summaryrefslogtreecommitdiff
path: root/lib/ftruncate.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/ftruncate.c')
-rw-r--r--lib/ftruncate.c90
1 files changed, 90 insertions, 0 deletions
diff --git a/lib/ftruncate.c b/lib/ftruncate.c
new file mode 100644
index 0000000..ff7d11b
--- /dev/null
+++ b/lib/ftruncate.c
@@ -0,0 +1,90 @@
+/* ftruncate emulations that work on some System V's.
+ This file is in the public domain. */
+
+#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <fcntl.h>
+
+#ifdef F_CHSIZE
+
+int
+ftruncate (int fd, off_t length)
+{
+ return fcntl (fd, F_CHSIZE, length);
+}
+
+#else /* not F_CHSIZE */
+# ifdef F_FREESP
+
+/* By William Kucharski <kucharsk@netcom.com>. */
+
+# include <sys/stat.h>
+# include <errno.h>
+
+int
+ftruncate (int fd, off_t length)
+{
+ struct flock fl;
+ struct stat filebuf;
+
+ if (fstat (fd, &filebuf) < 0)
+ return -1;
+
+ if (filebuf.st_size < length)
+ {
+ /* Extend file length. */
+ if (lseek (fd, (length - 1), SEEK_SET) < 0)
+ return -1;
+
+ /* Write a "0" byte. */
+ if (write (fd, "", 1) != 1)
+ return -1;
+ }
+ else
+ {
+
+ /* Truncate length. */
+
+ fl.l_whence = 0;
+ fl.l_len = 0;
+ fl.l_start = length;
+ fl.l_type = F_WRLCK; /* write lock on file space */
+
+ /* This relies on the *undocumented* F_FREESP argument to fcntl,
+ which truncates the file so that it ends at the position
+ indicated by fl.l_start. Will minor miracles never cease? */
+
+ if (fcntl (fd, F_FREESP, &fl) < 0)
+ return -1;
+ }
+
+ return 0;
+}
+
+# else /* not F_CHSIZE nor F_FREESP */
+# if HAVE_CHSIZE /* native Windows, e.g. mingw */
+
+int
+ftruncate (int fd, off_t length)
+{
+ return chsize (fd, length);
+}
+
+# else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
+
+# include <errno.h>
+
+int
+ftruncate (int fd, off_t length)
+{
+ errno = EIO;
+ return -1;
+}
+
+# endif /* not HAVE_CHSIZE */
+# endif /* not F_FREESP */
+#endif /* not F_CHSIZE */