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
|
/*
* Copyright (c) 2015 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Circular character buffer.
*/
#ifndef _KERN_CBUF_H
#define _KERN_CBUF_H
#include <stddef.h>
/*
* Circular buffer descriptor.
*
* The buffer capacity must be a power-of-two. Indexes are absolute values
* which can overflow. Their difference cannot exceed the capacity.
*/
struct cbuf {
char *buf;
size_t capacity;
size_t start;
size_t end;
};
static inline size_t
cbuf_capacity(const struct cbuf *cbuf)
{
return cbuf->capacity;
}
static inline size_t
cbuf_start(const struct cbuf *cbuf)
{
return cbuf->start;
}
static inline size_t
cbuf_end(const struct cbuf *cbuf)
{
return cbuf->end;
}
static inline size_t
cbuf_size(const struct cbuf *cbuf)
{
return cbuf->end - cbuf->start;
}
static inline void
cbuf_clear(struct cbuf *cbuf)
{
cbuf->start = cbuf->end;
}
/*
* Initialize a circular buffer.
*
* The descriptor is set to use the given buffer for storage. Capacity
* must be a power-of-two.
*/
void cbuf_init(struct cbuf *cbuf, char *buf, size_t capacity);
/*
* Append a byte to a circular buffer.
*
* The end index is incremented. If the buffer is full, the oldest byte
* is overwritten and the start index is updated accordingly.
*/
void cbuf_push(struct cbuf *cbuf, char byte);
/*
* Read a byte from a circular buffer.
*
* If the buffer is empty, ERROR_AGAIN is returned. Otherwise, the oldest
* byte is stored at the bytep address, the start index is incremented,
* and 0 is returned.
*/
int cbuf_pop(struct cbuf *cbuf, char *bytep);
/*
* Write into a circular buffer at a specific location.
*
* If the given index is outside buffer boundaries, ERROR_INVAL is returned.
* Otherwise size bytes are copied into the circular buffer. If the range
* in the circular buffer goes beyond its end, the end index is updated as
* appropriate. If the buffer is full when extending its end, the oldest
* bytes are overwritten and the start index is updated accordingly.
*/
int cbuf_write(struct cbuf *cbuf, size_t index, const void *buf, size_t size);
/*
* Read from a circular buffer at a specific location.
*
* If the given index is outside buffer boundaries, ERROR_INVAL is returned.
* Otherwise at most *sizep bytes are copied into the given byte buffer,
* and *sizep is updated to the number of bytes actually copied.
*
* The circular buffer isn't changed by this operation.
*/
int cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep);
#endif /* _KERN_CBUF_H */
|
