2 * Copyright (C) 2007 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. */
17 * Senders may use the chunk queue facility to deal with laggy connections. It
18 * allows them to enqueue chunks if they can not be sent out immediately.
20 * Chunk queues are "cheap" in the sense that only reference to the audio file
21 * data is stored, but not the data itsself.
24 /** The list of pending chunks for this client. */
26 /** The number of pending bytes for this client. */
27 unsigned long num_pending;
28 /** Enqueueing more than that many bytes is an error. */
29 unsigned long max_pending;
32 /** Describes one queued chunk in a chunk queue. */
34 /** The number of the queued chunk, -1U means header. */
36 /** The number of bytes already sent. */
38 /** Position of the chunk in the chunk queue. */
39 struct list_head node;
43 * Add a chunk to the given queue.
45 * \param cq the queue to add the chunk to.
46 * \param chunk_num The number of the chunk to be queued.
47 * \param sent The number of bytes of this chunk that the sender was able to
50 * \return Positive on success, negative on errors.
52 int cq_enqueue(struct chunk_queue *cq, long unsigned chunk_num,
55 struct queued_chunk *qc;
60 if (chunk_num != -1U) {
61 ret = vss_get_chunk(chunk_num, &buf, &len);
65 buf = vss_get_header(&len);
66 if (cq->num_pending + len > cq->max_pending)
68 qc = para_malloc(sizeof(struct queued_chunk));
69 cq->num_pending += len;
70 qc->chunk_num = chunk_num;
72 list_add_tail(&qc->node, &cq->q);
73 PARA_DEBUG_LOG("%lu bytes queued for %p\n", cq->num_pending, &cq->q);
78 * Lookup the next chunk in the queue.
80 * \param cq The chunk queue.
82 * \return The next queued chunk, or \p NULL if there is no chunk awailable.
84 struct queued_chunk *cq_peek(struct chunk_queue *cq)
86 if (list_empty(&cq->q))
88 return list_entry(cq->q.next, struct queued_chunk, node);
92 * Remove the current chunk from the queue.
94 * \param cq The chunk to remove.
96 void cq_dequeue(struct chunk_queue *cq)
98 struct queued_chunk *qc = cq_peek(cq);
105 * Change the number of bytes send for the current queued chunk.
107 * \param cq The chunk queue.
108 * \param sent Number of bytes successfully sent.
110 void cq_update(struct chunk_queue *cq, size_t sent)
112 struct queued_chunk *qc = cq_peek(cq);
115 cq->num_pending -= sent;
119 * Get a pointer to the given queued chunk.
121 * \param qc The queued chunk.
122 * \param buf Result pointer.
123 * \param len Number of bytes of \a buf.
125 * \return Positive on success, negative on errors.
127 int cq_get(struct queued_chunk *qc, char **buf, size_t *len)
131 if (qc->chunk_num != -1U) {
132 ret = vss_get_chunk(qc->chunk_num, buf, len);
136 *buf = vss_get_header(len);
137 assert(*len > qc->sent);
144 * Allocate and initialize a chunk queue.
146 * \param max_pending Maximal number of bytes that will be queued.
148 * \return A pointer to the new queue.
150 struct chunk_queue *cq_new(size_t max_pending)
152 struct chunk_queue *cq = para_malloc(sizeof(*cq));
153 INIT_LIST_HEAD(&cq->q);
154 cq->max_pending = max_pending;
160 * Deallocate all resources of this queue.
162 * \param cq The chunk queue.
164 void cq_destroy(struct chunk_queue *cq)
166 struct queued_chunk *qc, *tmp;
167 list_for_each_entry_safe(qc, tmp, &cq->q, node) {