **

    81 ** The return value is either the collation sequence to be used in database

    82 ** db for collation type name zName, length nName, or NULL, if no collation

    83 ** sequence can be found.

    84 */

    85 CollSeq *sqlite3GetCollSeq(

    86   sqlite3* db, 

    87   CollSeq *pColl, 

    88   const char *zName, 

    89   int nName

    90 ){

    91   CollSeq *p;

    92 

    93   p = pColl;

    94   if( !p ){

    95     p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);

    96   }

    97   if( !p || !p->xCmp ){

    98     /* No collation sequence of this type for this encoding is registered.

    99     ** Call the collation factory to see if it can supply us with one.

   100     */

   101     callCollNeeded(db, zName, nName);

   102     p = sqlite3FindCollSeq(db, ENC(db), zName, nName, 0);

   103   }

   104   if( p && !p->xCmp && synthCollSeq(db, p) ){

   105     p = 0;

   106   }

   107   assert( !p || p->xCmp );

   108   return p;

   109 }

   110 

   111 /*

   112 ** This routine is called on a collation sequence before it is used to

   113 ** check that it is defined. An undefined collation sequence exists when

   114 ** a database is loaded that contains references to collation sequences

   115 ** that have not been defined by sqlite3_create_collation() etc.

   116 **

   117 ** If required, this routine calls the 'collation needed' callback to

   118 ** request a definition of the collating sequence. If this doesn't work, 

   119 ** an equivalent collating sequence that uses a text encoding different

   120 ** from the main database is substituted, if one is available.

   121 */

   122 int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){

   123   if( pColl ){

   124     const char *zName = pColl->zName;

   125     CollSeq *p = sqlite3GetCollSeq(pParse->db, pColl, zName, -1);

   126     if( !p ){

   127       if( pParse->nErr==0 ){

   128         sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);

   129       }

   130       pParse->nErr++;

   131       return SQLITE_ERROR;

   132     }

   133     assert( p==pColl );

   134   }

   135   return SQLITE_OK;

   136 }

   137 

   138 

   139 

   140 /*

   141 ** Locate and return an entry from the db.aCollSeq hash table. If the entry

   142 ** specified by zName and nName is not found and parameter 'create' is

   143 ** true, then create a new entry. Otherwise return NULL.

   144 **

   145 ** Each pointer stored in the sqlite3.aCollSeq hash table contains an

   146 ** array of three CollSeq structures. The first is the collation sequence

   147 ** prefferred for UTF-8, the second UTF-16le, and the third UTF-16be.

   148 **

   149 ** Stored immediately after the three collation sequences is a copy of

   150 ** the collation sequence name. A pointer to this string is stored in

   151 ** each collation sequence structure.

   152 */

   153 static CollSeq *findCollSeqEntry(

   154   sqlite3 *db,

   155   const char *zName,

   156   int nName,

   157   int create

   158 ){

   159   CollSeq *pColl;

   160   if( nName<0 ) nName = strlen(zName);

   161   pColl = sqlite3HashFind(&db->aCollSeq, zName, nName);

   162 

   163   if( 0==pColl && create ){

   164     pColl = sqliteMalloc( 3*sizeof(*pColl) + nName + 1 );

   165     if( pColl ){

   166       CollSeq *pDel = 0;

   167       pColl[0].zName = (char*)&pColl[3];

   168       pColl[0].enc = SQLITE_UTF8;

   169       pColl[1].zName = (char*)&pColl[3];

   170       pColl[1].enc = SQLITE_UTF16LE;

   171       pColl[2].zName = (char*)&pColl[3];

   172       pColl[2].enc = SQLITE_UTF16BE;

   173       memcpy(pColl[0].zName, zName, nName);

   174       pColl[0].zName[nName] = 0;

   175       pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, nName, pColl);

   176 

   177       /* If a malloc() failure occured in sqlite3HashInsert(), it will 

   178       ** return the pColl pointer to be deleted (because it wasn't added

   179       ** to the hash table).

   180       */

   181       assert( !pDel || (sqlite3MallocFailed() && pDel==pColl) );

   182       if( pDel ){

   183         sqliteFree(pDel);

   184         pColl = 0;

   185       }

   186     }

   187   }

   188   return pColl;

   189 }

   190 

   191 /*

   192 ** Parameter zName points to a UTF-8 encoded string nName bytes long.

   193 ** Return the CollSeq* pointer for the collation sequence named zName

   194 ** for the encoding 'enc' from the database 'db'.

   195 **

   196 ** If the entry specified is not found and 'create' is true, then create a

   197 ** new entry.  Otherwise return NULL.

   198 */

   199 CollSeq *sqlite3FindCollSeq(

   200   sqlite3 *db,

   201   u8 enc,

   202   const char *zName,

   203   int nName,

   204   int create

   205 ){

   206   CollSeq *pColl;

   207   if( zName ){

   208     pColl = findCollSeqEntry(db, zName, nName, create);

   209   }else{

   210     pColl = db->pDfltColl;

   211   }

   212   assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );

   213   assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );

   214   if( pColl ) pColl += enc-1;

   215   return pColl;

   216 }

   217 

   218 /*

   219 ** Locate a user function given a name, a number of arguments and a flag

   220 ** indicating whether the function prefers UTF-16 over UTF-8.  Return a

   221 ** pointer to the FuncDef structure that defines that function, or return

   222 ** NULL if the function does not exist.

   223 **

   224 ** If the createFlag argument is true, then a new (blank) FuncDef

   225 ** structure is created and liked into the "db" structure if a

   226 ** no matching function previously existed.  When createFlag is true

   227 ** and the nArg parameter is -1, then only a function that accepts

   228 ** any number of arguments will be returned.

   229 **

   230 ** If createFlag is false and nArg is -1, then the first valid

   231 ** function found is returned.  A function is valid if either xFunc

   232 ** or xStep is non-zero.

   233 **

   234 ** If createFlag is false, then a function with the required name and

   235 ** number of arguments may be returned even if the eTextRep flag does not

   236 ** match that requested.

   237 */

   238 FuncDef *sqlite3FindFunction(

   239   sqlite3 *db,       /* An open database */

   240   const char *zName, /* Name of the function.  Not null-terminated */

   241   int nName,         /* Number of characters in the name */

   242   int nArg,          /* Number of arguments.  -1 means any number */

   243   u8 enc,            /* Preferred text encoding */

   244   int createFlag     /* Create new entry if true and does not otherwise exist */

   245 ){

   246   FuncDef *p;         /* Iterator variable */

   247   FuncDef *pFirst;    /* First function with this name */

   248   FuncDef *pBest = 0; /* Best match found so far */

   249   int bestmatch = 0;  

   250 

   251 

   252   assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );

   253   if( nArg<-1 ) nArg = -1;

   254 

   255   pFirst = (FuncDef*)sqlite3HashFind(&db->aFunc, zName, nName);

   256   for(p=pFirst; p; p=p->pNext){

   257     /* During the search for the best function definition, bestmatch is set

   258     ** as follows to indicate the quality of the match with the definition

   259     ** pointed to by pBest:

   260     **

   261     ** 0: pBest is NULL. No match has been found.

   262     ** 1: A variable arguments function that prefers UTF-8 when a UTF-16

   263     **    encoding is requested, or vice versa.

   264     ** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is

   265     **    requested, or vice versa.

   266     ** 3: A variable arguments function using the same text encoding.

   267     ** 4: A function with the exact number of arguments requested that

   268     **    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.

   269     ** 5: A function with the exact number of arguments requested that

   270     **    prefers UTF-16LE when UTF-16BE is requested, or vice versa.

   271     ** 6: An exact match.

   272     **

   273     ** A larger value of 'matchqual' indicates a more desirable match.

   274     */

   275     if( p->nArg==-1 || p->nArg==nArg || nArg==-1 ){

   276       int match = 1;          /* Quality of this match */

   277       if( p->nArg==nArg || nArg==-1 ){

   278         match = 4;

   279       }

   280       if( enc==p->iPrefEnc ){

   281         match += 2;

   282       }

   283       else if( (enc==SQLITE_UTF16LE && p->iPrefEnc==SQLITE_UTF16BE) ||

   284                (enc==SQLITE_UTF16BE && p->iPrefEnc==SQLITE_UTF16LE) ){

   285         match += 1;

   286       }

   287 

   288       if( match>bestmatch ){

   289         pBest = p;

   290         bestmatch = match;

   291       }

   292     }

   293   }

   294 

   295   /* If the createFlag parameter is true, and the seach did not reveal an

   296   ** exact match for the name, number of arguments and encoding, then add a

   297   ** new entry to the hash table and return it.

   298   */

   299   if( createFlag && bestmatch<6 && 

   300       (pBest = sqliteMalloc(sizeof(*pBest)+nName))!=0 ){

   301     pBest->nArg = nArg;

   302     pBest->pNext = pFirst;

   303     pBest->iPrefEnc = enc;

   304     memcpy(pBest->zName, zName, nName);

   305     pBest->zName[nName] = 0;

   306     if( pBest==sqlite3HashInsert(&db->aFunc,pBest->zName,nName,(void*)pBest) ){

   307       sqliteFree(pBest);

   308       return 0;

   309     }

   310   }

   311 

   312   if( pBest && (pBest->xStep || pBest->xFunc || createFlag) ){

   313     return pBest;

   314   }

   315   return 0;

   316 }

   317 

   318 /*

   319 ** Free all resources held by the schema structure. The void* argument points

   320 ** at a Schema struct. This function does not call sqliteFree() on the 

   321 ** pointer itself, it just cleans up subsiduary resources (i.e. the contents

   322 ** of the schema hash tables).

   323 */

   324 void sqlite3SchemaFree(void *p){

   325   Hash temp1;

   326   Hash temp2;

   327   HashElem *pElem;

   328   Schema *pSchema = (Schema *)p;

   329 

   330   temp1 = pSchema->tblHash;

   331   temp2 = pSchema->trigHash;

   332   sqlite3HashInit(&pSchema->trigHash, SQLITE_HASH_STRING, 0);

   333   sqlite3HashClear(&pSchema->aFKey);

   334   sqlite3HashClear(&pSchema->idxHash);

   335   for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){

   336     sqlite3DeleteTrigger((Trigger*)sqliteHashData(pElem));

   337   }

   338   sqlite3HashClear(&temp2);

   339   sqlite3HashInit(&pSchema->tblHash, SQLITE_HASH_STRING, 0);

   340   for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){

   341     Table *pTab = sqliteHashData(pElem);

   342     sqlite3DeleteTable(0, pTab);

   343   }

   344   sqlite3HashClear(&temp1);

   345   pSchema->pSeqTab = 0;

   346   pSchema->flags &= ~DB_SchemaLoaded;

   347 }

   348 

   349 /*

   350 ** Find and return the schema associated with a BTree.  Create

   351 ** a new one if necessary.

   352 */

   353 Schema *sqlite3SchemaGet(Btree *pBt){

   354   Schema * p;

   355   if( pBt ){

   356     p = (Schema *)sqlite3BtreeSchema(pBt,sizeof(Schema),sqlite3SchemaFree);

   357   }else{

   358     p = (Schema *)sqliteMalloc(sizeof(Schema));

   359   }

   360   if( p && 0==p->file_format ){

   361     sqlite3HashInit(&p->tblHash, SQLITE_HASH_STRING, 0);

   362     sqlite3HashInit(&p->idxHash, SQLITE_HASH_STRING, 0);

   363     sqlite3HashInit(&p->trigHash, SQLITE_HASH_STRING, 0);

   364     sqlite3HashInit(&p->aFKey, SQLITE_HASH_STRING, 1);

   365     p->enc = SQLITE_UTF8;

   366   }

   367   return p;

   368 }