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diff --git a/src/slz.c b/src/slz.c new file mode 100644 index 0000000..0ca9d27 --- /dev/null +++ b/src/slz.c @@ -0,0 +1,1341 @@ +/* + * Copyright (C) 2013-2015 Willy Tarreau <w@1wt.eu> + * + * 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. + */ + +#include <inttypes.h> +#include <stdio.h> +#include <string.h> +#include <import/slz.h> +#include <import/slz-tables.h> + +/* First, RFC1951-specific declarations and extracts from the RFC. + * + * RFC1951 - deflate stream format + + + * Data elements are packed into bytes in order of + increasing bit number within the byte, i.e., starting + with the least-significant bit of the byte. + * Data elements other than Huffman codes are packed + starting with the least-significant bit of the data + element. + * Huffman codes are packed starting with the most- + significant bit of the code. + + 3.2.3. Details of block format + + Each block of compressed data begins with 3 header bits + containing the following data: + + first bit BFINAL + next 2 bits BTYPE + + Note that the header bits do not necessarily begin on a byte + boundary, since a block does not necessarily occupy an integral + number of bytes. + + BFINAL is set if and only if this is the last block of the data + set. + + BTYPE specifies how the data are compressed, as follows: + + 00 - no compression + 01 - compressed with fixed Huffman codes + 10 - compressed with dynamic Huffman codes + 11 - reserved (error) + + 3.2.4. Non-compressed blocks (BTYPE=00) + + Any bits of input up to the next byte boundary are ignored. + The rest of the block consists of the following information: + + 0 1 2 3 4... + +---+---+---+---+================================+ + | LEN | NLEN |... LEN bytes of literal data...| + +---+---+---+---+================================+ + + LEN is the number of data bytes in the block. NLEN is the + one's complement of LEN. + + 3.2.5. Compressed blocks (length and distance codes) + + As noted above, encoded data blocks in the "deflate" format + consist of sequences of symbols drawn from three conceptually + distinct alphabets: either literal bytes, from the alphabet of + byte values (0..255), or <length, backward distance> pairs, + where the length is drawn from (3..258) and the distance is + drawn from (1..32,768). In fact, the literal and length + alphabets are merged into a single alphabet (0..285), where + values 0..255 represent literal bytes, the value 256 indicates + end-of-block, and values 257..285 represent length codes + (possibly in conjunction with extra bits following the symbol + code) as follows: + +Length encoding : + Extra Extra Extra + Code Bits Length(s) Code Bits Lengths Code Bits Length(s) + ---- ---- ------ ---- ---- ------- ---- ---- ------- + 257 0 3 267 1 15,16 277 4 67-82 + 258 0 4 268 1 17,18 278 4 83-98 + 259 0 5 269 2 19-22 279 4 99-114 + 260 0 6 270 2 23-26 280 4 115-130 + 261 0 7 271 2 27-30 281 5 131-162 + 262 0 8 272 2 31-34 282 5 163-194 + 263 0 9 273 3 35-42 283 5 195-226 + 264 0 10 274 3 43-50 284 5 227-257 + 265 1 11,12 275 3 51-58 285 0 258 + 266 1 13,14 276 3 59-66 + +Distance encoding : + Extra Extra Extra + Code Bits Dist Code Bits Dist Code Bits Distance + ---- ---- ---- ---- ---- ------ ---- ---- -------- + 0 0 1 10 4 33-48 20 9 1025-1536 + 1 0 2 11 4 49-64 21 9 1537-2048 + 2 0 3 12 5 65-96 22 10 2049-3072 + 3 0 4 13 5 97-128 23 10 3073-4096 + 4 1 5,6 14 6 129-192 24 11 4097-6144 + 5 1 7,8 15 6 193-256 25 11 6145-8192 + 6 2 9-12 16 7 257-384 26 12 8193-12288 + 7 2 13-16 17 7 385-512 27 12 12289-16384 + 8 3 17-24 18 8 513-768 28 13 16385-24576 + 9 3 25-32 19 8 769-1024 29 13 24577-32768 + + 3.2.6. Compression with fixed Huffman codes (BTYPE=01) + + The Huffman codes for the two alphabets are fixed, and are not + represented explicitly in the data. The Huffman code lengths + for the literal/length alphabet are: + + Lit Value Bits Codes + --------- ---- ----- + 0 - 143 8 00110000 through + 10111111 + 144 - 255 9 110010000 through + 111111111 + 256 - 279 7 0000000 through + 0010111 + 280 - 287 8 11000000 through + 11000111 + + The code lengths are sufficient to generate the actual codes, + as described above; we show the codes in the table for added + clarity. Literal/length values 286-287 will never actually + occur in the compressed data, but participate in the code + construction. + + Distance codes 0-31 are represented by (fixed-length) 5-bit + codes, with possible additional bits as shown in the table + shown in Paragraph 3.2.5, above. Note that distance codes 30- + 31 will never actually occur in the compressed data. + +*/ + +/* back references, built in a way that is optimal for 32/64 bits */ +union ref { + struct { + uint32_t pos; + uint32_t word; + } by32; + uint64_t by64; +}; + +#if defined(USE_64BIT_QUEUE) && defined(UNALIGNED_LE_OK) + +/* enqueue code x of <xbits> bits (LSB aligned, at most 24) and copy complete + * 32-bit words into output buffer. X must not contain non-zero bits above + * xbits. + */ +static inline void enqueue24(struct slz_stream *strm, uint32_t x, uint32_t xbits) +{ + uint64_t queue = strm->queue + ((uint64_t)x << strm->qbits); + uint32_t qbits = strm->qbits + xbits; + + if (__builtin_expect(qbits >= 32, 1)) { + *(uint32_t *)strm->outbuf = queue; + queue >>= 32; + qbits -= 32; + strm->outbuf += 4; + } + + strm->queue = queue; + strm->qbits = qbits; +} + +#define enqueue8 enqueue24 + +/* flush the queue and align to next byte */ +static inline void flush_bits(struct slz_stream *strm) +{ + if (strm->qbits > 0) + *strm->outbuf++ = strm->queue; + + if (strm->qbits > 8) + *strm->outbuf++ = strm->queue >> 8; + + if (strm->qbits > 16) + *strm->outbuf++ = strm->queue >> 16; + + if (strm->qbits > 24) + *strm->outbuf++ = strm->queue >> 24; + + strm->queue = 0; + strm->qbits = 0; +} + +#else /* non-64 bit or aligned or big endian */ + +/* enqueue code x of <xbits> bits (LSB aligned, at most 24) and copy complete + * bytes into out buf. X must not contain non-zero bits above xbits. Prefer + * enqueue8() when xbits is known for being 8 or less. + */ +static void enqueue24(struct slz_stream *strm, uint32_t x, uint32_t xbits) +{ + uint32_t queue = strm->queue + (x << strm->qbits); + uint32_t qbits = strm->qbits + xbits; + + if (qbits >= 16) { +#ifndef UNALIGNED_LE_OK + strm->outbuf[0] = queue; + strm->outbuf[1] = queue >> 8; +#else + *(uint16_t *)strm->outbuf = queue; +#endif + strm->outbuf += 2; + queue >>= 16; + qbits -= 16; + } + + if (qbits >= 8) { + qbits -= 8; + *strm->outbuf++ = queue; + queue >>= 8; + } + strm->qbits = qbits; + strm->queue = queue; + return; +} + +/* enqueue code x of <xbits> bits (at most 8) and copy complete bytes into + * out buf. X must not contain non-zero bits above xbits. + */ +static inline void enqueue8(struct slz_stream *strm, uint32_t x, uint32_t xbits) +{ + uint32_t queue = strm->queue + (x << strm->qbits); + uint32_t qbits = strm->qbits + xbits; + + if (__builtin_expect((signed)(qbits - 8) >= 0, 1)) { + qbits -= 8; + *strm->outbuf++ = queue; + queue >>= 8; + } + + strm->qbits = qbits; + strm->queue = queue; +} + +/* align to next byte */ +static inline void flush_bits(struct slz_stream *strm) +{ + if (strm->qbits > 0) + *strm->outbuf++ = strm->queue; + + if (strm->qbits > 8) + *strm->outbuf++ = strm->queue >> 8; + + strm->queue = 0; + strm->qbits = 0; +} +#endif + + +/* only valid if buffer is already aligned */ +static inline void copy_8b(struct slz_stream *strm, uint32_t x) +{ + *strm->outbuf++ = x; +} + +/* only valid if buffer is already aligned */ +static inline void copy_16b(struct slz_stream *strm, uint32_t x) +{ + strm->outbuf[0] = x; + strm->outbuf[1] = x >> 8; + strm->outbuf += 2; +} + +/* only valid if buffer is already aligned */ +static inline void copy_32b(struct slz_stream *strm, uint32_t x) +{ + strm->outbuf[0] = x; + strm->outbuf[1] = x >> 8; + strm->outbuf[2] = x >> 16; + strm->outbuf[3] = x >> 24; + strm->outbuf += 4; +} + +static inline void send_huff(struct slz_stream *strm, uint32_t code) +{ + uint32_t bits; + + code = fixed_huff[code]; + bits = code & 15; + code >>= 4; + enqueue24(strm, code, bits); +} + +static inline void send_eob(struct slz_stream *strm) +{ + enqueue8(strm, 0, 7); // direct encoding of 256 = EOB (cf RFC1951) +} + +/* copies <len> literals from <buf>. <more> indicates that there are data past + * buf + <len>. <len> must not be null. + */ +static void copy_lit(struct slz_stream *strm, const void *buf, uint32_t len, int more) +{ + uint32_t len2; + + do { + len2 = len; + if (__builtin_expect(len2 > 65535, 0)) + len2 = 65535; + + len -= len2; + + if (strm->state != SLZ_ST_EOB) + send_eob(strm); + + strm->state = (more || len) ? SLZ_ST_EOB : SLZ_ST_DONE; + + enqueue8(strm, !(more || len), 3); // BFINAL = !more ; BTYPE = 00 + flush_bits(strm); + copy_16b(strm, len2); // len2 + copy_16b(strm, ~len2); // nlen2 + memcpy(strm->outbuf, buf, len2); + buf += len2; + strm->outbuf += len2; + } while (len); +} + +/* copies <len> literals from <buf>. <more> indicates that there are data past + * buf + <len>. <len> must not be null. + */ +static void copy_lit_huff(struct slz_stream *strm, const unsigned char *buf, uint32_t len, int more) +{ + uint32_t pos; + + /* This ugly construct limits the mount of tests and optimizes for the + * most common case (more > 0). + */ + if (strm->state == SLZ_ST_EOB) { + eob: + strm->state = more ? SLZ_ST_FIXED : SLZ_ST_LAST; + enqueue8(strm, 2 + !more, 3); // BFINAL = !more ; BTYPE = 01 + } + else if (!more) { + send_eob(strm); + goto eob; + } + + pos = 0; + do { + send_huff(strm, buf[pos++]); + } while (pos < len); +} + +/* format: + * bit0..31 = word + * bit32..63 = last position in buffer of similar content + */ + +/* This hash provides good average results on HTML contents, and is among the + * few which provide almost optimal results on various different pages. + */ +static inline uint32_t slz_hash(uint32_t a) +{ +#if defined(__ARM_FEATURE_CRC32) +# if defined(__ARM_ARCH_ISA_A64) + // 64 bit mode + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(a) : "r"(0)); +# else + // 32 bit mode (e.g. armv7 compiler building for armv8 + __asm__ volatile("crc32w %0,%0,%1" : "+r"(a) : "r"(0)); +# endif + return a >> (32 - HASH_BITS); +#else + return ((a << 19) + (a << 6) - a) >> (32 - HASH_BITS); +#endif +} + +/* This function compares buffers <a> and <b> and reads 32 or 64 bits at a time + * during the approach. It makes us of unaligned little endian memory accesses + * on capable architectures. <max> is the maximum number of bytes that can be + * read, so both <a> and <b> must have at least <max> bytes ahead. <max> may + * safely be null or negative if that simplifies computations in the caller. + */ +static inline long memmatch(const unsigned char *a, const unsigned char *b, long max) +{ + long len = 0; + +#ifdef UNALIGNED_LE_OK + unsigned long xor; + + while (1) { + if ((long)(len + 2 * sizeof(long)) > max) { + while (len < max) { + if (a[len] != b[len]) + break; + len++; + } + return len; + } + + xor = *(long *)&a[len] ^ *(long *)&b[len]; + if (xor) + break; + len += sizeof(long); + + xor = *(long *)&a[len] ^ *(long *)&b[len]; + if (xor) + break; + len += sizeof(long); + } + +#if defined(__x86_64__) || defined(__i386__) || defined(__i486__) || defined(__i586__) || defined(__i686__) + /* x86 has bsf. We know that xor is non-null here */ + asm("bsf %1,%0\n" : "=r"(xor) : "0" (xor)); + return len + xor / 8; +#else + if (sizeof(long) > 4 && !(xor & 0xffffffff)) { + /* This code is optimized out on 32-bit archs, but we still + * need to shift in two passes to avoid a warning. It is + * properly optimized out as a single shift. + */ + xor >>= 16; xor >>= 16; + if (xor & 0xffff) { + if (xor & 0xff) + return len + 4; + return len + 5; + } + if (xor & 0xffffff) + return len + 6; + return len + 7; + } + + if (xor & 0xffff) { + if (xor & 0xff) + return len; + return len + 1; + } + if (xor & 0xffffff) + return len + 2; + return len + 3; +#endif // x86 + +#else // UNALIGNED_LE_OK + /* This is the generic version for big endian or unaligned-incompatible + * architectures. + */ + while (len < max) { + if (a[len] != b[len]) + break; + len++; + } + return len; + +#endif +} + +/* sets <count> BYTES to -32769 in <refs> so that any uninitialized entry will + * verify (pos-last-1 >= 32768) and be ignored. <count> must be a multiple of + * 128 bytes and <refs> must be at least one count in length. It's supposed to + * be applied to 64-bit aligned data exclusively, which makes it slightly + * faster than the regular memset() since no alignment check is performed. + */ +static void reset_refs(union ref *refs, long count) +{ + /* avoid a shift/mask by casting to void* */ + union ref *end = (void *)refs + count; + + do { + refs[ 0].by64 = -32769; + refs[ 1].by64 = -32769; + refs[ 2].by64 = -32769; + refs[ 3].by64 = -32769; + refs[ 4].by64 = -32769; + refs[ 5].by64 = -32769; + refs[ 6].by64 = -32769; + refs[ 7].by64 = -32769; + refs[ 8].by64 = -32769; + refs[ 9].by64 = -32769; + refs[10].by64 = -32769; + refs[11].by64 = -32769; + refs[12].by64 = -32769; + refs[13].by64 = -32769; + refs[14].by64 = -32769; + refs[15].by64 = -32769; + refs += 16; + } while (refs < end); +} + +/* Compresses <ilen> bytes from <in> into <out> according to RFC1951. The + * output result may be up to 5 bytes larger than the input, to which 2 extra + * bytes may be added to send the last chunk due to BFINAL+EOB encoding (10 + * bits) when <more> is not set. The caller is responsible for ensuring there + * is enough room in the output buffer for this. The amount of output bytes is + * returned, and no CRC is computed. + */ +long slz_rfc1951_encode(struct slz_stream *strm, unsigned char *out, const unsigned char *in, long ilen, int more) +{ + long rem = ilen; + unsigned long pos = 0; + unsigned long last; + uint32_t word = 0; + long mlen; + uint32_t h; + uint64_t ent; + + uint32_t plit = 0; + uint32_t bit9 = 0; + uint32_t dist, code; + union ref refs[1 << HASH_BITS]; + + if (!strm->level) { + /* force to send as literals (eg to preserve CPU) */ + strm->outbuf = out; + plit = pos = ilen; + bit9 = 52; /* force literal dump */ + goto final_lit_dump; + } + + reset_refs(refs, sizeof(refs)); + + strm->outbuf = out; + +#ifndef UNALIGNED_FASTER + word = ((unsigned char)in[pos] << 8) + ((unsigned char)in[pos + 1] << 16) + ((unsigned char)in[pos + 2] << 24); +#endif + while (rem >= 4) { +#ifndef UNALIGNED_FASTER + word = ((unsigned char)in[pos + 3] << 24) + (word >> 8); +#else + word = *(uint32_t *)&in[pos]; +#endif + h = slz_hash(word); + asm volatile ("" ::); // prevent gcc from trying to be smart with the prefetch + + if (sizeof(long) >= 8) { + ent = refs[h].by64; + last = (uint32_t)ent; + ent >>= 32; + refs[h].by64 = ((uint64_t)pos) + ((uint64_t)word << 32); + } else { + ent = refs[h].by32.word; + last = refs[h].by32.pos; + refs[h].by32.pos = pos; + refs[h].by32.word = word; + } + +#ifdef FIND_OPTIMAL_MATCH + /* Experimental code to see what could be saved with an ideal + * longest match lookup algorithm. This one is very slow but + * scans the whole window. In short, here are the savings : + * file orig fast(ratio) optimal(ratio) + * README 5185 3419 (65.9%) 3165 (61.0%) -7.5% + * index.html 76799 35662 (46.4%) 29875 (38.9%) -16.3% + * rfc1952.c 29383 13442 (45.7%) 11793 (40.1%) -12.3% + * + * Thus the savings to expect for large files is at best 16%. + * + * A non-colliding hash gives 33025 instead of 35662 (-7.4%), + * and keeping the last two entries gives 31724 (-11.0%). + */ + unsigned long scan; + int saved = 0; + int bestpos = 0; + int bestlen = 0; + int firstlen = 0; + int max_lookup = 2; // 0 = no limit + + for (scan = pos - 1; scan < pos && (unsigned long)(pos - scan - 1) < 32768; scan--) { + if (*(uint32_t *)(in + scan) != word) + continue; + + len = memmatch(in + pos, in + scan, rem); + if (!bestlen) + firstlen = len; + + if (len > bestlen) { + bestlen = len; + bestpos = scan; + } + if (!--max_lookup) + break; + } + if (bestlen) { + //printf("pos=%d last=%d bestpos=%d word=%08x ent=%08x len=%d\n", + // (int)pos, (int)last, (int)bestpos, (int)word, (int)ent, bestlen); + last = bestpos; + ent = word; + saved += bestlen - firstlen; + } + //fprintf(stderr, "first=%d best=%d saved_total=%d\n", firstlen, bestlen, saved); +#endif + + if ((uint32_t)ent != word) { + send_as_lit: + rem--; + plit++; + bit9 += ((unsigned char)word >= 144); + pos++; + continue; + } + + /* We reject pos = last and pos > last+32768 */ + if ((unsigned long)(pos - last - 1) >= 32768) + goto send_as_lit; + + /* Note: cannot encode a length larger than 258 bytes */ + mlen = memmatch(in + pos + 4, in + last + 4, (rem > 258 ? 258 : rem) - 4) + 4; + + /* found a matching entry */ + + if (bit9 >= 52 && mlen < 6) + goto send_as_lit; + + /* compute the output code, its size and the length's size in + * bits to know if the reference is cheaper than literals. + */ + code = len_fh[mlen]; + + /* direct mapping of dist->huffman code */ + dist = fh_dist_table[pos - last - 1]; + + /* if encoding the dist+length is more expensive than sending + * the equivalent as bytes, lets keep the literals. + */ + if ((dist & 0x1f) + (code >> 16) + 8 >= 8 * mlen + bit9) + goto send_as_lit; + + /* first, copy pending literals */ + if (plit) { + /* Huffman encoding requires 9 bits for octets 144..255, so this + * is a waste of space for binary data. Switching between Huffman + * and no-comp then huffman consumes 52 bits (7 for EOB + 3 for + * block type + 7 for alignment + 32 for LEN+NLEN + 3 for next + * block. Only use plain literals if there are more than 52 bits + * to save then. + */ + if (bit9 >= 52) + copy_lit(strm, in + pos - plit, plit, 1); + else + copy_lit_huff(strm, in + pos - plit, plit, 1); + + plit = 0; + } + + /* use mode 01 - fixed huffman */ + if (strm->state == SLZ_ST_EOB) { + strm->state = SLZ_ST_FIXED; + enqueue8(strm, 0x02, 3); // BTYPE = 01, BFINAL = 0 + } + + /* copy the length first */ + enqueue24(strm, code & 0xFFFF, code >> 16); + + /* in fixed huffman mode, dist is fixed 5 bits */ + enqueue24(strm, dist >> 5, dist & 0x1f); + bit9 = 0; + rem -= mlen; + pos += mlen; + +#ifndef UNALIGNED_FASTER +#ifdef UNALIGNED_LE_OK + word = *(uint32_t *)&in[pos - 1]; +#else + word = ((unsigned char)in[pos] << 8) + ((unsigned char)in[pos + 1] << 16) + ((unsigned char)in[pos + 2] << 24); +#endif +#endif + } + + if (__builtin_expect(rem, 0)) { + /* we're reading the 1..3 last bytes */ + plit += rem; + do { + bit9 += ((unsigned char)in[pos++] >= 144); + } while (--rem); + } + + final_lit_dump: + /* now copy remaining literals or mark the end */ + if (plit) { + if (bit9 >= 52) + copy_lit(strm, in + pos - plit, plit, more); + else + copy_lit_huff(strm, in + pos - plit, plit, more); + + plit = 0; + } + + strm->ilen += ilen; + return strm->outbuf - out; +} + +/* Initializes stream <strm> for use with raw deflate (rfc1951). The CRC is + * unused but set to zero. The compression level passed in <level> is set. This + * value can only be 0 (no compression) or 1 (compression) and other values + * will lead to unpredictable behaviour. The function always returns 0. + */ +int slz_rfc1951_init(struct slz_stream *strm, int level) +{ + strm->state = SLZ_ST_EOB; // no header + strm->level = level; + strm->format = SLZ_FMT_DEFLATE; + strm->crc32 = 0; + strm->ilen = 0; + strm->qbits = 0; + strm->queue = 0; + return 0; +} + +/* Flushes any pending for stream <strm> into buffer <buf>, then sends BTYPE=1 + * and BFINAL=1 if needed. The stream ends in SLZ_ST_DONE. It returns the number + * of bytes emitted. The trailer consists in flushing the possibly pending bits + * from the queue (up to 7 bits), then possibly EOB (7 bits), then 3 bits, EOB, + * a rounding to the next byte, which amounts to a total of 4 bytes max, that + * the caller must ensure are available before calling the function. + */ +int slz_rfc1951_finish(struct slz_stream *strm, unsigned char *buf) +{ + strm->outbuf = buf; + + if (strm->state == SLZ_ST_FIXED || strm->state == SLZ_ST_LAST) { + strm->state = (strm->state == SLZ_ST_LAST) ? SLZ_ST_DONE : SLZ_ST_EOB; + send_eob(strm); + } + + if (strm->state != SLZ_ST_DONE) { + /* send BTYPE=1, BFINAL=1 */ + enqueue8(strm, 3, 3); + send_eob(strm); + strm->state = SLZ_ST_DONE; + } + + flush_bits(strm); + return strm->outbuf - buf; +} + +/* Now RFC1952-specific declarations and extracts from RFC. + * From RFC1952 about the GZIP file format : + +A gzip file consists of a series of "members" ... + +2.3. Member format + + Each member has the following structure: + + +---+---+---+---+---+---+---+---+---+---+ + |ID1|ID2|CM |FLG| MTIME |XFL|OS | (more-->) + +---+---+---+---+---+---+---+---+---+---+ + + (if FLG.FEXTRA set) + + +---+---+=================================+ + | XLEN |...XLEN bytes of "extra field"...| (more-->) + +---+---+=================================+ + + (if FLG.FNAME set) + + +=========================================+ + |...original file name, zero-terminated...| (more-->) + +=========================================+ + + (if FLG.FCOMMENT set) + + +===================================+ + |...file comment, zero-terminated...| (more-->) + +===================================+ + + (if FLG.FHCRC set) + + +---+---+ + | CRC16 | + +---+---+ + + +=======================+ + |...compressed blocks...| (more-->) + +=======================+ + + 0 1 2 3 4 5 6 7 + +---+---+---+---+---+---+---+---+ + | CRC32 | ISIZE | + +---+---+---+---+---+---+---+---+ + + +2.3.1. Member header and trailer + + ID1 (IDentification 1) + ID2 (IDentification 2) + These have the fixed values ID1 = 31 (0x1f, \037), ID2 = 139 + (0x8b, \213), to identify the file as being in gzip format. + + CM (Compression Method) + This identifies the compression method used in the file. CM + = 0-7 are reserved. CM = 8 denotes the "deflate" + compression method, which is the one customarily used by + gzip and which is documented elsewhere. + + FLG (FLaGs) + This flag byte is divided into individual bits as follows: + + bit 0 FTEXT + bit 1 FHCRC + bit 2 FEXTRA + bit 3 FNAME + bit 4 FCOMMENT + bit 5 reserved + bit 6 reserved + bit 7 reserved + + Reserved FLG bits must be zero. + + MTIME (Modification TIME) + This gives the most recent modification time of the original + file being compressed. The time is in Unix format, i.e., + seconds since 00:00:00 GMT, Jan. 1, 1970. (Note that this + may cause problems for MS-DOS and other systems that use + local rather than Universal time.) If the compressed data + did not come from a file, MTIME is set to the time at which + compression started. MTIME = 0 means no time stamp is + available. + + XFL (eXtra FLags) + These flags are available for use by specific compression + methods. The "deflate" method (CM = 8) sets these flags as + follows: + + XFL = 2 - compressor used maximum compression, + slowest algorithm + XFL = 4 - compressor used fastest algorithm + + OS (Operating System) + This identifies the type of file system on which compression + took place. This may be useful in determining end-of-line + convention for text files. The currently defined values are + as follows: + + 0 - FAT filesystem (MS-DOS, OS/2, NT/Win32) + 1 - Amiga + 2 - VMS (or OpenVMS) + 3 - Unix + 4 - VM/CMS + 5 - Atari TOS + 6 - HPFS filesystem (OS/2, NT) + 7 - Macintosh + 8 - Z-System + 9 - CP/M + 10 - TOPS-20 + 11 - NTFS filesystem (NT) + 12 - QDOS + 13 - Acorn RISCOS + 255 - unknown + + ==> A file compressed using "gzip -1" on Unix-like systems can be : + + 1F 8B 08 00 00 00 00 00 04 03 + <deflate-compressed stream> + crc32 size32 +*/ + +static const unsigned char gzip_hdr[] = { 0x1F, 0x8B, // ID1, ID2 + 0x08, 0x00, // Deflate, flags (none) + 0x00, 0x00, 0x00, 0x00, // mtime: none + 0x04, 0x03 }; // fastest comp, OS=Unix + +static inline uint32_t crc32_char(uint32_t crc, uint8_t x) +{ +#if defined(__ARM_FEATURE_CRC32) + crc = ~crc; +# if defined(__ARM_ARCH_ISA_A64) + // 64 bit mode + __asm__ volatile("crc32b %w0,%w0,%w1" : "+r"(crc) : "r"(x)); +# else + // 32 bit mode (e.g. armv7 compiler building for armv8 + __asm__ volatile("crc32b %0,%0,%1" : "+r"(crc) : "r"(x)); +# endif + crc = ~crc; +#else + crc = crc32_fast[0][(crc ^ x) & 0xff] ^ (crc >> 8); +#endif + return crc; +} + +static inline uint32_t crc32_uint32(uint32_t data) +{ +#if defined(__ARM_FEATURE_CRC32) +# if defined(__ARM_ARCH_ISA_A64) + // 64 bit mode + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(data) : "r"(~0UL)); +# else + // 32 bit mode (e.g. armv7 compiler building for armv8 + __asm__ volatile("crc32w %0,%0,%1" : "+r"(data) : "r"(~0UL)); +# endif + data = ~data; +#else + data = crc32_fast[3][(data >> 0) & 0xff] ^ + crc32_fast[2][(data >> 8) & 0xff] ^ + crc32_fast[1][(data >> 16) & 0xff] ^ + crc32_fast[0][(data >> 24) & 0xff]; +#endif + return data; +} + +/* Modified version originally from RFC1952, working with non-inverting CRCs */ +uint32_t slz_crc32_by1(uint32_t crc, const unsigned char *buf, int len) +{ + int n; + + for (n = 0; n < len; n++) + crc = crc32_char(crc, buf[n]); + return crc; +} + +/* This version computes the crc32 of <buf> over <len> bytes, doing most of it + * in 32-bit chunks. + */ +uint32_t slz_crc32_by4(uint32_t crc, const unsigned char *buf, int len) +{ + const unsigned char *end = buf + len; + + while (buf <= end - 16) { +#ifdef UNALIGNED_LE_OK +#if defined(__ARM_FEATURE_CRC32) + crc = ~crc; +# if defined(__ARM_ARCH_ISA_A64) + // 64 bit mode + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(crc) : "r"(*(uint32_t*)(buf))); + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 4))); + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 8))); + __asm__ volatile("crc32w %w0,%w0,%w1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 12))); +# else + // 32 bit mode (e.g. armv7 compiler building for armv8 + __asm__ volatile("crc32w %0,%0,%1" : "+r"(crc) : "r"(*(uint32_t*)(buf))); + __asm__ volatile("crc32w %0,%0,%1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 4))); + __asm__ volatile("crc32w %0,%0,%1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 8))); + __asm__ volatile("crc32w %0,%0,%1" : "+r"(crc) : "r"(*(uint32_t*)(buf + 12))); +# endif + crc = ~crc; +#else + crc ^= *(uint32_t *)buf; + crc = crc32_uint32(crc); + + crc ^= *(uint32_t *)(buf + 4); + crc = crc32_uint32(crc); + + crc ^= *(uint32_t *)(buf + 8); + crc = crc32_uint32(crc); + + crc ^= *(uint32_t *)(buf + 12); + crc = crc32_uint32(crc); +#endif +#else + crc = crc32_fast[3][(buf[0] ^ (crc >> 0)) & 0xff] ^ + crc32_fast[2][(buf[1] ^ (crc >> 8)) & 0xff] ^ + crc32_fast[1][(buf[2] ^ (crc >> 16)) & 0xff] ^ + crc32_fast[0][(buf[3] ^ (crc >> 24)) & 0xff]; + + crc = crc32_fast[3][(buf[4] ^ (crc >> 0)) & 0xff] ^ + crc32_fast[2][(buf[5] ^ (crc >> 8)) & 0xff] ^ + crc32_fast[1][(buf[6] ^ (crc >> 16)) & 0xff] ^ + crc32_fast[0][(buf[7] ^ (crc >> 24)) & 0xff]; + + crc = crc32_fast[3][(buf[8] ^ (crc >> 0)) & 0xff] ^ + crc32_fast[2][(buf[9] ^ (crc >> 8)) & 0xff] ^ + crc32_fast[1][(buf[10] ^ (crc >> 16)) & 0xff] ^ + crc32_fast[0][(buf[11] ^ (crc >> 24)) & 0xff]; + + crc = crc32_fast[3][(buf[12] ^ (crc >> 0)) & 0xff] ^ + crc32_fast[2][(buf[13] ^ (crc >> 8)) & 0xff] ^ + crc32_fast[1][(buf[14] ^ (crc >> 16)) & 0xff] ^ + crc32_fast[0][(buf[15] ^ (crc >> 24)) & 0xff]; +#endif + buf += 16; + } + + while (buf <= end - 4) { +#ifdef UNALIGNED_LE_OK + crc ^= *(uint32_t *)buf; + crc = crc32_uint32(crc); +#else + crc = crc32_fast[3][(buf[0] ^ (crc >> 0)) & 0xff] ^ + crc32_fast[2][(buf[1] ^ (crc >> 8)) & 0xff] ^ + crc32_fast[1][(buf[2] ^ (crc >> 16)) & 0xff] ^ + crc32_fast[0][(buf[3] ^ (crc >> 24)) & 0xff]; +#endif + buf += 4; + } + + while (buf < end) + crc = crc32_char(crc, *buf++); + return crc; +} + +/* uses the most suitable crc32 function to update crc on <buf, len> */ +static inline uint32_t update_crc(uint32_t crc, const void *buf, int len) +{ + return slz_crc32_by4(crc, buf, len); +} + +/* Sends the gzip header for stream <strm> into buffer <buf>. When it's done, + * the stream state is updated to SLZ_ST_EOB. It returns the number of bytes + * emitted which is always 10. The caller is responsible for ensuring there's + * always enough room in the buffer. + */ +int slz_rfc1952_send_header(struct slz_stream *strm, unsigned char *buf) +{ + memcpy(buf, gzip_hdr, sizeof(gzip_hdr)); + strm->state = SLZ_ST_EOB; + return sizeof(gzip_hdr); +} + +/* Encodes the block according to rfc1952. This means that the CRC of the input + * block is computed according to the CRC32 algorithm. If the header was never + * sent, it may be sent first. The number of output bytes is returned. + */ +long slz_rfc1952_encode(struct slz_stream *strm, unsigned char *out, const unsigned char *in, long ilen, int more) +{ + long ret = 0; + + if (__builtin_expect(strm->state == SLZ_ST_INIT, 0)) + ret += slz_rfc1952_send_header(strm, out); + + strm->crc32 = update_crc(strm->crc32, in, ilen); + ret += slz_rfc1951_encode(strm, out + ret, in, ilen, more); + return ret; +} + +/* Initializes stream <strm> for use with the gzip format (rfc1952). The + * compression level passed in <level> is set. This value can only be 0 (no + * compression) or 1 (compression) and other values will lead to unpredictable + * behaviour. The function always returns 0. + */ +int slz_rfc1952_init(struct slz_stream *strm, int level) +{ + strm->state = SLZ_ST_INIT; + strm->level = level; + strm->format = SLZ_FMT_GZIP; + strm->crc32 = 0; + strm->ilen = 0; + strm->qbits = 0; + strm->queue = 0; + return 0; +} + +/* Flushes pending bits and sends the gzip trailer for stream <strm> into + * buffer <buf>. When it's done, the stream state is updated to SLZ_ST_END. It + * returns the number of bytes emitted. The trailer consists in flushing the + * possibly pending bits from the queue (up to 24 bits), rounding to the next + * byte, then 4 bytes for the CRC and another 4 bytes for the input length. + * That may about to 4+4+4 = 12 bytes, that the caller must ensure are + * available before calling the function. Note that if the initial header was + * never sent, it will be sent first as well (10 extra bytes). + */ +int slz_rfc1952_finish(struct slz_stream *strm, unsigned char *buf) +{ + strm->outbuf = buf; + + if (__builtin_expect(strm->state == SLZ_ST_INIT, 0)) + strm->outbuf += slz_rfc1952_send_header(strm, strm->outbuf); + + slz_rfc1951_finish(strm, strm->outbuf); + copy_32b(strm, strm->crc32); + copy_32b(strm, strm->ilen); + strm->state = SLZ_ST_END; + + return strm->outbuf - buf; +} + + +/* RFC1950-specific stuff. This is for the Zlib stream format. + * From RFC1950 (zlib) : + * + + 2.2. Data format + + A zlib stream has the following structure: + + 0 1 + +---+---+ + |CMF|FLG| (more-->) + +---+---+ + + + (if FLG.FDICT set) + + 0 1 2 3 + +---+---+---+---+ + | DICTID | (more-->) + +---+---+---+---+ + + +=====================+---+---+---+---+ + |...compressed data...| ADLER32 | + +=====================+---+---+---+---+ + + Any data which may appear after ADLER32 are not part of the zlib + stream. + + CMF (Compression Method and flags) + This byte is divided into a 4-bit compression method and a 4- + bit information field depending on the compression method. + + bits 0 to 3 CM Compression method + bits 4 to 7 CINFO Compression info + + CM (Compression method) + This identifies the compression method used in the file. CM = 8 + denotes the "deflate" compression method with a window size up + to 32K. This is the method used by gzip and PNG (see + references [1] and [2] in Chapter 3, below, for the reference + documents). CM = 15 is reserved. It might be used in a future + version of this specification to indicate the presence of an + extra field before the compressed data. + + CINFO (Compression info) + For CM = 8, CINFO is the base-2 logarithm of the LZ77 window + size, minus eight (CINFO=7 indicates a 32K window size). Values + of CINFO above 7 are not allowed in this version of the + specification. CINFO is not defined in this specification for + CM not equal to 8. + + FLG (FLaGs) + This flag byte is divided as follows: + + bits 0 to 4 FCHECK (check bits for CMF and FLG) + bit 5 FDICT (preset dictionary) + bits 6 to 7 FLEVEL (compression level) + + The FCHECK value must be such that CMF and FLG, when viewed as + a 16-bit unsigned integer stored in MSB order (CMF*256 + FLG), + is a multiple of 31. + + + FDICT (Preset dictionary) + If FDICT is set, a DICT dictionary identifier is present + immediately after the FLG byte. The dictionary is a sequence of + bytes which are initially fed to the compressor without + producing any compressed output. DICT is the Adler-32 checksum + of this sequence of bytes (see the definition of ADLER32 + below). The decompressor can use this identifier to determine + which dictionary has been used by the compressor. + + FLEVEL (Compression level) + These flags are available for use by specific compression + methods. The "deflate" method (CM = 8) sets these flags as + follows: + + 0 - compressor used fastest algorithm + 1 - compressor used fast algorithm + 2 - compressor used default algorithm + 3 - compressor used maximum compression, slowest algorithm + + The information in FLEVEL is not needed for decompression; it + is there to indicate if recompression might be worthwhile. + + compressed data + For compression method 8, the compressed data is stored in the + deflate compressed data format as described in the document + "DEFLATE Compressed Data Format Specification" by L. Peter + Deutsch. (See reference [3] in Chapter 3, below) + + Other compressed data formats are not specified in this version + of the zlib specification. + + ADLER32 (Adler-32 checksum) + This contains a checksum value of the uncompressed data + (excluding any dictionary data) computed according to Adler-32 + algorithm. This algorithm is a 32-bit extension and improvement + of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073 + standard. See references [4] and [5] in Chapter 3, below) + + Adler-32 is composed of two sums accumulated per byte: s1 is + the sum of all bytes, s2 is the sum of all s1 values. Both sums + are done modulo 65521. s1 is initialized to 1, s2 to zero. The + Adler-32 checksum is stored as s2*65536 + s1 in most- + significant-byte first (network) order. + + ==> The stream can start with only 2 bytes : + - CM = 0x78 : CMINFO=7 (32kB window), CM=8 (deflate) + - FLG = 0x01 : FLEVEL = 0 (fastest), FDICT=0 (no dict), FCHECK=1 so + that 0x7801 is a multiple of 31 (30721 = 991 * 31). + + ==> and it ends with only 4 bytes, the Adler-32 checksum in big-endian format. + + */ + +static const unsigned char zlib_hdr[] = { 0x78, 0x01 }; // 32k win, deflate, chk=1 + + +/* Original version from RFC1950, verified and works OK */ +uint32_t slz_adler32_by1(uint32_t crc, const unsigned char *buf, int len) +{ + uint32_t s1 = crc & 0xffff; + uint32_t s2 = (crc >> 16) & 0xffff; + int n; + + for (n = 0; n < len; n++) { + s1 = (s1 + buf[n]) % 65521; + s2 = (s2 + s1) % 65521; + } + return (s2 << 16) + s1; +} + +/* Computes the adler32 sum on <buf> for <len> bytes. It avoids the expensive + * modulus by retrofitting the number of bytes missed between 65521 and 65536 + * which is easy to count : For every sum above 65536, the modulus is offset + * by (65536-65521) = 15. So for any value, we can count the accumulated extra + * values by dividing the sum by 65536 and multiplying this value by + * (65536-65521). That's easier with a drawing with boxes and marbles. It gives + * this : + * x % 65521 = (x % 65536) + (x / 65536) * (65536 - 65521) + * = (x & 0xffff) + (x >> 16) * 15. + */ +uint32_t slz_adler32_block(uint32_t crc, const unsigned char *buf, long len) +{ + long s1 = crc & 0xffff; + long s2 = (crc >> 16); + long blk; + long n; + + do { + blk = len; + /* ensure we never overflow s2 (limit is about 2^((32-8)/2) */ + if (blk > (1U << 12)) + blk = 1U << 12; + len -= blk; + + for (n = 0; n < blk; n++) { + s1 = (s1 + buf[n]); + s2 = (s2 + s1); + } + + /* Largest value here is 2^12 * 255 = 1044480 < 2^20. We can + * still overflow once, but not twice because the right hand + * size is 225 max, so the total is 65761. However we also + * have to take care of the values between 65521 and 65536. + */ + s1 = (s1 & 0xffff) + 15 * (s1 >> 16); + if (s1 >= 65521) + s1 -= 65521; + + /* For s2, the largest value is estimated to 2^32-1 for + * simplicity, so the right hand side is about 15*65535 + * = 983025. We can overflow twice at most. + */ + s2 = (s2 & 0xffff) + 15 * (s2 >> 16); + s2 = (s2 & 0xffff) + 15 * (s2 >> 16); + if (s2 >= 65521) + s2 -= 65521; + + buf += blk; + } while (len); + return (s2 << 16) + s1; +} + +/* Sends the zlib header for stream <strm> into buffer <buf>. When it's done, + * the stream state is updated to SLZ_ST_EOB. It returns the number of bytes + * emitted which is always 2. The caller is responsible for ensuring there's + * always enough room in the buffer. + */ +int slz_rfc1950_send_header(struct slz_stream *strm, unsigned char *buf) +{ + memcpy(buf, zlib_hdr, sizeof(zlib_hdr)); + strm->state = SLZ_ST_EOB; + return sizeof(zlib_hdr); +} + +/* Encodes the block according to rfc1950. This means that the CRC of the input + * block is computed according to the ADLER32 algorithm. If the header was never + * sent, it may be sent first. The number of output bytes is returned. + */ +long slz_rfc1950_encode(struct slz_stream *strm, unsigned char *out, const unsigned char *in, long ilen, int more) +{ + long ret = 0; + + if (__builtin_expect(strm->state == SLZ_ST_INIT, 0)) + ret += slz_rfc1950_send_header(strm, out); + + strm->crc32 = slz_adler32_block(strm->crc32, in, ilen); + ret += slz_rfc1951_encode(strm, out + ret, in, ilen, more); + return ret; +} + +/* Initializes stream <strm> for use with the zlib format (rfc1952). The + * compression level passed in <level> is set. This value can only be 0 (no + * compression) or 1 (compression) and other values will lead to unpredictable + * behaviour. The function always returns 0. + */ +int slz_rfc1950_init(struct slz_stream *strm, int level) +{ + strm->state = SLZ_ST_INIT; + strm->level = level; + strm->format = SLZ_FMT_ZLIB; + strm->crc32 = 1; // rfc1950/zlib starts with initial crc=1 + strm->ilen = 0; + strm->qbits = 0; + strm->queue = 0; + return 0; +} + +/* Flushes pending bits and sends the gzip trailer for stream <strm> into + * buffer <buf>. When it's done, the stream state is updated to SLZ_ST_END. It + * returns the number of bytes emitted. The trailer consists in flushing the + * possibly pending bits from the queue (up to 24 bits), rounding to the next + * byte, then 4 bytes for the CRC. That may about to 4+4 = 8 bytes, that the + * caller must ensure are available before calling the function. Note that if + * the initial header was never sent, it will be sent first as well (2 extra + * bytes). + */ +int slz_rfc1950_finish(struct slz_stream *strm, unsigned char *buf) +{ + strm->outbuf = buf; + + if (__builtin_expect(strm->state == SLZ_ST_INIT, 0)) + strm->outbuf += slz_rfc1952_send_header(strm, strm->outbuf); + + slz_rfc1951_finish(strm, strm->outbuf); + copy_8b(strm, (strm->crc32 >> 24) & 0xff); + copy_8b(strm, (strm->crc32 >> 16) & 0xff); + copy_8b(strm, (strm->crc32 >> 8) & 0xff); + copy_8b(strm, (strm->crc32 >> 0) & 0xff); + strm->state = SLZ_ST_END; + return strm->outbuf - buf; +} + +__attribute__((constructor)) +static void __slz_initialize(void) +{ +#if !defined(__ARM_FEATURE_CRC32) + __slz_make_crc_table(); +#endif + __slz_prepare_dist_table(); +} |