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introduce macros STORE_OFFSET() and STORE_REPCODE()

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this meant to abstract the sumtype representation required
to transfert `offcode` to `ZSTD_storeSeq()`.

Unfortunately, the sumtype numeric representation is currently a leaky abstraction
that has permeated many other parts of the code,
especially within `zstd_lazy.c` and also within `zstd_opt.c` and `zstd_compress.c`.

While this PR makes a good job a transfering a large nb of call sites
to using the new macros, there are still a few sites where this transformation is more complex,
or where the numeric representation itself it used "as is".

One of the problematics area is the decision to use the numeric format of the sumtype
within the match finders of `zstd_lazy`.

This commit doesn't change the behavior, it only introduces and employes the macros,
but eventually the resulting code remains identical.

At target, if the numeric representation of the sumtype can be completely abstracted
and no other part of the code depends on it,
it will be possible to move it towards something slightly more efficient.
This commit is contained in:
Yann Collet
2021-12-23 22:03:30 -08:00
parent bec7bbb5a4
commit 1aed962216
8 changed files with 158 additions and 137 deletions
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lib/compress/zstd_compress_internal.h
+20 -7
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@@ -501,15 +501,20 @@ typedef struct repcodes_s {
U32 rep[3];
} repcodes_t;
MEM_STATIC repcodes_t ZSTD_updateRep(U32 const rep[3], U32 const offset, U32 const ll0)
/* ZSTD_updateRep() :
* @offcode : expects a scale where 0,1,2 represent repcodes 1-3, and 2+ represents real_offset+2
*/
MEM_STATIC repcodes_t
ZSTD_updateRep(U32 const rep[3], U32 const offcode, U32 const ll0)
{
repcodes_t newReps;
if (offset >= ZSTD_REP_NUM) { /* full offset */
if (offcode >= ZSTD_REP_NUM) { /* full offset */
newReps.rep[2] = rep[1];
newReps.rep[1] = rep[0];
newReps.rep[0] = offset - ZSTD_REP_MOVE;
newReps.rep[0] = offcode - ZSTD_REP_MOVE;
} else { /* repcode */
U32 const repCode = offset + ll0;
U32 const repCode = offcode + ll0;
if (repCode > 0) { /* note : if repCode==0, no change */
U32 const currentOffset = (repCode==ZSTD_REP_NUM) ? (rep[0] - 1) : rep[repCode];
newReps.rep[2] = (repCode >= 2) ? rep[1] : rep[2];
@@ -600,14 +605,22 @@ static void ZSTD_safecopyLiterals(BYTE* op, BYTE const* ip, BYTE const* const ie
while (ip < iend) *op++ = *ip++;
}
#define STORE_REPCODE_1 STORE_REPCODE(1)
#define STORE_REPCODE_2 STORE_REPCODE(2)
#define STORE_REPCODE_3 STORE_REPCODE(3)
#define STORE_REPCODE(r) (assert((r)>=1), assert((r)<=3), (r)-1)
#define STORE_OFFSET(o) (assert((o)>0), o + ZSTD_REP_MOVE)
/*! ZSTD_storeSeq() :
* Store a sequence (litlen, litPtr, offCode and matchLength) into seqStore_t.
* `offCode` : distance to match + ZSTD_REP_MOVE (values <= ZSTD_REP_MOVE are repCodes).
* @offBase_minus1 : distance to match + ZSTD_REP_MOVE (values <= ZSTD_REP_MOVE are repCodes).
* Users should not specify the encoded value directly,
* instead use macros STORE_REPCODE_X and STORE_OFFSET().
* @matchLength : must be >= MINMATCH
* Allowed to overread literals up to litLimit.
*/
HINT_INLINE UNUSED_ATTR
void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const BYTE* literals, const BYTE* litLimit, U32 offCode, size_t matchLength)
void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const BYTE* literals, const BYTE* litLimit, U32 offBase_minus1, size_t matchLength)
{
BYTE const* const litLimit_w = litLimit - WILDCOPY_OVERLENGTH;
BYTE const* const litEnd = literals + litLength;
@@ -647,7 +660,7 @@ void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const BYTE* litera
seqStorePtr->sequences[0].litLength = (U16)litLength;
/* match offset */
seqStorePtr->sequences[0].offBase = offCode + 1;
seqStorePtr->sequences[0].offBase = offBase_minus1 + 1;
/* match Length */
assert(matchLength >= MINMATCH);