1/* ftruncate emulations that work on some System V's.
2   This file is in the public domain.  */
3
4#include <config.h>
5
6/* Specification.  */
7#include <unistd.h>
8
9#include <sys/types.h>
10#include <fcntl.h>
11
12#ifdef F_CHSIZE
13
14int
15ftruncate (int fd, off_t length)
16{
17  return fcntl (fd, F_CHSIZE, length);
18}
19
20#else /* not F_CHSIZE */
21# ifdef F_FREESP
22
23/* By William Kucharski <kucharsk@netcom.com>.  */
24
25#  include <sys/stat.h>
26#  include <errno.h>
27
28int
29ftruncate (int fd, off_t length)
30{
31  struct flock fl;
32  struct stat filebuf;
33
34  if (fstat (fd, &filebuf) < 0)
35    return -1;
36
37  if (filebuf.st_size < length)
38    {
39      /* Extend file length. */
40      if (lseek (fd, (length - 1), SEEK_SET) < 0)
41	return -1;
42
43      /* Write a "0" byte. */
44      if (write (fd, "", 1) != 1)
45	return -1;
46    }
47  else
48    {
49
50      /* Truncate length. */
51
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 fcntl,
58	 which truncates the file so that it ends at the position
59	 indicated by fl.l_start.  Will minor miracles never cease?  */
60
61      if (fcntl (fd, F_FREESP, &fl) < 0)
62	return -1;
63    }
64
65  return 0;
66}
67
68# else /* not F_CHSIZE nor F_FREESP */
69#  if HAVE_CHSIZE                      /* native Windows, e.g. mingw */
70
71int
72ftruncate (int fd, off_t length)
73{
74  return chsize (fd, length);
75}
76
77#  else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
78
79#   include <errno.h>
80
81int
82ftruncate (int fd, off_t length)
83{
84  errno = EIO;
85  return -1;
86}
87
88#  endif /* not HAVE_CHSIZE */
89# endif /* not F_FREESP */
90#endif /* not F_CHSIZE */
91