src/liblzma/delta/delta_decoder.c

   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         size_t i;
  22
  23         for (i = 0; i < size; ++i) {
  24                 buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
  25                 coder->history[coder->pos-- & 0xFF] = buffer[i];
  26         }
  27 }
  28
  29
  30 static lzma_ret
  31 delta_decode(lzma_coder *coder, lzma_allocator *allocator,
  32                 const uint8_t *restrict in, size_t *restrict in_pos,
  33                 size_t in_size, uint8_t *restrict out,
  34                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  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         decode_buffer(coder, out + out_start, *out_pos - out_start);
  45
  46         return ret;
  47 }
  48
  49
  50 extern lzma_ret
  51 lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
  52                 const lzma_filter_info *filters)
  53 {
  54         next->code = &delta_decode;
  55         return lzma_delta_coder_init(next, allocator, filters);
  56 }
  57
  58
  59 extern lzma_ret
  60 lzma_delta_props_decode(void **options, lzma_allocator *allocator,
  61                 const uint8_t *props, size_t props_size)
  62 {
  63         if (props_size != 1)
  64                 return LZMA_OPTIONS_ERROR;
  65
  66         lzma_options_delta *opt
  67                         = lzma_alloc(sizeof(lzma_options_delta), allocator);
  68         if (opt == NULL)
  69                 return LZMA_MEM_ERROR;
  70
  71         opt->type = LZMA_DELTA_TYPE_BYTE;
  72         opt->dist = props[0] + 1;
  73
  74         *options = opt;
  75
  76         return LZMA_OK;
  77 }