1 #ifndef LINT
2 static const char rcsid[] = "$Id: ftruncate.c,v 1.3 2005/04/27 18:16:45 sra Exp $";
3 #endif
4 
5 /*! \file
6  * \brief
7  * ftruncate - set file size, BSD Style
8  *
9  * shortens or enlarges the file as neeeded
10  * uses some undocumented locking call. It is known to work on SCO unix,
11  * other vendors should try.
12  * The #error directive prevents unsupported OSes
13  */
14 
15 #include "port_before.h"
16 
17 #if defined(M_UNIX)
18 #define OWN_FTRUNCATE
19 #include <stdio.h>
20 #ifdef _XOPEN_SOURCE
21 #undef _XOPEN_SOURCE
22 #endif
23 #ifdef _POSIX_SOURCE
24 #undef _POSIX_SOURCE
25 #endif
26 
27 #include <fcntl.h>
28 
29 #include "port_after.h"
30 
31 int
32 __ftruncate(int fd, long wantsize) {
33 	long cursize;
34 
35 	/* determine current file size */
36 	if ((cursize = lseek(fd, 0L, 2)) == -1)
37 		return (-1);
38 
39 	/* maybe lengthen... */
40 	if (cursize < wantsize) {
41 		if (lseek(fd, wantsize - 1, 0) == -1 ||
42 		    write(fd, "", 1) == -1) {
43 			return (-1);
44 		}
45 		return (0);
46 	}
47 
48 	/* maybe shorten... */
49 	if (wantsize < cursize) {
50 		struct flock fl;
51 
52 		fl.l_whence = 0;
53 		fl.l_len = 0;
54 		fl.l_start = wantsize;
55 		fl.l_type = F_WRLCK;
56 		return (fcntl(fd, F_FREESP, &fl));
57 	}
58 	return (0);
59 }
60 #endif
61 
62 #ifndef OWN_FTRUNCATE
63 int __bindcompat_ftruncate;
64 #endif
65