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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 * v42bis.h
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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) 2005 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: v42bis.h,v 1.15 2006/11/30 15:41:47 steveu Exp $
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26 */
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27
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28 /*! \page v42bis_page V.42bis modem data compression
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29 \section v42bis_page_sec_1 What does it do?
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30 The v.42bis specification defines a data compression scheme, to work in
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31 conjunction with the error correction scheme defined in V.42.
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32
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33 \section v42bis_page_sec_2 How does it work?
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34 */
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35
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36 #if !defined(_V42BIS_H_)
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37 #define _V42BIS_H_
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38
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39 #define V42BIS_MAX_BITS 12
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40 #define V42BIS_MAX_CODEWORDS 4096 /* 2^V42BIS_MAX_BITS */
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41 #define V42BIS_TABLE_SIZE 5021 /* This should be a prime >(2^V42BIS_MAX_BITS) */
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42 #define V42BIS_MAX_STRING_SIZE 250
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43
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44 enum
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45 {
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46 V42BIS_P0_NEITHER_DIRECTION = 0,
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47 V42BIS_P0_INITIATOR_RESPONDER,
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48 V42BIS_P0_RESPONDER_INITIATOR,
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49 V42BIS_P0_BOTH_DIRECTIONS
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50 };
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51
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52 enum
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53 {
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54 V42BIS_COMPRESSION_MODE_DYNAMIC = 0,
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55 V42BIS_COMPRESSION_MODE_ALWAYS,
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56 V42BIS_COMPRESSION_MODE_NEVER
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57 };
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58
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59 typedef void (*v42bis_frame_handler_t)(void *user_data, const uint8_t *pkt, int len);
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60 typedef void (*v42bis_data_handler_t)(void *user_data, const uint8_t *buf, int len);
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61
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62 typedef struct
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63 {
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64 /*! \brief The prior code for each defined code. */
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65 uint16_t parent_code;
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66 /*! \brief The number of leaf nodes this node has */
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67 int16_t leaves;
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68 /*! \brief This leaf octet for each defined code. */
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69 uint8_t node_octet;
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70 /*! \brief Bit map of the children which exist */
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71 uint32_t children[8];
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72 } v42bis_dict_node_t;
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73
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74 typedef struct
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75 {
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76 /*! \brief Compression mode. */
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77 int compression_mode;
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78 /*! \brief Callback function to handle received frames. */
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79 v42bis_frame_handler_t handler;
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80 /*! \brief An opaque pointer passed in calls to frame_handler. */
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81 void *user_data;
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82 /*! \brief The maximum frame length allowed */
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83 int max_len;
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84
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85 uint32_t string_code;
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86 uint32_t latest_code;
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87 int string_length;
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88 uint32_t output_bit_buffer;
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89 int output_bit_count;
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90 int output_octet_count;
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91 uint8_t output_buf[1024];
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92 v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS];
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93 /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */
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94 int transparent;
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95 int change_transparency;
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96 int compressibility_filter;
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97 int compressibility_persistence;
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98
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99 /*! \brief Next empty dictionary entry */
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100 uint32_t v42bis_parm_c1;
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101 /*! \brief Current codeword size */
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102 int v42bis_parm_c2;
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103 /*! \brief Threshold for codeword size change */
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104 uint32_t v42bis_parm_c3;
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105
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106 /*! \brief Mark that this is the first octet/code to be processed */
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107 int first;
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108 uint8_t escape_code;
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109 } v42bis_compress_state_t;
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110
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111 typedef struct
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112 {
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113 /*! \brief Callback function to handle decompressed data. */
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114 v42bis_data_handler_t handler;
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115 /*! \brief An opaque pointer passed in calls to data_handler. */
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116 void *user_data;
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117 /*! \brief The maximum decompressed data block length allowed */
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118 int max_len;
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119
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120 uint32_t old_code;
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121 uint32_t last_old_code;
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122 uint32_t input_bit_buffer;
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123 int input_bit_count;
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124 int octet;
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125 int last_length;
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126 int output_octet_count;
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127 uint8_t output_buf[1024];
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128 v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS];
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129 /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */
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130 int transparent;
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131
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132 int last_extra_octet;
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133
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134 /*! \brief Next empty dictionary entry */
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135 int v42bis_parm_c1;
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136 /*! \brief Current codeword size */
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137 int v42bis_parm_c2;
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138 /*! \brief Threshold for codeword size change */
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139 int v42bis_parm_c3;
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140
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141 /*! \brief Mark that this is the first octet/code to be processed */
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142 int first;
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143 uint8_t escape_code;
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144 int escaped;
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145 } v42bis_decompress_state_t;
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146
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147 /*!
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148 V.42bis compression/decompression descriptor. This defines the working state for a
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149 single instance of V.42bis compress/decompression.
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150 */
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151 typedef struct
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152 {
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153 /*! \brief V.42bis data compression directions. */
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154 int v42bis_parm_p0;
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155
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156 v42bis_compress_state_t compress;
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157 v42bis_decompress_state_t decompress;
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158
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159 /*! \brief Maximum codeword size (bits) */
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160 int v42bis_parm_n1;
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161 /*! \brief Total number of codewords */
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162 uint32_t v42bis_parm_n2;
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163 /*! \brief Maximum string length */
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164 int v42bis_parm_n7;
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165 } v42bis_state_t;
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166
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167 #ifdef __cplusplus
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168 extern "C" {
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169 #endif
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170
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171 /*! Compress a block of octets.
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172 \param s The V.42bis context.
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173 \param buf The data to be compressed.
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174 \param len The length of the data buffer.
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175 \return 0 */
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176 int v42bis_compress(v42bis_state_t *s, const uint8_t *buf, int len);
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177
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178 /*! Flush out any data remaining in a compression buffer.
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179 \param s The V.42bis context.
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180 \return 0 */
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181 int v42bis_compress_flush(v42bis_state_t *s);
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182
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183 /*! Decompress a block of octets.
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184 \param s The V.42bis context.
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185 \param buf The data to be decompressed.
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186 \param len The length of the data buffer.
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187 \return 0 */
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188 int v42bis_decompress(v42bis_state_t *s, const uint8_t *buf, int len);
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189
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190 /*! Flush out any data remaining in the decompression buffer.
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191 \param s The V.42bis context.
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192 \return 0 */
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193 int v42bis_decompress_flush(v42bis_state_t *s);
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194
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195 /*! Initialise a V.42bis context.
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196 \param s The V.42bis context.
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197 \param negotiated_p0 The negotiated P0 parameter, from the V.42bis spec.
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198 \param negotiated_p1 The negotiated P1 parameter, from the V.42bis spec.
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199 \param negotiated_p2 The negotiated P2 parameter, from the V.42bis spec.
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200 \param frame_handler .
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201 \param frame_user_data .
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202 \param max_frame_len The maximum length that should be passed to the frame handler.
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203 \param data_handler .
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204 \param data_user_data .
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205 \param max_data_len The maximum length that should be passed to the data handler.
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206 \return The V.42bis context. */
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207 v42bis_state_t *v42bis_init(v42bis_state_t *s,
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208 int negotiated_p0,
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209 int negotiated_p1,
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210 int negotiated_p2,
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211 v42bis_frame_handler_t frame_handler,
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212 void *frame_user_data,
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213 int max_frame_len,
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214 v42bis_data_handler_t data_handler,
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215 void *data_user_data,
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216 int max_data_len);
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217
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218 /*! Set the compression mode.
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219 \param s The V.42bis context.
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220 \param mode One of the V.42bis compression modes -
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221 V42BIS_COMPRESSION_MODE_DYNAMIC,
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222 V42BIS_COMPRESSION_MODE_ALWAYS,
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223 V42BIS_COMPRESSION_MODE_NEVER */
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224 void v42bis_compression_control(v42bis_state_t *s, int mode);
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225
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226 /*! Release a V.42bis context.
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227 \param s The V.42bis context.
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228 \return 0 if OK */
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229 int v42bis_release(v42bis_state_t *s);
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230
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231 #ifdef __cplusplus
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232 }
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233 #endif
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234
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235 #endif
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236 /*- End of file ------------------------------------------------------------*/
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