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;
25typedef struct reactor_t reactor_t;
26
27typedef void (*fixed_queue_free_cb)(void *data);
28typedef void (*fixed_queue_cb)(fixed_queue_t *queue, void *context);
29
30// Creates a new fixed queue with the given |capacity|. If more elements than
31// |capacity| are added to the queue, the caller is blocked until space is
32// made available in the queue. Returns NULL on failure. The caller must free
33// the returned queue with |fixed_queue_free|.
34fixed_queue_t *fixed_queue_new(size_t capacity);
35
36// Freeing a queue that is currently in use (i.e. has waiters
37// blocked on it) results in undefined behaviour.
38void fixed_queue_free(fixed_queue_t *queue, fixed_queue_free_cb free_cb);
39
40// Returns a value indicating whether the given |queue| is empty. |queue| may
41// not be NULL.
42bool fixed_queue_is_empty(fixed_queue_t *queue);
43
44// Returns the maximum number of elements this queue may hold. |queue| may
45// not be NULL.
46size_t fixed_queue_capacity(fixed_queue_t *queue);
47
48// Enqueues the given |data| into the |queue|. The caller will be blocked
49// if nore more space is available in the queue. Neither |queue| nor |data|
50// may be NULL.
51void fixed_queue_enqueue(fixed_queue_t *queue, void *data);
52
53// Dequeues the next element from |queue|. If the queue is currently empty,
54// this function will block the caller until an item is enqueued. This
55// function will never return NULL. |queue| may not be NULL.
56void *fixed_queue_dequeue(fixed_queue_t *queue);
57
58// Tries to enqueue |data| into the |queue|. This function will never block
59// the caller. If the queue capacity would be exceeded by adding one more
60// element, this function returns false immediately. Otherwise, this function
61// returns true. Neither |queue| nor |data| may be NULL.
62bool fixed_queue_try_enqueue(fixed_queue_t *queue, void *data);
63
64// Tries to dequeue an element from |queue|. This function will never block
65// the caller. If the queue is empty, this function returns NULL immediately.
66// Otherwise, the next element in the queue is returned. |queue| may not be
67// NULL.
68void *fixed_queue_try_dequeue(fixed_queue_t *queue);
69
70// Returns the first element from |queue|, if present, without dequeuing it.
71// This function will never block the caller. Returns NULL if there are no elements
72// in the queue. |queue| may not be NULL.
73void *fixed_queue_try_peek(fixed_queue_t *queue);
74
75// This function returns a valid file descriptor. Callers may perform one
76// operation on the fd: select(2). If |select| indicates that the file
77// descriptor is readable, the caller may call |fixed_queue_enqueue| without
78// blocking. The caller must not close the returned file descriptor. |queue|
79// may not be NULL.
80int fixed_queue_get_enqueue_fd(const fixed_queue_t *queue);
81
82// This function returns a valid file descriptor. Callers may perform one
83// operation on the fd: select(2). If |select| indicates that the file
84// descriptor is readable, the caller may call |fixed_queue_dequeue| without
85// blocking. The caller must not close the returned file descriptor. |queue|
86// may not be NULL.
87int fixed_queue_get_dequeue_fd(const fixed_queue_t *queue);
88
89// Registers |queue| with |reactor| for dequeue operations. When there is an element
90// in the queue, ready_cb will be called. The |context| parameter is passed, untouched,
91// to the callback routine. Neither |queue|, nor |reactor|, nor |read_cb| may be NULL.
92// |context| may be NULL.
93void fixed_queue_register_dequeue(fixed_queue_t *queue, reactor_t *reactor, fixed_queue_cb ready_cb, void *context);
94
95// Unregisters the dequeue ready callback for |queue| from whichever reactor
96// it is registered with, if any. This function is idempotent.
97void fixed_queue_unregister_dequeue(fixed_queue_t *queue);
98