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 23 struct fixed_queue_t; 24 typedef struct fixed_queue_t fixed_queue_t; 25 26 typedef 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|. 32 fixed_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. 36 void 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. 41 void 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. 46 void *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. 52 bool 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. 58 void *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. 65 int 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. 72 int fixed_queue_get_dequeue_fd(const fixed_queue_t *queue); 73