aboutsummaryrefslogtreecommitdiffstats
path: root/src/util/ConstBuffer.hxx
blob: 319102126d05f9c20201f9b23d7cba5fd6a7f98a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
/*
 * Copyright (C) 2013-2014 Max Kellermann <max@duempel.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef CONST_BUFFER_HPP
#define CONST_BUFFER_HPP

#include "Compiler.h"

#include <cstddef>

#ifndef NDEBUG
#include <assert.h>
#endif

template<typename T>
struct ConstBuffer;

template<>
struct ConstBuffer<void> {
	typedef size_t size_type;
	typedef const void *pointer_type;
	typedef pointer_type const_pointer_type;
	typedef pointer_type iterator;
	typedef pointer_type const_iterator;

	pointer_type data;
	size_type size;

	ConstBuffer() = default;

	constexpr ConstBuffer(std::nullptr_t):data(nullptr), size(0) {}

	constexpr ConstBuffer(pointer_type _data, size_type _size)
		:data(_data), size(_size) {}

	constexpr static ConstBuffer Null() {
		return ConstBuffer(nullptr, 0);
	}

	constexpr static ConstBuffer<void> FromVoid(ConstBuffer<void> other) {
		return other;
	}

	constexpr ConstBuffer<void> ToVoid() const {
		return *this;
	}

	constexpr bool IsNull() const {
		return data == nullptr;
	}

	constexpr bool IsEmpty() const {
		return size == 0;
	}
};

/**
 * A reference to a memory area that is read-only.
 */
template<typename T>
struct ConstBuffer {
	typedef size_t size_type;
	typedef const T &reference_type;
	typedef reference_type const_reference_type;
	typedef const T *pointer_type;
	typedef pointer_type const_pointer_type;
	typedef pointer_type iterator;
	typedef pointer_type const_iterator;

	pointer_type data;
	size_type size;

	ConstBuffer() = default;

	constexpr ConstBuffer(std::nullptr_t):data(nullptr), size(0) {}

	constexpr ConstBuffer(pointer_type _data, size_type _size)
		:data(_data), size(_size) {}

	constexpr static ConstBuffer Null() {
		return ConstBuffer(nullptr, 0);
	}

	/**
	 * Cast a ConstBuffer<void> to a ConstBuffer<T>.  A "void"
	 * buffer records its size in bytes, and when casting to "T",
	 * the assertion below ensures that the size is a multiple of
	 * sizeof(T).
	 */
#ifdef NDEBUG
	constexpr
#endif
	static ConstBuffer<T> FromVoid(ConstBuffer<void> other) {
		static_assert(sizeof(T) > 0, "Empty base type");
#ifndef NDEBUG
		assert(other.size % sizeof(T) == 0);
#endif
		return ConstBuffer<T>(pointer_type(other.data),
				      other.size / sizeof(T));
	}

	constexpr ConstBuffer<void> ToVoid() const {
		static_assert(sizeof(T) > 0, "Empty base type");
		return ConstBuffer<void>(data, size * sizeof(T));
	}

	constexpr bool IsNull() const {
		return data == nullptr;
	}

	constexpr bool IsEmpty() const {
		return size == 0;
	}

	constexpr iterator begin() const {
		return data;
	}

	constexpr iterator end() const {
		return data + size;
	}

	constexpr const_iterator cbegin() const {
		return data;
	}

	constexpr const_iterator cend() const {
		return data + size;
	}

#ifdef NDEBUG
	constexpr
#endif
	reference_type operator[](size_type i) const {
#ifndef NDEBUG
		assert(i < size);
#endif

		return data[i];
	}

	/**
	 * Returns a reference to the first element.  Buffer must not
	 * be empty.
	 */
#ifdef NDEBUG
	constexpr
#endif
	reference_type front() const {
#ifndef NDEBUG
		assert(!IsEmpty());
#endif
		return data[0];
	}

	/**
	 * Returns a reference to the last element.  Buffer must not
	 * be empty.
	 */
#ifdef NDEBUG
	constexpr
#endif
	reference_type back() const {
#ifndef NDEBUG
		assert(!IsEmpty());
#endif
		return data[size - 1];
	}

	/**
	 * Remove the first element (by moving the head pointer, does
	 * not actually modify the buffer).  Buffer must not be empty.
	 */
	void pop_front() {
		assert(!IsEmpty());

		++data;
		--size;
	}

	/**
	 * Remove the last element (by moving the tail pointer, does
	 * not actually modify the buffer).  Buffer must not be empty.
	 */
	void pop_back() {
		assert(!IsEmpty());

		--size;
	}

	/**
	 * Remove the first element and return a reference to it.
	 * Buffer must not be empty.
	 */
	reference_type shift() {
		reference_type result = front();
		pop_front();
		return result;
	}
};

#endif