Line data    Source code

       1              : //
       2              : // Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.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              : // Official repository: https://github.com/cppalliance/capy
       8              : //
       9              : 
      10              : #ifndef BOOST_CAPY_BUFFERS_COPY_HPP
      11              : #define BOOST_CAPY_BUFFERS_COPY_HPP
      12              : 
      13              : #include <boost/capy/detail/config.hpp>
      14              : #include <boost/capy/buffers.hpp>
      15              : #include <cstring>
      16              : #include <utility>
      17              : 
      18              : namespace boost {
      19              : namespace capy {
      20              : 
      21              : /** Copy the contents of a buffer sequence into another buffer sequence
      22              : 
      23              :     This function copies no more than `at_most` bytes from the constant buffer
      24              :     sequence denoted by `src` into the mutable buffer sequence denoted by `dest`.
      25              : 
      26              :     @par Constraints
      27              :     @code
      28              :     mutable_buffer_sequence<decltype(dest)> &&
      29              :     const_buffer_sequence<decltype(src)>
      30              :     @endcode
      31              : 
      32              :     @return The number of bytes actually copied, which will be exactly equal to
      33              :     `std::min( size(dest), size(src), at_most )`.
      34              : 
      35              :     @param dest The destination buffer sequence
      36              : 
      37              :     @param src The source buffer sequence
      38              : */
      39              : constexpr struct copy_mrdocs_workaround_t
      40              : {
      41              :     template<
      42              :         mutable_buffer_sequence MutableBufferSequence,
      43              :         const_buffer_sequence ConstBufferSequence>
      44              :     std::size_t
      45       600020 :     operator()(
      46              :         MutableBufferSequence const& dest,
      47              :         ConstBufferSequence const& src,
      48              :         std::size_t at_most = std::size_t(-1)) const noexcept
      49              :     {
      50       600020 :         std::size_t total = 0;
      51       600020 :         std::size_t pos0 = 0;
      52       600020 :         std::size_t pos1 = 0;
      53       600020 :         auto const end0 = end(src);
      54       600020 :         auto const end1 = end(dest);
      55       600020 :         auto it0 = begin(src);
      56       600020 :         auto it1 = begin(dest);
      57       600020 :         while(
      58      1619783 :             total < at_most &&
      59      2939445 :             it0 != end0 &&
      60              :             it1 != end1)
      61              :         {
      62      1026225 :             const_buffer b0 = *it0;
      63      1026225 :             mutable_buffer b1 = *it1;
      64      1026225 :             b0 += pos0;
      65      1026225 :             b1 += pos1;
      66              :             std::size_t const amount =
      67      3078675 :             [&]
      68              :             {
      69      1026225 :                 std::size_t n = b0.size();
      70      1026225 :                 if( n > b1.size())
      71        23653 :                     n = b1.size();
      72      1026225 :                 if( n > at_most - total)
      73         4878 :                     n = at_most - total;
      74      1026225 :                 if(n != 0)
      75       772086 :                     std::memcpy(
      76              :                         b1.data(),
      77              :                         b0.data(),
      78              :                         n);
      79      1026225 :                 return n;
      80      1026225 :             }();
      81      1026225 :             total += amount;
      82      1026225 :             if(amount == b1.size())
      83              :             {
      84        32092 :                 ++it1;
      85        32092 :                 pos1 = 0;
      86              :             }
      87              :             else
      88              :             {
      89       994133 :                 pos1 += amount;
      90              :             }
      91      1026225 :             if(amount == b0.size())
      92              :             {
      93       999110 :                 ++it0;
      94       999110 :                 pos0 = 0;
      95              :             }
      96              :             else
      97              :             {
      98        27115 :                 pos0 += amount;
      99              :             }
     100              :         }
     101       600020 :         return total;
     102              :     }
     103              : } copy {};
     104              : 
     105              : } // capy
     106              : } // boost
     107              : 
     108              : #endif