1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file delta_decoder.c 4 /// \brief Delta filter decoder 5 // 6 // Author: Lasse Collin 7 // 8 // This file has been put into the public domain. 9 // You can do whatever you want with this file. 10 // 11 /////////////////////////////////////////////////////////////////////////////// 12 13 #include "delta_decoder.h" 14 #include "delta_private.h" 15 16 17 static void 18 decode_buffer(lzma_coder *coder, uint8_t *buffer, size_t size) 19 { 20 const size_t distance = coder->distance; 21 22 for (size_t i = 0; i < size; ++i) { 23 buffer[i] += coder->history[(distance + coder->pos) & 0xFF]; 24 coder->history[coder->pos-- & 0xFF] = buffer[i]; 25 } 26 } 27 28 29 static lzma_ret 30 delta_decode(lzma_coder *coder, lzma_allocator *allocator, 31 const uint8_t *restrict in, size_t *restrict in_pos, 32 size_t in_size, uint8_t *restrict out, 33 size_t *restrict out_pos, size_t out_size, lzma_action action) 34 { 35 assert(coder->next.code != NULL); 36 37 const size_t out_start = *out_pos; 38 39 const lzma_ret ret = coder->next.code(coder->next.coder, allocator, 40 in, in_pos, in_size, out, out_pos, out_size, 41 action); 42 43 decode_buffer(coder, out + out_start, *out_pos - out_start); 44 45 return ret; 46 } 47 48 49 extern lzma_ret 50 lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator, 51 const lzma_filter_info *filters) 52 { 53 next->code = &delta_decode; 54 return lzma_delta_coder_init(next, allocator, filters); 55 } 56 57 58 extern lzma_ret 59 lzma_delta_props_decode(void **options, lzma_allocator *allocator, 60 const uint8_t *props, size_t props_size) 61 { 62 if (props_size != 1) 63 return LZMA_OPTIONS_ERROR; 64 65 lzma_options_delta *opt 66 = lzma_alloc(sizeof(lzma_options_delta), allocator); 67 if (opt == NULL) 68 return LZMA_MEM_ERROR; 69 70 opt->type = LZMA_DELTA_TYPE_BYTE; 71 opt->dist = props[0] + 1; 72 73 *options = opt; 74 75 return LZMA_OK; 76 } 77