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+/*
+** 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.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+** * The FTS2 module is being built as an extension
+** (in which case SQLITE_CORE is not defined), or
+**
+** * The FTS2 module is being built into the core of
+** SQLite (in which case SQLITE_ENABLE_FTS2 is defined).
+*/
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2)
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "sqlite3.h"
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT3
+#include "fts2_hash.h"
+
+/*
+** Malloc and Free functions
+*/
+static void *fts2HashMalloc(int n){
+ void *p = sqlite3_malloc(n);
+ if( p ){
+ memset(p, 0, n);
+ }
+ return p;
+}
+static void fts2HashFree(void *p){
+ sqlite3_free(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
+** FTS2_HASH_BINARY or FTS2_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 sqlite3Fts2HashInit(fts2Hash *pNew, int keyClass, int copyKey){
+ assert( pNew!=0 );
+ assert( keyClass>=FTS2_HASH_STRING && keyClass<=FTS2_HASH_BINARY );
+ pNew->keyClass = keyClass;
+ 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 sqlite3Fts2HashClear(fts2Hash *pH){
+ fts2HashElem *elem; /* For looping over all elements of the table */
+
+ assert( pH!=0 );
+ elem = pH->first;
+ pH->first = 0;
+ fts2HashFree(pH->ht);
+ pH->ht = 0;
+ pH->htsize = 0;
+ while( elem ){
+ fts2HashElem *next_elem = elem->next;
+ if( pH->copyKey && elem->pKey ){
+ fts2HashFree(elem->pKey);
+ }
+ fts2HashFree(elem);
+ elem = next_elem;
+ }
+ pH->count = 0;
+}
+
+/*
+** Hash and comparison functions when the mode is FTS2_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 FTS2_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==FTS2_HASH_STRING ){
+ return &strHash;
+ }else{
+ assert( keyClass==FTS2_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==FTS2_HASH_STRING ){
+ return &strCompare;
+ }else{
+ assert( keyClass==FTS2_HASH_BINARY );
+ return &binCompare;
+ }
+}
+
+/* Link an element into the hash table
+*/
+static void insertElement(
+ fts2Hash *pH, /* The complete hash table */
+ struct _fts2ht *pEntry, /* The entry into which pNew is inserted */
+ fts2HashElem *pNew /* The element to be inserted */
+){
+ fts2HashElem *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(fts2Hash *pH, int new_size){
+ struct _fts2ht *new_ht; /* The new hash table */
+ fts2HashElem *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 _fts2ht *)fts2HashMalloc( new_size*sizeof(struct _fts2ht) );
+ if( new_ht==0 ) return;
+ fts2HashFree(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 fts2HashElem *findElementGivenHash(
+ const fts2Hash *pH, /* The pH to be searched */
+ const void *pKey, /* The key we are searching for */
+ int nKey,
+ int h /* The hash for this key. */
+){
+ fts2HashElem *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 _fts2ht *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(
+ fts2Hash *pH, /* The pH containing "elem" */
+ fts2HashElem* elem, /* The element to be removed from the pH */
+ int h /* Hash value for the element */
+){
+ struct _fts2ht *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 ){
+ fts2HashFree(elem->pKey);
+ }
+ fts2HashFree( elem );
+ pH->count--;
+ if( pH->count<=0 ){
+ assert( pH->first==0 );
+ assert( pH->count==0 );
+ fts2HashClear(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 *sqlite3Fts2HashFind(const fts2Hash *pH, const void *pKey, int nKey){
+ int h; /* A hash on key */
+ fts2HashElem *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 *sqlite3Fts2HashInsert(
+ fts2Hash *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 */
+ fts2HashElem *elem; /* Used to loop thru the element list */
+ fts2HashElem *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 = (fts2HashElem*)fts2HashMalloc( sizeof(fts2HashElem) );
+ if( new_elem==0 ) return data;
+ if( pH->copyKey && pKey!=0 ){
+ new_elem->pKey = fts2HashMalloc( nKey );
+ if( new_elem->pKey==0 ){
+ fts2HashFree(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;
+ fts2HashFree(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_FTS2) */
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-27 03:14:25 +0000