1 /******************************************************************************
3 * Copyright (C) 2014 Google, Inc.
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:
9 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 ******************************************************************************/
25 typedef struct fixed_queue_t fixed_queue_t;
26 typedef struct reactor_t reactor_t;
28 typedef void (*fixed_queue_free_cb)(void *data);
29 typedef void (*fixed_queue_cb)(fixed_queue_t *queue, void *context);
31 // Creates a new fixed queue with the given |capacity|. If more elements than
32 // |capacity| are added to the queue, the caller is blocked until space is
33 // made available in the queue. Returns NULL on failure. The caller must free
34 // the returned queue with |fixed_queue_free|.
35 fixed_queue_t *fixed_queue_new(size_t capacity);
37 // Freeing a queue that is currently in use (i.e. has waiters
38 // blocked on it) results in undefined behaviour.
39 void fixed_queue_free(fixed_queue_t *queue, fixed_queue_free_cb free_cb);
41 // Returns a value indicating whether the given |queue| is empty. |queue| may
43 bool fixed_queue_is_empty(fixed_queue_t *queue);
45 // Returns the maximum number of elements this queue may hold. |queue| may
47 size_t fixed_queue_capacity(fixed_queue_t *queue);
49 // Enqueues the given |data| into the |queue|. The caller will be blocked
50 // if nore more space is available in the queue. Neither |queue| nor |data|
52 void fixed_queue_enqueue(fixed_queue_t *queue, void *data);
54 // Dequeues the next element from |queue|. If the queue is currently empty,
55 // this function will block the caller until an item is enqueued. This
56 // function will never return NULL. |queue| may not be NULL.
57 void *fixed_queue_dequeue(fixed_queue_t *queue);
59 // Tries to enqueue |data| into the |queue|. This function will never block
60 // the caller. If the queue capacity would be exceeded by adding one more
61 // element, this function returns false immediately. Otherwise, this function
62 // returns true. Neither |queue| nor |data| may be NULL.
63 bool fixed_queue_try_enqueue(fixed_queue_t *queue, void *data);
65 // Tries to dequeue an element from |queue|. This function will never block
66 // the caller. If the queue is empty, this function returns NULL immediately.
67 // Otherwise, the next element in the queue is returned. |queue| may not be
69 void *fixed_queue_try_dequeue(fixed_queue_t *queue);
71 // Returns the first element from |queue|, if present, without dequeuing it.
72 // This function will never block the caller. Returns NULL if there are no elements
73 // in the queue. |queue| may not be NULL.
74 void *fixed_queue_try_peek(fixed_queue_t *queue);
76 // This function returns a valid file descriptor. Callers may perform one
77 // operation on the fd: select(2). If |select| indicates that the file
78 // descriptor is readable, the caller may call |fixed_queue_enqueue| without
79 // blocking. The caller must not close the returned file descriptor. |queue|
81 int fixed_queue_get_enqueue_fd(const fixed_queue_t *queue);
83 // This function returns a valid file descriptor. Callers may perform one
84 // operation on the fd: select(2). If |select| indicates that the file
85 // descriptor is readable, the caller may call |fixed_queue_dequeue| without
86 // blocking. The caller must not close the returned file descriptor. |queue|
88 int fixed_queue_get_dequeue_fd(const fixed_queue_t *queue);
90 // Registers |queue| with |reactor| for dequeue operations. When there is an element
91 // in the queue, ready_cb will be called. The |context| parameter is passed, untouched,
92 // to the callback routine. Neither |queue|, nor |reactor|, nor |read_cb| may be NULL.
93 // |context| may be NULL.
94 void fixed_queue_register_dequeue(fixed_queue_t *queue, reactor_t *reactor, fixed_queue_cb ready_cb, void *context);
96 // Unregisters the dequeue ready callback for |queue| from whichever reactor
97 // it is registered with, if any. This function is idempotent.
98 void fixed_queue_unregister_dequeue(fixed_queue_t *queue);