1 /* ftruncate emulations that work on some System V's.
2    This file is in the public domain.  */
3 
4 /* Copyright (C) 2012-2016 Free Software Foundation, Inc.
5 
6    This file is part of gold.
7 
8    This program is free software; you can redistribute it and/or modify
9    it under the terms of the GNU General Public License as published by
10    the Free Software Foundation; either version 3 of the License, or
11    (at your option) any later version.
12 
13    This program is distributed in the hope that it will be useful,
14    but WITHOUT ANY WARRANTY; without even the implied warranty of
15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16    GNU General Public License for more details.
17 
18    You should have received a copy of the GNU General Public License
19    along with this program; if not, write to the Free Software
20    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21    MA 02110-1301, USA.  */
22 
23 #include <config.h>
24 
25 /* Specification.  */
26 #include <unistd.h>
27 
28 #include <sys/types.h>
29 #include <fcntl.h>
30 
31 extern int ftruncate (int, off_t);
32 
33 #ifdef F_CHSIZE
34 
35 int
ftruncate(int fd,off_t length)36 ftruncate (int fd, off_t length)
37 {
38   return fcntl (fd, F_CHSIZE, length);
39 }
40 
41 #else /* not F_CHSIZE */
42 # ifdef F_FREESP
43 
44 /* By William Kucharski <kucharsk@netcom.com>.  */
45 
46 #  include <sys/stat.h>
47 #  include <errno.h>
48 
49 int
ftruncate(int fd,off_t length)50 ftruncate (int fd, off_t length)
51 {
52   struct flock fl;
53   struct stat filebuf;
54 
55   if (fstat (fd, &filebuf) < 0)
56     return -1;
57 
58   if (filebuf.st_size < length)
59     {
60       /* Extend file length. */
61       if (lseek (fd, (length - 1), SEEK_SET) < 0)
62 	return -1;
63 
64       /* Write a "0" byte. */
65       if (write (fd, "", 1) != 1)
66 	return -1;
67     }
68   else
69     {
70 
71       /* Truncate length. */
72 
73       fl.l_whence = 0;
74       fl.l_len = 0;
75       fl.l_start = length;
76       fl.l_type = F_WRLCK;	/* write lock on file space */
77 
78       /* This relies on the *undocumented* F_FREESP argument to fcntl,
79 	 which truncates the file so that it ends at the position
80 	 indicated by fl.l_start.  Will minor miracles never cease?  */
81 
82       if (fcntl (fd, F_FREESP, &fl) < 0)
83 	return -1;
84     }
85 
86   return 0;
87 }
88 
89 # else /* not F_CHSIZE nor F_FREESP */
90 #  if HAVE_CHSIZE                      /* native Windows, e.g. mingw */
91 
92 int
ftruncate(int fd,off_t length)93 ftruncate (int fd, off_t length)
94 {
95   return chsize (fd, length);
96 }
97 
98 #  else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
99 
100 #   include <errno.h>
101 
102 int
ftruncate(int fd,off_t length)103 ftruncate (int fd, off_t length)
104 {
105   errno = EIO;
106   return -1;
107 }
108 
109 #  endif /* not HAVE_CHSIZE */
110 # endif /* not F_FREESP */
111 #endif /* not F_CHSIZE */
112