/* ** 2001 September 22 ** ** 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 is the implementation of generic hash-tables ** used in SQLite. ** ** $Id: hash.c,v 1.1.1.1 2006/02/03 20:35:12 hoganrobert Exp $ */ #include "sqliteInt.h" #include /* Turn bulk memory into a hash table object by initializing the ** fields of the Hash structure. ** ** "pNew" is a pointer to the hash table that is to be initialized. ** keyClass is one of the constants SQLITE_HASH_INT, SQLITE_HASH_POINTER, ** SQLITE_HASH_BINARY, or SQLITE_HASH_STRING. The value of keyClass ** determines what kind of key the hash table will use. "copyKey" is ** true if the hash table should make its own private copy of keys and ** false if it should just use the supplied pointer. CopyKey only makes ** sense for SQLITE_HASH_STRING and SQLITE_HASH_BINARY and is ignored ** for other key classes. */ void sqlite3HashInit(Hash *pNew, int keyClass, int copyKey){ assert( pNew!=0 ); assert( keyClass>=SQLITE_HASH_STRING && keyClass<=SQLITE_HASH_BINARY ); pNew->keyClass = keyClass; #if 0 if( keyClass==SQLITE_HASH_POINTER || keyClass==SQLITE_HASH_INT ) copyKey = 0; #endif pNew->copyKey = copyKey; pNew->first = 0; pNew->count = 0; pNew->htsize = 0; pNew->ht = 0; } /* Remove all entries from a hash table. Reclaim all memory. ** Call this routine to delete a hash table or to reset a hash table ** to the empty state. */ void sqlite3HashClear(Hash *pH){ HashElem *elem; /* For looping over all elements of the table */ assert( pH!=0 ); elem = pH->first; pH->first = 0; if( pH->ht ) sqliteFree(pH->ht); pH->ht = 0; pH->htsize = 0; while( elem ){ HashElem *next_elem = elem->next; if( pH->copyKey && elem->pKey ){ sqliteFree(elem->pKey); } sqliteFree(elem); elem = next_elem; } pH->count = 0; } #if 0 /* NOT USED */ /* ** Hash and comparison functions when the mode is SQLITE_HASH_INT */ static int intHash(const void *pKey, int nKey){ return nKey ^ (nKey<<8) ^ (nKey>>8); } static int intCompare(const void *pKey1, int n1, const void *pKey2, int n2){ return n2 - n1; } #endif #if 0 /* NOT USED */ /* ** Hash and comparison functions when the mode is SQLITE_HASH_POINTER */ static int ptrHash(const void *pKey, int nKey){ uptr x = Addr(pKey); return x ^ (x<<8) ^ (x>>8); } static int ptrCompare(const void *pKey1, int n1, const void *pKey2, int n2){ if( pKey1==pKey2 ) return 0; if( pKey1 0 ){ h = (h<<3) ^ h ^ sqlite3UpperToLower[(unsigned char)*z++]; nKey--; } return h & 0x7fffffff; } static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){ if( n1!=n2 ) return 1; return sqlite3StrNICmp((const char*)pKey1,(const char*)pKey2,n1); } /* ** Hash and comparison functions when the mode is SQLITE_HASH_BINARY */ static int binHash(const void *pKey, int nKey){ int h = 0; const char *z = (const char *)pKey; while( nKey-- > 0 ){ h = (h<<3) ^ h ^ *(z++); } return h & 0x7fffffff; } static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){ if( n1!=n2 ) return 1; return memcmp(pKey1,pKey2,n1); } /* ** Return a pointer to the appropriate hash function given the key class. ** ** The C syntax in this function definition may be unfamilar to some ** programmers, so we provide the following additional explanation: ** ** The name of the function is "hashFunction". The function takes a ** single parameter "keyClass". The return value of hashFunction() ** is a pointer to another function. Specifically, the return value ** of hashFunction() is a pointer to a function that takes two parameters ** with types "const void*" and "int" and returns an "int". */ static int (*hashFunction(int keyClass))(const void*,int){ #if 0 /* HASH_INT and HASH_POINTER are never used */ switch( keyClass ){ case SQLITE_HASH_INT: return &intHash; case SQLITE_HASH_POINTER: return &ptrHash; case SQLITE_HASH_STRING: return &strHash; case SQLITE_HASH_BINARY: return &binHash;; default: break; } return 0; #else if( keyClass==SQLITE_HASH_STRING ){ return &strHash; }else{ assert( keyClass==SQLITE_HASH_BINARY ); return &binHash; } #endif } /* ** Return a pointer to the appropriate hash function given the key class. ** ** For help in interpreted the obscure C code in the function definition, ** see the header comment on the previous function. */ static int (*compareFunction(int keyClass))(const void*,int,const void*,int){ #if 0 /* HASH_INT and HASH_POINTER are never used */ switch( keyClass ){ case SQLITE_HASH_INT: return &intCompare; case SQLITE_HASH_POINTER: return &ptrCompare; case SQLITE_HASH_STRING: return &strCompare; case SQLITE_HASH_BINARY: return &binCompare; default: break; } return 0; #else if( keyClass==SQLITE_HASH_STRING ){ return &strCompare; }else{ assert( keyClass==SQLITE_HASH_BINARY ); return &binCompare; } #endif } /* Link an element into the hash table */ static void insertElement( Hash *pH, /* The complete hash table */ struct _ht *pEntry, /* The entry into which pNew is inserted */ HashElem *pNew /* The element to be inserted */ ){ HashElem *pHead; /* First element already in pEntry */ pHead = pEntry->chain; if( pHead ){ pNew->next = pHead; pNew->prev = pHead->prev; if( pHead->prev ){ pHead->prev->next = pNew; } else { pH->first = pNew; } pHead->prev = pNew; }else{ pNew->next = pH->first; if( pH->first ){ pH->first->prev = pNew; } pNew->prev = 0; pH->first = pNew; } pEntry->count++; pEntry->chain = pNew; } /* Resize the hash table so that it cantains "new_size" buckets. ** "new_size" must be a power of 2. The hash table might fail ** to resize if sqliteMalloc() fails. */ static void rehash(Hash *pH, int new_size){ struct _ht *new_ht; /* The new hash table */ HashElem *elem, *next_elem; /* For looping over existing elements */ int (*xHash)(const void*,int); /* The hash function */ assert( (new_size & (new_size-1))==0 ); new_ht = (struct _ht *)sqliteMalloc( new_size*sizeof(struct _ht) ); if( new_ht==0 ) return; if( pH->ht ) sqliteFree(pH->ht); pH->ht = new_ht; pH->htsize = new_size; xHash = hashFunction(pH->keyClass); for(elem=pH->first, pH->first=0; elem; elem = next_elem){ int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1); next_elem = elem->next; insertElement(pH, &new_ht[h], elem); } } /* This function (for internal use only) locates an element in an ** hash table that matches the given key. The hash for this key has ** already been computed and is passed as the 4th parameter. */ static HashElem *findElementGivenHash( const Hash *pH, /* The pH to be searched */ const void *pKey, /* The key we are searching for */ int nKey, int h /* The hash for this key. */ ){ HashElem *elem; /* Used to loop thru the element list */ int count; /* Number of elements left to test */ int (*xCompare)(const void*,int,const void*,int); /* comparison function */ if( pH->ht ){ struct _ht *pEntry = &pH->ht[h]; elem = pEntry->chain; count = pEntry->count; xCompare = compareFunction(pH->keyClass); while( count-- && elem ){ if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){ return elem; } elem = elem->next; } } return 0; } /* Remove a single entry from the hash table given a pointer to that ** element and a hash on the element's key. */ static void removeElementGivenHash( Hash *pH, /* The pH containing "elem" */ HashElem* elem, /* The element to be removed from the pH */ int h /* Hash value for the element */ ){ struct _ht *pEntry; if( elem->prev ){ elem->prev->next = elem->next; }else{ pH->first = elem->next; } if( elem->next ){ elem->next->prev = elem->prev; } pEntry = &pH->ht[h]; if( pEntry->chain==elem ){ pEntry->chain = elem->next; } pEntry->count--; if( pEntry->count<=0 ){ pEntry->chain = 0; } if( pH->copyKey && elem->pKey ){ sqliteFree(elem->pKey); } sqliteFree( elem ); pH->count--; } /* Attempt to locate an element of the hash table pH with a key ** that matches pKey,nKey. Return the data for this element if it is ** found, or NULL if there is no match. */ void *sqlite3HashFind(const Hash *pH, const void *pKey, int nKey){ int h; /* A hash on key */ HashElem *elem; /* The element that matches key */ int (*xHash)(const void*,int); /* The hash function */ if( pH==0 || pH->ht==0 ) return 0; xHash = hashFunction(pH->keyClass); assert( xHash!=0 ); h = (*xHash)(pKey,nKey); assert( (pH->htsize & (pH->htsize-1))==0 ); elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1)); return elem ? elem->data : 0; } /* Insert an element into the hash table pH. The key is pKey,nKey ** and the data is "data". ** ** If no element exists with a matching key, then a new ** element is created. A copy of the key is made if the copyKey ** flag is set. NULL is returned. ** ** If another element already exists with the same key, then the ** new data replaces the old data and the old data is returned. ** The key is not copied in this instance. If a malloc fails, then ** the new data is returned and the hash table is unchanged. ** ** If the "data" parameter to this function is NULL, then the ** element corresponding to "key" is removed from the hash table. */ void *sqlite3HashInsert(Hash *pH, const void *pKey, int nKey, void *data){ int hraw; /* Raw hash value of the key */ int h; /* the hash of the key modulo hash table size */ HashElem *elem; /* Used to loop thru the element list */ HashElem *new_elem; /* New element added to the pH */ int (*xHash)(const void*,int); /* The hash function */ assert( pH!=0 ); xHash = hashFunction(pH->keyClass); assert( xHash!=0 ); hraw = (*xHash)(pKey, nKey); assert( (pH->htsize & (pH->htsize-1))==0 ); h = hraw & (pH->htsize-1); elem = findElementGivenHash(pH,pKey,nKey,h); if( elem ){ void *old_data = elem->data; if( data==0 ){ removeElementGivenHash(pH,elem,h); }else{ elem->data = data; } return old_data; } if( data==0 ) return 0; new_elem = (HashElem*)sqliteMalloc( sizeof(HashElem) ); if( new_elem==0 ) return data; if( pH->copyKey && pKey!=0 ){ new_elem->pKey = sqliteMallocRaw( nKey ); if( new_elem->pKey==0 ){ sqliteFree(new_elem); return data; } memcpy((void*)new_elem->pKey, pKey, nKey); }else{ new_elem->pKey = (void*)pKey; } new_elem->nKey = nKey; pH->count++; if( pH->htsize==0 ){ rehash(pH,8); if( pH->htsize==0 ){ pH->count = 0; sqliteFree(new_elem); return data; } } if( pH->count > pH->htsize ){ rehash(pH,pH->htsize*2); } assert( pH->htsize>0 ); assert( (pH->htsize & (pH->htsize-1))==0 ); h = hraw & (pH->htsize-1); insertElement(pH, &pH->ht[h], new_elem); new_elem->data = data; return 0; }