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comparison spandsp-0.0.6pre17/src/spandsp/queue.h @ 4:26cd8f1ef0b1

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import spandsp-0.0.6pre17
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 15:50:58 +0200
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3:c6c5a16ce2f2 4:26cd8f1ef0b1
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * queue.h - simple in process message queuing
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2004 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Lesser General Public License version 2.1,
14 * as published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: queue.h,v 1.21 2009/02/10 13:06:47 steveu Exp $
26 */
27
28 /*! \file */
29
30 /*! \page queue_page Queuing
31 \section queue_page_sec_1 What does it do?
32 This module provides lock free queuing for either octet streams or messages.
33 Specifically, lock free means one thread can write and another can read without
34 locking the queue. It does NOT means a free-for-all is possible, with many
35 threads writing or many threads reading. Those things would require locking,
36 to avoid conflicts between the multiple threads acting on one end of the queue.
37
38 \section queue_page_sec_2 How does it work?
39 ???.
40 */
41
42 #if !defined(_SPANDSP_QUEUE_H_)
43 #define _SPANDSP_QUEUE_H_
44
45 /*! Flag bit to indicate queue reads are atomic operations. This must be set
46 if the queue is to be used with the message oriented functions. */
47 #define QUEUE_READ_ATOMIC 0x0001
48 /*! Flag bit to indicate queue writes are atomic operations. This must be set
49 if the queue is to be used with the message oriented functions. */
50 #define QUEUE_WRITE_ATOMIC 0x0002
51
52 /*!
53 Queue descriptor. This defines the working state for a single instance of
54 a byte stream or message oriented queue.
55 */
56 typedef struct queue_state_s queue_state_t;
57
58 #define QUEUE_STATE_T_SIZE(len) (sizeof(queue_state_t) + len + 1)
59
60 #if defined(__cplusplus)
61 extern "C"
62 {
63 #endif
64
65 /*! Check if a queue is empty.
66 \brief Check if a queue is empty.
67 \param s The queue context.
68 \return TRUE if empty, else FALSE. */
69 SPAN_DECLARE(int) queue_empty(queue_state_t *s);
70
71 /*! Check the available free space in a queue's buffer.
72 \brief Check available free space.
73 \param s The queue context.
74 \return The number of bytes of free space. */
75 SPAN_DECLARE(int) queue_free_space(queue_state_t *s);
76
77 /*! Check the contents of a queue.
78 \brief Check the contents of a queue.
79 \param s The queue context.
80 \return The number of bytes in the queue. */
81 SPAN_DECLARE(int) queue_contents(queue_state_t *s);
82
83 /*! Flush the contents of a queue.
84 \brief Flush the contents of a queue.
85 \param s The queue context. */
86 SPAN_DECLARE(void) queue_flush(queue_state_t *s);
87
88 /*! Copy bytes from a queue. This is similar to queue_read, but
89 the data remains in the queue.
90 \brief Copy bytes from a queue.
91 \param s The queue context.
92 \param buf The buffer into which the bytes will be read.
93 \param len The length of the buffer.
94 \return the number of bytes returned. */
95 SPAN_DECLARE(int) queue_view(queue_state_t *s, uint8_t *buf, int len);
96
97 /*! Read bytes from a queue.
98 \brief Read bytes from a queue.
99 \param s The queue context.
100 \param buf The buffer into which the bytes will be read.
101 \param len The length of the buffer.
102 \return the number of bytes returned. */
103 SPAN_DECLARE(int) queue_read(queue_state_t *s, uint8_t *buf, int len);
104
105 /*! Read a byte from a queue.
106 \brief Read a byte from a queue.
107 \param s The queue context.
108 \return the byte, or -1 if the queue is empty. */
109 SPAN_DECLARE(int) queue_read_byte(queue_state_t *s);
110
111 /*! Write bytes to a queue.
112 \brief Write bytes to a queue.
113 \param s The queue context.
114 \param buf The buffer containing the bytes to be written.
115 \param len The length of the buffer.
116 \return the number of bytes actually written. */
117 SPAN_DECLARE(int) queue_write(queue_state_t *s, const uint8_t *buf, int len);
118
119 /*! Write a byte to a queue.
120 \brief Write a byte to a queue.
121 \param s The queue context.
122 \param byte The byte to be written.
123 \return the number of bytes actually written. */
124 SPAN_DECLARE(int) queue_write_byte(queue_state_t *s, uint8_t byte);
125
126 /*! Test the length of the message at the head of a queue.
127 \brief Test message length.
128 \param s The queue context.
129 \return The length of the next message, in byte. If there are
130 no messages in the queue, -1 is returned. */
131 SPAN_DECLARE(int) queue_state_test_msg(queue_state_t *s);
132
133 /*! Read a message from a queue. If the message is longer than the buffer
134 provided, only the first len bytes of the message will be returned. The
135 remainder of the message will be discarded.
136 \brief Read a message from a queue.
137 \param s The queue context.
138 \param buf The buffer into which the message will be read.
139 \param len The length of the buffer.
140 \return The number of bytes returned. If there are
141 no messages in the queue, -1 is returned. */
142 SPAN_DECLARE(int) queue_read_msg(queue_state_t *s, uint8_t *buf, int len);
143
144 /*! Write a message to a queue.
145 \brief Write a message to a queue.
146 \param s The queue context.
147 \param buf The buffer from which the message will be written.
148 \param len The length of the message.
149 \return The number of bytes actually written. */
150 SPAN_DECLARE(int) queue_write_msg(queue_state_t *s, const uint8_t *buf, int len);
151
152 /*! Initialise a queue.
153 \brief Initialise a queue.
154 \param s The queue context. If is imperative that the context this
155 points to is immediately followed by a buffer of the required
156 size + 1 octet.
157 \param len The length of the queue's buffer.
158 \param flags Flags controlling the operation of the queue.
159 Valid flags are QUEUE_READ_ATOMIC and QUEUE_WRITE_ATOMIC.
160 \return A pointer to the context if OK, else NULL. */
161 SPAN_DECLARE(queue_state_t *) queue_init(queue_state_t *s, int len, int flags);
162
163 /*! Release a queue.
164 \brief Release a queue.
165 \param s The queue context.
166 \return 0 if OK, else -1. */
167 SPAN_DECLARE(int) queue_release(queue_state_t *s);
168
169 /*! Free a queue.
170 \brief Delete a queue.
171 \param s The queue context.
172 \return 0 if OK, else -1. */
173 SPAN_DECLARE(int) queue_free(queue_state_t *s);
174
175 #if defined(__cplusplus)
176 }
177 #endif
178
179 #endif
180 /*- End of file ------------------------------------------------------------*/

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