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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 <string.h>

 #include "cx/hash_map.h"

 #include "cx/utils.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.obj);

                 // 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,

         CxHashKey key,

         void *value

 ) {

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

     CxAllocator *allocator = map->allocator;

     unsigned hash = key.hash;

     if (hash == 0) {

         cx_hash_murmur(&key);

         hash = key.hash;

     }

     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 && elm->key.len == key.len &&

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

         // overwrite existing element

         elm->data = value;

     } else {

         // allocate new element

         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.obj, key.len);

         e->key.data.obj = 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++;

     }

     return 0;

 }

 static void cx_hash_map_unlink(

         struct cx_hash_map_s *hash_map,

         size_t slot,

         struct cx_hash_map_element_s *prev,

         struct cx_hash_map_element_s *elm

 ) {

     // unlink

     if (prev == NULL) {

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

     } else {

         prev->next = elm->next;

     }

     // free element

     cxFree(hash_map->base.allocator, elm->key.data.obj);

     cxFree(hash_map->base.allocator, elm);

     // decrease size

     hash_map->base.size--;

 }

 /**

  * 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,

         CxHashKey key,

         bool remove

 ) {

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

     unsigned hash = key.hash;

     if (hash == 0) {

         cx_hash_murmur(&key);

         hash = key.hash;

     }

     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.obj, key.data.obj, key.len) == 0) {

                 void *data = elm->data;

                 if (remove) {

                     cx_hash_map_unlink(hash_map, slot, prev, elm);

                 }

                 return data;

             }

         }

         prev = elm;

         elm = prev->next;

     }

     return NULL;

 }

 static void *cx_hash_map_get(

         CxMap const *map,

         CxHashKey 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,

         CxHashKey key

 ) {

     return cx_hash_map_get_remove(map, key, true);

 }

 static void *cx_hash_map_iter_current_entry(void const *it) {

     struct cx_iterator_s const *iter = it;

     // struct has to have a compatible signature

     return (struct cx_map_entry_s *) &(iter->kv_data);

 }

 static void *cx_hash_map_iter_current_key(void const *it) {

     struct cx_iterator_s const *iter = it;

     struct cx_hash_map_element_s *elm = iter->elem_handle;

     return &elm->key;

 }

 static void *cx_hash_map_iter_current_value(void const *it) {

     struct cx_iterator_s const *iter = it;

     struct cx_hash_map_element_s *elm = iter->elem_handle;

     // TODO: return a pointer to data if this map is storing copies

     return elm->data;

 }

 static bool cx_hash_map_iter_valid(void const *it) {

     struct cx_iterator_s const *iter = it;

     return iter->elem_handle != NULL;

 }

 static void cx_hash_map_iter_next(void *it) {

     struct cx_iterator_s *iter = it;

     struct cx_hash_map_element_s *elm = iter->elem_handle;

     // remove current element, if asked

     if (iter->base.remove) {

         // obtain mutable pointer to the map

         struct cx_mut_iterator_s *miter = it;

         struct cx_hash_map_s *map = miter->src_handle;

         // clear the flag

         iter->base.remove = false;

         // determine the next element

         struct cx_hash_map_element_s *next = elm->next;

         // search the previous element

         struct cx_hash_map_element_s *prev = NULL;

         if (map->buckets[iter->slot] != elm) {

             prev = map->buckets[iter->slot];

             while (prev->next != elm) {

                 prev = prev->next;

             }

         }

         // unlink

         cx_hash_map_unlink(map, iter->slot, prev, elm);

         // advance

         elm = next;

     } else {

         // just advance

         elm = elm->next;

         iter->index++;

     }

     // search the next bucket, if required

     struct cx_hash_map_s const *map = iter->src_handle;

     while (elm == NULL && ++iter->slot < map->bucket_count) {

         elm = map->buckets[iter->slot];

     }

     // fill the struct with the next element

     iter->elem_handle = elm;

     if (elm == NULL) {

         iter->kv_data.key = NULL;

         iter->kv_data.value = NULL;

     } else {

         iter->kv_data.key = &elm->key;

         // TODO: pointer to data if this map is storing copies

         iter->kv_data.value = elm->data;

     }

 }

 static bool cx_hash_map_iter_flag_rm(void *it) {

     struct cx_iterator_base_s *iter = it;

     if (iter->mutating) {

         iter->remove = true;

         return true;

     } else {

         return false;

     }

 }

 static CxIterator cx_hash_map_iterator(CxMap const *map) {

     CxIterator iter;

     iter.src_handle = map;

     iter.base.valid = cx_hash_map_iter_valid;

     iter.base.next = cx_hash_map_iter_next;

     iter.base.current = cx_hash_map_iter_current_entry;

     iter.base.flag_removal = cx_hash_map_iter_flag_rm;

     iter.base.remove = false;

     iter.base.mutating = false;

     iter.slot = 0;

     iter.index = 0;

     if (map->size > 0) {

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

         struct cx_hash_map_element_s *elm = hash_map->buckets[0];

         for (; elm == NULL; iter.slot++) {

             elm = hash_map->buckets[iter.slot];

         }

         iter.elem_handle = elm;

         iter.kv_data.key = &elm->key;

         // TODO: pointer to data if this map is storing copies

         iter.kv_data.value = elm->data;

     } else {

         iter.elem_handle = NULL;

         iter.kv_data.key = NULL;

         iter.kv_data.value = NULL;

     }

     return iter;

 }

 static CxIterator cx_hash_map_iterator_keys(CxMap const *map) {

     CxIterator iter = cx_hash_map_iterator(map);

     iter.base.current = cx_hash_map_iter_current_key;

     return iter;

 }

 static CxIterator cx_hash_map_iterator_values(CxMap const *map) {

     CxIterator iter = cx_hash_map_iterator(map);

     iter.base.current = cx_hash_map_iter_current_value;

     return iter;

 }

 static CxMutIterator cx_hash_map_mut_iterator(CxMap *map) {

     CxIterator it = cx_hash_map_iterator(map);

     it.base.mutating = true;

     // we know the iterators share the same memory layout

     CxMutIterator iter;

     memcpy(&iter, &it, sizeof(CxMutIterator));

     return iter;

 }

 static CxMutIterator cx_hash_map_mut_iterator_keys(CxMap *map) {

     CxMutIterator iter = cx_hash_map_mut_iterator(map);

     iter.base.current = cx_hash_map_iter_current_key;

     return iter;

 }

 static CxMutIterator cx_hash_map_mut_iterator_values(CxMap *map) {

     CxMutIterator iter = cx_hash_map_mut_iterator(map);

     iter.base.current = cx_hash_map_iter_current_value;

     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,

         cx_hash_map_mut_iterator,

         cx_hash_map_mut_iterator_keys,

         cx_hash_map_mut_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;

 }

 int cxMapRehash(CxMap *map) {

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

     if (map->size > ((hash_map->bucket_count * 3) >> 2)) {

         size_t new_bucket_count = (map->size * 5) >> 1;

         struct cx_hash_map_element_s **new_buckets = cxCalloc(map->allocator,

                                                               new_bucket_count, sizeof(struct cx_hash_map_element_s *));

         if (new_buckets == NULL) {

             return 1;

         }

         // iterate through the elements and assign them to their new slots

         cx_for_n(slot, hash_map->bucket_count) {

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

             while (elm != NULL) {

                 struct cx_hash_map_element_s *next = elm->next;

                 size_t new_slot = elm->key.hash % new_bucket_count;

                 // find position where to insert

                 struct cx_hash_map_element_s *bucket_next = new_buckets[new_slot];

                 struct cx_hash_map_element_s *bucket_prev = NULL;

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

                     bucket_prev = bucket_next;

                     bucket_next = bucket_next->next;

                 }

                 // insert

                 if (bucket_prev == NULL) {

                     elm->next = new_buckets[new_slot];

                     new_buckets[new_slot] = elm;

                 } else {

                     bucket_prev->next = elm;

                     elm->next = bucket_next;

                 }

                 // advance

                 elm = next;

             }

         }

         // assign result to the map

         hash_map->bucket_count = new_bucket_count;

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

         hash_map->buckets = new_buckets;

     }

     return 0;

 }