1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file lz_decoder.c 4 /// \brief LZ out window 5 /// 6 // Authors: Igor Pavlov 7 // Lasse Collin 8 // 9 // This file has been put into the public domain. 10 // You can do whatever you want with this file. 11 // 12 /////////////////////////////////////////////////////////////////////////////// 13 14 // liblzma supports multiple LZ77-based filters. The LZ part is shared 15 // between these filters. The LZ code takes care of dictionary handling 16 // and passing the data between filters in the chain. The filter-specific 17 // part decodes from the input buffer to the dictionary. 18 19 20 #include "lz_decoder.h" 21 22 23 typedef struct { 24 /// Dictionary (history buffer) 25 lzma_dict dict; 26 27 /// The actual LZ-based decoder e.g. LZMA 28 lzma_lz_decoder lz; 29 30 /// Next filter in the chain, if any. Note that LZMA and LZMA2 are 31 /// only allowed as the last filter, but the long-range filter in 32 /// future can be in the middle of the chain. 33 lzma_next_coder next; 34 35 /// True if the next filter in the chain has returned LZMA_STREAM_END. 36 bool next_finished; 37 38 /// True if the LZ decoder (e.g. LZMA) has detected end of payload 39 /// marker. This may become true before next_finished becomes true. 40 bool this_finished; 41 42 /// Temporary buffer needed when the LZ-based filter is not the last 43 /// filter in the chain. The output of the next filter is first 44 /// decoded into buffer[], which is then used as input for the actual 45 /// LZ-based decoder. 46 struct { 47 size_t pos; 48 size_t size; 49 uint8_t buffer[LZMA_BUFFER_SIZE]; 50 } temp; 51 } lzma_coder; 52 53 54 static void 55 lz_decoder_reset(lzma_coder *coder) 56 { 57 coder->dict.pos = 0; 58 coder->dict.full = 0; 59 coder->dict.buf[coder->dict.size - 1] = '\0'; 60 coder->dict.need_reset = false; 61 return; 62 } 63 64 65 static lzma_ret 66 decode_buffer(lzma_coder *coder, 67 const uint8_t *restrict in, size_t *restrict in_pos, 68 size_t in_size, uint8_t *restrict out, 69 size_t *restrict out_pos, size_t out_size) 70 { 71 while (true) { 72 // Wrap the dictionary if needed. 73 if (coder->dict.pos == coder->dict.size) 74 coder->dict.pos = 0; 75 76 // Store the current dictionary position. It is needed to know 77 // where to start copying to the out[] buffer. 78 const size_t dict_start = coder->dict.pos; 79 80 // Calculate how much we allow coder->lz.code() to decode. 81 // It must not decode past the end of the dictionary 82 // buffer, and we don't want it to decode more than is 83 // actually needed to fill the out[] buffer. 84 coder->dict.limit = coder->dict.pos 85 + my_min(out_size - *out_pos, 86 coder->dict.size - coder->dict.pos); 87 88 // Call the coder->lz.code() to do the actual decoding. 89 const lzma_ret ret = coder->lz.code( 90 coder->lz.coder, &coder->dict, 91 in, in_pos, in_size); 92 93 // Copy the decoded data from the dictionary to the out[] 94 // buffer. Do it conditionally because out can be NULL 95 // (in which case copy_size is always 0). Calling memcpy() 96 // with a null-pointer is undefined even if the third 97 // argument is 0. 98 const size_t copy_size = coder->dict.pos - dict_start; 99 assert(copy_size <= out_size - *out_pos); 100 101 if (copy_size > 0) 102 memcpy(out + *out_pos, coder->dict.buf + dict_start, 103 copy_size); 104 105 *out_pos += copy_size; 106 107 // Reset the dictionary if so requested by coder->lz.code(). 108 if (coder->dict.need_reset) { 109 lz_decoder_reset(coder); 110 111 // Since we reset dictionary, we don't check if 112 // dictionary became full. 113 if (ret != LZMA_OK || *out_pos == out_size) 114 return ret; 115 } else { 116 // Return if everything got decoded or an error 117 // occurred, or if there's no more data to decode. 118 // 119 // Note that detecting if there's something to decode 120 // is done by looking if dictionary become full 121 // instead of looking if *in_pos == in_size. This 122 // is because it is possible that all the input was 123 // consumed already but some data is pending to be 124 // written to the dictionary. 125 if (ret != LZMA_OK || *out_pos == out_size 126 || coder->dict.pos < coder->dict.size) 127 return ret; 128 } 129 } 130 } 131 132 133 static lzma_ret 134 lz_decode(void *coder_ptr, const lzma_allocator *allocator, 135 const uint8_t *restrict in, size_t *restrict in_pos, 136 size_t in_size, uint8_t *restrict out, 137 size_t *restrict out_pos, size_t out_size, 138 lzma_action action) 139 { 140 lzma_coder *coder = coder_ptr; 141 142 if (coder->next.code == NULL) 143 return decode_buffer(coder, in, in_pos, in_size, 144 out, out_pos, out_size); 145 146 // We aren't the last coder in the chain, we need to decode 147 // our input to a temporary buffer. 148 while (*out_pos < out_size) { 149 // Fill the temporary buffer if it is empty. 150 if (!coder->next_finished 151 && coder->temp.pos == coder->temp.size) { 152 coder->temp.pos = 0; 153 coder->temp.size = 0; 154 155 const lzma_ret ret = coder->next.code( 156 coder->next.coder, 157 allocator, in, in_pos, in_size, 158 coder->temp.buffer, &coder->temp.size, 159 LZMA_BUFFER_SIZE, action); 160 161 if (ret == LZMA_STREAM_END) 162 coder->next_finished = true; 163 else if (ret != LZMA_OK || coder->temp.size == 0) 164 return ret; 165 } 166 167 if (coder->this_finished) { 168 if (coder->temp.size != 0) 169 return LZMA_DATA_ERROR; 170 171 if (coder->next_finished) 172 return LZMA_STREAM_END; 173 174 return LZMA_OK; 175 } 176 177 const lzma_ret ret = decode_buffer(coder, coder->temp.buffer, 178 &coder->temp.pos, coder->temp.size, 179 out, out_pos, out_size); 180 181 if (ret == LZMA_STREAM_END) 182 coder->this_finished = true; 183 else if (ret != LZMA_OK) 184 return ret; 185 else if (coder->next_finished && *out_pos < out_size) 186 return LZMA_DATA_ERROR; 187 } 188 189 return LZMA_OK; 190 } 191 192 193 static void 194 lz_decoder_end(void *coder_ptr, const lzma_allocator *allocator) 195 { 196 lzma_coder *coder = coder_ptr; 197 198 lzma_next_end(&coder->next, allocator); 199 lzma_free(coder->dict.buf, allocator); 200 201 if (coder->lz.end != NULL) 202 coder->lz.end(coder->lz.coder, allocator); 203 else 204 lzma_free(coder->lz.coder, allocator); 205 206 lzma_free(coder, allocator); 207 return; 208 } 209 210 211 extern lzma_ret 212 lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, 213 const lzma_filter_info *filters, 214 lzma_ret (*lz_init)(lzma_lz_decoder *lz, 215 const lzma_allocator *allocator, 216 lzma_vli id, const void *options, 217 lzma_lz_options *lz_options)) 218 { 219 // Allocate the base structure if it isn't already allocated. 220 lzma_coder *coder = next->coder; 221 if (coder == NULL) { 222 coder = lzma_alloc(sizeof(lzma_coder), allocator); 223 if (coder == NULL) 224 return LZMA_MEM_ERROR; 225 226 next->coder = coder; 227 next->code = &lz_decode; 228 next->end = &lz_decoder_end; 229 230 coder->dict.buf = NULL; 231 coder->dict.size = 0; 232 coder->lz = LZMA_LZ_DECODER_INIT; 233 coder->next = LZMA_NEXT_CODER_INIT; 234 } 235 236 // Allocate and initialize the LZ-based decoder. It will also give 237 // us the dictionary size. 238 lzma_lz_options lz_options; 239 return_if_error(lz_init(&coder->lz, allocator, 240 filters[0].id, filters[0].options, &lz_options)); 241 242 // If the dictionary size is very small, increase it to 4096 bytes. 243 // This is to prevent constant wrapping of the dictionary, which 244 // would slow things down. The downside is that since we don't check 245 // separately for the real dictionary size, we may happily accept 246 // corrupt files. 247 if (lz_options.dict_size < 4096) 248 lz_options.dict_size = 4096; 249 250 // Make dictionary size a multiple of 16. Some LZ-based decoders like 251 // LZMA use the lowest bits lzma_dict.pos to know the alignment of the 252 // data. Aligned buffer is also good when memcpying from the 253 // dictionary to the output buffer, since applications are 254 // recommended to give aligned buffers to liblzma. 255 // 256 // Avoid integer overflow. 257 if (lz_options.dict_size > SIZE_MAX - 15) 258 return LZMA_MEM_ERROR; 259 260 lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15)); 261 262 // Allocate and initialize the dictionary. 263 if (coder->dict.size != lz_options.dict_size) { 264 lzma_free(coder->dict.buf, allocator); 265 coder->dict.buf 266 = lzma_alloc(lz_options.dict_size, allocator); 267 if (coder->dict.buf == NULL) 268 return LZMA_MEM_ERROR; 269 270 coder->dict.size = lz_options.dict_size; 271 } 272 273 lz_decoder_reset(next->coder); 274 275 // Use the preset dictionary if it was given to us. 276 if (lz_options.preset_dict != NULL 277 && lz_options.preset_dict_size > 0) { 278 // If the preset dictionary is bigger than the actual 279 // dictionary, copy only the tail. 280 const size_t copy_size = my_min(lz_options.preset_dict_size, 281 lz_options.dict_size); 282 const size_t offset = lz_options.preset_dict_size - copy_size; 283 memcpy(coder->dict.buf, lz_options.preset_dict + offset, 284 copy_size); 285 coder->dict.pos = copy_size; 286 coder->dict.full = copy_size; 287 } 288 289 // Miscellaneous initializations 290 coder->next_finished = false; 291 coder->this_finished = false; 292 coder->temp.pos = 0; 293 coder->temp.size = 0; 294 295 // Initialize the next filter in the chain, if any. 296 return lzma_next_filter_init(&coder->next, allocator, filters + 1); 297 } 298 299 300 extern uint64_t 301 lzma_lz_decoder_memusage(size_t dictionary_size) 302 { 303 return sizeof(lzma_coder) + (uint64_t)(dictionary_size); 304 } 305