/* 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 */