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separate newRep() from updateRep()

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the new contracts seems to make more sense :
updateRep() updates an array of repeat offsets _in place_,
while newRep() generates a new structure with the updated repeat-offset array.

Most callers are actually expecting the in-place variant,
and a limited sub-section, in `zstd_opt.c` mainly, prefer `newRep()`.
This commit is contained in:
Yann Collet
2021-12-28 11:52:33 -08:00
parent 321583ccf5
commit 6fa640ef70
4 changed files with 33 additions and 25 deletions
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lib/compress/zstd_compress_internal.h
+23 -15
View File
@@ -655,32 +655,40 @@ ZSTD_storeSeq(seqStore_t* seqStorePtr,
seqStorePtr->sequences++;
}
typedef struct repcodes_s {
U32 rep[3];
} repcodes_t;
/* ZSTD_updateRep() :
* @offcode : sum-type, with same numeric representation as ZSTD_storeSeq()
* updates in-place @rep (array of repeat offsets)
* @offBase_minus1 : sum-type, with same numeric representation as ZSTD_storeSeq()
*/
MEM_STATIC repcodes_t
ZSTD_updateRep(U32 const rep[3], U32 const offBase_minus1, U32 const ll0)
MEM_STATIC void
ZSTD_updateRep(U32 rep[ZSTD_REP_NUM], U32 const offBase_minus1, U32 const ll0)
{
repcodes_t newReps;
if (STORED_IS_OFFSET(offBase_minus1)) { /* full offset */
newReps.rep[2] = rep[1];
newReps.rep[1] = rep[0];
newReps.rep[0] = STORED_OFFSET(offBase_minus1);
rep[2] = rep[1];
rep[1] = rep[0];
rep[0] = STORED_OFFSET(offBase_minus1);
} else { /* repcode */
U32 const repCode = STORED_REPCODE(offBase_minus1) - 1 + 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];
newReps.rep[1] = rep[0];
newReps.rep[0] = currentOffset;
rep[2] = (repCode >= 2) ? rep[1] : rep[2];
rep[1] = rep[0];
rep[0] = currentOffset;
} else { /* repCode == 0 */
ZSTD_memcpy(&newReps, rep, sizeof(newReps));
/* nothing to do */
}
}
}
typedef struct repcodes_s {
U32 rep[3];
} repcodes_t;
MEM_STATIC repcodes_t
ZSTD_newRep(U32 const rep[ZSTD_REP_NUM], U32 const offBase_minus1, U32 const ll0)
{
repcodes_t newReps;
memcpy(&newReps, rep, sizeof(newReps));
ZSTD_updateRep(newReps.rep, offBase_minus1, ll0);
return newReps;
}