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/buffers
       8              : //
       9              : 
      10              : #ifndef BOOST_BUFFERS_COPY_HPP
      11              : #define BOOST_BUFFERS_COPY_HPP
      12              : 
      13              : #include <boost/buffers/detail/config.hpp>
      14              : #include <boost/buffers/buffer.hpp>
      15              : #include <cstring>
      16              : #include <utility>
      17              : 
      18              : namespace boost {
      19              : namespace buffers {
      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              :     requires is_mutable_buffer_sequence_v<decltype(dest)> &&
      29              :              is_const_buffer_sequence_v<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              :         class MutableBufferSequence,
      43              :         class ConstBufferSequence>
      44              :     auto
      45       599514 :     operator()(
      46              :         MutableBufferSequence const& dest,
      47              :         ConstBufferSequence const& src,
      48              :         std::size_t at_most = std::size_t(-1)) const noexcept -> typename std::enable_if<
      49              :             is_mutable_buffer_sequence<MutableBufferSequence>::value &&
      50              :             is_const_buffer_sequence<ConstBufferSequence>::value, std::size_t>::type
      51              :     {
      52       599514 :         std::size_t total = 0;
      53       599514 :         std::size_t pos0 = 0;
      54       599514 :         std::size_t pos1 = 0;
      55       599514 :         auto const end0 = end(src);
      56       599514 :         auto const end1 = end(dest);
      57       599514 :         auto it0 = begin(src);
      58       599514 :         auto it1 = begin(dest);
      59       599514 :         while(
      60      1617646 :             total < at_most &&
      61      2935171 :             it0 != end0 &&
      62            2 :             it1 != end1)
      63              :         {
      64      1024594 :             const_buffer b0 = *it0;
      65      1024594 :             mutable_buffer b1 = *it1;
      66      1024594 :             b0 += pos0;
      67      1024594 :             b1 += pos1;
      68              :             std::size_t const amount =
      69      3073782 :             [&]
      70              :             {
      71      1024594 :                 std::size_t n = b0.size();
      72      1024594 :                 if( n > b1.size())
      73        23653 :                     n = b1.size();
      74      1024594 :                 if( n > at_most - total)
      75         4878 :                     n = at_most - total;
      76      1024594 :                 if(n != 0)
      77       771415 :                     std::memcpy(
      78              :                         b1.data(),
      79              :                         b0.data(),
      80              :                         n);
      81      1024594 :                 return n;
      82      1024594 :             }();
      83      1024594 :             total += amount;
      84      1024594 :             if(amount == b1.size())
      85              :             {
      86        32093 :                 ++it1;
      87        32093 :                 pos1 = 0;
      88              :             }
      89              :             else
      90              :             {
      91       992501 :                 pos1 += amount;
      92              :             }
      93      1024594 :             if(amount == b0.size())
      94              :             {
      95       997479 :                 ++it0;
      96       997479 :                 pos0 = 0;
      97              :             }
      98              :             else
      99              :             {
     100        27115 :                 pos0 += amount;
     101              :             }
     102              :         }
     103       599516 :         return total;
     104            2 :     }
     105              : } copy {};
     106              : 
     107              : } // buffers
     108              : } // boost
     109              : 
     110              : #endif