| /* |
| ** 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. |
| ** We've modified it slightly to serve as a standalone hash table |
| ** implementation for the full-text indexing module. |
| */ |
| #include <assert.h> |
| #include <stdlib.h> |
| #include <string.h> |
| |
| /* |
| ** The code in this file is only compiled if: |
| ** |
| ** * The FTS1 module is being built as an extension |
| ** (in which case SQLITE_CORE is not defined), or |
| ** |
| ** * The FTS1 module is being built into the core of |
| ** SQLite (in which case SQLITE_ENABLE_FTS1 is defined). |
| */ |
| #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1) |
| |
| |
| #include "fts1_hash.h" |
| |
| static void *malloc_and_zero(int n){ |
| void *p = malloc(n); |
| if( p ){ |
| memset(p, 0, n); |
| } |
| return p; |
| } |
| |
| /* 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 |
| ** FTS1_HASH_BINARY or FTS1_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. |
| */ |
| void sqlite3Fts1HashInit(fts1Hash *pNew, int keyClass, int copyKey){ |
| assert( pNew!=0 ); |
| assert( keyClass>=FTS1_HASH_STRING && keyClass<=FTS1_HASH_BINARY ); |
| pNew->keyClass = keyClass; |
| pNew->copyKey = copyKey; |
| pNew->first = 0; |
| pNew->count = 0; |
| pNew->htsize = 0; |
| pNew->ht = 0; |
| pNew->xMalloc = malloc_and_zero; |
| pNew->xFree = free; |
| } |
| |
| /* 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 sqlite3Fts1HashClear(fts1Hash *pH){ |
| fts1HashElem *elem; /* For looping over all elements of the table */ |
| |
| assert( pH!=0 ); |
| elem = pH->first; |
| pH->first = 0; |
| if( pH->ht ) pH->xFree(pH->ht); |
| pH->ht = 0; |
| pH->htsize = 0; |
| while( elem ){ |
| fts1HashElem *next_elem = elem->next; |
| if( pH->copyKey && elem->pKey ){ |
| pH->xFree(elem->pKey); |
| } |
| pH->xFree(elem); |
| elem = next_elem; |
| } |
| pH->count = 0; |
| } |
| |
| /* |
| ** Hash and comparison functions when the mode is FTS1_HASH_STRING |
| */ |
| static int strHash(const void *pKey, int nKey){ |
| const char *z = (const char *)pKey; |
| int h = 0; |
| if( nKey<=0 ) nKey = (int) strlen(z); |
| while( nKey > 0 ){ |
| h = (h<<3) ^ h ^ *z++; |
| nKey--; |
| } |
| return h & 0x7fffffff; |
| } |
| static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){ |
| if( n1!=n2 ) return 1; |
| return strncmp((const char*)pKey1,(const char*)pKey2,n1); |
| } |
| |
| /* |
| ** Hash and comparison functions when the mode is FTS1_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( keyClass==FTS1_HASH_STRING ){ |
| return &strHash; |
| }else{ |
| assert( keyClass==FTS1_HASH_BINARY ); |
| return &binHash; |
| } |
| } |
| |
| /* |
| ** 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( keyClass==FTS1_HASH_STRING ){ |
| return &strCompare; |
| }else{ |
| assert( keyClass==FTS1_HASH_BINARY ); |
| return &binCompare; |
| } |
| } |
| |
| /* Link an element into the hash table |
| */ |
| static void insertElement( |
| fts1Hash *pH, /* The complete hash table */ |
| struct _fts1ht *pEntry, /* The entry into which pNew is inserted */ |
| fts1HashElem *pNew /* The element to be inserted */ |
| ){ |
| fts1HashElem *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(fts1Hash *pH, int new_size){ |
| struct _fts1ht *new_ht; /* The new hash table */ |
| fts1HashElem *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 _fts1ht *)pH->xMalloc( new_size*sizeof(struct _fts1ht) ); |
| if( new_ht==0 ) return; |
| if( pH->ht ) pH->xFree(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 fts1HashElem *findElementGivenHash( |
| const fts1Hash *pH, /* The pH to be searched */ |
| const void *pKey, /* The key we are searching for */ |
| int nKey, |
| int h /* The hash for this key. */ |
| ){ |
| fts1HashElem *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 _fts1ht *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( |
| fts1Hash *pH, /* The pH containing "elem" */ |
| fts1HashElem* elem, /* The element to be removed from the pH */ |
| int h /* Hash value for the element */ |
| ){ |
| struct _fts1ht *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 ){ |
| pH->xFree(elem->pKey); |
| } |
| pH->xFree( elem ); |
| pH->count--; |
| if( pH->count<=0 ){ |
| assert( pH->first==0 ); |
| assert( pH->count==0 ); |
| fts1HashClear(pH); |
| } |
| } |
| |
| /* 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 *sqlite3Fts1HashFind(const fts1Hash *pH, const void *pKey, int nKey){ |
| int h; /* A hash on key */ |
| fts1HashElem *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 *sqlite3Fts1HashInsert( |
| fts1Hash *pH, /* The hash table to insert into */ |
| const void *pKey, /* The key */ |
| int nKey, /* Number of bytes in the key */ |
| void *data /* The data */ |
| ){ |
| int hraw; /* Raw hash value of the key */ |
| int h; /* the hash of the key modulo hash table size */ |
| fts1HashElem *elem; /* Used to loop thru the element list */ |
| fts1HashElem *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 = (fts1HashElem*)pH->xMalloc( sizeof(fts1HashElem) ); |
| if( new_elem==0 ) return data; |
| if( pH->copyKey && pKey!=0 ){ |
| new_elem->pKey = pH->xMalloc( nKey ); |
| if( new_elem->pKey==0 ){ |
| pH->xFree(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; |
| pH->xFree(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; |
| } |
| |
| #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1) */ |