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/*************************************************************************//**
*
* Copyright © 2017 AT&T Intellectual Property. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
****************************************************************************/
/**************************************************************************//**
* @file
* A simple Hashtable.
*
* @note No thread protection so you will need to use appropriate
* synchronization if use spans multiple threads.
*
****************************************************************************/
#include <limits.h>
#include <assert.h>
#include <malloc.h>
#include <string.h>
#include "hashtable.h"
/**************************************************************************//**
* Hashtable initialization.
*
* Initialize the list supplied to be empty.
*
* @param size Size of hashtable
* @returns Hashtable pointer
******************************************************************************/
/* Create a new hashtable. */
HASHTABLE_T *ht_create( size_t size ) {
HASHTABLE_T *hashtable = NULL;
size_t i;
if( size < 1 ) return NULL;
/* Allocate the table itself. */
if( ( hashtable = malloc( sizeof( HASHTABLE_T ) ) ) == NULL ) {
return NULL;
}
/* Allocate pointers to the head nodes. */
if( ( hashtable->table = malloc( sizeof( ENTRY_T * ) * size ) ) == NULL ) {
return NULL;
}
for( i = 0; i < size; i++ ) {
hashtable->table[i] = NULL;
}
hashtable->size = size;
return hashtable;
}
/**************************************************************************//**
* Hash a string for a particular hash table.
*
* Initialize the list supplied to be empty.
*
* @param hashtable Pointer to the hashtable
* @param key String
* @returns hashvalue
******************************************************************************/
size_t ht_hash( HASHTABLE_T *hashtable, char *key )
{
size_t hash, i;
#ifdef HASHTABLE_USE_SIMPLE_HASH
for ( hash = i = 0; i < strlen(key); hash = hash << 8, hash += key[ i++ ] );
#else /* Use: Jenkins' "One At a Time Hash" === Perl "Like" Hashing */
// http://en.wikipedia.org/wiki/Jenkins_hash_function
for ( hash = i = 0; i < strlen(key); ++i ) {
hash += key[i], hash += ( hash << 10 ), hash ^= ( hash >> 6 );
}
hash += ( hash << 3 ), hash ^= ( hash >> 11 ), hash += ( hash << 15 );
#endif
return hash % hashtable->size;
}
/**************************************************************************//**
* Create a key-value pair.
*
* @param key key string
* @param value value string
*
* @returns hashtable entry
******************************************************************************/
ENTRY_T *ht_newpair( char *key, void *value )
{
ENTRY_T *newpair;
if( ( newpair = malloc( sizeof( ENTRY_T ) ) ) == NULL ) {
return NULL;
}
if( ( newpair->key = strdup( key ) ) == NULL ) {
return NULL;
}
if( ( newpair->value = value ) == NULL ) {
return NULL;
}
newpair->next = NULL;
return newpair;
}
/**************************************************************************//**
* Insert a key-value pair into a hash table.
*
* @param key key string
* @param value value string
*
* @returns Nothing
******************************************************************************/
void ht_set( HASHTABLE_T *hashtable, char *key, void *value ) {
size_t bin = 0;
ENTRY_T *newpair = NULL;
ENTRY_T *next = NULL;
ENTRY_T *last = NULL;
bin = ht_hash( hashtable, key );
next = hashtable->table[ bin ];
while( next != NULL && next->key != NULL && strcmp( key, next->key ) > 0 ) {
last = next;
next = next->next;
}
/* There's already a pair. Let's replace that string. */
if( next != NULL && next->key != NULL && strcmp( key, next->key ) == 0 ) {
free( next->value );
next->value = value ;
/* Nope, could't find it. Time to grow a pair. */
} else {
newpair = ht_newpair( key, value );
/* We're at the start of the linked list in this bin. */
if( next == hashtable->table[ bin ] ) {
newpair->next = next;
hashtable->table[ bin ] = newpair;
/* We're at the end of the linked list in this bin. */
} else if ( next == NULL ) {
last->next = newpair;
/* We're in the middle of the list. */
} else {
newpair->next = next;
last->next = newpair;
}
}
}
/**************************************************************************//**
* Retrieve a key-value pair from a hash table.
*
* @param key key string
*
* @returns value string
******************************************************************************/
void *ht_get( HASHTABLE_T *hashtable, char *key ) {
size_t bin = 0;
ENTRY_T *pair;
bin = ht_hash( hashtable, key );
/* Step through the bin, looking for our value. */
pair = hashtable->table[ bin ];
while( pair != NULL && pair->key != NULL && strcmp( key, pair->key ) > 0 ) {
pair = pair->next;
}
/* Did we actually find anything? */
if( pair == NULL || pair->key == NULL || strcmp( key, pair->key ) != 0 ) {
return NULL;
} else {
return pair->value;
}
}
/*
int main( int argc, char **argv ) {
HASHTABLE_T *hashtable = ht_create( 65536 );
ht_set( hashtable, "key1", "inky" );
ht_set( hashtable, "key2", "pinky" );
ht_set( hashtable, "key3", "blinky" );
ht_set( hashtable, "key4", "floyd" );
printf( "%s\n", ht_get( hashtable, "key1" ) );
printf( "%s\n", ht_get( hashtable, "key2" ) );
printf( "%s\n", ht_get( hashtable, "key3" ) );
printf( "%s\n", ht_get( hashtable, "key4" ) );
return 0;
}
*/
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