diff options
Diffstat (limited to 'ext/fts1/ft_hash.c')
| -rw-r--r-- | ext/fts1/ft_hash.c | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/ext/fts1/ft_hash.c b/ext/fts1/ft_hash.c new file mode 100644 index 0000000..8b3a706 --- /dev/null +++ b/ext/fts1/ft_hash.c @@ -0,0 +1,404 @@ +/* +** 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> + +#include "ft_hash.h" + +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 HASH_INT, HASH_POINTER, +** HASH_BINARY, or 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 HASH_STRING and HASH_BINARY and is ignored +** for other key classes. +*/ +void HashInit(Hash *pNew, int keyClass, int copyKey){ + assert( pNew!=0 ); + assert( keyClass>=HASH_STRING && keyClass<=HASH_BINARY ); + pNew->keyClass = keyClass; +#if 0 + if( keyClass==HASH_POINTER || keyClass==HASH_INT ) copyKey = 0; +#endif + 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 HashClear(Hash *pH){ + HashElem *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 ){ + HashElem *next_elem = elem->next; + if( pH->copyKey && elem->pKey ){ + pH->xFree(elem->pKey); + } + pH->xFree(elem); + elem = next_elem; + } + pH->count = 0; +} + +#if 0 /* NOT USED */ +/* +** Hash and comparison functions when the mode is 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 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<pKey2 ) return -1; + return 1; +} +#endif + +/* +** Hash and comparison functions when the mode is 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 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 HASH_INT: return &intHash; + case HASH_POINTER: return &ptrHash; + case HASH_STRING: return &strHash; + case HASH_BINARY: return &binHash;; + default: break; + } + return 0; +#else + if( keyClass==HASH_STRING ){ + return &strHash; + }else{ + assert( keyClass==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 HASH_INT: return &intCompare; + case HASH_POINTER: return &ptrCompare; + case HASH_STRING: return &strCompare; + case HASH_BINARY: return &binCompare; + default: break; + } + return 0; +#else + if( keyClass==HASH_STRING ){ + return &strCompare; + }else{ + assert( keyClass==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 *)pH->xMalloc( new_size*sizeof(struct _ht) ); + 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 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 ){ + pH->xFree(elem->pKey); + } + pH->xFree( elem ); + pH->count--; + if( pH->count<=0 ){ + assert( pH->first==0 ); + assert( pH->count==0 ); + HashClear(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 *HashFind(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 *HashInsert(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*)pH->xMalloc( sizeof(HashElem) ); + 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; +} |