deflate_stream.hpp

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//
// 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
//

#ifndef BOOST_BEAST_ZLIB_DEFLATE_STREAM_HPP
#define BOOST_BEAST_ZLIB_DEFLATE_STREAM_HPP

#include <boost/beast/config.hpp>
#include <boost/beast/zlib/error.hpp>
#include <boost/beast/zlib/zlib.hpp>
#include <boost/beast/zlib/detail/deflate_stream.hpp>
#include <algorithm>
#include <cstdlib>
#include <cstdint>
#include <cstring>
#include <memory>

namespace boost {
namespace beast {
namespace zlib {

// 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).
*/

class deflate_stream
    : private detail::deflate_stream
{
public:
    deflate_stream()
    {
        reset(6, 15, DEF_MEM_LEVEL, Strategy::normal);
    }

    void
    reset(
        int level,
        int windowBits,
        int memLevel,
        Strategy strategy)
    {
        doReset(level, windowBits, memLevel, strategy);
    }

    void
    reset()
    {
        doReset();
    }

    void
    clear()
    {
        doClear();
    }

    std::size_t
    upper_bound(std::size_t sourceLen) const
    {
        return doUpperBound(sourceLen);
    }

    void
    tune(
        int good_length,
        int max_lazy,
        int nice_length,
        int max_chain)
    {
        doTune(good_length, max_lazy, nice_length, max_chain);
    }

    void
    write(
        z_params& zs,
        Flush flush,
        error_code& ec)
    {
        doWrite(zs, flush, ec);
    }

    void
    params(
        z_params& zs,
        int level,
        Strategy strategy,
        error_code& ec)
    {
        doParams(zs, level, strategy, ec);
    }

    void
    pending(unsigned *value, int *bits)
    {
        doPending(value, bits);
    }

    void
    prime(int bits, int value, error_code& ec)
    {
        return doPrime(bits, value, ec);
    }
};

std::size_t
deflate_upper_bound(std::size_t bytes);

/*  For the default windowBits of 15 and memLevel of 8, this function returns
    a close to exact, as well as small, upper bound on the compressed size.
    They are coded as constants here for a reason--if the #define's are
    changed, then this function needs to be changed as well.  The return
    value for 15 and 8 only works for those exact settings.

    For any setting other than those defaults for windowBits and memLevel,
    the value returned is a conservative worst case for the maximum expansion
    resulting from using fixed blocks instead of stored blocks, which deflate
    can emit on compressed data for some combinations of the parameters.

    This function could be more sophisticated to provide closer upper bounds for
    every combination of windowBits and memLevel.  But even the conservative
    upper bound of about 14% expansion does not seem onerous for output buffer
    allocation.
*/
inline
std::size_t
deflate_upper_bound(std::size_t bytes)
{
    return bytes +
        ((bytes + 7) >> 3) +
        ((bytes + 63) >> 6) + 5 +
        6;
}

} // zlib
} // beast
} // boost

#endif