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
|
/* ProcFS - buf.c - output buffer management for read calls */
#include "inc.h"
#include <stdarg.h>
static char *buf;
static size_t left, used;
static off_t skip;
/*
* Initialize the buffer for fresh use. The output is to be stored into 'ptr'
* which is BUF_SIZE bytes in size, since that is the size we requested. Due
* to the way vsnprintf works, we cannot use the last byte of this buffer. The
* first 'start' bytes of the produced output are to be skipped. After that, a
* total of 'len' bytes are requested.
*/
void
buf_init(char * ptr, size_t len, off_t start)
{
buf = ptr;
skip = start;
left = MIN(len, BUF_SIZE - 1);
used = 0;
}
/*
* Add formatted text to the end of the buffer.
*/
void
buf_printf(char * fmt, ...)
{
va_list args;
ssize_t len, max;
if (left == 0)
return;
/*
* There is no way to estimate how much space the result will take, so
* we need to produce the string even when skipping part of the start.
* The null terminating character is not part of the result, so room
* must be given for it to be stored after completely filling up the
* requested part of the buffer.
*/
max = MIN(skip + left + 1, BUF_SIZE);
va_start(args, fmt);
len = vsnprintf(&buf[used], max, fmt, args);
va_end(args);
/*
* The snprintf family returns the number of bytes that would be stored
* if the buffer were large enough, excluding the null terminator.
*/
if (len >= BUF_SIZE)
len = BUF_SIZE - 1;
if (skip > 0) {
assert(used == 0);
if (skip >= len) {
skip -= len;
return;
}
memmove(buf, &buf[skip], len - skip);
len -= skip;
skip = 0;
}
assert(skip == 0);
assert(len >= 0);
assert((ssize_t) left >= 0);
if (len > (ssize_t)left)
len = left;
used += len;
left -= len;
}
/*
* Add arbitrary data to the end of the buffer.
*/
void
buf_append(char * data, size_t len)
{
if (left == 0)
return;
if (skip > 0) {
if (skip >= (ssize_t)len) {
skip -= len;
return;
}
data += skip;
len -= skip;
skip = 0;
}
if (len > left)
len = left;
memcpy(&buf[used], data, len);
used += len;
left -= len;
}
/*
* Return the resulting number of bytes produced, not counting the trailing
* null character in the buffer.
*/
ssize_t
buf_result(void)
{
return used;
}
|
