// this software is distributed under the MIT License (http://www.opensource.org/licenses/MIT): // // Copyright 2018-2020, CWI, TU Munich, FSU Jena // // Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files // (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, // merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is // furnished to do so, subject to the following conditions: // // - The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES // OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR // IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. // // You can contact the authors via the FSST source repository : https://github.com/cwida/fsst #include <algorithm> #include <cassert> #include <cstring> #include <fstream> #include <iostream> #include <numeric> #include <memory> #include <queue> #include <string> #include <unordered_set> #include <vector> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stddef.h> using namespace std; #include "fsst.h" // the official FSST API -- also usable by C mortals /* unsigned integers */ typedef uint8_t u8; typedef uint16_t u16; typedef uint32_t u32; typedef uint64_t u64; #define FSST_ENDIAN_MARKER ((u64) 1) #define FSST_VERSION_20190218 20190218 #define FSST_VERSION ((u64) FSST_VERSION_20190218) // "symbols" are character sequences (up to 8 bytes) // A symbol is compressed into a "code" of, in principle, one byte. But, we added an exception mechanism: // byte 255 followed by byte X represents the single-byte symbol X. Its code is 256+X. // we represent codes in u16 (not u8). 12 bits code (of which 10 are used), 4 bits length #define FSST_LEN_BITS 12 #define FSST_CODE_BITS 9 #define FSST_CODE_BASE 256UL /* first 256 codes [0,255] are pseudo codes: escaped bytes */ #define FSST_CODE_MAX (1UL<<FSST_CODE_BITS) /* all bits set: indicating a symbol that has not been assigned a code yet */ #define FSST_CODE_MASK (FSST_CODE_MAX-1UL) /* all bits set: indicating a symbol that has not been assigned a code yet */ struct Symbol { static const unsigned maxLength = 8; // the byte sequence that this symbol stands for union { char str[maxLength]; u64 num; } val; // usually we process it as a num(ber), as this is fast // icl = u64 ignoredBits:16,code:12,length:4,unused:32 -- but we avoid exposing this bit-field notation u64 icl; // use a single u64 to be sure "code" is accessed with one load and can be compared with one comparison Symbol() : icl(0) { val.num = 0; } explicit Symbol(u8 c, u16 code) : icl((1<<28)|(code<<16)|56) { val.num = c; } // single-char symbol explicit Symbol(const char* begin, const char* end) : Symbol(begin, (u32) (end-begin)) {} explicit Symbol(u8* begin, u8* end) : Symbol((const char*)begin, (u32) (end-begin)) {} explicit Symbol(const char* input, u32 len) { val.num = 0; if (len>=8) { len = 8; memcpy(val.str, input, 8); } else { memcpy(val.str, input, len); } set_code_len(FSST_CODE_MAX, len); } void set_code_len(u32 code, u32 len) { icl = (len<<28)|(code<<16)|((8-len)*8); } u32 length() const { return (u32) (icl >> 28); } u16 code() const { return (icl >> 16) & FSST_CODE_MASK; } u32 ignoredBits() const { return (u32) icl; } u8 first() const { assert( length() >= 1); return 0xFF & val.num; } u16 first2() const { assert( length() >= 2); return 0xFFFF & val.num; } #define FSST_HASH_LOG2SIZE 10 #define FSST_HASH_PRIME 2971215073LL #define FSST_SHIFT 15 #define FSST_HASH(w) (((w)*FSST_HASH_PRIME)^(((w)*FSST_HASH_PRIME)>>FSST_SHIFT)) size_t hash() const { size_t v = 0xFFFFFF & val.num; return FSST_HASH(v); } // hash on the next 3 bytes }; // Symbol that can be put in a queue, ordered on gain struct QSymbol{ Symbol symbol; mutable u32 gain; // mutable because gain value should be ignored in find() on unordered_set of QSymbols bool operator==(const QSymbol& other) const { return symbol.val.num == other.symbol.val.num && symbol.length() == other.symbol.length(); } }; // we construct FSST symbol tables using a random sample of about 16KB (1<<14) #define FSST_SAMPLETARGET (1<<14) #define FSST_SAMPLEMAXSZ ((long) 2*FSST_SAMPLETARGET) // two phases of compression, before and after optimize(): // // (1) to encode values we probe (and maintain) three datastructures: // - u16 byteCodes[65536] array at the position of the next byte (s.length==1) // - u16 shortCodes[65536] array at the position of the next twobyte pattern (s.length==2) // - Symbol hashtable[1024] (keyed by the next three bytes, ie for s.length>2), // this search will yield a u16 code, it points into Symbol symbols[]. You always find a hit, because the first 256 codes are // pseudo codes representing a single byte these will become escapes) // // (2) when we finished looking for the best symbol table we call optimize() to reshape it: // - it renumbers the codes by length (first symbols of length 2,3,4,5,6,7,8; then 1 (starting from byteLim are symbols of length 1) // length 2 codes for which no longer suffix symbol exists (< suffixLim) come first among the 2-byte codes // (allows shortcut during compression) // - for each two-byte combination, in all unused slots of shortCodes[], it enters the byteCode[] of the symbol corresponding // to the first byte (if such a single-byte symbol exists). This allows us to just probe the next two bytes (if there is only one // byte left in the string, there is still a terminator-byte added during compression) in shortCodes[]. That is, byteCodes[] // and its codepath is no longer required. This makes compression faster. The reason we use byteCodes[] during symbolTable construction // is that adding a new code/symbol is expensive (you have to touch shortCodes[] in 256 places). This optimization was // hence added to make symbolTable construction faster. // // this final layout allows for the fastest compression code, only currently present in compressBulk // in the hash table, the icl field contains (low-to-high) ignoredBits:16,code:12,length:4 #define FSST_ICL_FREE ((15<<28)|(((u32)FSST_CODE_MASK)<<16)) // high bits of icl (len=8,code=FSST_CODE_MASK) indicates free bucket // ignoredBits is (8-length)*8, which is the amount of high bits to zero in the input word before comparing with the hashtable key // ..it could of course be computed from len during lookup, but storing it precomputed in some loose bits is faster // // the gain field is only used in the symbol queue that sorts symbols on gain struct SymbolTable { static const u32 hashTabSize = 1<<FSST_HASH_LOG2SIZE; // smallest size that incurs no precision loss // lookup table using the next two bytes (65536 codes), or just the next single byte u16 shortCodes[65536]; // contains code for 2-byte symbol, otherwise code for pseudo byte (escaped byte) // lookup table (only used during symbolTable construction, not during normal text compression) u16 byteCodes[256]; // contains code for every 1-byte symbol, otherwise code for pseudo byte (escaped byte) // 'symbols' is the current symbol table symbol[code].symbol is the max 8-byte 'symbol' for single-byte 'code' Symbol symbols[FSST_CODE_MAX]; // x in [0,255]: pseudo symbols representing escaped byte x; x in [FSST_CODE_BASE=256,256+nSymbols]: real symbols // replicate long symbols in hashTab (avoid indirection). Symbol hashTab[hashTabSize]; // used for all symbols of 3 and more bytes u16 nSymbols; // amount of symbols in the map (max 255) u16 suffixLim; // codes higher than this do not have a longer suffix u16 terminator; // code of 1-byte symbol, that can be used as a terminator during compression bool zeroTerminated; // whether we are expecting zero-terminated strings (we then also produce zero-terminated compressed strings) u16 lenHisto[FSST_CODE_BITS]; // lenHisto[x] is the amount of symbols of byte-length (x+1) in this SymbolTable SymbolTable() : nSymbols(0), suffixLim(FSST_CODE_MAX), terminator(0), zeroTerminated(false) { // stuff done once at startup for (u32 i=0; i<256; i++) { symbols[i] = Symbol(i,i|(1<<FSST_LEN_BITS)); // pseudo symbols } Symbol unused = Symbol((u8) 0,FSST_CODE_MASK); // single-char symbol, exception code for (u32 i=256; i<FSST_CODE_MAX; i++) { symbols[i] = unused; // we start with all symbols unused } // empty hash table Symbol s; s.val.num = 0; s.icl = FSST_ICL_FREE; //marks empty in hashtab for(u32 i=0; i<hashTabSize; i++) hashTab[i] = s; // fill byteCodes[] with the pseudo code all bytes (escaped bytes) for(u32 i=0; i<256; i++) byteCodes[i] = (1<<FSST_LEN_BITS) | i; // fill shortCodes[] with the pseudo code for the first byte of each two-byte pattern for(u32 i=0; i<65536; i++) shortCodes[i] = (1<<FSST_LEN_BITS) | (i&255); memset(lenHisto, 0, sizeof(lenHisto)); // all unused } void clear() { // clear a symbolTable with minimal effort (only erase the used positions in it) memset(lenHisto, 0, sizeof(lenHisto)); // all unused for(u32 i=FSST_CODE_BASE; i<FSST_CODE_BASE+nSymbols; i++) { if (symbols[i].length() == 1) { u16 val = symbols[i].first(); byteCodes[val] = (1<<FSST_LEN_BITS) | val; } else if (symbols[i].length() == 2) { u16 val = symbols[i].first2(); shortCodes[val] = (1<<FSST_LEN_BITS) | (val&255); } else { u32 idx = symbols[i].hash() & (hashTabSize-1); hashTab[idx].val.num = 0; hashTab[idx].icl = FSST_ICL_FREE; //marks empty in hashtab } } nSymbols = 0; // no need to clean symbols[] as no symbols are used } bool hashInsert(Symbol s) { u32 idx = s.hash() & (hashTabSize-1); bool taken = (hashTab[idx].icl < FSST_ICL_FREE); if (taken) return false; // collision in hash table hashTab[idx].icl = s.icl; hashTab[idx].val.num = s.val.num & (0xFFFFFFFFFFFFFFFF >> (u8) s.icl); return true; } bool add(Symbol s) { assert(FSST_CODE_BASE + nSymbols < FSST_CODE_MAX); u32 len = s.length(); s.set_code_len(FSST_CODE_BASE + nSymbols, len); if (len == 1) { byteCodes[s.first()] = FSST_CODE_BASE + nSymbols + (1<<FSST_LEN_BITS); // len=1 (<<FSST_LEN_BITS) } else if (len == 2) { shortCodes[s.first2()] = FSST_CODE_BASE + nSymbols + (2<<FSST_LEN_BITS); // len=2 (<<FSST_LEN_BITS) } else if (!hashInsert(s)) { return false; } symbols[FSST_CODE_BASE + nSymbols++] = s; lenHisto[len-1]++; return true; } /// Find longest expansion, return code (= position in symbol table) u16 findLongestSymbol(Symbol s) const { size_t idx = s.hash() & (hashTabSize-1); if (hashTab[idx].icl <= s.icl && hashTab[idx].val.num == (s.val.num & (0xFFFFFFFFFFFFFFFF >> ((u8) hashTab[idx].icl)))) { return (hashTab[idx].icl>>16) & FSST_CODE_MASK; // matched a long symbol } if (s.length() >= 2) { u16 code = shortCodes[s.first2()] & FSST_CODE_MASK; if (code >= FSST_CODE_BASE) return code; } return byteCodes[s.first()] & FSST_CODE_MASK; } u16 findLongestSymbol(u8* cur, u8* end) const { return findLongestSymbol(Symbol(cur,end)); // represent the string as a temporary symbol } // rationale for finalize: // - during symbol table construction, we may create more than 256 codes, but bring it down to max 255 in the last makeTable() // consequently we needed more than 8 bits during symbol table contruction, but can simplify the codes to single bytes in finalize() // (this feature is in fact lo longer used, but could still be exploited: symbol construction creates no more than 255 symbols in each pass) // - we not only reduce the amount of codes to <255, but also *reorder* the symbols and renumber their codes, for higher compression perf. // we renumber codes so they are grouped by length, to allow optimized scalar string compression (byteLim and suffixLim optimizations). // - we make the use of byteCode[] no longer necessary by inserting single-byte codes in the free spots of shortCodes[] // Using shortCodes[] only makes compression faster. When creating the symbolTable, however, using shortCodes[] for the single-byte // symbols is slow, as each insert touches 256 positions in it. This optimization was added when optimizing symbolTable construction time. // // In all, we change the layout and coding, as follows.. // // before finalize(): // - The real symbols are symbols[256..256+nSymbols>. As we may have nSymbols > 255 // - The first 256 codes are pseudo symbols (all escaped bytes) // // after finalize(): // - table layout is symbols[0..nSymbols>, with nSymbols < 256. // - Real codes are [0,nSymbols>. 8-th bit not set. // - Escapes in shortCodes have the 8th bit set (value: 256+255=511). 255 because the code to be emitted is the escape byte 255 // - symbols are grouped by length: 2,3,4,5,6,7,8, then 1 (single-byte codes last) // the two-byte codes are split in two sections: // - first section contains codes for symbols for which there is no longer symbol (no suffix). It allows an early-out during compression // // finally, shortCodes[] is modified to also encode all single-byte symbols (hence byteCodes[] is not required on a critical path anymore). // void finalize(u8 zeroTerminated) { assert(nSymbols <= 255); u8 newCode[256], rsum[8], byteLim = nSymbols - (lenHisto[0] - zeroTerminated); // compute running sum of code lengths (starting offsets for each length) rsum[0] = byteLim; // 1-byte codes are highest rsum[1] = zeroTerminated; for(u32 i=1; i<7; i++) rsum[i+1] = rsum[i] + lenHisto[i]; // determine the new code for each symbol, ordered by length (and splitting 2byte symbols into two classes around suffixLim) suffixLim = rsum[1]; symbols[newCode[0] = 0] = symbols[256]; // keep symbol 0 in place (for zeroTerminated cases only) for(u32 i=zeroTerminated, j=rsum[2]; i<nSymbols; i++) { Symbol s1 = symbols[FSST_CODE_BASE+i]; u32 len = s1.length(), opt = (len == 2)*nSymbols; if (opt) { u16 first2 = s1.first2(); for(u32 k=0; k<opt; k++) { Symbol s2 = symbols[FSST_CODE_BASE+k]; if (k != i && s2.length() > 1 && first2 == s2.first2()) // test if symbol k is a suffix of s opt = 0; } newCode[i] = opt?suffixLim++:--j; // symbols without a larger suffix have a code < suffixLim } else newCode[i] = rsum[len-1]++; s1.set_code_len(newCode[i],len); symbols[newCode[i]] = s1; } // renumber the codes in byteCodes[] for(u32 i=0; i<256; i++) if ((byteCodes[i] & FSST_CODE_MASK) >= FSST_CODE_BASE) byteCodes[i] = newCode[(u8) byteCodes[i]] + (1 << FSST_LEN_BITS); else byteCodes[i] = 511 + (1 << FSST_LEN_BITS); // renumber the codes in shortCodes[] for(u32 i=0; i<65536; i++) if ((shortCodes[i] & FSST_CODE_MASK) >= FSST_CODE_BASE) shortCodes[i] = newCode[(u8) shortCodes[i]] + (shortCodes[i] & (15 << FSST_LEN_BITS)); else shortCodes[i] = byteCodes[i&0xFF]; // replace the symbols in the hash table for(u32 i=0; i<hashTabSize; i++) if (hashTab[i].icl < FSST_ICL_FREE) hashTab[i] = symbols[newCode[(u8) hashTab[i].code()]]; } }; #ifdef NONOPT_FSST struct Counters { u16 count1[FSST_CODE_MAX]; // array to count frequency of symbols as they occur in the sample u16 count2[FSST_CODE_MAX][FSST_CODE_MAX]; // array to count subsequent combinations of two symbols in the sample void count1Set(u32 pos1, u16 val) { count1[pos1] = val; } void count1Inc(u32 pos1) { count1[pos1]++; } void count2Inc(u32 pos1, u32 pos2) { count2[pos1][pos2]++; } u32 count1GetNext(u32 &pos1) { return count1[pos1]; } u32 count2GetNext(u32 pos1, u32 &pos2) { return count2[pos1][pos2]; } void backup1(u8 *buf) { memcpy(buf, count1, FSST_CODE_MAX*sizeof(u16)); } void restore1(u8 *buf) { memcpy(count1, buf, FSST_CODE_MAX*sizeof(u16)); } }; #else // we keep two counters count1[pos] and count2[pos1][pos2] of resp 16 and 12-bits. Both are split into two columns for performance reasons // first reason is to make the column we update the most during symbolTable construction (the low bits) thinner, thus reducing CPU cache pressure. // second reason is that when scanning the array, after seeing a 64-bits 0 in the high bits column, we can quickly skip over many codes (15 or 7) struct Counters { // high arrays come before low arrays, because our GetNext() methods may overrun their 64-bits reads a few bytes u8 count1High[FSST_CODE_MAX]; // array to count frequency of symbols as they occur in the sample (16-bits) u8 count1Low[FSST_CODE_MAX]; // it is split in a low and high byte: cnt = count1High*256 + count1Low u8 count2High[FSST_CODE_MAX][FSST_CODE_MAX/2]; // array to count subsequent combinations of two symbols in the sample (12-bits: 8-bits low, 4-bits high) u8 count2Low[FSST_CODE_MAX][FSST_CODE_MAX]; // its value is (count2High*256+count2Low) -- but high is 4-bits (we put two numbers in one, hence /2) // 385KB -- but hot area likely just 10 + 30*4 = 130 cache lines (=8KB) void count1Set(u32 pos1, u16 val) { count1Low[pos1] = val&255; count1High[pos1] = val>>8; } void count1Inc(u32 pos1) { if (!count1Low[pos1]++) // increment high early (when low==0, not when low==255). This means (high > 0) <=> (cnt > 0) count1High[pos1]++; //(0,0)->(1,1)->..->(255,1)->(0,1)->(1,2)->(2,2)->(3,2)..(255,2)->(0,2)->(1,3)->(2,3)... } void count2Inc(u32 pos1, u32 pos2) { if (!count2Low[pos1][pos2]++) // increment high early (when low==0, not when low==255). This means (high > 0) <=> (cnt > 0) // inc 4-bits high counter with 1<<0 (1) or 1<<4 (16) -- depending on whether pos2 is even or odd, repectively count2High[pos1][(pos2)>>1] += 1 << (((pos2)&1)<<2); // we take our chances with overflow.. (4K maxval, on a 8K sample) } u32 count1GetNext(u32 &pos1) { // note: we will advance pos1 to the next nonzero counter in register range // read 16-bits single symbol counter, split into two 8-bits numbers (count1Low, count1High), while skipping over zeros u64 high = *(u64*) &count1High[pos1]; // note: this reads 8 subsequent counters [pos1..pos1+7] u32 zero = high?(__builtin_ctzl(high)>>3):7UL; // number of zero bytes high = (high >> (zero << 3)) & 255; // advance to nonzero counter if (((pos1 += zero) >= FSST_CODE_MAX) || !high) // SKIP! advance pos2 return 0; // all zero u32 low = count1Low[pos1]; if (low) high--; // high is incremented early and low late, so decrement high (unless low==0) return (u32) ((high << 8) + low); } u32 count2GetNext(u32 pos1, u32 &pos2) { // note: we will advance pos2 to the next nonzero counter in register range // read 12-bits pairwise symbol counter, split into low 8-bits and high 4-bits number while skipping over zeros u64 high = *(u64*) &count2High[pos1][pos2>>1]; // note: this reads 16 subsequent counters [pos2..pos2+15] high >>= ((pos2&1) << 2); // odd pos2: ignore the lowest 4 bits & we see only 15 counters u32 zero = high?(__builtin_ctzl(high)>>2):(15UL-(pos2&1UL)); // number of zero 4-bits counters high = (high >> (zero << 2)) & 15; // advance to nonzero counter if (((pos2 += zero) >= FSST_CODE_MAX) || !high) // SKIP! advance pos2 return 0UL; // all zero u32 low = count2Low[pos1][pos2]; if (low) high--; // high is incremented early and low late, so decrement high (unless low==0) return (u32) ((high << 8) + low); } void backup1(u8 *buf) { memcpy(buf, count1High, FSST_CODE_MAX); memcpy(buf+FSST_CODE_MAX, count1Low, FSST_CODE_MAX); } void restore1(u8 *buf) { memcpy(count1High, buf, FSST_CODE_MAX); memcpy(count1Low, buf+FSST_CODE_MAX, FSST_CODE_MAX); } }; #endif #define FSST_BUFSZ (3<<19) // 768KB // an encoder is a symbolmap plus some bufferspace, needed during map construction as well as compression struct Encoder { shared_ptr<SymbolTable> symbolTable; // symbols, plus metadata and data structures for quick compression (shortCode,hashTab, etc) union { Counters counters; // for counting symbol occurences during map construction u8 simdbuf[FSST_BUFSZ]; // for compression: SIMD string staging area 768KB = 256KB in + 512KB out (worst case for 256KB in) }; }; // job control integer representable in one 64bits SIMD lane: cur/end=input, out=output, pos=which string (2^9=512 per call) struct SIMDjob { u64 out:19,pos:9,end:18,cur:18; // cur/end is input offsets (2^18=256KB), out is output offset (2^19=512KB) }; extern bool fsst_hasAVX512(); // runtime check for avx512 capability extern size_t fsst_compressAVX512( SymbolTable &symbolTable, u8* codeBase, // IN: base address for codes, i.e. compression output (points to simdbuf+256KB) u8* symbolBase, // IN: base address for string bytes, i.e. compression input (points to simdbuf) SIMDjob* input, // IN: input array (size n) with job information: what to encode, where to store it. SIMDjob* output, // OUT: output array (size n) with job information: how much got encoded, end output pointer. size_t n, // IN: size of arrays input and output (should be max 512) size_t unroll); // IN: degree of SIMD unrolling // C++ fsst-compress function with some more control of how the compression happens (algorithm flavor, simd unroll degree) size_t compressImpl(Encoder *encoder, size_t n, size_t lenIn[], u8 *strIn[], size_t size, u8 * output, size_t *lenOut, u8 *strOut[], bool noSuffixOpt, bool avoidBranch, int simd); size_t compressAuto(Encoder *encoder, size_t n, size_t lenIn[], u8 *strIn[], size_t size, u8 * output, size_t *lenOut, u8 *strOut[], int simd);