ddidderr/zstd-rs
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added negative compression levels

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negative compression level trade compression ratio for more compression speed.
They turn off huffman compression of literals,
and use row 0 as baseline with a stepSize = -cLevel.

added associated test in fuzzer

also added : new advanced parameter ZSTD_p_literalCompression
This commit is contained in:
Yann Collet
2018-03-11 05:21:53 -07:00
parent facc09aa03
commit a146ee04ae
5 changed files with 133 additions and 110 deletions
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lib/compress/zstd_compress_internal.h
+12 -9
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@@ -158,6 +158,7 @@ struct ZSTD_CCtx_params_s {
ZSTD_frameParameters fParams;
int compressionLevel;
int disableLiteralCompression;
int forceWindow; /* force back-references to respect limit of
* 1<<wLog, even for dictionary */
@@ -395,10 +396,12 @@ MEM_STATIC size_t ZSTD_count(const BYTE* pIn, const BYTE* pMatch, const BYTE* co
}
/** ZSTD_count_2segments() :
* can count match length with `ip` & `match` in 2 different segments.
* convention : on reaching mEnd, match count continue starting from iStart
*/
MEM_STATIC size_t ZSTD_count_2segments(const BYTE* ip, const BYTE* match, const BYTE* iEnd, const BYTE* mEnd, const BYTE* iStart)
* can count match length with `ip` & `match` in 2 different segments.
* convention : on reaching mEnd, match count continue starting from iStart
*/
MEM_STATIC size_t
ZSTD_count_2segments(const BYTE* ip, const BYTE* match,
const BYTE* iEnd, const BYTE* mEnd, const BYTE* iStart)
{
const BYTE* const vEnd = MIN( ip + (mEnd - match), iEnd);
size_t const matchLength = ZSTD_count(ip, match, vEnd);
@@ -408,8 +411,8 @@ MEM_STATIC size_t ZSTD_count_2segments(const BYTE* ip, const BYTE* match, const
/*-*************************************
* Hashes
***************************************/
* Hashes
***************************************/
static const U32 prime3bytes = 506832829U;
static U32 ZSTD_hash3(U32 u, U32 h) { return ((u << (32-24)) * prime3bytes) >> (32-h) ; }
MEM_STATIC size_t ZSTD_hash3Ptr(const void* ptr, U32 h) { return ZSTD_hash3(MEM_readLE32(ptr), h); } /* only in zstd_opt.h */
@@ -453,9 +456,9 @@ MEM_STATIC size_t ZSTD_hashPtr(const void* p, U32 hBits, U32 mls)
#define ZSTD_LOWLIMIT_MAX (3U << 29) /* Max lowLimit allowed */
/* Maximum chunk size before overflow correction needs to be called again */
#define ZSTD_CHUNKSIZE_MAX \
( ((U32)-1) /* Maximum ending current index */ \
- (1U << ZSTD_WINDOWLOG_MAX) /* Max distance from lowLimit to current */ \
#define ZSTD_CHUNKSIZE_MAX \
( ((U32)-1) /* Maximum ending current index */ \
- (1U << ZSTD_WINDOWLOG_MAX) /* Max distance from lowLimit to current */ \
- ZSTD_LOWLIMIT_MAX) /* Maximum beginning lowLimit */
/**