1 /* ftruncate emulations that work on some System V's.
2 This file is in the public domain. */
3
4 #ifdef HAVE_CONFIG_H
5 #include "config.h"
6 #endif
7
8 #include <sys/types.h>
9 #include <fcntl.h>
10
11 #ifdef F_CHSIZE
12 int
ftruncate(fd,length)13 ftruncate (fd, length)
14 int fd;
15 off_t length;
16 {
17 return fcntl (fd, F_CHSIZE, length);
18 }
19 #else
20 #ifdef F_FREESP
21 /* The following function was written by
22 kucharsk@Solbourne.com (William Kucharski) */
23
24 #include <sys/stat.h>
25 #include <errno.h>
26 #include <unistd.h>
27
28 int
ftruncate(fd,length)29 ftruncate (fd, length)
30 int fd;
31 off_t length;
32 {
33 struct flock fl;
34 struct stat filebuf;
35
36 if (fstat (fd, &filebuf) < 0)
37 return -1;
38
39 if (filebuf.st_size < length)
40 {
41 /* Extend file length. */
42 if (lseek (fd, (length - 1), SEEK_SET) < 0)
43 return -1;
44
45 /* Write a "0" byte. */
46 if (write (fd, "", 1) != 1)
47 return -1;
48 }
49 else
50 {
51 /* Truncate length. */
52 fl.l_whence = 0;
53 fl.l_len = 0;
54 fl.l_start = length;
55 fl.l_type = F_WRLCK; /* Write lock on file space. */
56
57 /* This relies on the UNDOCUMENTED F_FREESP argument to
58 fcntl, which truncates the file so that it ends at the
59 position indicated by fl.l_start.
60 Will minor miracles never cease? */
61 if (fcntl (fd, F_FREESP, &fl) < 0)
62 return -1;
63 }
64
65 return 0;
66 }
67 #else
68 int
ftruncate(fd,length)69 ftruncate (fd, length)
70 int fd;
71 off_t length;
72 {
73 return chsize (fd, length);
74 }
75 #endif
76 #endif
77