ceph/src/Beast/include/beast/zlib/detail/window.hpp

   1 //
   2 // Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // This is a derivative work based on Zlib, copyright below:
   8 /*
   9     Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
  10
  11     This software is provided 'as-is', without any express or implied
  12     warranty.  In no event will the authors be held liable for any damages
  13     arising from the use of this software.
  14
  15     Permission is granted to anyone to use this software for any purpose,
  16     including commercial applications, and to alter it and redistribute it
  17     freely, subject to the following restrictions:
  18
  19     1. The origin of this software must not be misrepresented; you must not
  20        claim that you wrote the original software. If you use this software
  21        in a product, an acknowledgment in the product documentation would be
  22        appreciated but is not required.
  23     2. Altered source versions must be plainly marked as such, and must not be
  24        misrepresented as being the original software.
  25     3. This notice may not be removed or altered from any source distribution.
  26
  27     Jean-loup Gailly        Mark Adler
  28     jloup@gzip.org          madler@alumni.caltech.edu
  29
  30     The data format used by the zlib library is described by RFCs (Request for
  31     Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
  32     (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
  33 */
  34
  35 #ifndef BEAST_ZLIB_DETAIL_WINDOW_HPP
  36 #define BEAST_ZLIB_DETAIL_WINDOW_HPP
  37
  38 #include <boost/assert.hpp>
  39 #include <cstdint>
  40 #include <cstring>
  41 #include <memory>
  42
  43 namespace beast {
  44 namespace zlib {
  45 namespace detail {
  46
  47 class window
  48 {
  49     std::unique_ptr<std::uint8_t[]> p_;
  50     std::uint16_t i_ = 0;
  51     std::uint16_t size_ = 0;
  52     std::uint16_t capacity_ = 0;
  53     std::uint8_t bits_ = 0;
  54
  55 public:
  56     int
  57     bits() const
  58     {
  59         return bits_;
  60     }
  61
  62     unsigned
  63     capacity() const
  64     {
  65         return capacity_;
  66     }
  67
  68     unsigned
  69     size() const
  70     {
  71         return size_;
  72     }
  73
  74     void
  75     reset(int bits);
  76
  77     void
  78     read(std::uint8_t* out, std::size_t pos, std::size_t n);
  79
  80     template<class = void>
  81     void
  82     write(std::uint8_t const* in, std::size_t n);
  83 };
  84
  85 inline
  86 void
  87 window::
  88 reset(int bits)
  89 {
  90     if(bits_ != bits)
  91     {
  92         p_.reset();
  93         bits_ = static_cast<std::uint8_t>(bits);
  94         capacity_ = 1U << bits_;
  95     }
  96     i_ = 0;
  97     size_ = 0;
  98 }
  99
 100 inline
 101 void
 102 window::
 103 read(std::uint8_t* out, std::size_t pos, std::size_t n)
 104 {
 105     if(i_ >= size_)
 106     {
 107         // window is contiguous
 108         std::memcpy(out, &p_[i_ - pos], n);
 109         return;
 110     }
 111     auto i = ((i_ - pos) + capacity_) % capacity_;
 112     auto m = capacity_ - i;
 113     if(n <= m)
 114     {
 115         std::memcpy(out, &p_[i], n);
 116         return;
 117     }
 118     std::memcpy(out, &p_[i], m);
 119     out += m;
 120     std::memcpy(out, &p_[0], n - m);
 121 }
 122
 123 template<class>
 124 void
 125 window::
 126 write(std::uint8_t const* in, std::size_t n)
 127 {
 128     if(! p_)
 129         p_.reset(new std::uint8_t[capacity_]);
 130     if(n >= capacity_)
 131     {
 132         i_ = 0;
 133         size_ = capacity_;
 134         std::memcpy(&p_[0], in + (n - size_), size_);
 135         return;
 136     }
 137     if(i_ + n <= capacity_)
 138     {
 139         std::memcpy(&p_[i_], in, n);
 140         if(size_ >= capacity_ - n)
 141             size_ = capacity_;
 142         else
 143             size_ = static_cast<std::uint16_t>(size_ + n);
 144
 145         i_ = static_cast<std::uint16_t>(
 146             (i_ + n) % capacity_);
 147         return;
 148     }
 149     auto m = capacity_ - i_;
 150     std::memcpy(&p_[i_], in, m);
 151     in += m;
 152     i_ = static_cast<std::uint16_t>(n - m);
 153     std::memcpy(&p_[0], in, i_);
 154     size_ = capacity_;
 155 }
 156
 157 } // detail
 158 } // zlib
 159 } // beast
 160
 161 #endif