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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 * g726.h - ITU G.726 codec.
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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 * Based on G.721/G.723 code which is:
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26 *
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27 * This source code is a product of Sun Microsystems, Inc. and is provided
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28 * for unrestricted use. Users may copy or modify this source code without
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29 * charge.
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30 *
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31 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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32 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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33 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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34 *
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35 * Sun source code is provided with no support and without any obligation on
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36 * the part of Sun Microsystems, Inc. to assist in its use, correction,
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37 * modification or enhancement.
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38 *
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39 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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40 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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41 * OR ANY PART THEREOF.
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42 *
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43 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
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44 * or profits or other special, indirect and consequential damages, even if
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45 * Sun has been advised of the possibility of such damages.
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46 *
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47 * Sun Microsystems, Inc.
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48 * 2550 Garcia Avenue
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49 * Mountain View, California 94043
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50 *
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51 * $Id: g726.h,v 1.13 2006/11/28 16:59:57 steveu Exp $
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52 */
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53
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54 /*! \file */
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55
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56 #if !defined(_G726_H_)
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57 #define _G726_H_
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58
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59 /*! \page g726_page G.726 encoding and decoding
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60 \section g726_page_sec_1 What does it do?
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61
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62 The G.726 module is a bit exact implementation of the full ITU G.726 specification.
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63 It supports:
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64 - 16 kbps, 24kbps, 32kbps, and 40kbps operation.
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65 - Tandem adjustment, for interworking with A-law and u-law.
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66 - Annex A support, for use in environments not using A-law or u-law.
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67
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68 It passes the ITU tests.
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69
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70 \section g726_page_sec_2 How does it work?
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71 ???.
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72 */
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73
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74 enum
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75 {
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76 G726_ENCODING_LINEAR = 0, /* Interworking with 16 bit signed linear */
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77 G726_ENCODING_ULAW, /* Interworking with u-law */
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78 G726_ENCODING_ALAW /* Interworking with A-law */
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79 };
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80
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81 enum
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82 {
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83 G726_PACKING_NONE = 0,
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84 G726_PACKING_LEFT = 1,
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85 G726_PACKING_RIGHT = 2
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86 };
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87
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88 struct g726_state_s;
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89
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90 typedef int16_t (*g726_decoder_func_t)(struct g726_state_s *s, uint8_t code);
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91
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92 typedef uint8_t (*g726_encoder_func_t)(struct g726_state_s *s, int16_t amp);
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93
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94 /*
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95 * The following is the definition of the state structure
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96 * used by the G.726 encoder and decoder to preserve their internal
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97 * state between successive calls. The meanings of the majority
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98 * of the state structure fields are explained in detail in the
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99 * CCITT Recommendation G.721. The field names are essentially indentical
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100 * to variable names in the bit level description of the coding algorithm
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101 * included in this Recommendation.
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102 */
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103 typedef struct g726_state_s
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104 {
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105 /*! The bit rate */
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106 int rate;
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107 /*! The external coding, for tandem operation */
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108 int ext_coding;
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109 /*! The number of bits per sample */
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110 unsigned int bits_per_sample;
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111 /*! One fo the G.726_PACKING_xxx options */
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112 int packing;
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113
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114 /*! Locked or steady state step size multiplier. */
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115 int32_t yl;
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116 /*! Unlocked or non-steady state step size multiplier. */
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117 int16_t yu;
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118 /*! int16_t term energy estimate. */
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119 int16_t dms;
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120 /*! Long term energy estimate. */
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121 int16_t dml;
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122 /*! Linear weighting coefficient of 'yl' and 'yu'. */
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123 int16_t ap;
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124
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125 /*! Coefficients of pole portion of prediction filter. */
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126 int16_t a[2];
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127 /*! Coefficients of zero portion of prediction filter. */
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128 int16_t b[6];
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129 /*! Signs of previous two samples of a partially reconstructed signal. */
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130 int16_t pk[2];
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131 /*! Previous 6 samples of the quantized difference signal represented in
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132 an internal floating point format. */
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133 int16_t dq[6];
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134 /*! Previous 2 samples of the quantized difference signal represented in an
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135 internal floating point format. */
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136 int16_t sr[2];
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137 /*! Delayed tone detect */
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138 int td;
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139
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140 bitstream_state_t bs;
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141
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142 g726_encoder_func_t enc_func;
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143 g726_decoder_func_t dec_func;
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144 } g726_state_t;
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145
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146 #ifdef __cplusplus
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147 extern "C" {
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148 #endif
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149
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150 /*! Initialise a G.726 encode or decode context.
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151 \param s The G.726 context.
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152 \param bit_rate The required bit rate for the ADPCM data.
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153 The valid rates are 16000, 24000, 32000 and 40000.
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154 \param ext_coding The coding used outside G.726.
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155 \param packing One of the G.726_PACKING_xxx options.
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156 \return A pointer to the G.726 context, or NULL for error. */
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157 g726_state_t *g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing);
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158
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159 /*! Free a G.726 encode or decode context.
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160 \param s The G.726 context.
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161 \return 0 for OK. */
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162 int g726_release(g726_state_t *s);
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163
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164 /*! Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.
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165 \param s The G.726 context.
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166 \param amp The audio sample buffer.
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167 \param g726_data
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168 \param g726_bytes
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169 \return The number of samples returned. */
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170 int g726_decode(g726_state_t *s,
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171 int16_t amp[],
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172 const uint8_t g726_data[],
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173 int g726_bytes);
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174
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175 /*! Encode a buffer of linear PCM data to G.726 ADPCM.
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176 \param s The G.726 context.
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177 \param g726_data The G.726 data produced.
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178 \param amp The audio sample buffer.
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179 \param len The number of samples in the buffer.
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180 \return The number of bytes of G.726 data produced. */
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181 int g726_encode(g726_state_t *s,
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182 uint8_t g726_data[],
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183 const int16_t amp[],
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184 int len);
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185
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186 #ifdef __cplusplus
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187 }
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188 #endif
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189
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190 #endif
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191 /*- End of file ------------------------------------------------------------*/
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