krak/zstd
1
0
Fork 0
mirror of https://github.com/facebook/zstd.git synced 2025-07-16 20:24:32 +02:00
Code Issues Releases 1 Activity

lib/compress: created ZSTD_LLcode() and ZSTD_MLcode()

Browse Source 
transform length into code.
Since transformation is needed in several places throughout the code,
better write the logic in one place.
This commit is contained in:
Yann Collet
2017-11-08 12:33:06 -08:00
parent 5aa0352742
commit 100d8ad6be
3 changed files with 40 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
lib/compress/zstd_compress_internal.h
View File

@ -195,30 +195,43 @@ struct ZSTD_CCtx_s {
};
static const BYTE LL_Code[64] = { 0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 16, 17, 17, 18, 18, 19, 19,
20, 20, 20, 20, 21, 21, 21, 21,
22, 22, 22, 22, 22, 22, 22, 22,
23, 23, 23, 23, 23, 23, 23, 23,
24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 24, 24, 24, 24 };
MEM_STATIC U32 ZSTD_LLcode(U32 litLength)
{
static const BYTE LL_Code[64] = { 0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 16, 17, 17, 18, 18, 19, 19,
20, 20, 20, 20, 21, 21, 21, 21,
22, 22, 22, 22, 22, 22, 22, 22,
23, 23, 23, 23, 23, 23, 23, 23,
24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 24, 24, 24, 24 };
static const U32 LL_deltaCode = 19;
return (litLength > 63) ? ZSTD_highbit32(litLength) + LL_deltaCode : LL_Code[litLength];
}
static const BYTE ML_Code[128] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 36, 36, 37, 37, 37, 37,
38, 38, 38, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 39, 39,
40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,
41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42 };
/* ZSTD_MLcode() :
* note : mlBase = matchLength - MINMATCH;
* because it's the format it's stored in seqStore->sequences */
MEM_STATIC U32 ZSTD_MLcode(U32 mlBase)
{
static const BYTE ML_Code[128] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 36, 36, 37, 37, 37, 37,
38, 38, 38, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 39, 39,
40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,
41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42 };
static const U32 ML_deltaCode = 36;
return (mlBase > 127) ? ZSTD_highbit32(mlBase) + ML_deltaCode : ML_Code[mlBase];
}
/*! ZSTD_storeSeq() :
* Store a sequence (literal length, literals, offset code and match length code) into seqStore_t.
* `offsetCode` : distance to match + 3 (values 1-3 are repCodes).
* `matchCode` : matchLength - MINMATCH
* `mlBase` : matchLength - MINMATCH
*/
MEM_STATIC void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const void* literals, U32 offsetCode, size_t matchCode)
MEM_STATIC void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const void* literals, U32 offsetCode, size_t mlBase)
{
#if defined(ZSTD_DEBUG) && (ZSTD_DEBUG >= 6)
static const BYTE* g_start = NULL;
@ -226,7 +239,7 @@ MEM_STATIC void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const v
if (g_start==NULL) g_start = (const BYTE*)literals; /* note : index only works for compression within a single segment */
if ((pos > 0) && (pos < 1000000000))
DEBUGLOG(6, "Cpos %6u :%5u literals & match %3u bytes at distance %6u",
pos, (U32)litLength, (U32)matchCode+MINMATCH, (U32)offsetCode);
pos, (U32)litLength, (U32)mlBase+MINMATCH, (U32)offsetCode);
#endif
/* copy Literals */
assert(seqStorePtr->lit + litLength <= seqStorePtr->litStart + 128 KB);
@ -245,12 +258,12 @@ MEM_STATIC void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const v
seqStorePtr->sequences[0].offset = offsetCode + 1;
/* match Length */
if (matchCode>0xFFFF) {
if (mlBase>0xFFFF) {
assert(seqStorePtr->longLengthID == 0); /* there can only be a single long length */
seqStorePtr->longLengthID = 2;
seqStorePtr->longLengthPos = (U32)(seqStorePtr->sequences - seqStorePtr->sequencesStart);
}
seqStorePtr->sequences[0].matchLength = (U16)matchCode;
seqStorePtr->sequences[0].matchLength = (U16)mlBase;
seqStorePtr->sequences++;
}