1 | ///////////////////////////////////////////////////////////////////////////////
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2 | //
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3 | /// \file lz_decoder.c
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4 | /// \brief LZ out window
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5 | ///
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6 | // Authors: Igor Pavlov
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7 | // Lasse Collin
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8 | //
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9 | // This file has been put into the public domain.
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10 | // You can do whatever you want with this file.
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11 | //
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12 | ///////////////////////////////////////////////////////////////////////////////
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13 |
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14 | // liblzma supports multiple LZ77-based filters. The LZ part is shared
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15 | // between these filters. The LZ code takes care of dictionary handling
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16 | // and passing the data between filters in the chain. The filter-specific
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17 | // part decodes from the input buffer to the dictionary.
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18 |
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19 |
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20 | #include "lz_decoder.h"
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21 |
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22 |
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23 | typedef struct {
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24 | /// Dictionary (history buffer)
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25 | lzma_dict dict;
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26 |
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27 | /// The actual LZ-based decoder e.g. LZMA
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28 | lzma_lz_decoder lz;
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29 |
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30 | /// Next filter in the chain, if any. Note that LZMA and LZMA2 are
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31 | /// only allowed as the last filter, but the long-range filter in
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32 | /// future can be in the middle of the chain.
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33 | lzma_next_coder next;
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34 |
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35 | /// True if the next filter in the chain has returned LZMA_STREAM_END.
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36 | bool next_finished;
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37 |
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38 | /// True if the LZ decoder (e.g. LZMA) has detected end of payload
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39 | /// marker. This may become true before next_finished becomes true.
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40 | bool this_finished;
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41 |
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42 | /// Temporary buffer needed when the LZ-based filter is not the last
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43 | /// filter in the chain. The output of the next filter is first
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44 | /// decoded into buffer[], which is then used as input for the actual
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45 | /// LZ-based decoder.
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46 | struct {
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47 | size_t pos;
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48 | size_t size;
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49 | uint8_t buffer[LZMA_BUFFER_SIZE];
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50 | } temp;
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51 | } lzma_coder;
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52 |
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53 |
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54 | static void
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55 | lz_decoder_reset(lzma_coder *coder)
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56 | {
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57 | coder->dict.pos = 0;
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58 | coder->dict.full = 0;
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59 | coder->dict.buf[coder->dict.size - 1] = '\0';
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60 | coder->dict.need_reset = false;
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61 | return;
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62 | }
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63 |
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64 |
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65 | static lzma_ret
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66 | decode_buffer(lzma_coder *coder,
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67 | const uint8_t *restrict in, size_t *restrict in_pos,
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68 | size_t in_size, uint8_t *restrict out,
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69 | size_t *restrict out_pos, size_t out_size)
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70 | {
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71 | while (true) {
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72 | // Wrap the dictionary if needed.
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73 | if (coder->dict.pos == coder->dict.size)
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74 | coder->dict.pos = 0;
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75 |
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76 | // Store the current dictionary position. It is needed to know
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77 | // where to start copying to the out[] buffer.
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78 | const size_t dict_start = coder->dict.pos;
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79 |
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80 | // Calculate how much we allow coder->lz.code() to decode.
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81 | // It must not decode past the end of the dictionary
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82 | // buffer, and we don't want it to decode more than is
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83 | // actually needed to fill the out[] buffer.
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84 | coder->dict.limit = coder->dict.pos
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85 | + my_min(out_size - *out_pos,
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86 | coder->dict.size - coder->dict.pos);
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87 |
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88 | // Call the coder->lz.code() to do the actual decoding.
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89 | const lzma_ret ret = coder->lz.code(
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90 | coder->lz.coder, &coder->dict,
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91 | in, in_pos, in_size);
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92 |
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93 | // Copy the decoded data from the dictionary to the out[]
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94 | // buffer. Do it conditionally because out can be NULL
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95 | // (in which case copy_size is always 0). Calling memcpy()
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96 | // with a null-pointer is undefined even if the third
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97 | // argument is 0.
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98 | const size_t copy_size = coder->dict.pos - dict_start;
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99 | assert(copy_size <= out_size - *out_pos);
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100 |
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101 | if (copy_size > 0)
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102 | memcpy(out + *out_pos, coder->dict.buf + dict_start,
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103 | copy_size);
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104 |
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105 | *out_pos += copy_size;
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106 |
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107 | // Reset the dictionary if so requested by coder->lz.code().
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108 | if (coder->dict.need_reset) {
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109 | lz_decoder_reset(coder);
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110 |
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111 | // Since we reset dictionary, we don't check if
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112 | // dictionary became full.
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113 | if (ret != LZMA_OK || *out_pos == out_size)
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114 | return ret;
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115 | } else {
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116 | // Return if everything got decoded or an error
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117 | // occurred, or if there's no more data to decode.
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118 | //
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119 | // Note that detecting if there's something to decode
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120 | // is done by looking if dictionary become full
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121 | // instead of looking if *in_pos == in_size. This
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122 | // is because it is possible that all the input was
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123 | // consumed already but some data is pending to be
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124 | // written to the dictionary.
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125 | if (ret != LZMA_OK || *out_pos == out_size
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126 | || coder->dict.pos < coder->dict.size)
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127 | return ret;
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128 | }
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129 | }
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130 | }
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131 |
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132 |
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133 | static lzma_ret
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134 | lz_decode(void *coder_ptr, const lzma_allocator *allocator,
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135 | const uint8_t *restrict in, size_t *restrict in_pos,
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136 | size_t in_size, uint8_t *restrict out,
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137 | size_t *restrict out_pos, size_t out_size,
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138 | lzma_action action)
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139 | {
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140 | lzma_coder *coder = coder_ptr;
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141 |
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142 | if (coder->next.code == NULL)
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143 | return decode_buffer(coder, in, in_pos, in_size,
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144 | out, out_pos, out_size);
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145 |
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146 | // We aren't the last coder in the chain, we need to decode
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147 | // our input to a temporary buffer.
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148 | while (*out_pos < out_size) {
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149 | // Fill the temporary buffer if it is empty.
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150 | if (!coder->next_finished
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151 | && coder->temp.pos == coder->temp.size) {
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152 | coder->temp.pos = 0;
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153 | coder->temp.size = 0;
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154 |
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155 | const lzma_ret ret = coder->next.code(
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156 | coder->next.coder,
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157 | allocator, in, in_pos, in_size,
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158 | coder->temp.buffer, &coder->temp.size,
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159 | LZMA_BUFFER_SIZE, action);
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160 |
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161 | if (ret == LZMA_STREAM_END)
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162 | coder->next_finished = true;
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163 | else if (ret != LZMA_OK || coder->temp.size == 0)
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164 | return ret;
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165 | }
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166 |
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167 | if (coder->this_finished) {
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168 | if (coder->temp.size != 0)
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169 | return LZMA_DATA_ERROR;
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170 |
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171 | if (coder->next_finished)
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172 | return LZMA_STREAM_END;
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173 |
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174 | return LZMA_OK;
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175 | }
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176 |
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177 | const lzma_ret ret = decode_buffer(coder, coder->temp.buffer,
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178 | &coder->temp.pos, coder->temp.size,
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179 | out, out_pos, out_size);
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180 |
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181 | if (ret == LZMA_STREAM_END)
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182 | coder->this_finished = true;
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183 | else if (ret != LZMA_OK)
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184 | return ret;
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185 | else if (coder->next_finished && *out_pos < out_size)
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186 | return LZMA_DATA_ERROR;
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187 | }
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188 |
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189 | return LZMA_OK;
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190 | }
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191 |
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192 |
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193 | static void
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194 | lz_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
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195 | {
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196 | lzma_coder *coder = coder_ptr;
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197 |
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198 | lzma_next_end(&coder->next, allocator);
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199 | lzma_free(coder->dict.buf, allocator);
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200 |
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201 | if (coder->lz.end != NULL)
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202 | coder->lz.end(coder->lz.coder, allocator);
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203 | else
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204 | lzma_free(coder->lz.coder, allocator);
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205 |
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206 | lzma_free(coder, allocator);
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207 | return;
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208 | }
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209 |
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210 |
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211 | extern lzma_ret
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212 | lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
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213 | const lzma_filter_info *filters,
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214 | lzma_ret (*lz_init)(lzma_lz_decoder *lz,
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215 | const lzma_allocator *allocator,
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216 | lzma_vli id, const void *options,
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217 | lzma_lz_options *lz_options))
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218 | {
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219 | // Allocate the base structure if it isn't already allocated.
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220 | lzma_coder *coder = next->coder;
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221 | if (coder == NULL) {
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222 | coder = lzma_alloc(sizeof(lzma_coder), allocator);
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223 | if (coder == NULL)
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224 | return LZMA_MEM_ERROR;
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225 |
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226 | next->coder = coder;
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227 | next->code = &lz_decode;
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228 | next->end = &lz_decoder_end;
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229 |
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230 | coder->dict.buf = NULL;
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231 | coder->dict.size = 0;
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232 | coder->lz = LZMA_LZ_DECODER_INIT;
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233 | coder->next = LZMA_NEXT_CODER_INIT;
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234 | }
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235 |
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236 | // Allocate and initialize the LZ-based decoder. It will also give
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237 | // us the dictionary size.
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238 | lzma_lz_options lz_options;
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239 | return_if_error(lz_init(&coder->lz, allocator,
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240 | filters[0].id, filters[0].options, &lz_options));
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241 |
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242 | // If the dictionary size is very small, increase it to 4096 bytes.
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243 | // This is to prevent constant wrapping of the dictionary, which
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244 | // would slow things down. The downside is that since we don't check
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245 | // separately for the real dictionary size, we may happily accept
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246 | // corrupt files.
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247 | if (lz_options.dict_size < 4096)
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248 | lz_options.dict_size = 4096;
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249 |
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250 | // Make dictionary size a multiple of 16. Some LZ-based decoders like
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251 | // LZMA use the lowest bits lzma_dict.pos to know the alignment of the
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252 | // data. Aligned buffer is also good when memcpying from the
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253 | // dictionary to the output buffer, since applications are
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254 | // recommended to give aligned buffers to liblzma.
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255 | //
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256 | // Avoid integer overflow.
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257 | if (lz_options.dict_size > SIZE_MAX - 15)
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258 | return LZMA_MEM_ERROR;
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259 |
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260 | lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15));
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261 |
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262 | // Allocate and initialize the dictionary.
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263 | if (coder->dict.size != lz_options.dict_size) {
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264 | lzma_free(coder->dict.buf, allocator);
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265 | coder->dict.buf
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266 | = lzma_alloc(lz_options.dict_size, allocator);
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267 | if (coder->dict.buf == NULL)
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268 | return LZMA_MEM_ERROR;
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269 |
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270 | coder->dict.size = lz_options.dict_size;
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271 | }
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272 |
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273 | lz_decoder_reset(next->coder);
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274 |
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275 | // Use the preset dictionary if it was given to us.
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276 | if (lz_options.preset_dict != NULL
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277 | && lz_options.preset_dict_size > 0) {
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278 | // If the preset dictionary is bigger than the actual
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279 | // dictionary, copy only the tail.
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280 | const size_t copy_size = my_min(lz_options.preset_dict_size,
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281 | lz_options.dict_size);
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282 | const size_t offset = lz_options.preset_dict_size - copy_size;
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283 | memcpy(coder->dict.buf, lz_options.preset_dict + offset,
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284 | copy_size);
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285 | coder->dict.pos = copy_size;
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286 | coder->dict.full = copy_size;
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287 | }
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288 |
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289 | // Miscellaneous initializations
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290 | coder->next_finished = false;
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291 | coder->this_finished = false;
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292 | coder->temp.pos = 0;
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293 | coder->temp.size = 0;
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294 |
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295 | // Initialize the next filter in the chain, if any.
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296 | return lzma_next_filter_init(&coder->next, allocator, filters + 1);
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297 | }
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298 |
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299 |
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300 | extern uint64_t
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301 | lzma_lz_decoder_memusage(size_t dictionary_size)
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302 | {
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303 | return sizeof(lzma_coder) + (uint64_t)(dictionary_size);
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304 | }
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