1 // SPDX-License-Identifier: 0BSD 2 3 /////////////////////////////////////////////////////////////////////////////// 4 // 5 /// \file delta_decoder.c 6 /// \brief Delta filter decoder 7 // 8 // Author: Lasse Collin 9 // 10 /////////////////////////////////////////////////////////////////////////////// 11 12 #include "delta_decoder.h" 13 #include "delta_private.h" 14 15 16 static void 17 decode_buffer(lzma_delta_coder *coder, uint8_t *buffer, size_t size) 18 { 19 const size_t distance = coder->distance; 20 21 for (size_t i = 0; i < size; ++i) { 22 buffer[i] += coder->history[(distance + coder->pos) & 0xFF]; 23 coder->history[coder->pos-- & 0xFF] = buffer[i]; 24 } 25 } 26 27 28 static lzma_ret 29 delta_decode(void *coder_ptr, const lzma_allocator *allocator, 30 const uint8_t *restrict in, size_t *restrict in_pos, 31 size_t in_size, uint8_t *restrict out, 32 size_t *restrict out_pos, size_t out_size, lzma_action action) 33 { 34 lzma_delta_coder *coder = coder_ptr; 35 36 assert(coder->next.code != NULL); 37 38 const size_t out_start = *out_pos; 39 40 const lzma_ret ret = coder->next.code(coder->next.coder, allocator, 41 in, in_pos, in_size, out, out_pos, out_size, 42 action); 43 44 // out might be NULL. In that case size == 0. Null pointer + 0 is 45 // undefined behavior so skip the call in that case as it would 46 // do nothing anyway. 47 const size_t size = *out_pos - out_start; 48 if (size > 0) 49 decode_buffer(coder, out + out_start, size); 50 51 return ret; 52 } 53 54 55 extern lzma_ret 56 lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, 57 const lzma_filter_info *filters) 58 { 59 next->code = &delta_decode; 60 return lzma_delta_coder_init(next, allocator, filters); 61 } 62 63 64 extern lzma_ret 65 lzma_delta_props_decode(void **options, const lzma_allocator *allocator, 66 const uint8_t *props, size_t props_size) 67 { 68 if (props_size != 1) 69 return LZMA_OPTIONS_ERROR; 70 71 lzma_options_delta *opt 72 = lzma_alloc(sizeof(lzma_options_delta), allocator); 73 if (opt == NULL) 74 return LZMA_MEM_ERROR; 75 76 opt->type = LZMA_DELTA_TYPE_BYTE; 77 opt->dist = props[0] + 1U; 78 79 *options = opt; 80 81 return LZMA_OK; 82 } 83