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. */
16 * Senders may use the chunk queue facility to deal with laggy connections. It
17 * allows them to enqueue chunks if they can not be sent out immediately.
19 * Chunk queues are "cheap" in the sense that only reference to the audio file
20 * data is stored, but not the data itsself.
23 /** The list of pending chunks for this client. */
25 /** The number of pending bytes for this client. */
26 unsigned long num_pending;
27 /** Enqueueing more than that many bytes is an error. */
28 unsigned long max_pending;
31 /** Describes one queued chunk in a chunk queue. */
33 /** The number of the queued chunk, -1U means header. */
35 /** The number of bytes already sent. */
37 /** Position of the chunk in the chunk queue. */
38 struct list_head node;
42 * Add a chunk to the given queue.
44 * \param cq the queue to add the chunk to.
45 * \param chunk_num The number of the chunk to be queued.
46 * \param sent The number of bytes of this chunk that the sender was able to
49 * \return Positive on success, negative on errors.
51 int cq_enqueue(struct chunk_queue *cq, long unsigned chunk_num,
54 struct queued_chunk *qc;
59 if (chunk_num != -1U) {
60 ret = vss_get_chunk(chunk_num, &buf, &len);
64 buf = vss_get_header(&len);
65 if (cq->num_pending + len > cq->max_pending)
67 qc = para_malloc(sizeof(struct queued_chunk));
68 cq->num_pending += len;
69 qc->chunk_num = chunk_num;
71 list_add_tail(&qc->node, &cq->q);
72 PARA_DEBUG_LOG("%lu bytes queued for %p\n", cq->num_pending, &cq->q);
77 * Lookup the next chunk in the queue.
79 * \param cq The chunk queue.
81 * \return The next queued chunk, or \p NULL if there is no chunk awailable.
83 struct queued_chunk *cq_peek(struct chunk_queue *cq)
85 if (list_empty(&cq->q))
87 return list_entry(cq->q.next, struct queued_chunk, node);
91 * Remove the current chunk from the queue.
93 * \param cq The chunk to remove.
95 void cq_dequeue(struct chunk_queue *cq)
97 struct queued_chunk *qc = cq_peek(cq);
104 * Change the number of bytes send for the current queued chunk.
106 * \param cq The chunk queue.
107 * \param sent Number of bytes successfully sent.
109 void cq_update(struct chunk_queue *cq, size_t sent)
111 struct queued_chunk *qc = cq_peek(cq);
114 cq->num_pending -= sent;
118 * Get a pointer to the given queued chunk.
120 * \param qc The queued chunk.
121 * \param buf Result pointer.
122 * \param len Number of bytes of \a buf.
124 * \return Positive on success, negative on errors.
126 int cq_get(struct queued_chunk *qc, char **buf, size_t *len)
130 if (qc->chunk_num != -1U) {
131 ret = vss_get_chunk(qc->chunk_num, buf, len);
135 *buf = vss_get_header(len);
136 assert(*len > qc->sent);
143 * Allocate and initialize a chunk queue.
145 * \param max_pending Maximal number of bytes that will be queued.
147 * \return A pointer to the new queue.
149 struct chunk_queue *cq_new(size_t max_pending)
151 struct chunk_queue *cq = para_malloc(sizeof(*cq));
152 INIT_LIST_HEAD(&cq->q);
153 cq->max_pending = max_pending;
159 * Deallocate all resources of this queue.
161 * \param cq The chunk queue.
163 void cq_destroy(struct chunk_queue *cq)
165 struct queued_chunk *qc, *tmp;
166 list_for_each_entry_safe(qc, tmp, &cq->q, node) {