/*

 ** 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 1.32 2008/10/10 17:41:29 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 = sqlite3Strlen(db, zName);

   if( db->xCollNeeded ){

     char *zExternal = sqlite3DbStrNDup(db, zName, nName);

     if( !zExternal ) return;

     db->xCollNeeded(db->pCollNeededArg, db, (int)ENC(db), zExternal);

     sqlite3DbFree(db, zExternal);

   }

 #ifndef SQLITE_OMIT_UTF16

   if( db->xCollNeeded16 ){

     char const *zExternal;

     sqlite3_value *pTmp = sqlite3ValueNew(db);

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

     zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);

     if( zExternal ){

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

     }

     sqlite3ValueFree(pTmp);

   }

 #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));

       pColl->xDel = 0;         /* Do not copy the destructor */

       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, ENC(db), 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, ENC(db), 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;

     }

     assert( p==pColl );

   }

   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 = sqlite3Strlen(db, zName);

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

   if( 0==pColl && create ){

     pColl = sqlite3DbMallocZero(db, 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==0 || pDel==pColl );

       if( pDel!=0 ){

         db->mallocFailed = 1;

         sqlite3DbFree(db, pDel);

         pColl = 0;

       }

     }

   }

   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.

 **

 ** A separate function sqlite3LocateCollSeq() is a wrapper around

 ** this routine.  sqlite3LocateCollSeq() invokes the collation factory

 ** if necessary and generates an error message if the collating sequence

 ** cannot be found.

 */

 CollSeq *sqlite3FindCollSeq(

   sqlite3 *db,

   u8 enc,

   const char *zName,

   int nName,

   int create

 ){

   CollSeq *pColl;

   if( zName ){

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

   }else{

     pColl = db->pDfltColl;

   }

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

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

   if( pColl ) pColl += enc-1;

   return pColl;

 }

 /* During the search for the best function definition, this procedure

 ** is called to test how well the function passed as the first argument

 ** matches the request for a function with nArg arguments in a system

 ** that uses encoding enc. The value returned indicates how well the

 ** request is matched. A higher value indicates a better match.

 **

 ** The returned value is always between 1 and 6, as follows:

 **

 ** 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.

 **

 */

 static int matchQuality(FuncDef *p, int nArg, u8 enc){

   int match = 0;

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

     match = 1;

     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;

     }

   }

   return match;

 }

 /*

 ** Search a FuncDefHash for a function with the given name.  Return

 ** a pointer to the matching FuncDef if found, or 0 if there is no match.

 */

 static FuncDef *functionSearch(

   FuncDefHash *pHash,  /* Hash table to search */

   int h,               /* Hash of the name */

   const char *zFunc,   /* Name of function */

   int nFunc            /* Number of bytes in zFunc */

 ){

   FuncDef *p;

   for(p=pHash->a[h]; p; p=p->pHash){

     if( sqlite3StrNICmp(p->zName, zFunc, nFunc)==0 && p->zName[nFunc]==0 ){

       return p;

     }

   }

   return 0;

 }

 /*

 ** Insert a new FuncDef into a FuncDefHash hash table.

 */

 void sqlite3FuncDefInsert(

   FuncDefHash *pHash,  /* The hash table into which to insert */

   FuncDef *pDef        /* The function definition to insert */

 ){

   FuncDef *pOther;

   int nName = strlen(pDef->zName);

   u8 c1 = (u8)pDef->zName[0];

   int h = (sqlite3UpperToLower[c1] + nName) % ArraySize(pHash->a);

   pOther = functionSearch(pHash, h, pDef->zName, nName);

   if( pOther ){

     pDef->pNext = pOther->pNext;

     pOther->pNext = pDef;

   }else{

     pDef->pNext = 0;

     pDef->pHash = pHash->a[h];

     pHash->a[h] = pDef;

   }

 }

 /*

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

   int bestScore = 0;  /* Score of best match */

   int h;              /* Hash value */

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

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

   h = (sqlite3UpperToLower[(u8)zName[0]] + nName) % ArraySize(db->aFunc.a);

   /* First search for a match amongst the application-defined functions.

   */

   p = functionSearch(&db->aFunc, h, zName, nName);

   while( p ){

     int score = matchQuality(p, nArg, enc);

     if( score>bestScore ){

       pBest = p;

       bestScore = score;

     }

     p = p->pNext;

   }

   /* If no match is found, search the built-in functions.

   **

   ** Except, if createFlag is true, that means that we are trying to

   ** install a new function.  Whatever FuncDef structure is returned will

   ** have fields overwritten with new information appropriate for the

   ** new function.  But the FuncDefs for built-in functions are read-only.

   ** So we must not search for built-ins when creating a new function.

   */ 

   if( !createFlag && !pBest ){

     FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);

     p = functionSearch(pHash, h, zName, nName);

     while( p ){

       int score = matchQuality(p, nArg, enc);

       if( score>bestScore ){

         pBest = p;

         bestScore = score;

       }

       p = p->pNext;

     }

   }

   /* If the createFlag parameter is true and the search 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 && (bestScore<6 || pBest->nArg!=nArg) && 

       (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){

     pBest->zName = (char *)&pBest[1];

     pBest->nArg = nArg;

     pBest->iPrefEnc = enc;

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

     pBest->zName[nName] = 0;

     sqlite3FuncDefInsert(&db->aFunc, pBest);

   }

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

     return pBest;

   }

   return 0;

 }

 /*

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

 ** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the 

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

 ** of the schema hash tables).

 **

 ** The Schema.cache_size variable is not cleared.

 */

 void sqlite3SchemaFree(void *p){

   Hash temp1;

   Hash temp2;

   HashElem *pElem;

   Schema *pSchema = (Schema *)p;

   temp1 = pSchema->tblHash;

   temp2 = pSchema->trigHash;

   sqlite3HashInit(&pSchema->trigHash, 0);

   sqlite3HashClear(&pSchema->aFKey);

   sqlite3HashClear(&pSchema->idxHash);

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

     sqlite3DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));

   }

   sqlite3HashClear(&temp2);

   sqlite3HashInit(&pSchema->tblHash, 0);

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

     Table *pTab = sqliteHashData(pElem);

     sqlite3DeleteTable(pTab);

   }

   sqlite3HashClear(&temp1);

   pSchema->pSeqTab = 0;

   pSchema->flags &= ~DB_SchemaLoaded;

 }

 /*

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

 ** a new one if necessary.

 */

 Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){

   Schema * p;

   if( pBt ){

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

   }else{

     p = (Schema *)sqlite3MallocZero(sizeof(Schema));

   }

   if( !p ){

     db->mallocFailed = 1;

   }else if ( 0==p->file_format ){

     sqlite3HashInit(&p->tblHash, 0);

     sqlite3HashInit(&p->idxHash, 0);

     sqlite3HashInit(&p->trigHash, 0);

     sqlite3HashInit(&p->aFKey, 1);

     p->enc = SQLITE_UTF8;

   }

   return p;

 }