274 lines
7.3 KiB
C
274 lines
7.3 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
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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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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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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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#include "SDL_internal.h"
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#include "SDL_hashtable.h"
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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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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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SDL_HashTable *SDL_CreateHashTable(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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// 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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table = (SDL_HashTable *) SDL_calloc(1, sizeof (SDL_HashTable));
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if (!table) {
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return NULL;
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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) {
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SDL_free(table);
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return NULL;
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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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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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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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if ( (!table->stackable) && (SDL_FindInHashTable(table, key, NULL)) ) {
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return SDL_FALSE;
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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) {
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return SDL_FALSE;
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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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return SDL_TRUE;
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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 *i;
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for (i = table->table[hash]; i; i = i->next) {
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if (table->keymatch(key, i->key, data)) {
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if (_value) {
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*_value = i->value;
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}
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return SDL_TRUE;
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}
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}
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return SDL_FALSE;
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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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for (item = table->table[hash]; item; item = item->next) {
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if (table->keymatch(key, item->key, data)) {
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if (prev) {
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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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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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prev = item;
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}
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return SDL_FALSE;
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}
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SDL_bool SDL_IterateHashTableKey(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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while (item) {
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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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// 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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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 = (SDL_HashItem *) *iter;
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Uint32 idx = 0;
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if (item) {
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const SDL_HashItem *orig = item;
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item = item->next;
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if (!item) {
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idx = calc_hash(table, orig->key) + 1; // !!! FIXME: we probably shouldn't rehash each time.
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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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if (!item) { // 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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*_key = item->key;
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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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SDL_bool SDL_HashTableEmpty(SDL_HashTable *table)
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{
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if (table) {
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Uint32 i;
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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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if (item) {
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return SDL_FALSE;
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}
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}
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}
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return SDL_TRUE;
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}
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void SDL_DestroyHashTable(SDL_HashTable *table)
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{
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if (table) {
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void *data = table->data;
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Uint32 i;
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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) {
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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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SDL_free(table->table);
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SDL_free(table);
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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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Uint32 SDL_HashString(const void *key, void *data)
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{
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const char *str = (const char *)key;
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return hash_string_djbxor(str, SDL_strlen(str));
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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); // Check against actual string contents.
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}
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// We assume we can fit the ID in the key directly
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SDL_COMPILE_TIME_ASSERT(SDL_HashID_KeySize, sizeof(Uint32) <= sizeof(const void *));
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Uint32 SDL_HashID(const void *key, void *unused)
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{
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return (Uint32)(uintptr_t)key;
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}
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SDL_bool SDL_KeyMatchID(const void *a, const void *b, void *unused)
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{
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if (a == b) {
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return SDL_TRUE;
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}
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return SDL_FALSE;
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}
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