boost/beast/zlib/detail/bitstream.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_BITSTREAM_HPP #define BOOST_BEAST_ZLIB_DETAIL_BITSTREAM_HPP #include <boost/assert.hpp> #include <cstdint> #include <iterator> namespace boost { namespace beast { namespace zlib { namespace detail { class bitstream { using value_type = std::uint32_t; value_type v_ = 0; unsigned n_ = 0; public: // returns the number of bits in the reservoir unsigned size() const { return n_; } // discard n bits void drop(std::size_t n) { BOOST_ASSERT(n <= n_); n_ -= static_cast<unsigned>(n); v_ >>= n; } // flush everything void flush() { n_ = 0; v_ = 0; } // flush to the next byte boundary void flush_byte() { drop(n_ % 8); } // ensure at least n bits template<class FwdIt> bool fill(std::size_t n, FwdIt& first, FwdIt const& last); // fill 8 bits, unchecked template<class FwdIt> void fill_8(FwdIt& it); // fill 16 bits, unchecked template<class FwdIt> void fill_16(FwdIt& it); // return n bits template<class Unsigned> void peek(Unsigned& value, std::size_t n); // return everything in the reservoir value_type peek_fast() const { return v_; } // return n bits, and consume template<class Unsigned> void read(Unsigned& value, std::size_t n); // rewind by the number of whole bytes stored (unchecked) template<class BidirIt> void rewind(BidirIt& it); }; template<class FwdIt> bool bitstream:: fill(std::size_t n, FwdIt& first, FwdIt const& last) { while(n_ < n) { if(first == last) return false; v_ += static_cast<value_type>(*first++) << n_; n_ += 8; } return true; } template<class FwdIt> void bitstream:: fill_8(FwdIt& it) { v_ += static_cast<value_type>(*it++) << n_; n_ += 8; } template<class FwdIt> void bitstream:: fill_16(FwdIt& it) { v_ += static_cast<value_type>(*it++) << n_; n_ += 8; v_ += static_cast<value_type>(*it++) << n_; n_ += 8; } template<class Unsigned> void bitstream:: peek(Unsigned& value, std::size_t n) { BOOST_ASSERT(n <= sizeof(value)*8); BOOST_ASSERT(n <= n_); value = static_cast<Unsigned>( v_ & ((1ULL << n) - 1)); } template<class Unsigned> void bitstream:: read(Unsigned& value, std::size_t n) { BOOST_ASSERT(n < sizeof(v_)*8); BOOST_ASSERT(n <= n_); value = static_cast<Unsigned>( v_ & ((1ULL << n) - 1)); v_ >>= n; n_ -= static_cast<unsigned>(n); } template<class BidirIt> void bitstream:: rewind(BidirIt& it) { auto len = n_ >> 3; it = std::prev(it, len); n_ &= 7; v_ &= (1U << n_) - 1; } } // detail } // zlib } // beast } // boost #endif