2 * Copyright (C) 2007-2010 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file chunk_queue.c Queuing functions for paraslash senders. */
18 * Senders may use the chunk queue facility to deal with laggy connections. It
19 * allows them to enqueue chunks if they can not be sent out immediately.
21 * Chunk queues are "cheap" in the sense that only reference to the audio file
22 * data is stored, but not the data itself.
25 /** The list of pending chunks for this client. */
27 /** The number of pending bytes for this client. */
28 unsigned long num_pending;
29 /** More than that many bytes in the queue is considered an error. */
30 unsigned long max_pending;
33 /** Describes one queued chunk in a chunk queue. */
35 /** Pointer to the data to be queued. */
37 /** The number of bytes of this chunk. */
39 /** Position of the chunk in the chunk queue. */
40 struct list_head node;
44 * Add a chunk to the given queue.
46 * \param cq the queue to add the chunk to.
47 * \param buf Pointer to the data to be queued.
48 * \param num_bytes The size of \a buf.
52 int cq_enqueue(struct chunk_queue *cq, const char *buf, size_t num_bytes)
54 struct queued_chunk *qc;
56 if (cq->num_pending + num_bytes > cq->max_pending)
58 qc = para_malloc(sizeof(struct queued_chunk));
59 cq->num_pending += num_bytes;
61 qc->num_bytes = num_bytes;
62 list_add_tail(&qc->node, &cq->q);
63 PARA_DEBUG_LOG("%lu bytes queued for %p\n", cq->num_pending, &cq->q);
68 * Lookup the next chunk in the queue.
70 * \param cq The chunk queue.
72 * \return The next queued chunk, or \p NULL if there is no chunk available.
74 struct queued_chunk *cq_peek(struct chunk_queue *cq)
76 if (list_empty(&cq->q))
78 return list_entry(cq->q.next, struct queued_chunk, node);
82 * Remove the current chunk from the queue.
84 * \param cq The queue to remove from.
86 void cq_dequeue(struct chunk_queue *cq)
88 struct queued_chunk *qc = cq_peek(cq);
90 assert(cq->num_pending >= qc->num_bytes);
91 cq->num_pending -= qc->num_bytes;
97 * Force to add a chunk to the given queue.
99 * \param cq See \ref cq_enqueue.
100 * \param buf See \ref cq_enqueue.
101 * \param num_bytes See \ref cq_enqueue.
103 * If queuing the given buffer would result in exceeding the maximal queue
104 * size, buffers are dropped from the beginning of the queue. Note that this
105 * function still might fail.
109 int cq_force_enqueue(struct chunk_queue *cq, const char *buf, size_t num_bytes)
113 if (num_bytes > cq->max_pending)
116 ret = cq_enqueue(cq, buf, num_bytes);
125 * Change the number of bytes sent for the current queued chunk.
127 * \param cq The chunk queue.
128 * \param sent Number of bytes successfully sent.
130 void cq_update(struct chunk_queue *cq, size_t sent)
132 struct queued_chunk *qc = cq_peek(cq);
134 qc->num_bytes -= sent;
136 cq->num_pending -= sent;
140 * Get a pointer to the given queued chunk.
142 * \param qc The queued chunk.
143 * \param buf Result pointer.
144 * \param num_bytes Number of bytes of \a buf.
146 * \return Positive on success, negative on errors.
148 int cq_get(struct queued_chunk *qc, const char **buf, size_t *num_bytes)
151 *num_bytes = qc->num_bytes;
156 * Allocate and initialize a chunk queue.
158 * \param max_pending Maximal number of bytes that will be queued.
160 * \return A pointer to the new queue.
162 struct chunk_queue *cq_new(size_t max_pending)
164 struct chunk_queue *cq = para_malloc(sizeof(*cq));
165 INIT_LIST_HEAD(&cq->q);
166 cq->max_pending = max_pending;
172 * Deallocate all resources of this queue.
174 * \param cq The chunk queue.
176 void cq_destroy(struct chunk_queue *cq)
178 struct queued_chunk *qc, *tmp;
179 list_for_each_entry_safe(qc, tmp, &cq->q, node) {