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authorYann Collet <cyan@fb.com>2017-03-20 09:57:41 (GMT)
committerYann Collet <cyan@fb.com>2017-03-20 12:04:12 (GMT)
commitb8bc70022bb5b9f1775796c3df90dac5d2f55686 (patch)
tree60944dfd0b6327f320f3c314b0e35b9f42a24b30 /lib
parentcea8f60df14d3c538e0a420eb15b808159ab6c09 (diff)
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minor refactor
Diffstat (limited to 'lib')
-rw-r--r--lib/lz4hc.c4
-rw-r--r--lib/lz4opt.h143
2 files changed, 75 insertions, 72 deletions
diff --git a/lib/lz4hc.c b/lib/lz4hc.c
index f3c9946..03a0301 100644
--- a/lib/lz4hc.c
+++ b/lib/lz4hc.c
@@ -243,6 +243,10 @@ typedef enum {
static unsigned debug = 0;
#endif
+
+/* LZ4HC_encodeSequence() :
+ * @return : 0 if ok,
+ * 1 if buffer issue detected */
FORCE_INLINE int LZ4HC_encodeSequence (
const BYTE** ip,
BYTE** op,
diff --git a/lib/lz4opt.h b/lib/lz4opt.h
index 36c84bb..d51d491 100644
--- a/lib/lz4opt.h
+++ b/lib/lz4opt.h
@@ -53,7 +53,7 @@ typedef struct {
FORCE_INLINE size_t LZ4HC_literalsPrice(size_t litlen)
{
size_t price = litlen;
- if (litlen >= (size_t)RUN_MASK) price += 1+(litlen-RUN_MASK)/255;
+ if (litlen >= (size_t)RUN_MASK) price += 1 + (litlen-RUN_MASK)/255;
return price;
}
@@ -213,9 +213,6 @@ static int LZ4HC_compress_optimal (
{
LZ4HC_optimal_t opt[LZ4_OPT_NUM + 1]; /* this uses a bit too much stack memory to my taste ... */
LZ4HC_match_t matches[LZ4_OPT_NUM + 1];
- const BYTE *inr = NULL;
- size_t res, cur, cur2;
- size_t i, llen, litlen, mlen, best_mlen, price, offset, best_off, match_num, last_pos;
const BYTE* ip = (const BYTE*) source;
const BYTE* anchor = ip;
@@ -232,13 +229,16 @@ static int LZ4HC_compress_optimal (
/* Main Loop */
while (ip < mflimit) {
+ size_t const llen = ip - anchor;
+ size_t last_pos = 0;
+ size_t match_num, cur, best_mlen, best_off;
memset(opt, 0, sizeof(LZ4HC_optimal_t));
- last_pos = 0;
- llen = ip - anchor;
+
match_num = LZ4HC_BinTree_GetAllMatches(ctx, ip, matchlimit, MINMATCH-1, matches, fullUpdate);
if (!match_num) { ip++; continue; }
if ((size_t)matches[match_num-1].len > sufficient_len) {
+ /* good enough solution : immediate encoding */
best_mlen = matches[match_num-1].len;
best_off = matches[match_num-1].off;
cur = 0;
@@ -247,43 +247,45 @@ static int LZ4HC_compress_optimal (
}
/* set prices using matches at position = 0 */
- for (i = 0; i < match_num; i++) {
- mlen = (i>0) ? (size_t)matches[i-1].len+1 : MINMATCH;
- best_mlen = matches[i].len; /* necessarily < LZ4_OPT_NUM */
- while (mlen <= best_mlen) {
- price = LZ4HC_sequencePrice(llen, mlen) - LZ4HC_literalsPrice(llen);
- SET_PRICE(mlen, mlen, matches[i].off, 0, price); /* updates last_pos and opt[pos] */
- mlen++;
- }
- }
+ { size_t matchNb;
+ for (matchNb = 0; matchNb < match_num; matchNb++) {
+ size_t mlen = (matchNb>0) ? (size_t)matches[matchNb-1].len+1 : MINMATCH;
+ best_mlen = matches[matchNb].len; /* necessarily < sufficient_len < LZ4_OPT_NUM */
+ for ( ; mlen <= best_mlen ; mlen++) {
+ size_t const cost = LZ4HC_sequencePrice(llen, mlen) - LZ4HC_literalsPrice(llen);
+ SET_PRICE(mlen, mlen, matches[matchNb].off, 0, cost); /* updates last_pos and opt[pos] */
+ } } }
- if (last_pos < MINMATCH) { ip++; continue; }
+ if (last_pos < MINMATCH) { ip++; continue; } /* note : on clang at least, this test improves performance */
/* check further positions */
opt[0].mlen = opt[1].mlen = 1;
for (cur = 1; cur <= last_pos; cur++) {
- inr = ip + cur;
-
- if (opt[cur-1].mlen == 1) {
- litlen = opt[cur-1].litlen + 1;
- if (cur != litlen) {
- price = opt[cur - litlen].price + LZ4HC_literalsPrice(litlen);
+ const BYTE* const curPtr = ip + cur;
+
+ /* establish baseline price if cur is literal */
+ { size_t price, litlen;
+ if (opt[cur-1].mlen == 1) {
+ /* no match at previous position */
+ litlen = opt[cur-1].litlen + 1;
+ if (cur > litlen) {
+ price = opt[cur - litlen].price + LZ4HC_literalsPrice(litlen);
+ } else {
+ price = LZ4HC_literalsPrice(llen + litlen) - LZ4HC_literalsPrice(llen);
+ }
} else {
- price = LZ4HC_literalsPrice(llen + litlen) - LZ4HC_literalsPrice(llen);
+ litlen = 1;
+ price = opt[cur - 1].price + LZ4HC_literalsPrice(1);
}
- } else {
- litlen = 1;
- price = opt[cur - 1].price + LZ4HC_literalsPrice(litlen);
- }
- mlen = 1;
- best_mlen = 0;
- if (price < (size_t)opt[cur].price)
- SET_PRICE(cur, mlen, best_mlen, litlen, price); /* note : increases last_pos */
+ best_mlen = 0;
+ if (price < (size_t)opt[cur].price)
+ SET_PRICE(cur, 1, 0, litlen, price); /* note : increases last_pos */
+ }
- if (cur == last_pos || inr >= mflimit) break;
+ if (cur == last_pos || curPtr >= mflimit) break;
- match_num = LZ4HC_BinTree_GetAllMatches(ctx, inr, matchlimit, MINMATCH-1, matches, fullUpdate);
+ match_num = LZ4HC_BinTree_GetAllMatches(ctx, curPtr, matchlimit, MINMATCH-1, matches, fullUpdate);
if ((match_num > 0) && (size_t)matches[match_num-1].len > sufficient_len) {
/* immediate encoding */
best_mlen = matches[match_num-1].len;
@@ -293,60 +295,57 @@ static int LZ4HC_compress_optimal (
}
/* set prices using matches at position = cur */
- for (i = 0; i < match_num; i++) {
- mlen = (i>0) ? (size_t)matches[i-1].len+1 : MINMATCH;
- cur2 = cur;
- best_mlen = (cur2 + matches[i].len < LZ4_OPT_NUM) ? (size_t)matches[i].len : LZ4_OPT_NUM - cur2;
-
- while (mlen <= best_mlen) {
- if (opt[cur2].mlen == 1) {
- litlen = opt[cur2].litlen;
-
- if (cur2 != litlen)
- price = opt[cur2 - litlen].price + LZ4HC_sequencePrice(litlen, mlen);
- else
- price = LZ4HC_sequencePrice(llen + litlen, mlen) - LZ4HC_literalsPrice(llen);
- } else {
- litlen = 0;
- price = opt[cur2].price + LZ4HC_sequencePrice(litlen, mlen);
- }
-
- if (cur2 + mlen > last_pos || price < (size_t)opt[cur2 + mlen].price) { // || (((int)price == opt[cur2 + mlen].price) && (opt[cur2 + mlen-1].mlen == 1))) {
- SET_PRICE(cur2 + mlen, mlen, matches[i].off, litlen, price);
- }
- mlen++;
- }
- }
+ { size_t matchNb;
+ for (matchNb = 0; matchNb < match_num; matchNb++) {
+ size_t ml = (matchNb>0) ? (size_t)matches[matchNb-1].len+1 : MINMATCH;
+ best_mlen = (cur + matches[matchNb].len < LZ4_OPT_NUM) ?
+ (size_t)matches[matchNb].len : LZ4_OPT_NUM - cur;
+
+ for ( ; ml <= best_mlen ; ml++) {
+ size_t ll, price;
+ if (opt[cur].mlen == 1) {
+ ll = opt[cur].litlen;
+ if (cur > ll)
+ price = opt[cur - ll].price + LZ4HC_sequencePrice(ll, ml);
+ else
+ price = LZ4HC_sequencePrice(llen + ll, ml) - LZ4HC_literalsPrice(llen);
+ } else {
+ ll = 0;
+ price = opt[cur].price + LZ4HC_sequencePrice(0, ml);
+ }
+
+ if (cur + ml > last_pos || price < (size_t)opt[cur + ml].price) {
+ SET_PRICE(cur + ml, ml, matches[matchNb].off, ll, price);
+ } } } }
} /* for (cur = 1; cur <= last_pos; cur++) */
best_mlen = opt[last_pos].mlen;
best_off = opt[last_pos].off;
cur = last_pos - best_mlen;
-encode: /* cur, last_pos, best_mlen, best_off have to be set */
+encode: /* cur, last_pos, best_mlen, best_off must be set */
opt[0].mlen = 1;
- while (1) {
- mlen = opt[cur].mlen;
- offset = opt[cur].off;
+ while (1) { /* from end to beginning */
+ size_t const ml = opt[cur].mlen;
+ int const offset = opt[cur].off;
opt[cur].mlen = (int)best_mlen;
opt[cur].off = (int)best_off;
- best_mlen = mlen;
+ best_mlen = ml;
best_off = offset;
- if (mlen > cur) break;
- cur -= mlen;
+ if (ml > cur) break;
+ cur -= ml;
}
+ /* encode all recorded sequences */
cur = 0;
while (cur < last_pos) {
- mlen = opt[cur].mlen;
- if (mlen == 1) { ip++; cur++; continue; }
- offset = opt[cur].off;
- cur += mlen;
-
- res = LZ4HC_encodeSequence(&ip, &op, &anchor, (int)mlen, ip - offset, limit, oend);
- if (res) return 0;
+ int const ml = opt[cur].mlen;
+ int const offset = opt[cur].off;
+ if (ml == 1) { ip++; cur++; continue; }
+ cur += ml;
+ if ( LZ4HC_encodeSequence(&ip, &op, &anchor, ml, ip - offset, limit, oend) ) return 0;
}
- }
+ } /* while (ip < mflimit) */
/* Encode Last Literals */
{ int lastRun = (int)(iend - anchor);