Line data    Source code

       1              : /***************************************************************************\
       2              : * Name        : buffered reader                                             *
       3              : * Description : buffer between io::reader and detail::istream              *
       4              : * Author      : antonin.kriz@gmail.com                                      *
       5              : * ------------------------------------------------------------------------- *
       6              : * This is free software; you can redistribute it and/or modify it under the *
       7              : * terms of the MIT license. A copy of the license can be found in the file  *
       8              : * "LICENSE" at the root of this distribution.                               *
       9              : \***************************************************************************/
      10              : 
      11              : #pragma once
      12              : #include "io.hpp"
      13              : #include <array>
      14              : #include <cstdlib>
      15              : #include <cstring>
      16              : #include <string_view>
      17              : 
      18              : namespace spb::io
      19              : {
      20              : #ifndef SPB_READ_BUFFER_SIZE
      21              : #define SPB_READ_BUFFER_SIZE 256U
      22              : #endif
      23              : 
      24              : class buffered_reader
      25              : {
      26              :   private:
      27              :     io::reader on_read;
      28              :     std::array<char, SPB_READ_BUFFER_SIZE> buffer;
      29              :     size_t begin_index = 0;
      30              :     size_t end_index = 0;
      31              :     bool eof_reached = false;
      32              : 
      33       190756 :     auto bytes_in_buffer() const noexcept -> size_t
      34              :     {
      35       190756 :         return end_index - begin_index;
      36              :     }
      37              : 
      38        26333 :     auto space_left_in_buffer() const noexcept -> size_t
      39              :     {
      40        26333 :         return SPB_READ_BUFFER_SIZE - end_index;
      41              :     }
      42              : 
      43        27608 :     void shift_data_to_start() noexcept
      44              :     {
      45        27608 :         if (begin_index > 0)
      46              :         {
      47        47016 :             memmove(buffer.data(), buffer.data() + begin_index, bytes_in_buffer());
      48        23508 :             end_index -= begin_index;
      49        23508 :             begin_index = 0;
      50              :         }
      51        27608 :     }
      52              : 
      53        27608 :     void read_buffer()
      54              :     {
      55        27608 :         shift_data_to_start();
      56              : 
      57        53941 :         while (bytes_in_buffer() < SPB_READ_BUFFER_SIZE && !eof_reached)
      58              :         {
      59        26333 :             auto bytes_in = on_read(&buffer[end_index], space_left_in_buffer());
      60        26333 :             eof_reached |= bytes_in == 0;
      61        26333 :             end_index += bytes_in;
      62              :         }
      63        27608 :     }
      64              : 
      65              :   public:
      66         3941 :     explicit buffered_reader(io::reader reader) : on_read(reader)
      67              :     {
      68         3941 :     }
      69              : 
      70        36935 :     [[nodiscard]] auto view(size_t minimal_size) -> std::string_view
      71              :     {
      72        36935 :         minimal_size = std::max<size_t>(minimal_size, 1U);
      73        36935 :         if (bytes_in_buffer() < minimal_size)
      74        27608 :             read_buffer();
      75              : 
      76        36935 :         return std::string_view(&buffer[begin_index], bytes_in_buffer());
      77              :     }
      78              : 
      79        39437 :     void skip(size_t size) noexcept
      80              :     {
      81        39437 :         begin_index += std::min(size, bytes_in_buffer());
      82        39437 :     }
      83              : };
      84              : 
      85              : } // namespace spb::io