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author | mm <mm@FreeBSD.org> | 2010-05-10 06:59:50 +0000 |
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committer | mm <mm@FreeBSD.org> | 2010-05-10 06:59:50 +0000 |
commit | 5c358d45429b654efa9c8177ecd370a7965ec1a7 (patch) | |
tree | d2d916954c6a66a3168ee356b5f24da01c2017d6 /contrib/xz/src/liblzma/rangecoder/range_common.h | |
parent | 3e09decd1986826f54af1a47be97bb87c1220783 (diff) | |
parent | 1008b7c6744a190c5b15aaf8cab1054671e4c7c3 (diff) | |
download | FreeBSD-src-5c358d45429b654efa9c8177ecd370a7965ec1a7.zip FreeBSD-src-5c358d45429b654efa9c8177ecd370a7965ec1a7.tar.gz |
Import of liblzma, xz, xzdec, lzmainfo from vendor branch
Add support for xz and lzma to lesspipe.sh (xzless, lzless)
Bump __FreeBSD_version
Approved by: delphij (mentor)
MFC after: 2 weeks
Diffstat (limited to 'contrib/xz/src/liblzma/rangecoder/range_common.h')
-rw-r--r-- | contrib/xz/src/liblzma/rangecoder/range_common.h | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/contrib/xz/src/liblzma/rangecoder/range_common.h b/contrib/xz/src/liblzma/rangecoder/range_common.h new file mode 100644 index 0000000..0e64241 --- /dev/null +++ b/contrib/xz/src/liblzma/rangecoder/range_common.h @@ -0,0 +1,73 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file range_common.h +/// \brief Common things for range encoder and decoder +/// +// Authors: Igor Pavlov +// Lasse Collin +// +// This file has been put into the public domain. +// You can do whatever you want with this file. +// +/////////////////////////////////////////////////////////////////////////////// + +#ifndef LZMA_RANGE_COMMON_H +#define LZMA_RANGE_COMMON_H + +#ifdef HAVE_CONFIG_H +# include "common.h" +#endif + + +/////////////// +// Constants // +/////////////// + +#define RC_SHIFT_BITS 8 +#define RC_TOP_BITS 24 +#define RC_TOP_VALUE (UINT32_C(1) << RC_TOP_BITS) +#define RC_BIT_MODEL_TOTAL_BITS 11 +#define RC_BIT_MODEL_TOTAL (UINT32_C(1) << RC_BIT_MODEL_TOTAL_BITS) +#define RC_MOVE_BITS 5 + + +//////////// +// Macros // +//////////// + +// Resets the probability so that both 0 and 1 have probability of 50 % +#define bit_reset(prob) \ + prob = RC_BIT_MODEL_TOTAL >> 1 + +// This does the same for a complete bit tree. +// (A tree represented as an array.) +#define bittree_reset(probs, bit_levels) \ + for (uint32_t bt_i = 0; bt_i < (1 << (bit_levels)); ++bt_i) \ + bit_reset((probs)[bt_i]) + + +////////////////////// +// Type definitions // +////////////////////// + +/// \brief Type of probabilities used with range coder +/// +/// This needs to be at least 12-bit integer, so uint16_t is a logical choice. +/// However, on some architecture and compiler combinations, a bigger type +/// may give better speed, because the probability variables are accessed +/// a lot. On the other hand, bigger probability type increases cache +/// footprint, since there are 2 to 14 thousand probability variables in +/// LZMA (assuming the limit of lc + lp <= 4; with lc + lp <= 12 there +/// would be about 1.5 million variables). +/// +/// With malicious files, the initialization speed of the LZMA decoder can +/// become important. In that case, smaller probability variables mean that +/// there is less bytes to write to RAM, which makes initialization faster. +/// With big probability type, the initialization can become so slow that it +/// can be a problem e.g. for email servers doing virus scanning. +/// +/// I will be sticking to uint16_t unless some specific architectures +/// are *much* faster (20-50 %) with uint32_t. +typedef uint16_t probability; + +#endif |