src/liblzma/common/block_encoder.h

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       block_encoder.h
   6 /// \brief      Encodes .xz Blocks
   7 //
   8 //  Author:     Lasse Collin
   9 //
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 #ifndef LZMA_BLOCK_ENCODER_H
  13 #define LZMA_BLOCK_ENCODER_H
  14
  15 #include "common.h"
  16
  17
  18 /// \brief      Biggest Compressed Size value that the Block encoder supports
  19 ///
  20 /// The maximum size of a single Block is limited by the maximum size of
  21 /// a Stream, which in theory is 2^63 - 3 bytes (i.e. LZMA_VLI_MAX - 3).
  22 /// While the size is really big and no one should hit it in practice, we
  23 /// take it into account in some places anyway to catch some errors e.g. if
  24 /// application passes insanely big value to some function.
  25 ///
  26 /// We could take into account the headers etc. to determine the exact
  27 /// maximum size of the Compressed Data field, but the complexity would give
  28 /// us nothing useful. Instead, limit the size of Compressed Data so that
  29 /// even with biggest possible Block Header and Check fields the total
  30 /// encoded size of the Block stays as a valid VLI. This doesn't guarantee
  31 /// that the size of the Stream doesn't grow too big, but that problem is
  32 /// taken care outside the Block handling code.
  33 ///
  34 /// ~LZMA_VLI_C(3) is to guarantee that if we need padding at the end of
  35 /// the Compressed Data field, it will still stay in the proper limit.
  36 ///
  37 /// This constant is in this file because it is needed in both
  38 /// block_encoder.c and block_buffer_encoder.c.
  39 #define COMPRESSED_SIZE_MAX ((LZMA_VLI_MAX - LZMA_BLOCK_HEADER_SIZE_MAX \
  40                 - LZMA_CHECK_SIZE_MAX) & ~LZMA_VLI_C(3))
  41
  42
  43 extern lzma_ret lzma_block_encoder_init(lzma_next_coder *next,
  44                 const lzma_allocator *allocator, lzma_block *block);
  45
  46 #endif