src/liblzma/delta/delta_common.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       delta_common.c
   4 /// \brief      Common stuff for Delta encoder and 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_common.h"
  14 #include "delta_private.h"
  15
  16
  17 static void
  18 delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
  19 {
  20         lzma_delta_coder *coder = coder_ptr;
  21         lzma_next_end(&coder->next, allocator);
  22         lzma_free(coder, allocator);
  23         return;
  24 }
  25
  26
  27 extern lzma_ret
  28 lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
  29                 const lzma_filter_info *filters)
  30 {
  31         // Allocate memory for the decoder if needed.
  32         lzma_delta_coder *coder = next->coder;
  33         if (coder == NULL) {
  34                 coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
  35                 if (coder == NULL)
  36                         return LZMA_MEM_ERROR;
  37
  38                 next->coder = coder;
  39
  40                 // End function is the same for encoder and decoder.
  41                 next->end = &delta_coder_end;
  42                 coder->next = LZMA_NEXT_CODER_INIT;
  43         }
  44
  45         // Validate the options.
  46         if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
  47                 return LZMA_OPTIONS_ERROR;
  48
  49         // Set the delta distance.
  50         const lzma_options_delta *opt = filters[0].options;
  51         coder->distance = opt->dist;
  52
  53         // Initialize the rest of the variables.
  54         coder->pos = 0;
  55         memzero(coder->history, LZMA_DELTA_DIST_MAX);
  56
  57         // Initialize the next decoder in the chain, if any.
  58         return lzma_next_filter_init(&coder->next, allocator, filters + 1);
  59 }
  60
  61
  62 extern uint64_t
  63 lzma_delta_coder_memusage(const void *options)
  64 {
  65         const lzma_options_delta *opt = options;
  66
  67         if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
  68                         || opt->dist < LZMA_DELTA_DIST_MIN
  69                         || opt->dist > LZMA_DELTA_DIST_MAX)
  70                 return UINT64_MAX;
  71
  72         return sizeof(lzma_delta_coder);
  73 }