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author | Lasse Collin <lasse.collin@tukaani.org> | 2010-10-26 10:36:41 +0300 |
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committer | Lasse Collin <lasse.collin@tukaani.org> | 2010-10-26 10:36:41 +0300 |
commit | 974ebe63497bdf0d262e06474f0dd5a70b1dd000 (patch) | |
tree | b64367c4f90a4856439502ef3265a676e8019704 /src/liblzma/lzma/fastpos.h | |
parent | Bump version 5.1.0alpha. (diff) | |
download | xz-974ebe63497bdf0d262e06474f0dd5a70b1dd000.tar.xz |
liblzma: Rename a few variables and constants.
This has no semantic changes. I find the new names slightly
more logical and they match the names that are already used
in XZ Embedded.
The name fastpos wasn't changed (not worth the hassle).
Diffstat (limited to '')
-rw-r--r-- | src/liblzma/lzma/fastpos.h | 55 |
1 files changed, 28 insertions, 27 deletions
diff --git a/src/liblzma/lzma/fastpos.h b/src/liblzma/lzma/fastpos.h index 4aea2318..a3feea58 100644 --- a/src/liblzma/lzma/fastpos.h +++ b/src/liblzma/lzma/fastpos.h @@ -14,15 +14,15 @@ #ifndef LZMA_FASTPOS_H #define LZMA_FASTPOS_H -// LZMA encodes match distances (positions) by storing the highest two -// bits using a six-bit value [0, 63], and then the missing lower bits. -// Dictionary size is also stored using this encoding in the new .lzma +// LZMA encodes match distances by storing the highest two bits using +// a six-bit value [0, 63], and then the missing lower bits. +// Dictionary size is also stored using this encoding in the .xz // file format header. // // fastpos.h provides a way to quickly find out the correct six-bit // values. The following table gives some examples of this encoding: // -// pos return +// dist return // 0 0 // 1 1 // 2 2 @@ -48,10 +48,10 @@ // Provided functions or macros // ---------------------------- // -// get_pos_slot(pos) is the basic version. get_pos_slot_2(pos) -// assumes that pos >= FULL_DISTANCES, thus the result is at least -// FULL_DISTANCES_BITS * 2. Using get_pos_slot(pos) instead of -// get_pos_slot_2(pos) would give the same result, but get_pos_slot_2(pos) +// get_dist_slot(dist) is the basic version. get_dist_slot_2(dist) +// assumes that dist >= FULL_DISTANCES, thus the result is at least +// FULL_DISTANCES_BITS * 2. Using get_dist_slot(dist) instead of +// get_dist_slot_2(dist) would give the same result, but get_dist_slot_2(dist) // should be tiny bit faster due to the assumption being made. // // @@ -76,13 +76,14 @@ // slightly faster, but sometimes it is a lot slower. #ifdef HAVE_SMALL -# define get_pos_slot(pos) ((pos) <= 4 ? (pos) : get_pos_slot_2(pos)) +# define get_dist_slot(dist) \ + ((dist) <= 4 ? (dist) : get_dist_slot_2(dist)) static inline uint32_t -get_pos_slot_2(uint32_t pos) +get_dist_slot_2(uint32_t dist) { - const uint32_t i = bsr32(pos); - return (i + i) + ((pos >> (i - 1)) & 1); + const uint32_t i = bsr32(dist); + return (i + i) + ((dist >> (i - 1)) & 1); } @@ -99,39 +100,39 @@ extern const uint8_t lzma_fastpos[1 << FASTPOS_BITS]; #define fastpos_limit(extra, n) \ (UINT32_C(1) << (FASTPOS_BITS + fastpos_shift(extra, n))) -#define fastpos_result(pos, extra, n) \ - lzma_fastpos[(pos) >> fastpos_shift(extra, n)] \ +#define fastpos_result(dist, extra, n) \ + lzma_fastpos[(dist) >> fastpos_shift(extra, n)] \ + 2 * fastpos_shift(extra, n) static inline uint32_t -get_pos_slot(uint32_t pos) +get_dist_slot(uint32_t dist) { // If it is small enough, we can pick the result directly from // the precalculated table. - if (pos < fastpos_limit(0, 0)) - return lzma_fastpos[pos]; + if (dist < fastpos_limit(0, 0)) + return lzma_fastpos[dist]; - if (pos < fastpos_limit(0, 1)) - return fastpos_result(pos, 0, 1); + if (dist < fastpos_limit(0, 1)) + return fastpos_result(dist, 0, 1); - return fastpos_result(pos, 0, 2); + return fastpos_result(dist, 0, 2); } #ifdef FULL_DISTANCES_BITS static inline uint32_t -get_pos_slot_2(uint32_t pos) +get_dist_slot_2(uint32_t dist) { - assert(pos >= FULL_DISTANCES); + assert(dist >= FULL_DISTANCES); - if (pos < fastpos_limit(FULL_DISTANCES_BITS - 1, 0)) - return fastpos_result(pos, FULL_DISTANCES_BITS - 1, 0); + if (dist < fastpos_limit(FULL_DISTANCES_BITS - 1, 0)) + return fastpos_result(dist, FULL_DISTANCES_BITS - 1, 0); - if (pos < fastpos_limit(FULL_DISTANCES_BITS - 1, 1)) - return fastpos_result(pos, FULL_DISTANCES_BITS - 1, 1); + if (dist < fastpos_limit(FULL_DISTANCES_BITS - 1, 1)) + return fastpos_result(dist, FULL_DISTANCES_BITS - 1, 1); - return fastpos_result(pos, FULL_DISTANCES_BITS - 1, 2); + return fastpos_result(dist, FULL_DISTANCES_BITS - 1, 2); } #endif |