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
|
/*
* 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/>.
*/
#include <assert.h>
#include <kern/cbuf.h>
#include <kern/error.h>
#include <kern/macros.h>
/* Negative close to 0 so that an overflow occurs early */
#define CBUF_INIT_INDEX ((unsigned long)-500)
void
cbuf_init(struct cbuf *cbuf, char *buf, unsigned long capacity)
{
assert(ISP2(capacity));
cbuf->buf = buf;
cbuf->capacity = capacity;
cbuf->start = CBUF_INIT_INDEX;
cbuf->end = cbuf->start;
}
static unsigned long
cbuf_index(const struct cbuf *cbuf, unsigned long abs_index)
{
return abs_index & (cbuf->capacity - 1);
}
void
cbuf_push(struct cbuf *cbuf, char byte)
{
cbuf->buf[cbuf_index(cbuf, cbuf->end)] = byte;
cbuf->end++;
/* Mind integer overflows */
if (cbuf_size(cbuf) > cbuf->capacity) {
cbuf->start = cbuf->end - cbuf->capacity;
}
}
int
cbuf_pop(struct cbuf *cbuf, char *bytep)
{
if (cbuf_size(cbuf) == 0) {
return ERROR_AGAIN;
}
*bytep = cbuf->buf[cbuf_index(cbuf, cbuf->start)];
cbuf->start++;
return 0;
}
int
cbuf_read(const struct cbuf *cbuf, unsigned long index, char *bytep)
{
/* Mind integer overflows */
if ((cbuf->end - index - 1) >= cbuf_size(cbuf)) {
return ERROR_INVAL;
}
*bytep = cbuf->buf[cbuf_index(cbuf, index)];
return 0;
}
|
