boost/beast/zlib/detail/inflate_stream.hpp
// // Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // // Official repository: https://github.com/boostorg/beast // // This is a derivative work based on Zlib, copyright below: /* Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software. Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. 3. This notice may not be removed or altered from any source distribution. Jean-loup Gailly Mark Adler jloup@gzip.org madler@alumni.caltech.edu The data format used by the zlib library is described by RFCs (Request for Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950 (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format). */ #ifndef BOOST_BEAST_ZLIB_DETAIL_INFLATE_STREAM_HPP #define BOOST_BEAST_ZLIB_DETAIL_INFLATE_STREAM_HPP #include <boost/beast/zlib/error.hpp> #include <boost/beast/zlib/zlib.hpp> #include <boost/beast/zlib/detail/bitstream.hpp> #include <boost/beast/zlib/detail/ranges.hpp> #include <boost/beast/zlib/detail/window.hpp> #include <boost/beast/core/detail/type_traits.hpp> #include <boost/throw_exception.hpp> #include <algorithm> #include <array> #include <cstdint> #include <cstring> #include <stdexcept> namespace boost { namespace beast { namespace zlib { namespace detail { class inflate_stream { protected: inflate_stream() { w_.reset(15); } template<class = void> void doClear(); template<class = void> void doReset(int windowBits); template<class = void> void doWrite(z_params& zs, Flush flush, error_code& ec); void doReset() { doReset(w_.bits()); } private: enum Mode { HEAD, // i: waiting for magic header FLAGS, // i: waiting for method and flags (gzip) TIME, // i: waiting for modification time (gzip) OS, // i: waiting for extra flags and operating system (gzip) EXLEN, // i: waiting for extra length (gzip) EXTRA, // i: waiting for extra bytes (gzip) NAME, // i: waiting for end of file name (gzip) COMMENT, // i: waiting for end of comment (gzip) HCRC, // i: waiting for header crc (gzip) TYPE, // i: waiting for type bits, including last-flag bit TYPEDO, // i: same, but skip check to exit inflate on new block STORED, // i: waiting for stored size (length and complement) COPY_, // i/o: same as COPY below, but only first time in COPY, // i/o: waiting for input or output to copy stored block TABLE, // i: waiting for dynamic block table lengths LENLENS, // i: waiting for code length code lengths CODELENS, // i: waiting for length/lit and distance code lengths LEN_, // i: same as LEN below, but only first time in LEN, // i: waiting for length/lit/eob code LENEXT, // i: waiting for length extra bits DIST, // i: waiting for distance code DISTEXT,// i: waiting for distance extra bits MATCH, // o: waiting for output space to copy string LIT, // o: waiting for output space to write literal CHECK, // i: waiting for 32-bit check value LENGTH, // i: waiting for 32-bit length (gzip) DONE, // finished check, done -- remain here until reset BAD, // got a data error -- remain here until reset SYNC // looking for synchronization bytes to restart inflate() }; /* Structure for decoding tables. Each entry provides either the information needed to do the operation requested by the code that indexed that table entry, or it provides a pointer to another table that indexes more bits of the code. op indicates whether the entry is a pointer to another table, a literal, a length or distance, an end-of-block, or an invalid code. For a table pointer, the low four bits of op is the number of index bits of that table. For a length or distance, the low four bits of op is the number of extra bits to get after the code. bits is the number of bits in this code or part of the code to drop off of the bit buffer. val is the actual byte to output in the case of a literal, the base length or distance, or the offset from the current table to the next table. Each entry is four bytes. op values as set by inflate_table(): 00000000 - literal 0000tttt - table link, tttt != 0 is the number of table index bits 0001eeee - length or distance, eeee is the number of extra bits 01100000 - end of block 01000000 - invalid code */ struct code { std::uint8_t op; // operation, extra bits, table bits std::uint8_t bits; // bits in this part of the code std::uint16_t val; // offset in table or code value }; /* Maximum size of the dynamic table. The maximum number of code structures is 1444, which is the sum of 852 for literal/length codes and 592 for distance codes. These values were found by exhaustive searches using the program examples/enough.c found in the zlib distribtution. The arguments to that program are the number of symbols, the initial root table size, and the maximum bit length of a code. "enough 286 9 15" for literal/length codes returns returns 852, and "enough 30 6 15" for distance codes returns 592. The initial root table size (9 or 6) is found in the fifth argument of the inflate_table() calls in inflate.c and infback.c. If the root table size is changed, then these maximum sizes would be need to be recalculated and updated. */ static std::uint16_t constexpr kEnoughLens = 852; static std::uint16_t constexpr kEnoughDists = 592; static std::uint16_t constexpr kEnough = kEnoughLens + kEnoughDists; struct codes { code const* lencode; code const* distcode; unsigned lenbits; // VFALCO use std::uint8_t unsigned distbits; }; // Type of code to build for inflate_table() enum class build { codes, lens, dists }; template<class = void> static void inflate_table( build type, std::uint16_t* lens, std::size_t codes, code** table, unsigned *bits, std::uint16_t* work, error_code& ec); template<class = void> static codes const& get_fixed_tables(); template<class = void> void fixedTables(); template<class = void> void inflate_fast(ranges& r, error_code& ec); bitstream bi_; Mode mode_ = HEAD; // current inflate mode int last_ = 0; // true if processing last block unsigned dmax_ = 32768U; // zlib header max distance (INFLATE_STRICT) // sliding window window w_; // for string and stored block copying unsigned length_; // literal or length of data to copy unsigned offset_; // distance back to copy string from // for table and code decoding unsigned extra_; // extra bits needed // dynamic table building unsigned ncode_; // number of code length code lengths unsigned nlen_; // number of length code lengths unsigned ndist_; // number of distance code lengths unsigned have_; // number of code lengths in lens[] unsigned short lens_[320]; // temporary storage for code lengths unsigned short work_[288]; // work area for code table building code codes_[kEnough]; // space for code tables code *next_ = codes_; // next available space in codes[] int back_ = -1; // bits back of last unprocessed length/lit unsigned was_; // initial length of match // fixed and dynamic code tables code const* lencode_ = codes_ ; // starting table for length/literal codes code const* distcode_ = codes_; // starting table for distance codes unsigned lenbits_; // index bits for lencode unsigned distbits_; // index bits for distcode }; //------------------------------------------------------------------------------ template<class> void inflate_stream:: doReset(int windowBits) { if(windowBits < 8 || windowBits > 15) BOOST_THROW_EXCEPTION(std::domain_error{ "windowBits out of range"}); w_.reset(windowBits); bi_.flush(); mode_ = HEAD; last_ = 0; dmax_ = 32768U; lencode_ = codes_; distcode_ = codes_; next_ = codes_; back_ = -1; } template<class> void inflate_stream:: doClear() { } template<class> void inflate_stream:: doWrite(z_params& zs, Flush flush, error_code& ec) { ranges r; r.in.first = static_cast< std::uint8_t const*>(zs.next_in); r.in.last = r.in.first + zs.avail_in; r.in.next = r.in.first; r.out.first = static_cast< std::uint8_t*>(zs.next_out); r.out.last = r.out.first + zs.avail_out; r.out.next = r.out.first; auto const done = [&] { /* Return from inflate(), updating the total counts and the check value. If there was no progress during the inflate() call, return a buffer error. Call updatewindow() to create and/or update the window state. Note: a memory error from inflate() is non-recoverable. */ // VFALCO TODO Don't allocate update the window unless necessary if(/*wsize_ ||*/ (r.out.used() && mode_ < BAD && (mode_ < CHECK || flush != Flush::finish))) w_.write(r.out.first, r.out.used()); zs.next_in = r.in.next; zs.avail_in = r.in.avail(); zs.next_out = r.out.next; zs.avail_out = r.out.avail(); zs.total_in += r.in.used(); zs.total_out += r.out.used(); zs.data_type = bi_.size() + (last_ ? 64 : 0) + (mode_ == TYPE ? 128 : 0) + (mode_ == LEN_ || mode_ == COPY_ ? 256 : 0); if(((! r.in.used() && ! r.out.used()) || flush == Flush::finish) && ! ec) ec = error::need_buffers; }; auto const err = [&](error e) { ec = e; mode_ = BAD; }; if(mode_ == TYPE) mode_ = TYPEDO; for(;;) { switch(mode_) { case HEAD: mode_ = TYPEDO; break; case TYPE: if(flush == Flush::block || flush == Flush::trees) return done(); // fall through case TYPEDO: { if(last_) { bi_.flush_byte(); mode_ = CHECK; break; } if(! bi_.fill(3, r.in.next, r.in.last)) return done(); std::uint8_t v; bi_.read(v, 1); last_ = v != 0; bi_.read(v, 2); switch(v) { case 0: // uncompressed block mode_ = STORED; break; case 1: // fixed Huffman table fixedTables(); mode_ = LEN_; /* decode codes */ if(flush == Flush::trees) return done(); break; case 2: // dynamic Huffman table mode_ = TABLE; break; default: return err(error::invalid_block_type); } break; } case STORED: { bi_.flush_byte(); std::uint32_t v; if(! bi_.fill(32, r.in.next, r.in.last)) return done(); bi_.peek(v, 32); length_ = v & 0xffff; if(length_ != ((v >> 16) ^ 0xffff)) return err(error::invalid_stored_length); // flush instead of read, otherwise // undefined right shift behavior. bi_.flush(); mode_ = COPY_; if(flush == Flush::trees) return done(); BOOST_FALLTHROUGH; } case COPY_: mode_ = COPY; BOOST_FALLTHROUGH; case COPY: { auto copy = length_; if(copy == 0) { mode_ = TYPE; break; } copy = clamp(copy, r.in.avail()); copy = clamp(copy, r.out.avail()); if(copy == 0) return done(); std::memcpy(r.out.next, r.in.next, copy); r.in.next += copy; r.out.next += copy; length_ -= copy; break; } case TABLE: if(! bi_.fill(5 + 5 + 4, r.in.next, r.in.last)) return done(); bi_.read(nlen_, 5); nlen_ += 257; bi_.read(ndist_, 5); ndist_ += 1; bi_.read(ncode_, 4); ncode_ += 4; if(nlen_ > 286 || ndist_ > 30) return err(error::too_many_symbols); have_ = 0; mode_ = LENLENS; BOOST_FALLTHROUGH; case LENLENS: { static std::array<std::uint8_t, 19> constexpr order = {{ 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}}; while(have_ < ncode_) { if(! bi_.fill(3, r.in.next, r.in.last)) return done(); bi_.read(lens_[order[have_]], 3); ++have_; } while(have_ < order.size()) lens_[order[have_++]] = 0; next_ = &codes_[0]; lencode_ = next_; lenbits_ = 7; inflate_table(build::codes, &lens_[0], order.size(), &next_, &lenbits_, work_, ec); if(ec) { mode_ = BAD; break; } have_ = 0; mode_ = CODELENS; BOOST_FALLTHROUGH; } case CODELENS: { while(have_ < nlen_ + ndist_) { std::uint16_t v; if(! bi_.fill(lenbits_, r.in.next, r.in.last)) return done(); bi_.peek(v, lenbits_); auto cp = &lencode_[v]; if(cp->val < 16) { bi_.drop(cp->bits); lens_[have_++] = cp->val; } else { std::uint16_t len; std::uint16_t copy; if(cp->val == 16) { if(! bi_.fill(cp->bits + 2, r.in.next, r.in.last)) return done(); bi_.drop(cp->bits); if(have_ == 0) return err(error::invalid_bit_length_repeat); bi_.read(copy, 2); len = lens_[have_ - 1]; copy += 3; } else if(cp->val == 17) { if(! bi_.fill(cp->bits + 3, r.in.next, r.in.last)) return done(); bi_.drop(cp->bits); bi_.read(copy, 3); len = 0; copy += 3; } else { if(! bi_.fill(cp->bits + 7, r.in.next, r.in.last)) return done(); bi_.drop(cp->bits); bi_.read(copy, 7); len = 0; copy += 11; } if(have_ + copy > nlen_ + ndist_) return err(error::invalid_bit_length_repeat); std::fill(&lens_[have_], &lens_[have_ + copy], len); have_ += copy; copy = 0; } } // handle error breaks in while if(mode_ == BAD) break; // check for end-of-block code (better have one) if(lens_[256] == 0) return err(error::missing_eob); /* build code tables -- note: do not change the lenbits or distbits values here (9 and 6) without reading the comments in inftrees.hpp concerning the kEnough constants, which depend on those values */ next_ = &codes_[0]; lencode_ = next_; lenbits_ = 9; inflate_table(build::lens, &lens_[0], nlen_, &next_, &lenbits_, work_, ec); if(ec) { mode_ = BAD; return; } distcode_ = next_; distbits_ = 6; inflate_table(build::dists, lens_ + nlen_, ndist_, &next_, &distbits_, work_, ec); if(ec) { mode_ = BAD; return; } mode_ = LEN_; if(flush == Flush::trees) return done(); BOOST_FALLTHROUGH; } case LEN_: mode_ = LEN; BOOST_FALLTHROUGH; case LEN: { if(r.in.avail() >= 6 && r.out.avail() >= 258) { inflate_fast(r, ec); if(ec) { mode_ = BAD; return; } if(mode_ == TYPE) back_ = -1; break; } if(! bi_.fill(lenbits_, r.in.next, r.in.last)) return done(); std::uint16_t v; back_ = 0; bi_.peek(v, lenbits_); auto cp = &lencode_[v]; if(cp->op && (cp->op & 0xf0) == 0) { auto prev = cp; if(! bi_.fill(prev->bits + prev->op, r.in.next, r.in.last)) return done(); bi_.peek(v, prev->bits + prev->op); cp = &lencode_[prev->val + (v >> prev->bits)]; bi_.drop(prev->bits + cp->bits); back_ += prev->bits + cp->bits; } else { bi_.drop(cp->bits); back_ += cp->bits; } length_ = cp->val; if(cp->op == 0) { mode_ = LIT; break; } if(cp->op & 32) { back_ = -1; mode_ = TYPE; break; } if(cp->op & 64) return err(error::invalid_literal_length); extra_ = cp->op & 15; mode_ = LENEXT; BOOST_FALLTHROUGH; } case LENEXT: if(extra_) { if(! bi_.fill(extra_, r.in.next, r.in.last)) return done(); std::uint16_t v; bi_.read(v, extra_); length_ += v; back_ += extra_; } was_ = length_; mode_ = DIST; BOOST_FALLTHROUGH; case DIST: { if(! bi_.fill(distbits_, r.in.next, r.in.last)) return done(); std::uint16_t v; bi_.peek(v, distbits_); auto cp = &distcode_[v]; if((cp->op & 0xf0) == 0) { auto prev = cp; if(! bi_.fill(prev->bits + prev->op, r.in.next, r.in.last)) return done(); bi_.peek(v, prev->bits + prev->op); cp = &distcode_[prev->val + (v >> prev->bits)]; bi_.drop(prev->bits + cp->bits); back_ += prev->bits + cp->bits; } else { bi_.drop(cp->bits); back_ += cp->bits; } if(cp->op & 64) return err(error::invalid_distance_code); offset_ = cp->val; extra_ = cp->op & 15; mode_ = DISTEXT; BOOST_FALLTHROUGH; } case DISTEXT: if(extra_) { std::uint16_t v; if(! bi_.fill(extra_, r.in.next, r.in.last)) return done(); bi_.read(v, extra_); offset_ += v; back_ += extra_; } #ifdef INFLATE_STRICT if(offset_ > dmax_) return err(error::invalid_distance); #endif mode_ = MATCH; BOOST_FALLTHROUGH; case MATCH: { if(! r.out.avail()) return done(); if(offset_ > r.out.used()) { // copy from window auto offset = static_cast<std::uint16_t>( offset_ - r.out.used()); if(offset > w_.size()) return err(error::invalid_distance); auto const n = clamp(clamp( length_, offset), r.out.avail()); w_.read(r.out.next, offset, n); r.out.next += n; length_ -= n; } else { // copy from output auto in = r.out.next - offset_; auto n = clamp(length_, r.out.avail()); length_ -= n; while(n--) *r.out.next++ = *in++; } if(length_ == 0) mode_ = LEN; break; } case LIT: { if(! r.out.avail()) return done(); auto const v = static_cast<std::uint8_t>(length_); *r.out.next++ = v; mode_ = LEN; break; } case CHECK: mode_ = DONE; BOOST_FALLTHROUGH; case DONE: ec = error::end_of_stream; return done(); case BAD: return done(); case SYNC: default: BOOST_THROW_EXCEPTION(std::logic_error{ "stream error"}); } } } //------------------------------------------------------------------------------ /* Build a set of tables to decode the provided canonical Huffman code. The code lengths are lens[0..codes-1]. The result starts at *table, whose indices are 0..2^bits-1. work is a writable array of at least lens shorts, which is used as a work area. type is the type of code to be generated, build::codes, build::lens, or build::dists. On return, zero is success, -1 is an invalid code, and +1 means that kEnough isn't enough. table on return points to the next available entry's address. bits is the requested root table index bits, and on return it is the actual root table index bits. It will differ if the request is greater than the longest code or if it is less than the shortest code. */ template<class> void inflate_stream:: inflate_table( build type, std::uint16_t* lens, std::size_t codes, code** table, unsigned *bits, std::uint16_t* work, error_code& ec) { unsigned len; // a code's length in bits unsigned sym; // index of code symbols unsigned min, max; // minimum and maximum code lengths unsigned root; // number of index bits for root table unsigned curr; // number of index bits for current table unsigned drop; // code bits to drop for sub-table int left; // number of prefix codes available unsigned used; // code entries in table used unsigned huff; // Huffman code unsigned incr; // for incrementing code, index unsigned fill; // index for replicating entries unsigned low; // low bits for current root entry unsigned mask; // mask for low root bits code here; // table entry for duplication code *next; // next available space in table std::uint16_t const* base; // base value table to use std::uint16_t const* extra; // extra bits table to use int end; // use base and extra for symbol > end std::uint16_t count[15+1]; // number of codes of each length std::uint16_t offs[15+1]; // offsets in table for each length // Length codes 257..285 base static std::uint16_t constexpr lbase[31] = { 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; // Length codes 257..285 extra static std::uint16_t constexpr lext[31] = { 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 72, 78}; // Distance codes 0..29 base static std::uint16_t constexpr dbase[32] = { 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577, 0, 0}; // Distance codes 0..29 extra static std::uint16_t constexpr dext[32] = { 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 29, 29, 64, 64}; /* Process a set of code lengths to create a canonical Huffman code. The code lengths are lens[0..codes-1]. Each length corresponds to the symbols 0..codes-1. The Huffman code is generated by first sorting the symbols by length from short to long, and retaining the symbol order for codes with equal lengths. Then the code starts with all zero bits for the first code of the shortest length, and the codes are integer increments for the same length, and zeros are appended as the length increases. For the deflate format, these bits are stored backwards from their more natural integer increment ordering, and so when the decoding tables are built in the large loop below, the integer codes are incremented backwards. This routine assumes, but does not check, that all of the entries in lens[] are in the range 0..15. The caller must assure this. 1..15 is interpreted as that code length. zero means that that symbol does not occur in this code. The codes are sorted by computing a count of codes for each length, creating from that a table of starting indices for each length in the sorted table, and then entering the symbols in order in the sorted table. The sorted table is work[], with that space being provided by the caller. The length counts are used for other purposes as well, i.e. finding the minimum and maximum length codes, determining if there are any codes at all, checking for a valid set of lengths, and looking ahead at length counts to determine sub-table sizes when building the decoding tables. */ /* accumulate lengths for codes (assumes lens[] all in 0..15) */ for (len = 0; len <= 15; len++) count[len] = 0; for (sym = 0; sym < codes; sym++) count[lens[sym]]++; /* bound code lengths, force root to be within code lengths */ root = *bits; for (max = 15; max >= 1; max--) if (count[max] != 0) break; if (root > max) root = max; if (max == 0) { /* no symbols to code at all */ here.op = (std::uint8_t)64; /* invalid code marker */ here.bits = (std::uint8_t)1; here.val = (std::uint16_t)0; *(*table)++ = here; /* make a table to force an error */ *(*table)++ = here; *bits = 1; return; /* no symbols, but wait for decoding to report error */ } for (min = 1; min < max; min++) if (count[min] != 0) break; if (root < min) root = min; /* check for an over-subscribed or incomplete set of lengths */ left = 1; for (len = 1; len <= 15; len++) { left <<= 1; left -= count[len]; if (left < 0) { ec = error::over_subscribed_length; return; } } if (left > 0 && (type == build::codes || max != 1)) { ec = error::incomplete_length_set; return; } /* generate offsets into symbol table for each length for sorting */ offs[1] = 0; for (len = 1; len < 15; len++) offs[len + 1] = offs[len] + count[len]; /* sort symbols by length, by symbol order within each length */ for (sym = 0; sym < codes; sym++) if (lens[sym] != 0) work[offs[lens[sym]]++] = (std::uint16_t)sym; /* Create and fill in decoding tables. In this loop, the table being filled is at next and has curr index bits. The code being used is huff with length len. That code is converted to an index by dropping drop bits off of the bottom. For codes where len is less than drop + curr, those top drop + curr - len bits are incremented through all values to fill the table with replicated entries. root is the number of index bits for the root table. When len exceeds root, sub-tables are created pointed to by the root entry with an index of the low root bits of huff. This is saved in low to check for when a new sub-table should be started. drop is zero when the root table is being filled, and drop is root when sub-tables are being filled. When a new sub-table is needed, it is necessary to look ahead in the code lengths to determine what size sub-table is needed. The length counts are used for this, and so count[] is decremented as codes are entered in the tables. used keeps track of how many table entries have been allocated from the provided *table space. It is checked for build::lens and DIST tables against the constants kEnoughLens and kEnoughDists to guard against changes in the initial root table size constants. See the comments in inftrees.hpp for more information. sym increments through all symbols, and the loop terminates when all codes of length max, i.e. all codes, have been processed. This routine permits incomplete codes, so another loop after this one fills in the rest of the decoding tables with invalid code markers. */ /* set up for code type */ switch (type) { case build::codes: base = extra = work; /* dummy value--not used */ end = 19; break; case build::lens: base = lbase; base -= 257; extra = lext; extra -= 257; end = 256; break; default: /* build::dists */ base = dbase; extra = dext; end = -1; } /* initialize state for loop */ huff = 0; /* starting code */ sym = 0; /* starting code symbol */ len = min; /* starting code length */ next = *table; /* current table to fill in */ curr = root; /* current table index bits */ drop = 0; /* current bits to drop from code for index */ low = (unsigned)(-1); /* trigger new sub-table when len > root */ used = 1U << root; /* use root table entries */ mask = used - 1; /* mask for comparing low */ auto const not_enough = [] { BOOST_THROW_EXCEPTION(std::logic_error{ "insufficient output size when inflating tables"}); }; // check available table space if ((type == build::lens && used > kEnoughLens) || (type == build::dists && used > kEnoughDists)) return not_enough(); /* process all codes and make table entries */ for (;;) { /* create table entry */ here.bits = (std::uint8_t)(len - drop); if ((int)(work[sym]) < end) { here.op = (std::uint8_t)0; here.val = work[sym]; } else if ((int)(work[sym]) > end) { here.op = (std::uint8_t)(extra[work[sym]]); here.val = base[work[sym]]; } else { here.op = (std::uint8_t)(32 + 64); /* end of block */ here.val = 0; } /* replicate for those indices with low len bits equal to huff */ incr = 1U << (len - drop); fill = 1U << curr; min = fill; /* save offset to next table */ do { fill -= incr; next[(huff >> drop) + fill] = here; } while (fill != 0); /* backwards increment the len-bit code huff */ incr = 1U << (len - 1); while (huff & incr) incr >>= 1; if (incr != 0) { huff &= incr - 1; huff += incr; } else huff = 0; /* go to next symbol, update count, len */ sym++; if (--(count[len]) == 0) { if (len == max) break; len = lens[work[sym]]; } /* create new sub-table if needed */ if (len > root && (huff & mask) != low) { /* if first time, transition to sub-tables */ if (drop == 0) drop = root; /* increment past last table */ next += min; /* here min is 1 << curr */ /* determine length of next table */ curr = len - drop; left = (int)(1 << curr); while (curr + drop < max) { left -= count[curr + drop]; if (left <= 0) break; curr++; left <<= 1; } /* check for enough space */ used += 1U << curr; if ((type == build::lens && used > kEnoughLens) || (type == build::dists && used > kEnoughDists)) return not_enough(); /* point entry in root table to sub-table */ low = huff & mask; (*table)[low].op = (std::uint8_t)curr; (*table)[low].bits = (std::uint8_t)root; (*table)[low].val = (std::uint16_t)(next - *table); } } /* fill in remaining table entry if code is incomplete (guaranteed to have at most one remaining entry, since if the code is incomplete, the maximum code length that was allowed to get this far is one bit) */ if (huff != 0) { here.op = 64; // invalid code marker here.bits = (std::uint8_t)(len - drop); here.val = 0; next[huff] = here; } *table += used; *bits = root; } template<class> auto inflate_stream:: get_fixed_tables() -> codes const& { struct fixed_codes : codes { code len_[512]; code dist_[32]; fixed_codes() { lencode = len_; lenbits = 9; distcode = dist_; distbits = 5; std::uint16_t lens[320]; std::uint16_t work[288]; std::fill(&lens[ 0], &lens[144], std::uint16_t{8}); std::fill(&lens[144], &lens[256], std::uint16_t{9}); std::fill(&lens[256], &lens[280], std::uint16_t{7}); std::fill(&lens[280], &lens[288], std::uint16_t{8}); { error_code ec; auto next = &len_[0]; inflate_table(build::lens, lens, 288, &next, &lenbits, work, ec); if(ec) BOOST_THROW_EXCEPTION(std::logic_error{ec.message()}); } // VFALCO These fixups are from ZLib len_[ 99].op = 64; len_[227].op = 64; len_[355].op = 64; len_[483].op = 64; { error_code ec; auto next = &dist_[0]; std::fill(&lens[0], &lens[32], std::uint16_t{5}); inflate_table(build::dists, lens, 32, &next, &distbits, work, ec); if(ec) BOOST_THROW_EXCEPTION(std::logic_error{ec.message()}); } } }; static fixed_codes const fc; return fc; } template<class> void inflate_stream:: fixedTables() { auto const fc = get_fixed_tables(); lencode_ = fc.lencode; lenbits_ = fc.lenbits; distcode_ = fc.distcode; distbits_ = fc.distbits; } /* Decode literal, length, and distance codes and write out the resulting literal and match bytes until either not enough input or output is available, an end-of-block is encountered, or a data error is encountered. When large enough input and output buffers are supplied to inflate(), for example, a 16K input buffer and a 64K output buffer, more than 95% of the inflate execution time is spent in this routine. Entry assumptions: state->mode_ == LEN zs.avail_in >= 6 zs.avail_out >= 258 start >= zs.avail_out state->bits_ < 8 On return, state->mode_ is one of: LEN -- ran out of enough output space or enough available input TYPE -- reached end of block code, inflate() to interpret next block BAD -- error in block data Notes: - The maximum input bits used by a length/distance pair is 15 bits for the length code, 5 bits for the length extra, 15 bits for the distance code, and 13 bits for the distance extra. This totals 48 bits, or six bytes. Therefore if zs.avail_in >= 6, then there is enough input to avoid checking for available input while decoding. - The maximum bytes that a single length/distance pair can output is 258 bytes, which is the maximum length that can be coded. inflate_fast() requires zs.avail_out >= 258 for each loop to avoid checking for output space. inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): - Using bit fields for code structure - Different op definition to avoid & for extra bits (do & for table bits) - Three separate decoding do-loops for direct, window, and wnext == 0 - Special case for distance > 1 copies to do overlapped load and store copy - Explicit branch predictions (based on measured branch probabilities) - Deferring match copy and interspersed it with decoding subsequent codes - Swapping literal/length else - Swapping window/direct else - Larger unrolled copy loops (three is about right) - Moving len -= 3 statement into middle of loop */ template<class> void inflate_stream:: inflate_fast(ranges& r, error_code& ec) { unsigned char const* last; // have enough input while in < last unsigned char *end; // while out < end, enough space available std::size_t op; // code bits, operation, extra bits, or window position, window bytes to copy unsigned len; // match length, unused bytes unsigned dist; // match distance unsigned const lmask = (1U << lenbits_) - 1; // mask for first level of length codes unsigned const dmask = (1U << distbits_) - 1; // mask for first level of distance codes last = r.in.next + (r.in.avail() - 5); end = r.out.next + (r.out.avail() - 257); /* decode literals and length/distances until end-of-block or not enough input data or output space */ do { if(bi_.size() < 15) bi_.fill_16(r.in.next); auto cp = &lencode_[bi_.peek_fast() & lmask]; dolen: bi_.drop(cp->bits); op = (unsigned)(cp->op); if(op == 0) { // literal *r.out.next++ = (unsigned char)(cp->val); } else if(op & 16) { // length base len = (unsigned)(cp->val); op &= 15; // number of extra bits if(op) { if(bi_.size() < op) bi_.fill_8(r.in.next); len += (unsigned)bi_.peek_fast() & ((1U << op) - 1); bi_.drop(op); } if(bi_.size() < 15) bi_.fill_16(r.in.next); cp = &distcode_[bi_.peek_fast() & dmask]; dodist: bi_.drop(cp->bits); op = (unsigned)(cp->op); if(op & 16) { // distance base dist = (unsigned)(cp->val); op &= 15; // number of extra bits if(bi_.size() < op) { bi_.fill_8(r.in.next); if(bi_.size() < op) bi_.fill_8(r.in.next); } dist += (unsigned)bi_.peek_fast() & ((1U << op) - 1); #ifdef INFLATE_STRICT if(dist > dmax_) { ec = error::invalid_distance; mode_ = BAD; break; } #endif bi_.drop(op); op = r.out.used(); if(dist > op) { // copy from window op = dist - op; // distance back in window if(op > w_.size()) { ec = error::invalid_distance; mode_ = BAD; break; } auto const n = clamp(len, op); w_.read(r.out.next, op, n); r.out.next += n; len -= n; } if(len > 0) { // copy from output auto in = r.out.next - dist; auto n = clamp(len, r.out.avail()); len -= n; while(n--) *r.out.next++ = *in++; } } else if((op & 64) == 0) { // 2nd level distance code cp = &distcode_[cp->val + (bi_.peek_fast() & ((1U << op) - 1))]; goto dodist; } else { ec = error::invalid_distance_code; mode_ = BAD; break; } } else if((op & 64) == 0) { // 2nd level length code cp = &lencode_[cp->val + (bi_.peek_fast() & ((1U << op) - 1))]; goto dolen; } else if(op & 32) { // end-of-block mode_ = TYPE; break; } else { ec = error::invalid_literal_length; mode_ = BAD; break; } } while(r.in.next < last && r.out.next < end); // return unused bytes (on entry, bits < 8, so in won't go too far back) bi_.rewind(r.in.next); } } // detail } // zlib } // beast } // boost #endif