libcutils/include/cutils/hashmap.h

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Hash map.
 *
 * Use std::map or std::unordered_map instead.
 * https://en.cppreference.com/w/cpp/container
 */

#ifndef __HASHMAP_H
#define __HASHMAP_H

#include <stdbool.h>
#include <stdlib.h>

#ifdef __cplusplus
extern "C" {
#endif

/** A hash map. */
typedef struct Hashmap Hashmap;

/**
 * Creates a new hash map. Returns NULL if memory allocation fails.
 *
 * @param initialCapacity number of expected entries
 * @param hash function which hashes keys
 * @param equals function which compares keys for equality
 */
Hashmap* hashmapCreate(size_t initialCapacity,
        int (*hash)(void* key), bool (*equals)(void* keyA, void* keyB));

/**
 * Frees the hash map. Does not free the keys or values themselves.
 */
void hashmapFree(Hashmap* map);

/**
 * Hashes the memory pointed to by key with the given size. Useful for
 * implementing hash functions.
 */
int hashmapHash(void* key, size_t keySize);

/**
 * Puts value for the given key in the map. Returns pre-existing value if
 * any.
 *
 * If memory allocation fails, this function returns NULL, the map's size
 * does not increase, and errno is set to ENOMEM.
 */
void* hashmapPut(Hashmap* map, void* key, void* value);

/**
 * Gets a value from the map. Returns NULL if no entry for the given key is
 * found or if the value itself is NULL.
 */
void* hashmapGet(Hashmap* map, void* key);

/**
 * Removes an entry from the map. Returns the removed value or NULL if no
 * entry was present.
 */
void* hashmapRemove(Hashmap* map, void* key);

/**
 * Invokes the given callback on each entry in the map. Stops iterating if
 * the callback returns false.
 */
void hashmapForEach(Hashmap* map, bool (*callback)(void* key, void* value, void* context),
                    void* context);

/**
 * Concurrency support.
 */

/**
 * Locks the hash map so only the current thread can access it.
 */
void hashmapLock(Hashmap* map);

/**
 * Unlocks the hash map so other threads can access it.
 */
void hashmapUnlock(Hashmap* map);

#ifdef __cplusplus
}
#endif

#endif /* __HASHMAP_H */