include/boost/capy/buffers/buffer_copy.hpp

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buffer_copy.hpp

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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_BUFFER_COPY_HPP
11		#define BOOST_CAPY_BUFFERS_BUFFER_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		@functionobject
24		*/
25		constexpr struct
26		{
27		/** Copy the contents of a buffer sequence into another buffer sequence.
28
29		Copies bytes from the constant buffer sequence `src` into the
30		mutable buffer sequence `dest`, stopping when any limit is
31		reached.
32
33		@param dest The destination buffer sequence.
34
35		@param src The source buffer sequence.
36
37		@param at_most The maximum bytes to copy. Default copies all
38		available.
39
40		@return The number of bytes copied, equal to
41		`std::min(size(dest), size(src), at_most)`.
42		*/
43		template<
44		MutableBufferSequence MB,
45		ConstBufferSequence CB>
46		std::size_t
47	10071x	operator()(
48		MB const& dest,
49		CB const& src,
50		std::size_t at_most = std::size_t(-1)) const noexcept
51		{
52	10071x	std::size_t total = 0;
53	10071x	std::size_t pos0 = 0;
54	10071x	std::size_t pos1 = 0;
55	10071x	auto const end0 = end(src);
56	10071x	auto const end1 = end(dest);
57	10071x	auto it0 = begin(src);
58	10071x	auto it1 = begin(dest);
59	10071x	while(
60	33186x	total < at_most &&
61	47165x	it0 != end0 &&
62	8469x	it1 != end1)
63		{
64	17359x	const_buffer b0 = *it0;
65	17359x	mutable_buffer b1 = *it1;
66	17359x	b0 += pos0;
67	17359x	b1 += pos1;
68		std::size_t const amount =
69	52077x	[&]
70		{
71	17359x	std::size_t n = b0.size();
72	17359x	if( n > b1.size())
73	5275x	n = b1.size();
74	17359x	if( n > at_most - total)
75	4905x	n = at_most - total;
76	17359x	if(n != 0)
77	16506x	std::memcpy(
78		b1.data(),
79		b0.data(),
80		n);
81	17359x	return n;
82	17359x	}();
83	17359x	total += amount;
84	17359x	if(amount == b1.size())
85		{
86	5489x	++it1;
87	5489x	pos1 = 0;
88		}
89		else
90		{
91	11870x	pos1 += amount;
92		}
93	17359x	if(amount == b0.size())
94		{
95	8596x	++it0;
96	8596x	pos0 = 0;
97		}
98		else
99		{
100	8763x	pos0 += amount;
101		}
102		}
103	10071x	return total;
104		}
105		} buffer_copy {};
106
107		} // capy
108		} // boost
109
110		#endif
111