include/boost/capy/buffers/buffers_front.hpp

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buffers_front.hpp

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1		//
2		// Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com)
3		// Copyright (c) 2026 Steve Gerbino
4		//
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)
7		//
8		// Official repository: https://github.com/cppalliance/capy
9		//
10
11		#ifndef BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP
12		#define BOOST_CAPY_BUFFERS_BUFFERS_FRONT_HPP
13
14		#include <boost/capy/detail/config.hpp>
15		#include <boost/capy/buffers.hpp>
16
17		namespace boost {
18		namespace capy {
19
20		// MrDocs 0.8.0 flags this object as `buffers_front: variable is
21		// undocumented`, as it does the other five buffer CPOs
22		// (buffer_sequence_begin, buffer_sequence_end, buffer_size, buffers_empty,
23		// buffer_copy). The finding is grandfathered in doc/lint/baseline.json.
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,
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.
28		/** Return the first buffer in a sequence.
29
30		@functionobject
31		*/
32		constexpr struct
33		{
34		/** Return the first mutable buffer, or an empty buffer.
35
36		@param bs The buffer sequence to inspect.
37
38		@return The first buffer in `bs`, or an empty buffer if `bs`
39		contains no buffers.
40		*/
41		template<MutableBufferSequence MutableBufferSequence>
42		mutable_buffer
43	5x	operator()(
44		MutableBufferSequence const& bs) const noexcept
45		{
46	5x	auto const it = buffer_sequence_begin(bs);
47	5x	if(it != buffer_sequence_end(bs))
48	4x	return *it;
49	1x	return {};
50		}
51
52		/** Return the first const buffer, or an empty buffer.
53
54		@param bs The buffer sequence to inspect.
55
56		@return The first buffer in `bs`, or an empty buffer if `bs`
57		contains no buffers.
58		*/
59		template<ConstBufferSequence ConstBufferSequence>
60		const_buffer
61	5x	operator()(
62		ConstBufferSequence const& bs) const noexcept
63		{
64	5x	auto const it = buffer_sequence_begin(bs);
65	5x	if(it != buffer_sequence_end(bs))
66	4x	return *it;
67	1x	return {};
68		}
69		} const buffers_front{};
70
71		} // capy
72		} // boost
73
74		#endif
75