| /* |
| 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 |
| ***************************************/ |
| |
| LZ4_FORCE_INLINE |
| int LZ4HC_FindLongerMatch(LZ4HC_CCtx_internal* const ctx, /* Index table will be updated */ |
| const BYTE* const ip, const BYTE* const iHighLimit, |
| int longest, |
| const BYTE** matchpos, |
| const int maxNbAttempts) |
| { |
| const BYTE* uselessPtr = ip; |
| return LZ4HC_InsertAndGetWiderMatch(ctx, ip, ip, iHighLimit, longest, matchpos, &uselessPtr, maxNbAttempts); |
| } |
| |
| typedef struct { |
| int off; |
| int len; |
| } LZ4HC_match_t; |
| |
| LZ4_FORCE_INLINE |
| LZ4HC_match_t LZ4HC_HashChain_GetAllMatches (LZ4HC_CCtx_internal* const ctx, |
| const BYTE* const ip, const BYTE* const iHighLimit, |
| size_t best_mlen, int nbSearches) |
| { |
| LZ4HC_match_t match = { 0 , 0 }; |
| const BYTE* matchPtr = NULL; |
| int matchLength = LZ4HC_FindLongerMatch(ctx, ip, iHighLimit, (int)best_mlen, &matchPtr, nbSearches); |
| if ((size_t)matchLength <= best_mlen) 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 inputSize, |
| int dstCapacity, |
| limitedOutput_directive limit, |
| int const nbSearches, |
| size_t sufficient_len, |
| int const fullUpdate |
| ) |
| { |
| LZ4HC_optimal_t opt[LZ4_OPT_NUM + 3]; /* 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 + inputSize; |
| const BYTE* const mflimit = iend - MFLIMIT; |
| const BYTE* const matchlimit = iend - LASTLITERALS; |
| BYTE* op = (BYTE*) dst; |
| BYTE* const oend = op + dstCapacity; |
| |
| /* init */ |
| DEBUGLOG(5, "LZ4HC_compress_optimal"); |
| if (sufficient_len >= LZ4_OPT_NUM) sufficient_len = LZ4_OPT_NUM-1; |
| ip++; |
| |
| /* 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_HashChain_GetAllMatches(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; |
| if ( LZ4HC_encodeSequence(&ip, &op, &anchor, firstML, matchPos, limit, oend) ) /* updates ip, op and anchor */ |
| return 0; /* error */ |
| 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 <= 3; 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) { |
| if ((opt[cur+1].price <= opt[cur].price) && (opt[cur+4].price < opt[cur].price+3)) continue; |
| } else { |
| if (opt[cur+1].price <= opt[cur].price) continue; |
| } |
| |
| DEBUGLOG(7, "search at rPos:%u", cur); |
| if (fullUpdate) |
| newMatch = LZ4HC_HashChain_GetAllMatches(ctx, curPtr, matchlimit, MINMATCH-1, nbSearches); |
| else |
| /* only test matches of minimum length; slightly faster, but misses a few bytes */ |
| newMatch = LZ4HC_HashChain_GetAllMatches(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+3 || 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 <= 3; 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)); |
| if ( LZ4HC_encodeSequence(&ip, &op, &anchor, ml, ip - offset, limit, oend) ) /* updates ip, op and anchor */ |
| return 0; /* error */ |
| } } |
| } /* while (ip < mflimit) */ |
| |
| /* Encode Last Literals */ |
| { int lastRun = (int)(iend - anchor); |
| if ( (limit) |
| && (((char*)op - dst) + lastRun + 1 + ((lastRun+255-RUN_MASK)/255) > (U32)dstCapacity)) |
| return 0; /* Check output limit */ |
| if (lastRun >= (int)RUN_MASK) { |
| *op++=(RUN_MASK<<ML_BITS); |
| lastRun-=RUN_MASK; |
| for (; lastRun > 254 ; lastRun-=255) *op++ = 255; |
| *op++ = (BYTE) lastRun; |
| } else *op++ = (BYTE)(lastRun<<ML_BITS); |
| memcpy(op, anchor, iend - anchor); |
| op += iend-anchor; |
| } |
| |
| /* End */ |
| return (int) ((char*)op-dst); |
| } |