| /* 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> |
| |
| extern int ftruncate (int, off_t); |
| |
| #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 */ |