1/****************************************************************************** 2 * 3 * Copyright (C) 2014 Google, Inc. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ******************************************************************************/ 18 19#pragma once 20 21#include <stdbool.h> 22 23struct fixed_queue_t; 24typedef struct fixed_queue_t fixed_queue_t; 25 26typedef void (*fixed_queue_free_cb)(void *data); 27 28// Creates a new fixed queue with the given |capacity|. If more elements than 29// |capacity| are added to the queue, the caller is blocked until space is 30// made available in the queue. Returns NULL on failure. The caller must free 31// the returned queue with |fixed_queue_free|. 32fixed_queue_t *fixed_queue_new(size_t capacity); 33 34// Freeing a queue that is currently in use (i.e. has waiters 35// blocked on it) results in undefined behaviour. 36void fixed_queue_free(fixed_queue_t *queue, fixed_queue_free_cb free_cb); 37 38// Enqueues the given |data| into the |queue|. The caller will be blocked 39// if nore more space is available in the queue. Neither |queue| nor |data| 40// may be NULL. 41void fixed_queue_enqueue(fixed_queue_t *queue, void *data); 42 43// Dequeues the next element from |queue|. If the queue is currently empty, 44// this function will block the caller until an item is enqueued. This 45// function will never return NULL. |queue| may not be NULL. 46void *fixed_queue_dequeue(fixed_queue_t *queue); 47 48// Tries to enqueue |data| into the |queue|. This function will never block 49// the caller. If the queue capacity would be exceeded by adding one more 50// element, this function returns false immediately. Otherwise, this function 51// returns true. Neither |queue| nor |data| may be NULL. 52bool fixed_queue_try_enqueue(fixed_queue_t *queue, void *data); 53 54// Tries to dequeue an element from |queue|. This function will never block 55// the caller. If the queue is empty, this function returns NULL immediately. 56// Otherwise, the next element in the queue is returned. |queue| may not be 57// NULL. 58void *fixed_queue_try_dequeue(fixed_queue_t *queue); 59 60// This function returns a valid file descriptor. Callers may perform one 61// operation on the fd: select(2). If |select| indicates that the file 62// descriptor is readable, the caller may call |fixed_queue_enqueue| without 63// blocking. The caller must not close the returned file descriptor. |queue| 64// may not be NULL. 65int fixed_queue_get_enqueue_fd(const fixed_queue_t *queue); 66 67// This function returns a valid file descriptor. Callers may perform one 68// operation on the fd: select(2). If |select| indicates that the file 69// descriptor is readable, the caller may call |fixed_queue_dequeue| without 70// blocking. The caller must not close the returned file descriptor. |queue| 71// may not be NULL. 72int fixed_queue_get_dequeue_fd(const fixed_queue_t *queue); 73