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5
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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * bitstream.c - Bitstream composition and decomposition routines.
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2006 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: bitstream.c,v 1.6 2006/11/30 15:41:47 steveu Exp $
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26 */
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27
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28 /*! \file */
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29
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30 #ifdef HAVE_CONFIG_H
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31 #include <config.h>
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32 #endif
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33
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34 #include <inttypes.h>
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35 #include <stdlib.h>
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36 #include <string.h>
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37 #include <assert.h>
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38
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39 #include "spandsp/telephony.h"
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40 #include "spandsp/logging.h"
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41 #include "spandsp/bitstream.h"
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42
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43 void bitstream_put(bitstream_state_t *s, uint8_t **c, unsigned int value, int bits)
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44 {
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45 value &= ((1 << bits) - 1);
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46 if (s->residue + bits <= 32)
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47 {
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48 s->bitstream |= (value << s->residue);
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49 s->residue += bits;
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50 }
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51 while (s->residue >= 8)
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52 {
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53 s->residue -= 8;
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54 *(*c)++ = (uint8_t)(s->bitstream & 0xFF);
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55 s->bitstream >>= 8;
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56 }
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57 }
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58 /*- End of function --------------------------------------------------------*/
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59
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60 void bitstream_flush(bitstream_state_t *s, uint8_t **c)
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61 {
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62 if (s->residue > 0)
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63 {
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64 *(*c)++ = (uint8_t)((s->bitstream << (8 - s->residue)) & 0xFF);
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65 s->residue = 0;
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66 }
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67 }
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68 /*- End of function --------------------------------------------------------*/
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69
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70 unsigned int bitstream_get(bitstream_state_t *s, const uint8_t **c, int bits)
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71 {
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72 unsigned int x;
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73
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74 while (s->residue < bits)
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75 {
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76 x = (unsigned int) *(*c)++;
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77 s->bitstream |= (x << s->residue);
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78 s->residue += 8;
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79 }
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80 s->residue -= bits;
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81 x = s->bitstream & ((1 << bits) - 1);
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82 s->bitstream >>= bits;
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83 return x;
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84 }
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85 /*- End of function --------------------------------------------------------*/
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86
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87 void bitstream_put2(bitstream_state_t *s, uint8_t **c, unsigned int value, int bits)
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88 {
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89 value &= ((1 << bits) - 1);
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90 if (s->residue + bits <= 32)
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91 {
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92 s->bitstream = (s->bitstream << bits) | value;
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93 s->residue += bits;
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94 }
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95 while (s->residue >= 8)
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96 {
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97 s->residue -= 8;
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98 *(*c)++ = (uint8_t) ((s->bitstream >> s->residue) & 0xFF);
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99 }
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100 }
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101 /*- End of function --------------------------------------------------------*/
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102
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103 void bitstream_flush2(bitstream_state_t *s, uint8_t **c)
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104 {
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105 if (s->residue > 0)
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106 {
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107 *(*c)++ = (uint8_t) ((s->bitstream << (8 - s->residue)) & 0xFF);
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108 s->residue = 0;
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109 }
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110 }
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111 /*- End of function --------------------------------------------------------*/
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112
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113 unsigned int bitstream_get2(bitstream_state_t *s, const uint8_t **c, int bits)
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114 {
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115 unsigned int x;
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116
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117 while (s->residue < bits)
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118 {
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119 x = (unsigned int) *(*c)++;
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120 s->bitstream = (s->bitstream << 8) | x;
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121 s->residue += 8;
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122 }
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123 s->residue -= bits;
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124 x = (s->bitstream >> s->residue) & ((1 << bits) - 1);
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125 return x;
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126 }
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127 /*- End of function --------------------------------------------------------*/
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128
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129 bitstream_state_t *bitstream_init(bitstream_state_t *s)
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130 {
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131 if (s)
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132 memset(s, 0, sizeof(*s));
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133 return s;
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134 }
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135 /*- End of function --------------------------------------------------------*/
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136 /*- End of file ------------------------------------------------------------*/
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