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+/**************************************************************************//**
+ * @file
+ * A simple Hashtable.
+ *
+ * @note No thread protection so you will need to use appropriate
+ * synchronization if use spans multiple threads.
+ *
+ * License
+ * -------
+ *
+ * Copyright(c) <2016>, AT&T Intellectual Property. All other rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement: This product includes
+ * software developed by the AT&T.
+ * 4. Neither the name of AT&T nor the names of its contributors may be used to
+ * endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AT&T INTELLECTUAL PROPERTY ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL AT&T INTELLECTUAL PROPERTY BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *****************************************************************************/
+
+#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;
+}
+*/