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zstd_opt: refactor code for improved readability 

renamed variables to be more meaningful
reduced scope of multiple variables
removed some useless var attribution
dev
Yann Collet 2017-11-08 11:36:38 -08:00
parent 4191efa993
commit bf730e2044
1 changed files with 33 additions and 30 deletions
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63
lib/compress/zstd_opt.c
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@ -440,42 +440,44 @@ size_t ZSTD_compressBlock_opt_generic(ZSTD_CCtx* ctx,
ctx->nextToUpdate3 = ctx->nextToUpdate;
ZSTD_rescaleFreqs(optStatePtr, (const BYTE*)src, srcSize);
ip += (ip==prefixStart);
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) rep[i]=seqStorePtr->rep[i]; }
{ int i; for (i=0; i<ZSTD_REP_NUM; i++) rep[i]=seqStorePtr->rep[i]; }
/* Match Loop */
while (ip < ilimit) {
U32 cur, match_num, last_pos, litlen, price;
U32 cur, match_num, last_pos = 0, litlen, price;
U32 u, mlen, best_mlen, best_off, litLength, offset;
memset(opt, 0, sizeof(ZSTD_optimal_t));
last_pos = 0;
litlen = (U32)(ip - anchor);
/* check repCode */
{ U32 i, last_i = ZSTD_REP_CHECK + (ip==anchor);
for (i = (ip==anchor); i < last_i; i++) {
S32 const repCur = (i==ZSTD_REP_MOVE_OPT) ? (rep[0] - 1) : rep[i];
if ( (repCur > 0)
&& (repCur < (S32)(ip-prefixStart)) /* only check within current mem segment */
&& (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(ip - repCur, minMatch))) {
mlen = (U32)ZSTD_count(ip+minMatch, ip+minMatch-repCur, iend) + minMatch;
if (mlen > sufficient_len) {
best_mlen = mlen; best_off = i; cur = 0; last_pos = 1;
{ U32 const ll0 = (ip==anchor);
U32 const lastR = ZSTD_REP_CHECK + ll0;
U32 repCode;
for (repCode = ll0; repCode < lastR; repCode++) {
S32 const repOffset = (repCode==ZSTD_REP_MOVE_OPT) ? (rep[0] - 1) : rep[repCode];
if ( (repOffset > 0)
&& (repOffset < (S32)(ip-prefixStart)) /* only check within current mem segment */
&& (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(ip - repOffset, minMatch))) {
U32 repLen = (U32)ZSTD_count(ip+minMatch, ip+minMatch-repOffset, iend) + minMatch;
if (repLen > sufficient_len) {
/* large repMatch => immediate encoding */
best_mlen = repLen; best_off = repCode; cur = 0; last_pos = 1;
goto _storeSequence;
}
best_off = i - (ip == anchor);
do {
price = ZSTD_getPrice(optStatePtr, litlen, anchor, best_off, mlen - MINMATCH, ultra);
if (mlen > last_pos || price < opt[mlen].price)
SET_PRICE(mlen, mlen, i, litlen, price); /* note : macro modifies last_pos */
mlen--;
} while (mlen >= minMatch);
U32 const repPrice = ZSTD_getPrice(optStatePtr, litlen, anchor, repCode - ll0, repLen - MINMATCH, ultra);
if (repLen > last_pos || repPrice < opt[repLen].price)
SET_PRICE(repLen, repLen, repCode, litlen, repPrice); /* note : macro modifies last_pos */
repLen--;
} while (repLen >= minMatch);
} } }
match_num = ZSTD_BtGetAllMatches_selectMLS(ctx, ip, iend, maxSearches, mls, matches, minMatch);
if (!last_pos && !match_num) { ip++; continue; }
if (!last_pos /*no repCode*/ && !match_num /*no match*/) { ip++; continue; }
if (match_num && (matches[match_num-1].len > sufficient_len)) {
/* large match => immediate encoding */
best_mlen = matches[match_num-1].len;
best_off = matches[match_num-1].off;
cur = 0;
@ -483,17 +485,18 @@ size_t ZSTD_compressBlock_opt_generic(ZSTD_CCtx* ctx,
goto _storeSequence;
}
/* set prices using matches at position = 0 */
best_mlen = (last_pos) ? last_pos : minMatch;
for (u = 0; u < match_num; u++) {
mlen = (u>0) ? matches[u-1].len+1 : best_mlen;
best_mlen = matches[u].len;
while (mlen <= best_mlen) {
price = ZSTD_getPrice(optStatePtr, litlen, anchor, matches[u].off-1, mlen - MINMATCH, ultra);
if (mlen > last_pos || price < opt[mlen].price)
SET_PRICE(mlen, mlen, matches[u].off, litlen, price); /* note : macro modifies last_pos */
mlen++;
} }
/* set prices for first matches from position == 0 */
{ U32 matchNb;
for (matchNb = 0; matchNb < match_num; matchNb++) {
U32 pos = (matchNb==0) ? (last_pos /*some repCode (assumed cheaper)*/ ? last_pos : minMatch)
: matches[matchNb-1].len+1;
U32 const end = matches[matchNb].len;
while (pos <= end) {
U32 const matchPrice = ZSTD_getPrice(optStatePtr, litlen, anchor, matches[matchNb].off-1, pos - MINMATCH, ultra);
if (pos > last_pos || matchPrice < opt[pos].price)
SET_PRICE(pos, pos, matches[matchNb].off, litlen, matchPrice); /* note : macro modifies last_pos */
pos++;
} } }
if (last_pos < minMatch) { ip++; continue; }