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-rw-r--r--lib/lz4opt.h356
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diff --git a/lib/lz4opt.h b/lib/lz4opt.h
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-/*
- lz4opt.h - Optimal Mode of LZ4
- Copyright (C) 2015-2017, Przemyslaw Skibinski <inikep@gmail.com>
- Note : this file is intended to be included within lz4hc.c
-
- BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions are
- met:
-
- * Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above
- copyright notice, this list of conditions and the following disclaimer
- in the documentation and/or other materials provided with the
- distribution.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
- You can contact the author at :
- - LZ4 source repository : https://github.com/lz4/lz4
- - LZ4 public forum : https://groups.google.com/forum/#!forum/lz4c
-*/
-
-#define LZ4_OPT_NUM (1<<12)
-
-typedef struct {
- int price;
- int off;
- int mlen;
- int litlen;
-} LZ4HC_optimal_t;
-
-
-/* price in bytes */
-LZ4_FORCE_INLINE int LZ4HC_literalsPrice(int const litlen)
-{
- int price = litlen;
- if (litlen >= (int)RUN_MASK)
- price += 1 + (litlen-RUN_MASK)/255;
- return price;
-}
-
-
-/* requires mlen >= MINMATCH */
-LZ4_FORCE_INLINE int LZ4HC_sequencePrice(int litlen, int mlen)
-{
- int price = 1 + 2 ; /* token + 16-bit offset */
-
- price += LZ4HC_literalsPrice(litlen);
-
- if (mlen >= (int)(ML_MASK+MINMATCH))
- price += 1 + (mlen-(ML_MASK+MINMATCH))/255;
-
- return price;
-}
-
-
-/*-*************************************
-* Match finder
-***************************************/
-typedef struct {
- int off;
- int len;
-} LZ4HC_match_t;
-
-LZ4_FORCE_INLINE
-LZ4HC_match_t LZ4HC_FindLongerMatch(LZ4HC_CCtx_internal* const ctx,
- const BYTE* ip, const BYTE* const iHighLimit,
- int minLen, int nbSearches)
-{
- LZ4HC_match_t match = { 0 , 0 };
- const BYTE* matchPtr = NULL;
- /* note : LZ4HC_InsertAndGetWiderMatch() is able to modify the starting position of a match (*startpos),
- * but this won't be the case here, as we define iLowLimit==ip,
- * so LZ4HC_InsertAndGetWiderMatch() won't be allowed to search past ip */
- int const matchLength = LZ4HC_InsertAndGetWiderMatch(ctx,
- ip, ip, iHighLimit, minLen, &matchPtr, &ip,
- nbSearches, 1 /* patternAnalysis */);
- if (matchLength <= minLen) return match;
- match.len = matchLength;
- match.off = (int)(ip-matchPtr);
- return match;
-}
-
-
-static int LZ4HC_compress_optimal (
- LZ4HC_CCtx_internal* ctx,
- const char* const source,
- char* dst,
- int* srcSizePtr,
- int dstCapacity,
- int const nbSearches,
- size_t sufficient_len,
- limitedOutput_directive limit,
- int const fullUpdate
- )
-{
-#define TRAILING_LITERALS 3
- LZ4HC_optimal_t opt[LZ4_OPT_NUM + TRAILING_LITERALS]; /* this uses a bit too much stack memory to my taste ... */
-
- const BYTE* ip = (const BYTE*) source;
- const BYTE* anchor = ip;
- const BYTE* const iend = ip + *srcSizePtr;
- const BYTE* const mflimit = iend - MFLIMIT;
- const BYTE* const matchlimit = iend - LASTLITERALS;
- BYTE* op = (BYTE*) dst;
- BYTE* opSaved = (BYTE*) dst;
- BYTE* oend = op + dstCapacity;
-
- /* init */
- DEBUGLOG(5, "LZ4HC_compress_optimal");
- *srcSizePtr = 0;
- if (limit == limitedDestSize) oend -= LASTLITERALS; /* Hack for support LZ4 format restriction */
- if (sufficient_len >= LZ4_OPT_NUM) sufficient_len = LZ4_OPT_NUM-1;
-
- /* Main Loop */
- assert(ip - anchor < LZ4_MAX_INPUT_SIZE);
- while (ip < mflimit) {
- int const llen = (int)(ip - anchor);
- int best_mlen, best_off;
- int cur, last_match_pos = 0;
-
- LZ4HC_match_t const firstMatch = LZ4HC_FindLongerMatch(ctx, ip, matchlimit, MINMATCH-1, nbSearches);
- if (firstMatch.len==0) { ip++; continue; }
-
- if ((size_t)firstMatch.len > sufficient_len) {
- /* good enough solution : immediate encoding */
- int const firstML = firstMatch.len;
- const BYTE* const matchPos = ip - firstMatch.off;
- opSaved = op;
- if ( LZ4HC_encodeSequence(&ip, &op, &anchor, firstML, matchPos, limit, oend) ) /* updates ip, op and anchor */
- goto _dest_overflow;
- continue;
- }
-
- /* set prices for first positions (literals) */
- { int rPos;
- for (rPos = 0 ; rPos < MINMATCH ; rPos++) {
- int const cost = LZ4HC_literalsPrice(llen + rPos);
- opt[rPos].mlen = 1;
- opt[rPos].off = 0;
- opt[rPos].litlen = llen + rPos;
- opt[rPos].price = cost;
- DEBUGLOG(7, "rPos:%3i => price:%3i (litlen=%i) -- initial setup",
- rPos, cost, opt[rPos].litlen);
- } }
- /* set prices using initial match */
- { int mlen = MINMATCH;
- int const matchML = firstMatch.len; /* necessarily < sufficient_len < LZ4_OPT_NUM */
- int const offset = firstMatch.off;
- assert(matchML < LZ4_OPT_NUM);
- for ( ; mlen <= matchML ; mlen++) {
- int const cost = LZ4HC_sequencePrice(llen, mlen);
- opt[mlen].mlen = mlen;
- opt[mlen].off = offset;
- opt[mlen].litlen = llen;
- opt[mlen].price = cost;
- DEBUGLOG(7, "rPos:%3i => price:%3i (matchlen=%i) -- initial setup",
- mlen, cost, mlen);
- } }
- last_match_pos = firstMatch.len;
- { int addLit;
- for (addLit = 1; addLit <= TRAILING_LITERALS; addLit ++) {
- opt[last_match_pos+addLit].mlen = 1; /* literal */
- opt[last_match_pos+addLit].off = 0;
- opt[last_match_pos+addLit].litlen = addLit;
- opt[last_match_pos+addLit].price = opt[last_match_pos].price + LZ4HC_literalsPrice(addLit);
- DEBUGLOG(7, "rPos:%3i => price:%3i (litlen=%i) -- initial setup",
- last_match_pos+addLit, opt[last_match_pos+addLit].price, addLit);
- } }
-
- /* check further positions */
- for (cur = 1; cur < last_match_pos; cur++) {
- const BYTE* const curPtr = ip + cur;
- LZ4HC_match_t newMatch;
-
- if (curPtr >= mflimit) break;
- DEBUGLOG(7, "rPos:%u[%u] vs [%u]%u",
- cur, opt[cur].price, opt[cur+1].price, cur+1);
- if (fullUpdate) {
- /* not useful to search here if next position has same (or lower) cost */
- if ( (opt[cur+1].price <= opt[cur].price)
- /* in some cases, next position has same cost, but cost rises sharply after, so a small match would still be beneficial */
- && (opt[cur+MINMATCH].price < opt[cur].price + 3/*min seq price*/) )
- continue;
- } else {
- /* not useful to search here if next position has same (or lower) cost */
- if (opt[cur+1].price <= opt[cur].price) continue;
- }
-
- DEBUGLOG(7, "search at rPos:%u", cur);
- if (fullUpdate)
- newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, MINMATCH-1, nbSearches);
- else
- /* only test matches of minimum length; slightly faster, but misses a few bytes */
- newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, last_match_pos - cur, nbSearches);
- if (!newMatch.len) continue;
-
- if ( ((size_t)newMatch.len > sufficient_len)
- || (newMatch.len + cur >= LZ4_OPT_NUM) ) {
- /* immediate encoding */
- best_mlen = newMatch.len;
- best_off = newMatch.off;
- last_match_pos = cur + 1;
- goto encode;
- }
-
- /* before match : set price with literals at beginning */
- { int const baseLitlen = opt[cur].litlen;
- int litlen;
- for (litlen = 1; litlen < MINMATCH; litlen++) {
- int const price = opt[cur].price - LZ4HC_literalsPrice(baseLitlen) + LZ4HC_literalsPrice(baseLitlen+litlen);
- int const pos = cur + litlen;
- if (price < opt[pos].price) {
- opt[pos].mlen = 1; /* literal */
- opt[pos].off = 0;
- opt[pos].litlen = baseLitlen+litlen;
- opt[pos].price = price;
- DEBUGLOG(7, "rPos:%3i => price:%3i (litlen=%i)",
- pos, price, opt[pos].litlen);
- } } }
-
- /* set prices using match at position = cur */
- { int const matchML = newMatch.len;
- int ml = MINMATCH;
-
- assert(cur + newMatch.len < LZ4_OPT_NUM);
- for ( ; ml <= matchML ; ml++) {
- int const pos = cur + ml;
- int const offset = newMatch.off;
- int price;
- int ll;
- DEBUGLOG(7, "testing price rPos %i (last_match_pos=%i)",
- pos, last_match_pos);
- if (opt[cur].mlen == 1) {
- ll = opt[cur].litlen;
- price = ((cur > ll) ? opt[cur - ll].price : 0)
- + LZ4HC_sequencePrice(ll, ml);
- } else {
- ll = 0;
- price = opt[cur].price + LZ4HC_sequencePrice(0, ml);
- }
-
- if (pos > last_match_pos+TRAILING_LITERALS || price <= opt[pos].price) {
- DEBUGLOG(7, "rPos:%3i => price:%3i (matchlen=%i)",
- pos, price, ml);
- assert(pos < LZ4_OPT_NUM);
- if ( (ml == matchML) /* last pos of last match */
- && (last_match_pos < pos) )
- last_match_pos = pos;
- opt[pos].mlen = ml;
- opt[pos].off = offset;
- opt[pos].litlen = ll;
- opt[pos].price = price;
- } } }
- /* complete following positions with literals */
- { int addLit;
- for (addLit = 1; addLit <= TRAILING_LITERALS; addLit ++) {
- opt[last_match_pos+addLit].mlen = 1; /* literal */
- opt[last_match_pos+addLit].off = 0;
- opt[last_match_pos+addLit].litlen = addLit;
- opt[last_match_pos+addLit].price = opt[last_match_pos].price + LZ4HC_literalsPrice(addLit);
- DEBUGLOG(7, "rPos:%3i => price:%3i (litlen=%i)", last_match_pos+addLit, opt[last_match_pos+addLit].price, addLit);
- } }
- } /* for (cur = 1; cur <= last_match_pos; cur++) */
-
- best_mlen = opt[last_match_pos].mlen;
- best_off = opt[last_match_pos].off;
- cur = last_match_pos - best_mlen;
-
-encode: /* cur, last_match_pos, best_mlen, best_off must be set */
- assert(cur < LZ4_OPT_NUM);
- assert(last_match_pos >= 1); /* == 1 when only one candidate */
- DEBUGLOG(6, "reverse traversal, looking for shortest path")
- DEBUGLOG(6, "last_match_pos = %i", last_match_pos);
- { int candidate_pos = cur;
- int selected_matchLength = best_mlen;
- int selected_offset = best_off;
- while (1) { /* from end to beginning */
- int const next_matchLength = opt[candidate_pos].mlen; /* can be 1, means literal */
- int const next_offset = opt[candidate_pos].off;
- DEBUGLOG(6, "pos %i: sequence length %i", candidate_pos, selected_matchLength);
- opt[candidate_pos].mlen = selected_matchLength;
- opt[candidate_pos].off = selected_offset;
- selected_matchLength = next_matchLength;
- selected_offset = next_offset;
- if (next_matchLength > candidate_pos) break; /* last match elected, first match to encode */
- assert(next_matchLength > 0); /* can be 1, means literal */
- candidate_pos -= next_matchLength;
- } }
-
- /* encode all recorded sequences in order */
- { int rPos = 0; /* relative position (to ip) */
- while (rPos < last_match_pos) {
- int const ml = opt[rPos].mlen;
- int const offset = opt[rPos].off;
- if (ml == 1) { ip++; rPos++; continue; } /* literal; note: can end up with several literals, in which case, skip them */
- rPos += ml;
- assert(ml >= MINMATCH);
- assert((offset >= 1) && (offset <= MAX_DISTANCE));
- opSaved = op;
- if ( LZ4HC_encodeSequence(&ip, &op, &anchor, ml, ip - offset, limit, oend) ) /* updates ip, op and anchor */
- goto _dest_overflow;
- } }
- } /* while (ip < mflimit) */
-
-_last_literals:
- /* Encode Last Literals */
- { size_t lastRunSize = (size_t)(iend - anchor); /* literals */
- size_t litLength = (lastRunSize + 255 - RUN_MASK) / 255;
- size_t const totalSize = 1 + litLength + lastRunSize;
- if (limit == limitedDestSize) oend += LASTLITERALS; /* restore correct value */
- if (limit && (op + totalSize > oend)) {
- if (limit == limitedOutput) return 0; /* Check output limit */
- /* adapt lastRunSize to fill 'dst' */
- lastRunSize = (size_t)(oend - op) - 1;
- litLength = (lastRunSize + 255 - RUN_MASK) / 255;
- lastRunSize -= litLength;
- }
- ip = anchor + lastRunSize;
-
- if (lastRunSize >= RUN_MASK) {
- size_t accumulator = lastRunSize - RUN_MASK;
- *op++ = (RUN_MASK << ML_BITS);
- for(; accumulator >= 255 ; accumulator -= 255) *op++ = 255;
- *op++ = (BYTE) accumulator;
- } else {
- *op++ = (BYTE)(lastRunSize << ML_BITS);
- }
- memcpy(op, anchor, lastRunSize);
- op += lastRunSize;
- }
-
- /* End */
- *srcSizePtr = (int) (((const char*)ip) - source);
- return (int) ((char*)op-dst);
-
-_dest_overflow:
- if (limit == limitedDestSize) {
- op = opSaved; /* restore correct out pointer */
- goto _last_literals;
- }
- return 0;
-}
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