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/*
* Copyright (c) 2021 NVIDIA Corporation.
*
* 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.
*/
#ifndef ID_FPOOL_H
#define ID_FPOOL_H
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
/*
* Fast ID pool.
* =============
*
* Unordered pool of unique 32 bits IDs.
*
* Multiple users are registered at initialization. Each one gets a cache
* of ID. When each thread allocates from the pool using its own user ID,
* the pool scales for concurrent allocation.
*
* New IDs are always in the range of '[floor, next_id]', where 'next_id' is
* in the range of '[last_allocated_ID + nb_user * cache_size + 1]'.
* This means that a new ID is not always the smallest available ID, but it is
* still from a limited range.
*
* Users should ensure that an ID is *never* freed twice. Not doing so will
* have the effect of double-allocating such ID afterward.
*
* Thread-safety
* =============
*
* APIs are thread safe.
* Multiple threads can share the same user ID if necessary.
*/
#define ID_FPOOL_CACHE_SIZE 64
struct id_fpool;
/* nb_user is the number of expected users of the pool,
* in terms of execution threads. */
struct id_fpool *id_fpool_create(unsigned int nb_user,
uint32_t base, uint32_t n_ids);
void id_fpool_destroy(struct id_fpool *pool);
/* uid is the thread user-id. It should be within '[0, nb_user)'. */
bool id_fpool_new_id(struct id_fpool *pool, unsigned int uid, uint32_t *id);
/* uid is the thread user-id. It should be within '[0, nb_user)'.
* An allocated ID must never be freed twice. */
void id_fpool_free_id(struct id_fpool *pool, unsigned int uid, uint32_t id);
#endif /* ID_FPOOL_H */
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