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      1 /**************************************************************************
      2  *
      3  * Copyright 2007 VMware, Inc.
      4  * All Rights Reserved.
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a
      7  * copy of this software and associated documentation files (the
      8  * "Software"), to deal in the Software without restriction, including
      9  * without limitation the rights to use, copy, modify, merge, publish,
     10  * distribute, sub license, and/or sell copies of the Software, and to
     11  * permit persons to whom the Software is furnished to do so, subject to
     12  * the following conditions:
     13  *
     14  * The above copyright notice and this permission notice (including the
     15  * next paragraph) shall be included in all copies or substantial portions
     16  * of the Software.
     17  *
     18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
     19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
     21  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
     22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
     23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
     24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
     25  *
     26  **************************************************************************/
     27 
     28  /*
     29   * Authors:
     30   *   Zack Rusin <zackr (at) vmware.com>
     31   */
     32 
     33 #ifdef HAVE_CONFIG_H
     34 #include "config.h"
     35 #endif
     36 
     37 #include "util_hash.h"
     38 
     39 #include <stdlib.h>
     40 #include <assert.h>
     41 
     42 #define MAX(a, b) ((a > b) ? (a) : (b))
     43 
     44 static const int MinNumBits = 4;
     45 
     46 static const unsigned char prime_deltas[] = {
     47 	0,  0,  1,  3,  1,  5,  3,  3,  1,  9,  7,  5,  3,  9, 25,  3,
     48 	1, 21,  3, 21,  7, 15,  9,  5,  3, 29, 15,  0,  0,  0,  0,  0
     49 };
     50 
     51 static int primeForNumBits(int numBits)
     52 {
     53 	return (1 << numBits) + prime_deltas[numBits];
     54 }
     55 
     56 /* Returns the smallest integer n such that
     57    primeForNumBits(n) >= hint.
     58 */
     59 static int countBits(int hint)
     60 {
     61 	int numBits = 0;
     62 	int bits = hint;
     63 
     64 	while (bits > 1) {
     65 		bits >>= 1;
     66 		numBits++;
     67 	}
     68 
     69 	if (numBits >= (int)sizeof(prime_deltas)) {
     70 		numBits = sizeof(prime_deltas) - 1;
     71 	} else if (primeForNumBits(numBits) < hint) {
     72 		++numBits;
     73 	}
     74 	return numBits;
     75 }
     76 
     77 struct util_node {
     78    struct util_node *next;
     79    unsigned key;
     80    void *value;
     81 };
     82 
     83 struct util_hash_data {
     84    struct util_node *fakeNext;
     85    struct util_node **buckets;
     86    int size;
     87    int nodeSize;
     88    short userNumBits;
     89    short numBits;
     90    int numBuckets;
     91 };
     92 
     93 struct util_hash {
     94    union {
     95       struct util_hash_data *d;
     96       struct util_node      *e;
     97    } data;
     98 };
     99 
    100 static void *util_data_allocate_node(struct util_hash_data *hash)
    101 {
    102    return malloc(hash->nodeSize);
    103 }
    104 
    105 static void util_free_node(struct util_node *node)
    106 {
    107    free(node);
    108 }
    109 
    110 static struct util_node *
    111 util_hash_create_node(struct util_hash *hash,
    112                       unsigned akey, void *avalue,
    113                       struct util_node **anextNode)
    114 {
    115    struct util_node *node = util_data_allocate_node(hash->data.d);
    116 
    117    if (!node)
    118       return NULL;
    119 
    120    node->key = akey;
    121    node->value = avalue;
    122 
    123    node->next = (struct util_node*)(*anextNode);
    124    *anextNode = node;
    125    ++hash->data.d->size;
    126    return node;
    127 }
    128 
    129 static void util_data_rehash(struct util_hash_data *hash, int hint)
    130 {
    131    if (hint < 0) {
    132       hint = countBits(-hint);
    133       if (hint < MinNumBits)
    134          hint = MinNumBits;
    135       hash->userNumBits = (short)hint;
    136       while (primeForNumBits(hint) < (hash->size >> 1))
    137          ++hint;
    138    } else if (hint < MinNumBits) {
    139       hint = MinNumBits;
    140    }
    141 
    142    if (hash->numBits != hint) {
    143       struct util_node *e = (struct util_node *)(hash);
    144       struct util_node **oldBuckets = hash->buckets;
    145       int oldNumBuckets = hash->numBuckets;
    146       int  i = 0;
    147 
    148       hash->numBits = (short)hint;
    149       hash->numBuckets = primeForNumBits(hint);
    150       hash->buckets = malloc(sizeof(struct util_node*) * hash->numBuckets);
    151       for (i = 0; i < hash->numBuckets; ++i)
    152          hash->buckets[i] = e;
    153 
    154       for (i = 0; i < oldNumBuckets; ++i) {
    155          struct util_node *firstNode = oldBuckets[i];
    156          while (firstNode != e) {
    157             unsigned h = firstNode->key;
    158             struct util_node *lastNode = firstNode;
    159             struct util_node *afterLastNode;
    160             struct util_node **beforeFirstNode;
    161 
    162             while (lastNode->next != e && lastNode->next->key == h)
    163                lastNode = lastNode->next;
    164 
    165             afterLastNode = lastNode->next;
    166             beforeFirstNode = &hash->buckets[h % hash->numBuckets];
    167             while (*beforeFirstNode != e)
    168                beforeFirstNode = &(*beforeFirstNode)->next;
    169             lastNode->next = *beforeFirstNode;
    170             *beforeFirstNode = firstNode;
    171             firstNode = afterLastNode;
    172          }
    173       }
    174       free(oldBuckets);
    175    }
    176 }
    177 
    178 static void util_data_might_grow(struct util_hash_data *hash)
    179 {
    180    if (hash->size >= hash->numBuckets)
    181       util_data_rehash(hash, hash->numBits + 1);
    182 }
    183 
    184 static void util_data_has_shrunk(struct util_hash_data *hash)
    185 {
    186    if (hash->size <= (hash->numBuckets >> 3) &&
    187        hash->numBits > hash->userNumBits) {
    188       int max = MAX(hash->numBits-2, hash->userNumBits);
    189       util_data_rehash(hash,  max);
    190    }
    191 }
    192 
    193 static struct util_node *util_data_first_node(struct util_hash_data *hash)
    194 {
    195    struct util_node *e = (struct util_node *)(hash);
    196    struct util_node **bucket = hash->buckets;
    197    int n = hash->numBuckets;
    198    while (n--) {
    199       if (*bucket != e)
    200          return *bucket;
    201       ++bucket;
    202    }
    203    return e;
    204 }
    205 
    206 static struct util_node **util_hash_find_node(struct util_hash *hash, unsigned akey)
    207 {
    208    struct util_node **node;
    209 
    210    if (hash->data.d->numBuckets) {
    211       node = (struct util_node **)(&hash->data.d->buckets[akey % hash->data.d->numBuckets]);
    212       assert(*node == hash->data.e || (*node)->next);
    213       while (*node != hash->data.e && (*node)->key != akey)
    214          node = &(*node)->next;
    215    } else {
    216       node = (struct util_node **)((const struct util_node * const *)(&hash->data.e));
    217    }
    218    return node;
    219 }
    220 
    221 drm_private struct util_hash_iter
    222 util_hash_insert(struct util_hash *hash, unsigned key, void *data)
    223 {
    224    util_data_might_grow(hash->data.d);
    225 
    226    {
    227       struct util_node **nextNode = util_hash_find_node(hash, key);
    228       struct util_node *node = util_hash_create_node(hash, key, data, nextNode);
    229       if (!node) {
    230          struct util_hash_iter null_iter = {hash, 0};
    231          return null_iter;
    232       }
    233 
    234       {
    235          struct util_hash_iter iter = {hash, node};
    236          return iter;
    237       }
    238    }
    239 }
    240 
    241 drm_private struct util_hash *util_hash_create(void)
    242 {
    243    struct util_hash *hash = malloc(sizeof(struct util_hash));
    244    if (!hash)
    245       return NULL;
    246 
    247    hash->data.d = malloc(sizeof(struct util_hash_data));
    248    if (!hash->data.d) {
    249       free(hash);
    250       return NULL;
    251    }
    252 
    253    hash->data.d->fakeNext = 0;
    254    hash->data.d->buckets = 0;
    255    hash->data.d->size = 0;
    256    hash->data.d->nodeSize = sizeof(struct util_node);
    257    hash->data.d->userNumBits = (short)MinNumBits;
    258    hash->data.d->numBits = 0;
    259    hash->data.d->numBuckets = 0;
    260 
    261    return hash;
    262 }
    263 
    264 drm_private void util_hash_delete(struct util_hash *hash)
    265 {
    266    struct util_node *e_for_x = (struct util_node *)(hash->data.d);
    267    struct util_node **bucket = (struct util_node **)(hash->data.d->buckets);
    268    int n = hash->data.d->numBuckets;
    269    while (n--) {
    270       struct util_node *cur = *bucket++;
    271       while (cur != e_for_x) {
    272          struct util_node *next = cur->next;
    273          util_free_node(cur);
    274          cur = next;
    275       }
    276    }
    277    free(hash->data.d->buckets);
    278    free(hash->data.d);
    279    free(hash);
    280 }
    281 
    282 drm_private struct util_hash_iter
    283 util_hash_find(struct util_hash *hash, unsigned key)
    284 {
    285    struct util_node **nextNode = util_hash_find_node(hash, key);
    286    struct util_hash_iter iter = {hash, *nextNode};
    287    return iter;
    288 }
    289 
    290 drm_private unsigned util_hash_iter_key(struct util_hash_iter iter)
    291 {
    292    if (!iter.node || iter.hash->data.e == iter.node)
    293       return 0;
    294    return iter.node->key;
    295 }
    296 
    297 drm_private void *util_hash_iter_data(struct util_hash_iter iter)
    298 {
    299    if (!iter.node || iter.hash->data.e == iter.node)
    300       return 0;
    301    return iter.node->value;
    302 }
    303 
    304 static struct util_node *util_hash_data_next(struct util_node *node)
    305 {
    306    union {
    307       struct util_node *next;
    308       struct util_node *e;
    309       struct util_hash_data *d;
    310    } a;
    311    int start;
    312    struct util_node **bucket;
    313    int n;
    314 
    315    a.next = node->next;
    316    if (!a.next) {
    317       /* iterating beyond the last element */
    318       return 0;
    319    }
    320    if (a.next->next)
    321       return a.next;
    322 
    323    start = (node->key % a.d->numBuckets) + 1;
    324    bucket = a.d->buckets + start;
    325    n = a.d->numBuckets - start;
    326    while (n--) {
    327       if (*bucket != a.e)
    328          return *bucket;
    329       ++bucket;
    330    }
    331    return a.e;
    332 }
    333 
    334 drm_private struct util_hash_iter
    335 util_hash_iter_next(struct util_hash_iter iter)
    336 {
    337    struct util_hash_iter next = {iter.hash, util_hash_data_next(iter.node)};
    338    return next;
    339 }
    340 
    341 drm_private int util_hash_iter_is_null(struct util_hash_iter iter)
    342 {
    343    if (!iter.node || iter.node == iter.hash->data.e)
    344       return 1;
    345    return 0;
    346 }
    347 
    348 drm_private void *util_hash_take(struct util_hash *hash, unsigned akey)
    349 {
    350    struct util_node **node = util_hash_find_node(hash, akey);
    351    if (*node != hash->data.e) {
    352       void *t = (*node)->value;
    353       struct util_node *next = (*node)->next;
    354       util_free_node(*node);
    355       *node = next;
    356       --hash->data.d->size;
    357       util_data_has_shrunk(hash->data.d);
    358       return t;
    359    }
    360    return 0;
    361 }
    362 
    363 drm_private struct util_hash_iter util_hash_first_node(struct util_hash *hash)
    364 {
    365    struct util_hash_iter iter = {hash, util_data_first_node(hash->data.d)};
    366    return iter;
    367 }
    368 
    369 drm_private struct util_hash_iter
    370 util_hash_erase(struct util_hash *hash, struct util_hash_iter iter)
    371 {
    372    struct util_hash_iter ret = iter;
    373    struct util_node *node = iter.node;
    374    struct util_node **node_ptr;
    375 
    376    if (node == hash->data.e)
    377       return iter;
    378 
    379    ret = util_hash_iter_next(ret);
    380    node_ptr = (struct util_node**)(&hash->data.d->buckets[node->key % hash->data.d->numBuckets]);
    381    while (*node_ptr != node)
    382       node_ptr = &(*node_ptr)->next;
    383    *node_ptr = node->next;
    384    util_free_node(node);
    385    --hash->data.d->size;
    386    return ret;
    387 }
    388