include/boost/capy/detail/consuming_buffers.hpp

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//

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//

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// Distributed under the Boost Software License, Version 1.0. (See accompanying

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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

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//

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// Official repository: https://github.com/cppalliance/capy

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//

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#ifndef BOOST_CAPY_DETAIL_CONSUMING_BUFFERS_HPP

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#define BOOST_CAPY_DETAIL_CONSUMING_BUFFERS_HPP

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#include <boost/capy/detail/config.hpp>

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#include <boost/capy/buffers.hpp>

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#include <boost/capy/detail/slice_of.hpp>

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#include <cstddef>

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#include <utility>

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namespace boost {

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namespace capy {

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namespace detail {

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/** A cursor that drives consumption of a buffer sequence.

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`consuming_buffers` is the dedicated driver for `read_some`/`write_some`

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loops. It presents the not-yet-consumed bytes of a buffer sequence via

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`data()`, and `consume(n)` advances past `n` transferred bytes **in

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place**.

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It is deliberately **not** itself a buffer sequence — it hands out the

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remaining bytes through `data()` (returning a `slice_of` view). It

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**borrows** the underlying sequence (iterators + a consumed-byte offset).

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The sequence must outlive the cursor. That is the natural case when the

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cursor is a local of a composed operation that took its buffers by value.

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*/

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template<class Seq>

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requires ConstBufferSequence<Seq>

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class consuming_buffers

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{

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public:

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/// Names the buffer type the underlying sequence `Seq` yields.

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using buffer_type = capy::buffer_type<Seq>;

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private:

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using iterator_type =

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decltype(capy::buffer_sequence_begin(std::declval<Seq const&>()));

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iterator_type first_{};

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iterator_type last_{};

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std::size_t front_skip_ = 0; // bytes consumed from *first_

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public:

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/** Construct a cursor over `s`.

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@param s The sequence to consume. Must outlive the cursor.

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*/

DCB

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explicit consuming_buffers(Seq const& s) noexcept

DCB

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: first_(capy::buffer_sequence_begin(s))

DCB

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, last_(capy::buffer_sequence_end(s))

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{

DCB

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}

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/** Reject construction from a temporary (the view would dangle).

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@param s The sequence that would be consumed.

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*/

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consuming_buffers(Seq const&& s) = delete;

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/** Return the remaining (unconsumed) bytes as a buffer sequence.

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@return The bytes not yet consumed, as a buffer sequence.

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*/

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slice_of<Seq>

DCB

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data() const noexcept

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{

DCB

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return slice_of<Seq>(first_, last_, front_skip_, 0);

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}

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/** Discard `n` bytes from the front, in place.

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Advances past `min(n, remaining)` bytes.

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@param n The number of bytes consumed.

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*/

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void

DCB

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consume(std::size_t n) noexcept

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{

DCB

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while (n > 0 && first_ != last_)

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{

DCB

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std::size_t const sz = buffer_type(*first_).size();

DCB

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std::size_t const avail = sz - front_skip_;

DCB

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if (n < avail)

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{

DCB

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front_skip_ += n;

DCB

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return;

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}

DCB

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n -= avail;

DCB

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++first_;

DCB

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front_skip_ = 0;

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}

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}

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};

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/** Deduce the sequence type from the constructor argument.

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@tparam Seq The buffer sequence type.

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*/

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template<class Seq>

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consuming_buffers(Seq const&) -> consuming_buffers<Seq>;

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} // namespace detail

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} // namespace capy

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} // namespace boost

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#endif

TLA	Baseline				Branch
TLA	Line		Hits	Code	Line	Hits	Code
	1	-		//
	2	-		// Copyright (c) 2026 Steve Gerbino
	3	-		// Copyright (c) 2026 Michael Vandeberg
	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_DETAIL_CONSUMING_BUFFERS_HPP
	12	-		#define BOOST_CAPY_DETAIL_CONSUMING_BUFFERS_HPP
	13	-
	14	-		#include <boost/capy/detail/config.hpp>
	15	-		#include <boost/capy/buffers.hpp>
	16	-		#include <boost/capy/detail/slice_of.hpp>
	17	-
	18	-		#include <cstddef>
	19	-		#include <utility>
	20	-
	21	-		namespace boost {
	22	-		namespace capy {
	23	-		namespace detail {
	24	-
	25	-		/** A cursor that drives consumption of a buffer sequence.
	26	-
	27	-		`consuming_buffers` is the dedicated driver for `read_some`/`write_some`
	28	-		loops. It presents the not-yet-consumed bytes of a buffer sequence via
	29	-		`data()`, and `consume(n)` advances past `n` transferred bytes **in
	30	-		place**.
	31	-
	32	-		It is deliberately not itself a buffer sequence — it hands out the
	33	-		remaining bytes through `data()` (returning a `slice_of` view). It
	34	-		borrows the underlying sequence (iterators + a consumed-byte offset).
	35	-		The sequence must outlive the cursor. That is the natural case when the
	36	-		cursor is a local of a composed operation that took its buffers by value.
	37	-		*/
	38	-		template<class Seq>
	39	-		requires ConstBufferSequence<Seq>
	40	-		class consuming_buffers
	41	-		{
	42	-		public:
	43	-		/// Names the buffer type the underlying sequence `Seq` yields.
	44	-		using buffer_type = capy::buffer_type<Seq>;
	45	-
	46	-		private:
	47	-		using iterator_type =
	48	-		decltype(capy::buffer_sequence_begin(std::declval<Seq const&>()));
	49	-
	50	-		iterator_type first_{};
	51	-		iterator_type last_{};
	52	-		std::size_t front_skip_ = 0; // bytes consumed from *first_
	53	-
	54	-		public:
	55	-		/** Construct a cursor over `s`.
	56	-
	57	-		@param s The sequence to consume. Must outlive the cursor.
	58	-		*/
DCB	59	-	306	explicit consuming_buffers(Seq const& s) noexcept
DCB	60	-	306	: first_(capy::buffer_sequence_begin(s))
DCB	61	-	306	, last_(capy::buffer_sequence_end(s))
	62	-		{
DCB	63	-	306	}
	64	-
	65	-		/** Reject construction from a temporary (the view would dangle).
	66	-
	67	-		@param s The sequence that would be consumed.
	68	-		*/
	69	-		consuming_buffers(Seq const&& s) = delete;
	70	-
	71	-		/** Return the remaining (unconsumed) bytes as a buffer sequence.
	72	-
	73	-		@return The bytes not yet consumed, as a buffer sequence.
	74	-		*/
	75	-		slice_of<Seq>
DCB	76	-	354	data() const noexcept
	77	-		{
DCB	78	-	354	return slice_of<Seq>(first_, last_, front_skip_, 0);
	79	-		}
	80	-
	81	-		/** Discard `n` bytes from the front, in place.
	82	-
	83	-		Advances past `min(n, remaining)` bytes.
	84	-
	85	-		@param n The number of bytes consumed.
	86	-		*/
	87	-		void
DCB	88	-	262	consume(std::size_t n) noexcept
	89	-		{
DCB	90	-	387	while (n > 0 && first_ != last_)
	91	-		{
DCB	92	-	199	std::size_t const sz = buffer_type(*first_).size();
DCB	93	-	199	std::size_t const avail = sz - front_skip_;
DCB	94	-	199	if (n < avail)
	95	-		{
DCB	96	-	74	front_skip_ += n;
DCB	97	-	74	return;
	98	-		}
DCB	99	-	125	n -= avail;
DCB	100	-	125	++first_;
DCB	101	-	125	front_skip_ = 0;
	102	-		}
	103	-		}
	104	-		};
	105	-
	106	-		/** Deduce the sequence type from the constructor argument.
	107	-
	108	-		@tparam Seq The buffer sequence type.
	109	-		*/
	110	-		template<class Seq>
	111	-		consuming_buffers(Seq const&) -> consuming_buffers<Seq>;
	112	-
	113	-		} // namespace detail
	114	-		} // namespace capy
	115	-		} // namespace boost
	116	-
	117	-		#endif