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_delta_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(void *coder_ptr, const 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 lzma_delta_coder *coder = coder_ptr; 36 37 assert(coder->next.code != NULL); 38 39 const size_t out_start = *out_pos; 40 41 const lzma_ret ret = coder->next.code(coder->next.coder, allocator, 42 in, in_pos, in_size, out, out_pos, out_size, 43 action); 44 45 // out might be NULL. In that case size == 0. Null pointer + 0 is 46 // undefined behavior so skip the call in that case as it would 47 // do nothing anyway. 48 const size_t size = *out_pos - out_start; 49 if (size > 0) 50 decode_buffer(coder, out + out_start, size); 51 52 return ret; 53 } 54 55 56 extern lzma_ret 57 lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, 58 const lzma_filter_info *filters) 59 { 60 next->code = &delta_decode; 61 return lzma_delta_coder_init(next, allocator, filters); 62 } 63 64 65 extern lzma_ret 66 lzma_delta_props_decode(void **options, const lzma_allocator *allocator, 67 const uint8_t *props, size_t props_size) 68 { 69 if (props_size != 1) 70 return LZMA_OPTIONS_ERROR; 71 72 lzma_options_delta *opt 73 = lzma_alloc(sizeof(lzma_options_delta), allocator); 74 if (opt == NULL) 75 return LZMA_MEM_ERROR; 76 77 opt->type = LZMA_DELTA_TYPE_BYTE; 78 opt->dist = props[0] + 1U; 79 80 *options = opt; 81 82 return LZMA_OK; 83 } 84