summaryrefslogtreecommitdiffstats
path: root/veslibrary/ves_clibrary/evel/evel-library/code/evel_library/hashtable.c
blob: 0e2f7641b5c66be2171288ea6d432af36bf56932 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
/*************************************************************************//**
 *
 * 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;
}
*/