377 lines
11 KiB
C
377 lines
11 KiB
C
/*
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** 2001 September 22
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This is the implementation of generic hash-tables used in SQLite.
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** We've modified it slightly to serve as a standalone hash table
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** implementation for the full-text indexing module.
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*/
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/*
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** The code in this file is only compiled if:
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**
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** * The FTS2 module is being built as an extension
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** (in which case SQLITE_CORE is not defined), or
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**
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** * The FTS2 module is being built into the core of
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** SQLite (in which case SQLITE_ENABLE_FTS2 is defined).
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*/
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#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2)
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include "sqlite3.h"
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#include "sqlite3ext.h"
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SQLITE_EXTENSION_INIT3
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#include "fts2_hash.h"
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/*
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** Malloc and Free functions
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*/
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static void *fts2HashMalloc(int n){
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void *p = sqlite3_malloc(n);
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if( p ){
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memset(p, 0, n);
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}
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return p;
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}
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static void fts2HashFree(void *p){
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sqlite3_free(p);
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}
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/* Turn bulk memory into a hash table object by initializing the
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** fields of the Hash structure.
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**
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** "pNew" is a pointer to the hash table that is to be initialized.
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** keyClass is one of the constants
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** FTS2_HASH_BINARY or FTS2_HASH_STRING. The value of keyClass
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** determines what kind of key the hash table will use. "copyKey" is
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** true if the hash table should make its own private copy of keys and
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** false if it should just use the supplied pointer.
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*/
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void sqlite3Fts2HashInit(fts2Hash *pNew, int keyClass, int copyKey){
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assert( pNew!=0 );
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assert( keyClass>=FTS2_HASH_STRING && keyClass<=FTS2_HASH_BINARY );
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pNew->keyClass = keyClass;
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pNew->copyKey = copyKey;
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pNew->first = 0;
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pNew->count = 0;
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pNew->htsize = 0;
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pNew->ht = 0;
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}
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/* Remove all entries from a hash table. Reclaim all memory.
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** Call this routine to delete a hash table or to reset a hash table
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** to the empty state.
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*/
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void sqlite3Fts2HashClear(fts2Hash *pH){
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fts2HashElem *elem; /* For looping over all elements of the table */
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assert( pH!=0 );
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elem = pH->first;
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pH->first = 0;
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fts2HashFree(pH->ht);
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pH->ht = 0;
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pH->htsize = 0;
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while( elem ){
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fts2HashElem *next_elem = elem->next;
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if( pH->copyKey && elem->pKey ){
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fts2HashFree(elem->pKey);
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}
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fts2HashFree(elem);
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elem = next_elem;
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}
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pH->count = 0;
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}
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/*
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** Hash and comparison functions when the mode is FTS2_HASH_STRING
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*/
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static int strHash(const void *pKey, int nKey){
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const char *z = (const char *)pKey;
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int h = 0;
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if( nKey<=0 ) nKey = (int) strlen(z);
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while( nKey > 0 ){
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h = (h<<3) ^ h ^ *z++;
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nKey--;
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}
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return h & 0x7fffffff;
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}
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static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
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if( n1!=n2 ) return 1;
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return strncmp((const char*)pKey1,(const char*)pKey2,n1);
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}
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/*
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** Hash and comparison functions when the mode is FTS2_HASH_BINARY
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*/
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static int binHash(const void *pKey, int nKey){
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int h = 0;
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const char *z = (const char *)pKey;
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while( nKey-- > 0 ){
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h = (h<<3) ^ h ^ *(z++);
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}
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return h & 0x7fffffff;
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}
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static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
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if( n1!=n2 ) return 1;
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return memcmp(pKey1,pKey2,n1);
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}
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/*
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** Return a pointer to the appropriate hash function given the key class.
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**
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** The C syntax in this function definition may be unfamilar to some
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** programmers, so we provide the following additional explanation:
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**
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** The name of the function is "hashFunction". The function takes a
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** single parameter "keyClass". The return value of hashFunction()
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** is a pointer to another function. Specifically, the return value
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** of hashFunction() is a pointer to a function that takes two parameters
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** with types "const void*" and "int" and returns an "int".
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*/
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static int (*hashFunction(int keyClass))(const void*,int){
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if( keyClass==FTS2_HASH_STRING ){
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return &strHash;
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}else{
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assert( keyClass==FTS2_HASH_BINARY );
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return &binHash;
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}
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}
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/*
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** Return a pointer to the appropriate hash function given the key class.
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**
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** For help in interpreted the obscure C code in the function definition,
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** see the header comment on the previous function.
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*/
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static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
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if( keyClass==FTS2_HASH_STRING ){
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return &strCompare;
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}else{
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assert( keyClass==FTS2_HASH_BINARY );
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return &binCompare;
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}
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}
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/* Link an element into the hash table
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*/
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static void insertElement(
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fts2Hash *pH, /* The complete hash table */
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struct _fts2ht *pEntry, /* The entry into which pNew is inserted */
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fts2HashElem *pNew /* The element to be inserted */
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){
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fts2HashElem *pHead; /* First element already in pEntry */
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pHead = pEntry->chain;
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if( pHead ){
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pNew->next = pHead;
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pNew->prev = pHead->prev;
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if( pHead->prev ){ pHead->prev->next = pNew; }
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else { pH->first = pNew; }
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pHead->prev = pNew;
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}else{
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pNew->next = pH->first;
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if( pH->first ){ pH->first->prev = pNew; }
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pNew->prev = 0;
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pH->first = pNew;
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}
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pEntry->count++;
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pEntry->chain = pNew;
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}
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/* Resize the hash table so that it cantains "new_size" buckets.
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** "new_size" must be a power of 2. The hash table might fail
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** to resize if sqliteMalloc() fails.
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*/
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static void rehash(fts2Hash *pH, int new_size){
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struct _fts2ht *new_ht; /* The new hash table */
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fts2HashElem *elem, *next_elem; /* For looping over existing elements */
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int (*xHash)(const void*,int); /* The hash function */
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assert( (new_size & (new_size-1))==0 );
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new_ht = (struct _fts2ht *)fts2HashMalloc( new_size*sizeof(struct _fts2ht) );
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if( new_ht==0 ) return;
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fts2HashFree(pH->ht);
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pH->ht = new_ht;
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pH->htsize = new_size;
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xHash = hashFunction(pH->keyClass);
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for(elem=pH->first, pH->first=0; elem; elem = next_elem){
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int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
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next_elem = elem->next;
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insertElement(pH, &new_ht[h], elem);
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}
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}
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/* This function (for internal use only) locates an element in an
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** hash table that matches the given key. The hash for this key has
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** already been computed and is passed as the 4th parameter.
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*/
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static fts2HashElem *findElementGivenHash(
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const fts2Hash *pH, /* The pH to be searched */
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const void *pKey, /* The key we are searching for */
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int nKey,
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int h /* The hash for this key. */
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){
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fts2HashElem *elem; /* Used to loop thru the element list */
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int count; /* Number of elements left to test */
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int (*xCompare)(const void*,int,const void*,int); /* comparison function */
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if( pH->ht ){
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struct _fts2ht *pEntry = &pH->ht[h];
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elem = pEntry->chain;
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count = pEntry->count;
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xCompare = compareFunction(pH->keyClass);
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while( count-- && elem ){
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if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
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return elem;
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}
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elem = elem->next;
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}
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}
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return 0;
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}
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/* Remove a single entry from the hash table given a pointer to that
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** element and a hash on the element's key.
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*/
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static void removeElementGivenHash(
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fts2Hash *pH, /* The pH containing "elem" */
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fts2HashElem* elem, /* The element to be removed from the pH */
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int h /* Hash value for the element */
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){
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struct _fts2ht *pEntry;
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if( elem->prev ){
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elem->prev->next = elem->next;
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}else{
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pH->first = elem->next;
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}
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if( elem->next ){
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elem->next->prev = elem->prev;
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}
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pEntry = &pH->ht[h];
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if( pEntry->chain==elem ){
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pEntry->chain = elem->next;
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}
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pEntry->count--;
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if( pEntry->count<=0 ){
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pEntry->chain = 0;
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}
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if( pH->copyKey && elem->pKey ){
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fts2HashFree(elem->pKey);
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}
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fts2HashFree( elem );
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pH->count--;
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if( pH->count<=0 ){
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assert( pH->first==0 );
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assert( pH->count==0 );
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fts2HashClear(pH);
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}
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}
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/* Attempt to locate an element of the hash table pH with a key
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** that matches pKey,nKey. Return the data for this element if it is
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** found, or NULL if there is no match.
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*/
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void *sqlite3Fts2HashFind(const fts2Hash *pH, const void *pKey, int nKey){
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int h; /* A hash on key */
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fts2HashElem *elem; /* The element that matches key */
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int (*xHash)(const void*,int); /* The hash function */
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if( pH==0 || pH->ht==0 ) return 0;
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xHash = hashFunction(pH->keyClass);
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assert( xHash!=0 );
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h = (*xHash)(pKey,nKey);
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assert( (pH->htsize & (pH->htsize-1))==0 );
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elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
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return elem ? elem->data : 0;
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}
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/* Insert an element into the hash table pH. The key is pKey,nKey
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** and the data is "data".
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**
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** If no element exists with a matching key, then a new
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** element is created. A copy of the key is made if the copyKey
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** flag is set. NULL is returned.
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**
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** If another element already exists with the same key, then the
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** new data replaces the old data and the old data is returned.
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** The key is not copied in this instance. If a malloc fails, then
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** the new data is returned and the hash table is unchanged.
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**
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** If the "data" parameter to this function is NULL, then the
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** element corresponding to "key" is removed from the hash table.
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*/
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void *sqlite3Fts2HashInsert(
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fts2Hash *pH, /* The hash table to insert into */
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const void *pKey, /* The key */
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int nKey, /* Number of bytes in the key */
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void *data /* The data */
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){
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int hraw; /* Raw hash value of the key */
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int h; /* the hash of the key modulo hash table size */
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fts2HashElem *elem; /* Used to loop thru the element list */
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fts2HashElem *new_elem; /* New element added to the pH */
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int (*xHash)(const void*,int); /* The hash function */
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assert( pH!=0 );
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xHash = hashFunction(pH->keyClass);
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assert( xHash!=0 );
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hraw = (*xHash)(pKey, nKey);
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assert( (pH->htsize & (pH->htsize-1))==0 );
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h = hraw & (pH->htsize-1);
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elem = findElementGivenHash(pH,pKey,nKey,h);
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if( elem ){
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void *old_data = elem->data;
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if( data==0 ){
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removeElementGivenHash(pH,elem,h);
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}else{
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elem->data = data;
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}
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return old_data;
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}
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if( data==0 ) return 0;
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new_elem = (fts2HashElem*)fts2HashMalloc( sizeof(fts2HashElem) );
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if( new_elem==0 ) return data;
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if( pH->copyKey && pKey!=0 ){
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new_elem->pKey = fts2HashMalloc( nKey );
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if( new_elem->pKey==0 ){
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fts2HashFree(new_elem);
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return data;
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}
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memcpy((void*)new_elem->pKey, pKey, nKey);
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}else{
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new_elem->pKey = (void*)pKey;
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}
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new_elem->nKey = nKey;
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pH->count++;
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if( pH->htsize==0 ){
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rehash(pH,8);
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if( pH->htsize==0 ){
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pH->count = 0;
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fts2HashFree(new_elem);
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return data;
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}
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}
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if( pH->count > pH->htsize ){
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rehash(pH,pH->htsize*2);
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}
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assert( pH->htsize>0 );
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assert( (pH->htsize & (pH->htsize-1))==0 );
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h = hraw & (pH->htsize-1);
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insertElement(pH, &pH->ht[h], new_elem);
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new_elem->data = data;
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return 0;
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}
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#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2) */
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