include/boost/capy/buffers/flat_dynamic_buffer.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_FLAT_DYNAMIC_BUFFER_HPP
11			#define BOOST_CAPY_BUFFERS_FLAT_DYNAMIC_BUFFER_HPP
12
13			#include <boost/capy/detail/config.hpp>
14			#include <boost/capy/buffers.hpp>
15			#include <boost/capy/detail/except.hpp>
16
17			namespace boost {
18			namespace capy {
19
20			/** A fixed-capacity linear buffer satisfying DynamicBuffer.
21
22			This class provides a contiguous buffer with fixed capacity
23			determined at construction. Buffer sequences returned from
24			@ref data and @ref prepare always contain exactly one element,
25			making it suitable for APIs requiring contiguous memory.
26
27			@par Example
28			@code
29			char storage[1024];
30			flat_dynamic_buffer fb( storage, sizeof( storage ) );
31
32			// Write data
33			auto mb = fb.prepare( 100 );
34			std::memcpy( mb.data(), "hello", 5 );
35			fb.commit( 5 );
36
37			// Read data
38			auto data = fb.data();
39			// process data...
40			fb.consume( 5 );
41			@endcode
42
43			@par Thread Safety
44			Distinct objects: Safe.
45			Shared objects: Unsafe.
46
47			@see circular_dynamic_buffer, string_dynamic_buffer
48			*/
49			class flat_dynamic_buffer
50			{
51			unsigned char* data_ = nullptr;
52			std::size_t cap_ = 0;
53			std::size_t in_pos_ = 0;
54			std::size_t in_size_ = 0;
55			std::size_t out_size_ = 0;
56
57			public:
58			/// Indicates this is a DynamicBuffer adapter over external storage.
59			using is_dynamic_buffer_adapter = void;
60
61			/// The ConstBufferSequence type for readable bytes.
62			using const_buffers_type = const_buffer;
63
64			/// The MutableBufferSequence type for writable bytes.
65			using mutable_buffers_type = mutable_buffer;
66
67			/// Construct an empty flat buffer with zero capacity.
68			flat_dynamic_buffer() = default;
69
70			/** Construct a flat buffer over existing storage.
71
72			@param data Pointer to the storage.
73			@param capacity Size of the storage in bytes.
74			@param initial_size Number of bytes already present as
75			readable. Must not exceed @p capacity.
76
77			@throws std::invalid_argument if initial_size > capacity.
78			*/
79		223x	flat_dynamic_buffer(
80			void* data,
81			std::size_t capacity,
82			std::size_t initial_size = 0)
83		223x	: data_(static_cast<
84			unsigned char*>(data))
85		223x	, cap_(capacity)
86		223x	, in_size_(initial_size)
87			{
88	2/2 ✓ Branch 0 taken 1 time. ✓ Branch 1 taken 222 times.	223x	if(in_size_ > cap_)
89		1x	detail::throw_invalid_argument();
90		222x	}
91
92			/// Construct a copy.
93			flat_dynamic_buffer(
94			flat_dynamic_buffer const&) = default;
95
96			/// Assign by copying.
97			flat_dynamic_buffer& operator=(
98			flat_dynamic_buffer const&) = default;
99
100			/// Return the number of readable bytes.
101			std::size_t
102		856x	size() const noexcept
103			{
104		856x	return in_size_;
105			}
106
107			/// Return the maximum number of bytes the buffer can hold.
108			std::size_t
109		10x	max_size() const noexcept
110			{
111		10x	return cap_;
112			}
113
114			/// Return the number of writable bytes without reallocation.
115			std::size_t
116		238x	capacity() const noexcept
117			{
118		238x	return cap_ - (in_pos_ + in_size_);
119			}
120
121			/// Return a buffer sequence representing the readable bytes.
122			const_buffers_type
123		161x	data() const noexcept
124			{
125		322x	return const_buffers_type(
126		161x	data_ + in_pos_, in_size_);
127			}
128
129			/** Return a buffer sequence for writing.
130
131			Invalidates buffer sequences previously obtained
132			from @ref prepare.
133
134			@param n The desired number of writable bytes.
135
136			@return A mutable buffer sequence of size @p n.
137
138			@throws std::invalid_argument if `n > capacity()`.
139			*/
140			mutable_buffers_type
141		197x	prepare(std::size_t n)
142			{
143	2/2 ✓ Branch 1 taken 3 times. ✓ Branch 2 taken 194 times.	197x	if( n > capacity() )
144		3x	detail::throw_invalid_argument();
145
146		194x	out_size_ = n;
147		388x	return mutable_buffers_type(
148		194x	data_ + in_pos_ + in_size_, n);
149			}
150
151			/** Move bytes from the output to the input sequence.
152
153			Invalidates buffer sequences previously obtained
154			from @ref prepare. Buffer sequences from @ref data
155			remain valid.
156
157			@param n The number of bytes to commit. If greater
158			than the prepared size, all prepared bytes
159			are committed.
160			*/
161			void
162		160x	commit(
163			std::size_t n) noexcept
164			{
165	2/2 ✓ Branch 0 taken 15 times. ✓ Branch 1 taken 145 times.	160x	if(n < out_size_)
166		15x	in_size_ += n;
167			else
168		145x	in_size_ += out_size_;
169		160x	out_size_ = 0;
170		160x	}
171
172			/** Remove bytes from the beginning of the input sequence.
173
174			Invalidates buffer sequences previously obtained
175			from @ref data. Buffer sequences from @ref prepare
176			remain valid.
177
178			@param n The number of bytes to consume. If greater
179			than @ref size(), all readable bytes are consumed.
180			*/
181			void
182		180x	consume(
183			std::size_t n) noexcept
184			{
185	2/2 ✓ Branch 0 taken 15 times. ✓ Branch 1 taken 165 times.	180x	if(n < in_size_)
186			{
187		15x	in_pos_ += n;
188		15x	in_size_ -= n;
189			}
190			else
191			{
192		165x	in_pos_ = 0;
193		165x	in_size_ = 0;
194			}
195		180x	}
196			};
197
198			} // capy
199			} // boost
200
201			#endif
202