boost/beast/zlib/detail/inflate_stream.hpp
// // Copyright (c) 2016-2019 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> #if 0 #include <boost/beast/core/detail/type_traits.hpp> #include <boost/throw_exception.hpp> #include <algorithm> #include <array> #include <cstdint> #include <cstring> #include <stdexcept> #endif namespace boost { namespace beast { namespace zlib { namespace detail { class inflate_stream { protected: inflate_stream() { w_.reset(15); } BOOST_BEAST_DECL void doClear(); BOOST_BEAST_DECL void doReset(int windowBits); BOOST_BEAST_DECL 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 }; BOOST_BEAST_DECL 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); BOOST_BEAST_DECL static codes const& get_fixed_tables(); BOOST_BEAST_DECL void fixedTables(); BOOST_BEAST_DECL 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 }; } // detail } // zlib } // beast } // boost #ifdef BOOST_BEAST_HEADER_ONLY #include <boost/beast/zlib/detail/inflate_stream.ipp> #endif #endif