include/boost/capy/buffers/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_BUFFERS_CONSUMING_BUFFERS_HPP

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#define BOOST_CAPY_BUFFERS_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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/** 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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@par Example

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@par !example example

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@see @ref buffer_slice

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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::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::begin(s))

DCB

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, last_(capy::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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detail::slice_of<Seq>

DCB

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data() const noexcept

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{

DCB

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return detail::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 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_BUFFERS_CONSUMING_BUFFERS_HPP
	12	-		#define BOOST_CAPY_BUFFERS_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	-
	24	-		/** A cursor that drives consumption of a buffer sequence.
	25	-
	26	-		`consuming_buffers` is the dedicated driver for `read_some`/`write_some`
	27	-		loops. It presents the not-yet-consumed bytes of a buffer sequence via
	28	-		`data()`, and `consume(n)` advances past `n` transferred bytes **in
	29	-		place**.
	30	-
	31	-		It is deliberately not itself a buffer sequence — it hands out the
	32	-		remaining bytes through `data()` (returning a `slice_of` view). It
	33	-		borrows the underlying sequence (iterators + a consumed-byte offset).
	34	-		The sequence must outlive the cursor. That is the natural case when the
	35	-		cursor is a local of a composed operation that took its buffers by value.
	36	-
	37	-		@par Example
	38	-		@par !example example
	39	-
	40	-
	41	-		@see @ref buffer_slice
	42	-		*/
	43	-		template<class Seq>
	44	-		requires ConstBufferSequence<Seq>
	45	-		class consuming_buffers
	46	-		{
	47	-		public:
	48	-		/// Names the buffer type the underlying sequence `Seq` yields.
	49	-		using buffer_type = capy::buffer_type<Seq>;
	50	-
	51	-		private:
	52	-		using iterator_type =
	53	-		decltype(capy::begin(std::declval<Seq const&>()));
	54	-
	55	-		iterator_type first_{};
	56	-		iterator_type last_{};
	57	-		std::size_t front_skip_ = 0; // bytes consumed from *first_
	58	-
	59	-		public:
	60	-		/** Construct a cursor over `s`.
	61	-
	62	-		@param s The sequence to consume. Must outlive the cursor.
	63	-		*/
DCB	64	-	307	explicit consuming_buffers(Seq const& s) noexcept
DCB	65	-	307	: first_(capy::begin(s))
DCB	66	-	307	, last_(capy::end(s))
	67	-		{
DCB	68	-	307	}
	69	-
	70	-		/** Reject construction from a temporary (the view would dangle).
	71	-
	72	-		@param s The sequence that would be consumed.
	73	-		*/
	74	-		consuming_buffers(Seq const&& s) = delete;
	75	-
	76	-		/** Return the remaining (unconsumed) bytes as a buffer sequence.
	77	-
	78	-		@return The bytes not yet consumed, as a buffer sequence.
	79	-		*/
	80	-		detail::slice_of<Seq>
DCB	81	-	357	data() const noexcept
	82	-		{
DCB	83	-	357	return detail::slice_of<Seq>(first_, last_, front_skip_, 0);
	84	-		}
	85	-
	86	-		/** Discard `n` bytes from the front, in place.
	87	-
	88	-		Advances past `min(n, remaining)` bytes.
	89	-
	90	-		@param n The number of bytes consumed.
	91	-		*/
	92	-		void
DCB	93	-	265	consume(std::size_t n) noexcept
	94	-		{
DCB	95	-	395	while (n > 0 && first_ != last_)
	96	-		{
DCB	97	-	204	std::size_t const sz = buffer_type(*first_).size();
DCB	98	-	204	std::size_t const avail = sz - front_skip_;
DCB	99	-	204	if (n < avail)
	100	-		{
DCB	101	-	74	front_skip_ += n;
DCB	102	-	74	return;
	103	-		}
DCB	104	-	130	n -= avail;
DCB	105	-	130	++first_;
DCB	106	-	130	front_skip_ = 0;
	107	-		}
	108	-		}
	109	-		};
	110	-
	111	-		/** Deduce the sequence type from the constructor argument.
	112	-
	113	-		@tparam Seq The buffer sequence type.
	114	-		*/
	115	-		template<class Seq>
	116	-		consuming_buffers(Seq const&) -> consuming_buffers<Seq>;
	117	-
	118	-		} // namespace capy
	119	-		} // namespace boost
	120	-
	121	-		#endif