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
|
/*-
* Copyright (c) 2007-2009 Dag-Erling Coïdan Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer
* in this position and unchanged.
* 2. 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 AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/file.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdarg.h>
#include <unistd.h>
#include <libutil.h>
/*
* Reliably open and lock a file.
*
* Please do not modify this code without first reading the revision history
* and discussing your changes with <des@freebsd.org>. Don't be fooled by the
* code's apparent simplicity; there would be no need for this function if it
* was easy to get right.
*/
int
flopen(const char *path, int flags, ...)
{
int fd, operation, serrno, trunc;
struct stat sb, fsb;
mode_t mode;
#ifdef O_EXLOCK
flags &= ~O_EXLOCK;
#endif
mode = 0;
if (flags & O_CREAT) {
va_list ap;
va_start(ap, flags);
mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
va_end(ap);
}
operation = LOCK_EX;
if (flags & O_NONBLOCK)
operation |= LOCK_NB;
trunc = (flags & O_TRUNC);
flags &= ~O_TRUNC;
for (;;) {
if ((fd = open(path, flags, mode)) == -1)
/* non-existent or no access */
return (-1);
if (flock(fd, operation) == -1) {
/* unsupported or interrupted */
serrno = errno;
(void)close(fd);
errno = serrno;
return (-1);
}
if (stat(path, &sb) == -1) {
/* disappeared from under our feet */
(void)close(fd);
continue;
}
if (fstat(fd, &fsb) == -1) {
/* can't happen [tm] */
serrno = errno;
(void)close(fd);
errno = serrno;
return (-1);
}
if (sb.st_dev != fsb.st_dev ||
sb.st_ino != fsb.st_ino) {
/* changed under our feet */
(void)close(fd);
continue;
}
if (trunc && ftruncate(fd, 0) != 0) {
/* can't happen [tm] */
serrno = errno;
(void)close(fd);
errno = serrno;
return (-1);
}
/*
* The following change is provided as a specific example to
* avoid.
*/
#if 0
if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) {
serrno = errno;
(void)close(fd);
errno = serrno;
return (-1);
}
#endif
return (fd);
}
}
|
