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		namespace detail {
22		struct buffer_copy_fn
23		{
24		template<
25		MutableBufferSequence MB,
26		ConstBufferSequence CB>
27		std::size_t
28	12256x	operator()(
29		MB const& dest,
30		CB const& src,
31		std::size_t at_most = std::size_t(-1)) const noexcept
32		{
33	12256x	std::size_t total = 0;
34	12256x	std::size_t pos0 = 0;
35	12256x	std::size_t pos1 = 0;
36	12256x	auto const end0 = end(src);
37	12256x	auto const end1 = end(dest);
38	12256x	auto it0 = begin(src);
39	12256x	auto it1 = begin(dest);
40	12256x	while(
41	38002x	total < at_most &&
42	54380x	it0 != end0 &&
43	9402x	it1 != end1)
44		{
45	19805x	const_buffer b0 = *it0;
46	19805x	mutable_buffer b1 = *it1;
47	19805x	b0 += pos0;
48	19805x	b1 += pos1;
49		std::size_t const amount =
50	59415x	[&]
51		{
52	19805x	std::size_t n = b0.size();
53	19805x	if( n > b1.size())
54	5750x	n = b1.size();
55	19805x	if( n > at_most - total)
56	4902x	n = at_most - total;
57	19805x	if(n != 0)
58	18953x	std::memcpy(
59		b1.data(),
60		b0.data(),
61		n);
62	19805x	return n;
63	19805x	}();
64	19805x	total += amount;
65	19805x	if(amount == b1.size())
66		{
67	7301x	++it1;
68	7301x	pos1 = 0;
69		}
70		else
71		{
72	12504x	pos1 += amount;
73		}
74	19805x	if(amount == b0.size())
75		{
76	10569x	++it0;
77	10569x	pos0 = 0;
78		}
79		else
80		{
81	9236x	pos0 += amount;
82		}
83		}
84	12256x	return total;
85		}
86		};
87		} // detail
88
89		/** Copy the contents of a buffer sequence into another buffer sequence.
90
91		This function copies bytes from the constant buffer sequence `src` into
92		the mutable buffer sequence `dest`, stopping when any limit is reached.
93
94		@par Constraints
95		@code
96		MutableBufferSequence<decltype(dest)> &&
97		ConstBufferSequence<decltype(src)>
98		@endcode
99
100		@return The number of bytes copied, equal to
101		`std::min(size(dest), size(src), at_most)`.
102
103		@param dest The destination buffer sequence.
104		@param src The source buffer sequence.
105		@param at_most The maximum bytes to copy. Default copies all available.
106		*/
107		constexpr detail::buffer_copy_fn buffer_copy {};
108
109		} // capy
110		} // boost
111
112		#endif
113