. /include/boost/capy /buffers /buffers_front.hpp
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1   // 1   //
2   // Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com)
3   // Copyright (c) 2026 Steve Gerbino 3   // Copyright (c) 2026 Steve Gerbino
4   // 4   //
5   // Distributed under the Boost Software License, Version 1.0. (See accompanying 5   // Distributed under the Boost Software License, Version 1.0. (See accompanying
6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7   // 7   //
8   // Official repository: https://github.com/cppalliance/capy 8   // Official repository: https://github.com/cppalliance/capy
9   // 9   //
10   10  
11   #ifndef BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP 11   #ifndef BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP
12   #define BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP 12   #define BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP
13   13  
14   #include <boost/capy/detail/config.hpp> 14   #include <boost/capy/detail/config.hpp>
15   #include <boost/capy/buffers.hpp> 15   #include <boost/capy/buffers.hpp>
16   16  
17   namespace boost { 17   namespace boost {
18   namespace capy { 18   namespace capy {
19   19  
20   // MrDocs 0.8.0 flags this object as `buffers_front: variable is 20   // MrDocs 0.8.0 flags this object as `buffers_front: variable is
21   // undocumented`, as it does the other five buffer CPOs 21   // undocumented`, as it does the other five buffer CPOs
22   // (buffer_sequence_begin, buffer_sequence_end, buffer_size, buffers_empty, 22   // (buffer_sequence_begin, buffer_sequence_end, buffer_size, buffers_empty,
23   // buffer_copy). The finding is grandfathered in doc/lint/baseline.json. 23   // buffer_copy). The finding is grandfathered in doc/lint/baseline.json.
24   // Silencing it buys nothing: on the synthesised overload page MrDocs renders 24   // Silencing it buys nothing: on the synthesised overload page MrDocs renders
25   // neither the record-level docstring below nor one attached to the variable, 25   // neither the record-level docstring below nor one attached to the variable,
26   // so any docstring that clears the warning is invisible to readers -- a 26   // so any docstring that clears the warning is invisible to readers -- a
27   // second, dead copy of this prose. Verified twice against the built site. 27   // second, dead copy of this prose. Verified twice against the built site.
28   /** Return the first buffer in a sequence. 28   /** Return the first buffer in a sequence.
29   29  
30   @functionobject 30   @functionobject
31   */ 31   */
32   constexpr struct 32   constexpr struct
33   { 33   {
34   /** Return the first mutable buffer, or an empty buffer. 34   /** Return the first mutable buffer, or an empty buffer.
35   35  
36   @param bs The buffer sequence to inspect. 36   @param bs The buffer sequence to inspect.
37   37  
38   @return The first buffer in `bs`, or an empty buffer if `bs` 38   @return The first buffer in `bs`, or an empty buffer if `bs`
39   contains no buffers. 39   contains no buffers.
40   */ 40   */
41   template<MutableBufferSequence MutableBufferSequence> 41   template<MutableBufferSequence MutableBufferSequence>
42   mutable_buffer 42   mutable_buffer
HITCBC 43   5 operator()( 43   5 operator()(
44   MutableBufferSequence const& bs) const noexcept 44   MutableBufferSequence const& bs) const noexcept
45   { 45   {
HITCBC 46   5 auto const it = buffer_sequence_begin(bs); 46   5 auto const it = buffer_sequence_begin(bs);
HITCBC 47   5 if(it != buffer_sequence_end(bs)) 47   5 if(it != buffer_sequence_end(bs))
HITCBC 48   4 return *it; 48   4 return *it;
HITCBC 49   1 return {}; 49   1 return {};
50   } 50   }
51   51  
52   /** Return the first const buffer, or an empty buffer. 52   /** Return the first const buffer, or an empty buffer.
53   53  
54   @param bs The buffer sequence to inspect. 54   @param bs The buffer sequence to inspect.
55   55  
56   @return The first buffer in `bs`, or an empty buffer if `bs` 56   @return The first buffer in `bs`, or an empty buffer if `bs`
57   contains no buffers. 57   contains no buffers.
58   */ 58   */
59   template<ConstBufferSequence ConstBufferSequence> 59   template<ConstBufferSequence ConstBufferSequence>
60   const_buffer 60   const_buffer
HITCBC 61   5 operator()( 61   5 operator()(
62   ConstBufferSequence const& bs) const noexcept 62   ConstBufferSequence const& bs) const noexcept
63   { 63   {
HITCBC 64   5 auto const it = buffer_sequence_begin(bs); 64   5 auto const it = buffer_sequence_begin(bs);
HITCBC 65   5 if(it != buffer_sequence_end(bs)) 65   5 if(it != buffer_sequence_end(bs))
HITCBC 66   4 return *it; 66   4 return *it;
HITCBC 67   1 return {}; 67   1 return {};
68   } 68   }
69   } const buffers_front{}; 69   } const buffers_front{};
70   70  
71   } // capy 71   } // capy
72   } // boost 72   } // boost
73   73  
74   #endif 74   #endif