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@@ -0,0 +1,259 @@
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+/*
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+ Simple DirectMedia Layer
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+ Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
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+
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+ This software is provided 'as-is', without any express or implied
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+ warranty. In no event will the authors be held liable for any damages
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+ arising from the use of this software.
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+
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+ Permission is granted to anyone to use this software for any purpose,
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+ including commercial applications, and to alter it and redistribute it
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+ freely, subject to the following restrictions:
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+
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+ 1. The origin of this software must not be misrepresented; you must not
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+ claim that you wrote the original software. If you use this software
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+ in a product, an acknowledgment in the product documentation would be
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+ appreciated but is not required.
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+ 2. Altered source versions must be plainly marked as such, and must not be
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+ misrepresented as being the original software.
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+ 3. This notice may not be removed or altered from any source distribution.
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+*/
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+
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+#include "SDL_internal.h"
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+#include "SDL_hashtable.h"
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+
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+typedef struct SDL_HashItem
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+{
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+ const void *key;
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+ const void *value;
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+ struct SDL_HashItem *next;
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+} SDL_HashItem;
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+
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+struct SDL_HashTable
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+{
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+ SDL_HashItem **table;
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+ Uint32 table_len;
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+ SDL_bool stackable;
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+ void *data;
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+ SDL_HashTable_HashFn hash;
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+ SDL_HashTable_KeyMatchFn keymatch;
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+ SDL_HashTable_NukeFn nuke;
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+};
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+
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+SDL_HashTable *SDL_NewHashTable(void *data, const Uint32 num_buckets, const SDL_HashTable_HashFn hashfn,
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+ const SDL_HashTable_KeyMatchFn keymatchfn,
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+ const SDL_HashTable_NukeFn nukefn,
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+ const SDL_bool stackable)
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+{
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+ SDL_HashTable *table;
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+
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+ /* num_buckets must be a power of two so we get a solid block of bits to mask hash values against. */
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+ if ((num_buckets == 0) || ((num_buckets & (num_buckets - 1)) != 0)) {
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+ SDL_SetError("num_buckets must be a power of two");
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+ return NULL;
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+ }
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+
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+ table = (SDL_HashTable *) SDL_calloc(1, sizeof (SDL_HashTable));
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+ if (table == NULL) {
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+ SDL_OutOfMemory();
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+ return NULL;
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+ }
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+
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+ table->table = (SDL_HashItem **) SDL_calloc(num_buckets, sizeof (SDL_HashItem *));
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+ if (table->table == NULL) {
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+ SDL_free(table);
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+ SDL_OutOfMemory();
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+ return NULL;
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+ }
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+
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+ table->table_len = num_buckets;
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+ table->stackable = stackable;
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+ table->data = data;
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+ table->hash = hashfn;
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+ table->keymatch = keymatchfn;
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+ table->nuke = nukefn;
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+ return table;
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+}
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+
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+static SDL_INLINE Uint32 calc_hash(const SDL_HashTable *table, const void *key)
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+{
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+ return table->hash(key, table->data) & (table->table_len - 1);
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+}
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+
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+
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+SDL_bool SDL_InsertIntoHashTable(SDL_HashTable *table, const void *key, const void *value)
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+{
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+ SDL_HashItem *item;
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+ const Uint32 hash = calc_hash(table, key);
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+
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+ if ( (!table->stackable) && (SDL_FindInHashTable(table, key, NULL)) ) {
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+ return SDL_FALSE;
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+ }
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+
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+ /* !!! FIXME: grow and rehash table if it gets too saturated. */
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+ item = (SDL_HashItem *) SDL_malloc(sizeof (SDL_HashItem));
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+ if (item == NULL) {
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+ SDL_OutOfMemory();
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+ return SDL_FALSE;
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+ }
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+
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+ item->key = key;
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+ item->value = value;
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+ item->next = table->table[hash];
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+ table->table[hash] = item;
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+
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+ return SDL_TRUE;
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+}
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+
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+SDL_bool SDL_FindInHashTable(const SDL_HashTable *table, const void *key, const void **_value)
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+{
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+ const Uint32 hash = calc_hash(table, key);
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+ void *data = table->data;
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+ SDL_HashItem *prev = NULL;
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+ SDL_HashItem *i;
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+
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+ for (i = table->table[hash]; i != NULL; i = i->next) {
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+ if (table->keymatch(key, i->key, data)) {
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+ if (_value != NULL) {
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+ *_value = i->value;
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+ }
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+
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+ /* Matched! Move to the front of list for faster lookup next time.
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+ (stackable tables have to remain in the same order, though!) */
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+ if ((!table->stackable) && (prev != NULL)) {
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+ SDL_assert(prev->next == i);
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+ prev->next = i->next;
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+ i->next = table->table[hash];
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+ table->table[hash] = i;
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+ }
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+
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+ return SDL_TRUE;
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+ }
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+
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+ prev = i;
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+ }
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+
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+ return SDL_FALSE;
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+}
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+
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+SDL_bool SDL_RemoveFromHashTable(SDL_HashTable *table, const void *key)
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+{
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+ const Uint32 hash = calc_hash(table, key);
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+ SDL_HashItem *item = NULL;
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+ SDL_HashItem *prev = NULL;
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+ void *data = table->data;
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+
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+ for (item = table->table[hash]; item != NULL; item = item->next) {
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+ if (table->keymatch(key, item->key, data)) {
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+ if (prev != NULL) {
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+ prev->next = item->next;
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+ } else {
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+ table->table[hash] = item->next;
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+ }
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+
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+ table->nuke(item->key, item->value, data);
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+ SDL_free(item);
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+ return SDL_TRUE;
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+ }
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+
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+ prev = item;
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+ }
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+
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+ return SDL_FALSE;
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+}
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+
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+SDL_bool SDL_IterateHashTable(const SDL_HashTable *table, const void *key, const void **_value, void **iter)
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+{
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+ SDL_HashItem *item = iter ? ((SDL_HashItem *) *iter)->next : table->table[calc_hash(table, key)];
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+
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+ while (item != NULL) {
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+ if (table->keymatch(key, item->key, table->data)) {
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+ *_value = item->value;
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+ *iter = item;
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+ return SDL_TRUE;
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+ }
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+ item = item->next;
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+ }
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+
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+ /* no more matches. */
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+ *_value = NULL;
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+ *iter = NULL;
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+ return SDL_FALSE;
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+}
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+
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+SDL_bool SDL_IterateHashTableKeys(const SDL_HashTable *table, const void **_key, void **iter)
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+{
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+ SDL_HashItem *item = (SDL_HashItem *) *iter;
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+ Uint32 idx = 0;
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+
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+ if (item != NULL) {
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+ const SDL_HashItem *orig = item;
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+ item = item->next;
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+ if (item == NULL) {
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+ idx = calc_hash(table, orig->key) + 1;
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+ }
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+ }
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+
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+ while (!item && (idx < table->table_len)) {
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+ item = table->table[idx++]; /* skip empty buckets... */
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+ }
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+
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+ if (item == NULL) { /* no more matches? */
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+ *_key = NULL;
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+ *iter = NULL;
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+ return SDL_FALSE;
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+ }
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+
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+ *_key = item->key;
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+ *iter = item;
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+ return SDL_TRUE;
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+}
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+
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+void SDL_FreeHashTable(SDL_HashTable *table)
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+{
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+ if (table != NULL) {
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+ void *data = table->data;
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+ Uint32 i;
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+
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+ for (i = 0; i < table->table_len; i++) {
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+ SDL_HashItem *item = table->table[i];
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+ while (item != NULL) {
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+ SDL_HashItem *next = item->next;
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+ table->nuke(item->key, item->value, data);
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+ SDL_free(item);
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+ item = next;
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+ }
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+ }
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+
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+ SDL_free(table->table);
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+ SDL_free(table);
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+ }
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+}
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+
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+/* this is djb's xor hashing function. */
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+static SDL_INLINE Uint32 hash_string_djbxor(const char *str, size_t len)
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+{
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+ Uint32 hash = 5381;
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+ while (len--) {
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+ hash = ((hash << 5) + hash) ^ *(str++);
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+ }
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+ return hash;
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+}
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+
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+Uint32 SDL_HashString(const void *sym, void *data)
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+{
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+ const char *str = (const char*) sym;
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+ return hash_string_djbxor(str, SDL_strlen((const char *) str));
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+}
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+
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+SDL_bool SDL_KeyMatchString(const void *a, const void *b, void *data)
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+{
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+ if (a == b) {
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+ return SDL_TRUE; /* same pointer, must match. */
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+ } else if (!a || !b) {
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+ return SDL_FALSE; /* one pointer is NULL (and first test shows they aren't the same pointer), must not match. */
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+ }
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+ return (SDL_strcmp((const char *) a, (const char *) b) == 0) ? SDL_TRUE : SDL_FALSE; /* Check against actual string contents. */
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+}
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+
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+/* vi: set ts=4 sw=4 expandtab: */
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Ryan C. Gordon