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 /*

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  *

  * Copyright 2021 Mike Becker, Olaf Wintermann All 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.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 THE COPYRIGHT HOLDER OR CONTRIBUTORS 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 <errno.h>

 #include <string.h>

 #include "cx/hash_map.h"

 #include "cx/utils.h"

 /**

  * Computes a murmur hash-2.

  *

  * @param data the data to hash

  * @param len the length of the data

  * @return the murmur hash-2 of the data

  */

 static unsigned cx_hash_map_murmur(

         unsigned char const *data,

         size_t len

 ) {

     unsigned m = 0x5bd1e995;

     unsigned r = 24;

     unsigned h = 25 ^ len;

     unsigned i = 0;

     while (len >= 4) {

         unsigned k = data[i + 0] & 0xFF;

         k |= (data[i + 1] & 0xFF) << 8;

         k |= (data[i + 2] & 0xFF) << 16;

         k |= (data[i + 3] & 0xFF) << 24;

         k *= m;

         k ^= k >> r;

         k *= m;

         h *= m;

         h ^= k;

         i += 4;

         len -= 4;

     }

     switch (len) {

         case 3:

             h ^= (data[i + 2] & 0xFF) << 16;

                     __attribute__((__fallthrough__));

         case 2:

             h ^= (data[i + 1] & 0xFF) << 8;

                     __attribute__((__fallthrough__));

         case 1:

             h ^= (data[i + 0] & 0xFF);

             h *= m;

                     __attribute__((__fallthrough__));

         default:

             /* do nothing */;

     }

     h ^= h >> 13;

     h *= m;

     h ^= h >> 15;

     return h;

 }

 static void cx_hash_map_clear(struct cx_map_s *map) {

     struct cx_hash_map_s *hash_map = (struct cx_hash_map_s *) map;

     cx_for_n(i, hash_map->bucket_count) {

         struct cx_hash_map_element_s *elem = hash_map->buckets[i];

         if (elem != NULL) {

             do {

                 struct cx_hash_map_element_s *next = elem->next;

                 // free the key data

                 cxFree(map->allocator, elem->key.data);

                 // free the node

                 cxFree(map->allocator, elem);

                 // proceed

                 elem = next;

             } while (elem != NULL);

             // do not leave a dangling pointer

             hash_map->buckets[i] = NULL;

         }

     }

     map->size = 0;

 }

 static void cx_hash_map_destructor(struct cx_map_s *map) {

     struct cx_hash_map_s *hash_map = (struct cx_hash_map_s *) map;

     // free the buckets

     cx_hash_map_clear(map);

     cxFree(map->allocator, hash_map->buckets);

     // free the map structure

     cxFree(map->allocator, map);

 }

 static int cx_hash_map_put(

         CxMap *map,

         CxDataPtr key,

         void *value

 ) {

     struct cx_hash_map_s *hash_map = (struct cx_hash_map_s *) map;

     CxAllocator *allocator = map->allocator;

     unsigned hash = cx_hash_map_murmur(key.data, key.len);

     size_t slot = hash % hash_map->bucket_count;

     struct cx_hash_map_element_s *elm = hash_map->buckets[slot];

     struct cx_hash_map_element_s *prev = NULL;

     while (elm != NULL && elm->key.hash < hash) {

         prev = elm;

         elm = elm->next;

     }

     if (elm == NULL || elm->key.hash != hash) {

         struct cx_hash_map_element_s *e = cxMalloc(allocator, sizeof(struct cx_hash_map_element_s));

         if (e == NULL) {

             return -1;

         }

         // write the value

         // TODO: depending on future map features, we may want to copy here

         e->data = value;

         // copy the key

         void *kd = cxMalloc(allocator, key.len);

         if (kd == NULL) {

             return -1;

         }

         memcpy(kd, key.data, key.len);

         e->key.data = kd;

         e->key.len = key.len;

         e->key.hash = hash;

         // insert the element into the linked list

         if (prev == NULL) {

             hash_map->buckets[slot] = e;

         } else {

             prev->next = e;

         }

         e->next = elm;

         // increase the size

         map->size++;

     } else {

         // (elem != NULL && elem->key.hash == hash) - overwrite value of existing element

         elm->data = value;

     }

     return 0;

 }

 /**

  * Helper function to avoid code duplication.

  *

  * @param map the map

  * @param key the key to look up

  * @param remove flag indicating whether the looked up entry shall be removed

  * @return the value corresponding to the key or \c NULL

  */

 static void *cx_hash_map_get_remove(

         CxMap *map,

         CxDataPtr key,

         bool remove

 ) {

     struct cx_hash_map_s *hash_map = (struct cx_hash_map_s *) map;

     unsigned hash = cx_hash_map_murmur(key.data, key.len);

     size_t slot = hash % hash_map->bucket_count;

     struct cx_hash_map_element_s *elm = hash_map->buckets[slot];

     struct cx_hash_map_element_s *prev = NULL;

     while (elm && elm->key.hash <= hash) {

         if (elm->key.hash == hash && elm->key.len == key.len) {

             if (memcmp(elm->key.data, key.data, key.len) == 0) {

                 void *data = elm->data;

                 if (remove) {

                     // unlink

                     if (prev) {

                         prev->next = elm->next;

                     } else {

                         hash_map->buckets[slot] = elm->next;

                     }

                     // free element

                     cxFree(map->allocator, elm->key.data);

                     cxFree(map->allocator, elm);

                     // decrease size

                     map->size--;

                 }

                 return data;

             }

         }

         prev = elm;

         elm = prev->next;

     }

     return NULL;

 }

 static void *cx_hash_map_get(

         CxMap const *map,

         CxDataPtr key

 ) {

     // we can safely cast, because we know when remove=false, the map stays untouched

     return cx_hash_map_get_remove((CxMap *) map, key, false);

 }

 static void *cx_hash_map_remove(

         CxMap *map,

         CxDataPtr key

 ) {

     return cx_hash_map_get_remove(map, key, true);

 }

 static CxIterator cx_hash_map_iterator(CxMap const *map) {

     CxIterator iter;

     // TODO: initialize iter

     return iter;

 }

 static CxIterator cx_hash_map_iterator_keys(CxMap const *map) {

     CxIterator iter;

     // TODO: initialize iter

     return iter;

 }

 static CxIterator cx_hash_map_iterator_values(CxMap const *map) {

     CxIterator iter;

     // TODO: initialize iter

     return iter;

 }

 static cx_map_class cx_hash_map_class = {

         cx_hash_map_destructor,

         cx_hash_map_clear,

         cx_hash_map_put,

         cx_hash_map_get,

         cx_hash_map_remove,

         cx_hash_map_iterator,

         cx_hash_map_iterator_keys,

         cx_hash_map_iterator_values,

 };

 CxMap *cxHashMapCreate(

         CxAllocator *allocator,

         size_t buckets

 ) {

     if (buckets == 0) {

         // implementation defined default

         buckets = 16;

     }

     struct cx_hash_map_s *map = cxMalloc(allocator, sizeof(struct cx_hash_map_s));

     if (map == NULL) return NULL;

     // initialize hash map members

     map->bucket_count = buckets;

     map->buckets = cxCalloc(allocator, buckets, sizeof(struct cx_hash_map_element_s *));

     if (map->buckets == NULL) {

         cxFree(allocator, map);

         return NULL;

     }

     // initialize base members

     map->base.cl = &cx_hash_map_class;

     map->base.allocator = allocator;

     map->base.size = 0;

     return (CxMap *) map;

 }