include/boost/capy/buffers/consuming_buffers.hpp

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1			//
2			// Copyright (c) 2025 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_CONSUMING_BUFFERS_HPP
11			#define BOOST_CAPY_BUFFERS_CONSUMING_BUFFERS_HPP
12
13			#include <boost/capy/detail/config.hpp>
14			#include <boost/capy/buffers.hpp>
15
16			#include <cstddef>
17			#include <iterator>
18			#include <ranges>
19			#include <type_traits>
20
21			namespace boost {
22			namespace capy {
23
24			namespace detail {
25
26			template<class T>
27			struct buffer_type_for;
28
29			template<MutableBufferSequence T>
30			struct buffer_type_for<T>
31			{
32			using type = mutable_buffer;
33			};
34
35			template<ConstBufferSequence T>
36			requires (!MutableBufferSequence<T>)
37			struct buffer_type_for<T>
38			{
39			using type = const_buffer;
40			};
41
42			} // namespace detail
43
44			/** Wrapper for consuming a buffer sequence incrementally.
45
46			This class wraps a buffer sequence and tracks the current
47			position. It provides a `consume(n)` function that advances
48			through the sequence as bytes are processed.
49
50			Works with both mutable and const buffer sequences.
51
52			@tparam BufferSequence The buffer sequence type.
53			*/
54			template<class BufferSequence>
55			requires MutableBufferSequence<BufferSequence> \|\|
56			ConstBufferSequence<BufferSequence>
57			class consuming_buffers
58			{
59			using iterator_type = decltype(capy::begin(std::declval<BufferSequence const&>()));
60			using end_iterator_type = decltype(capy::end(std::declval<BufferSequence const&>()));
61			using buffer_type = typename detail::buffer_type_for<BufferSequence>::type;
62
63			BufferSequence const& bufs_;
64			iterator_type it_;
65			end_iterator_type end_;
66			std::size_t consumed_ = 0; // Bytes consumed in current buffer
67
68			public:
69			/** Construct from a buffer sequence.
70
71			@param bufs The buffer sequence to wrap.
72			*/
73		165x	explicit consuming_buffers(BufferSequence const& bufs) noexcept
74		165x	: bufs_(bufs)
75		165x	, it_(capy::begin(bufs))
76		165x	, end_(capy::end(bufs))
77			{
78		165x	}
79
80			/** Consume n bytes from the buffer sequence.
81
82			Advances the current position by n bytes, moving to the
83			next buffer when the current one is exhausted.
84
85			@param n The number of bytes to consume.
86			*/
87		74x	void consume(std::size_t n) noexcept
88			{
89	12/16 boost::capy::consuming_buffers<boost::capy::const_buffer>::consume(unsigned long): ✓ Branch 0 taken 38 times. ✓ Branch 1 taken 38 times. ✓ Branch 2 taken 38 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<boost::capy::mutable_buffer>::consume(unsigned long): ✓ Branch 0 taken 10 times. ✓ Branch 1 taken 10 times. ✓ Branch 2 taken 10 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<std::array<boost::capy::const_buffer, 2ul> >::consume(unsigned long): ✓ Branch 0 taken 28 times. ✓ Branch 1 taken 14 times. ✓ Branch 2 taken 28 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<std::array<boost::capy::mutable_buffer, 2ul> >::consume(unsigned long): ✓ Branch 0 taken 16 times. ✓ Branch 1 taken 12 times. ✓ Branch 2 taken 16 times. ✗ Branch 3 not taken.	166x	while (n > 0 && it_ != end_)
90			{
91		92x	auto const& buf = *it_;
92		92x	std::size_t const buf_size = buf.size();
93		92x	std::size_t const remaining = buf_size - consumed_;
94
95	7/8 boost::capy::consuming_buffers<boost::capy::const_buffer>::consume(unsigned long): ✓ Branch 0 taken 18 times. ✓ Branch 1 taken 20 times. boost::capy::consuming_buffers<boost::capy::mutable_buffer>::consume(unsigned long): ✓ Branch 0 taken 4 times. ✓ Branch 1 taken 6 times. boost::capy::consuming_buffers<std::array<boost::capy::const_buffer, 2ul> >::consume(unsigned long): ✗ Branch 0 not taken. ✓ Branch 1 taken 28 times. boost::capy::consuming_buffers<std::array<boost::capy::mutable_buffer, 2ul> >::consume(unsigned long): ✓ Branch 0 taken 8 times. ✓ Branch 1 taken 8 times.	92x	if (n < remaining)
96			{
97			// Consume part of current buffer
98		30x	consumed_ += n;
99		30x	n = 0;
100			}
101			else
102			{
103			// Consume rest of current buffer and move to next
104		62x	n -= remaining;
105		62x	consumed_ = 0;
106		62x	++it_;
107			}
108			}
109		74x	}
110
111			/** Iterator for the consuming buffer sequence.
112
113			Returns buffers starting from the current position,
114			with the first buffer adjusted for consumed bytes.
115			*/
116			class const_iterator
117			{
118			iterator_type it_;
119			end_iterator_type end_;
120			std::size_t consumed_;
121
122			public:
123			using iterator_category = std::bidirectional_iterator_tag;
124			using value_type = buffer_type;
125			using difference_type = std::ptrdiff_t;
126			using pointer = value_type*;
127			using reference = value_type;
128
129			// Default constructor required for forward_iterator
130			const_iterator() noexcept = default;
131
132		634x	const_iterator(
133			iterator_type it,
134			end_iterator_type end,
135			std::size_t consumed) noexcept
136		634x	: it_(it)
137		634x	, end_(end)
138		634x	, consumed_(consumed)
139			{
140		634x	}
141
142		418x	bool operator==(const_iterator const& other) const noexcept
143			{
144	12/16 boost::capy::consuming_buffers<boost::capy::const_buffer>::const_iterator::operator==(boost::capy::consuming_buffers<boost::capy::const_buffer>::const_iterator const&) const: ✓ Branch 0 taken 38 times. ✓ Branch 1 taken 154 times. ✓ Branch 2 taken 38 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<boost::capy::mutable_buffer>::const_iterator::operator==(boost::capy::consuming_buffers<boost::capy::mutable_buffer>::const_iterator const&) const: ✓ Branch 0 taken 3 times. ✓ Branch 1 taken 43 times. ✓ Branch 2 taken 3 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<std::array<boost::capy::const_buffer, 2ul> >::const_iterator::operator==(boost::capy::consuming_buffers<std::array<boost::capy::const_buffer, 2ul> >::const_iterator const&) const: ✓ Branch 0 taken 14 times. ✓ Branch 1 taken 110 times. ✓ Branch 2 taken 14 times. ✗ Branch 3 not taken. boost::capy::consuming_buffers<std::array<boost::capy::mutable_buffer, 2ul> >::const_iterator::operator==(boost::capy::consuming_buffers<std::array<boost::capy::mutable_buffer, 2ul> >::const_iterator const&) const: ✓ Branch 0 taken 1 time. ✓ Branch 1 taken 55 times. ✓ Branch 2 taken 1 time. ✗ Branch 3 not taken.	418x	return it_ == other.it_ && consumed_ == other.consumed_;
145			}
146
147			// != operator required for equality_comparable
148		418x	bool operator!=(const_iterator const& other) const noexcept
149			{
150		418x	return !(*this == other);
151			}
152
153		361x	value_type operator*() const noexcept
154			{
155		361x	auto const& buf = *it_;
156			if constexpr (std::is_same_v<buffer_type, mutable_buffer>)
157			{
158		291x	return buffer_type(
159		97x	static_cast<char*>(buf.data()) + consumed_,
160		194x	buf.size() - consumed_);
161			}
162			else
163			{
164		792x	return buffer_type(
165		264x	static_cast<char const*>(buf.data()) + consumed_,
166		528x	buf.size() - consumed_);
167			}
168			}
169
170		331x	const_iterator& operator++() noexcept
171			{
172		331x	consumed_ = 0;
173		331x	++it_;
174		331x	return *this;
175			}
176
177		198x	const_iterator operator++(int) noexcept
178			{
179		198x	const_iterator tmp = *this;
180		198x	++*this;
181		198x	return tmp;
182			}
183
184			const_iterator& operator--() noexcept
185			{
186			if (consumed_ == 0)
187			{
188			--it_;
189			// Set consumed_ to the size of the previous buffer
190			// This is a simplified implementation for bidirectional requirement
191			if (it_ != end_)
192			{
193			auto const& buf = *it_;
194			consumed_ = buf.size();
195			}
196			}
197			else
198			{
199			consumed_ = 0;
200			}
201			return *this;
202			}
203
204			const_iterator operator--(int) noexcept
205			{
206			const_iterator tmp = *this;
207			--*this;
208			return tmp;
209			}
210			};
211
212			/** Return iterator to beginning of remaining buffers.
213
214			@return Iterator pointing to the first remaining buffer,
215			adjusted for consumed bytes in the current buffer.
216			*/
217		317x	const_iterator begin() const noexcept
218			{
219		317x	return const_iterator(it_, end_, consumed_);
220			}
221
222			/** Return iterator to end of buffer sequence.
223
224			@return End iterator.
225			*/
226		317x	const_iterator end() const noexcept
227			{
228		317x	return const_iterator(end_, end_, 0);
229			}
230			};
231
232			} // namespace capy
233			} // namespace boost
234
235			#endif
236