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
|
/*
* Copyright (C) 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 CIRCULAR_BUFFER_HPP
#define CIRCULAR_BUFFER_HPP
#include "WritableBuffer.hxx"
#include <assert.h>
#include <stddef.h>
/**
* A circular buffer.
*
* This class does not manage buffer memory. It will not allocate or
* free any memory, it only manages the contents of an existing
* buffer given to the constructor.
*
* Everything between #head and #tail is valid data (may wrap around).
* If both are equal, then the buffer is empty. Due to this
* implementation detail, the buffer is empty when #size-1 items are
* stored; the last buffer cell cannot be used.
*/
template<typename T>
class CircularBuffer {
public:
typedef WritableBuffer<T> Range;
typedef typename Range::pointer_type pointer_type;
typedef typename Range::size_type size_type;
protected:
/**
* The next index to be read.
*/
size_type head;
/**
* The next index to be written to.
*/
size_type tail;
const size_type size;
const pointer_type data;
public:
constexpr CircularBuffer(pointer_type _data, size_type _size)
:head(0), tail(0), size(_size), data(_data) {}
CircularBuffer(const CircularBuffer &other) = delete;
protected:
constexpr size_type Next(size_type i) const {
return i + 1 == size
? 0
: i + 1;
}
public:
void Clear() {
head = tail = 0;
}
size_type GetSize() const {
return size;
}
constexpr bool IsEmpty() const {
return head == tail;
}
constexpr bool IsFull() const {
return Next(tail) == head;
}
/**
* Prepares writing. Returns a buffer range which may be written.
* When you are finished, call Append().
*/
Range Write() {
assert(head < size);
assert(tail < size);
size_type end = tail < head
? head - 1
/* the "head==0" is there so we don't write
the last cell, as this situation cannot be
represented by head/tail */
: size - (head == 0);
return Range(data + tail, end - tail);
}
/**
* Expands the tail of the buffer, after data has been written
* to the buffer returned by Write().
*/
void Append(size_type n) {
assert(head < size);
assert(tail < size);
assert(n < size);
assert(tail + n <= size);
assert(head <= tail || tail + n < head);
tail += n;
if (tail == size) {
assert(head > 0);
tail = 0;
}
}
/**
* Return a buffer range which may be read. The buffer pointer is
* writable, to allow modifications while parsing.
*/
Range Read() {
assert(head < size);
assert(tail < size);
return Range(data + head, (tail < head ? size : tail) - head);
}
/**
* Marks a chunk as consumed.
*/
void Consume(size_type n) {
assert(head < size);
assert(tail < size);
assert(n < size);
assert(head + n <= size);
assert(tail < head || head + n <= tail);
head += n;
if (head == size)
head = 0;
}
};
#endif
|
