src/liblzma/delta/delta_common.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       delta_common.c
   6 /// \brief      Common stuff for Delta encoder and decoder
   7 //
   8 //  Author:     Lasse Collin
   9 //
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 #include "delta_common.h"
  13 #include "delta_private.h"
  14
  15
  16 static void
  17 delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
  18 {
  19         lzma_delta_coder *coder = coder_ptr;
  20         lzma_next_end(&coder->next, allocator);
  21         lzma_free(coder, allocator);
  22         return;
  23 }
  24
  25
  26 extern lzma_ret
  27 lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
  28                 const lzma_filter_info *filters)
  29 {
  30         // Allocate memory for the decoder if needed.
  31         lzma_delta_coder *coder = next->coder;
  32         if (coder == NULL) {
  33                 coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
  34                 if (coder == NULL)
  35                         return LZMA_MEM_ERROR;
  36
  37                 next->coder = coder;
  38
  39                 // End function is the same for encoder and decoder.
  40                 next->end = &delta_coder_end;
  41                 coder->next = LZMA_NEXT_CODER_INIT;
  42         }
  43
  44         // Validate the options.
  45         if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
  46                 return LZMA_OPTIONS_ERROR;
  47
  48         // Set the delta distance.
  49         const lzma_options_delta *opt = filters[0].options;
  50         coder->distance = opt->dist;
  51
  52         // Initialize the rest of the variables.
  53         coder->pos = 0;
  54         memzero(coder->history, LZMA_DELTA_DIST_MAX);
  55
  56         // Initialize the next decoder in the chain, if any.
  57         return lzma_next_filter_init(&coder->next, allocator, filters + 1);
  58 }
  59
  60
  61 extern uint64_t
  62 lzma_delta_coder_memusage(const void *options)
  63 {
  64         const lzma_options_delta *opt = options;
  65
  66         if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
  67                         || opt->dist < LZMA_DELTA_DIST_MIN
  68                         || opt->dist > LZMA_DELTA_DIST_MAX)
  69                 return UINT64_MAX;
  70
  71         return sizeof(lzma_delta_coder);
  72 }