xref: /minix3/lib/libc/stdio/ftell.c (revision f14fb602092e015ff630df58e17c2a9cd57d29b3)
1*f14fb602SLionel Sambuc /*	$NetBSD: ftell.c,v 1.20 2012/03/27 15:05:42 christos Exp $	*/
22fe8fb19SBen Gras 
32fe8fb19SBen Gras /*-
42fe8fb19SBen Gras  * Copyright (c) 1990, 1993
52fe8fb19SBen Gras  *	The Regents of the University of California.  All rights reserved.
62fe8fb19SBen Gras  *
72fe8fb19SBen Gras  * This code is derived from software contributed to Berkeley by
82fe8fb19SBen Gras  * Chris Torek.
92fe8fb19SBen Gras  *
102fe8fb19SBen Gras  * Redistribution and use in source and binary forms, with or without
112fe8fb19SBen Gras  * modification, are permitted provided that the following conditions
122fe8fb19SBen Gras  * are met:
132fe8fb19SBen Gras  * 1. Redistributions of source code must retain the above copyright
142fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer.
152fe8fb19SBen Gras  * 2. Redistributions in binary form must reproduce the above copyright
162fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer in the
172fe8fb19SBen Gras  *    documentation and/or other materials provided with the distribution.
182fe8fb19SBen Gras  * 3. Neither the name of the University nor the names of its contributors
192fe8fb19SBen Gras  *    may be used to endorse or promote products derived from this software
202fe8fb19SBen Gras  *    without specific prior written permission.
212fe8fb19SBen Gras  *
222fe8fb19SBen Gras  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
232fe8fb19SBen Gras  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
242fe8fb19SBen Gras  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
252fe8fb19SBen Gras  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
262fe8fb19SBen Gras  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
272fe8fb19SBen Gras  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
282fe8fb19SBen Gras  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
292fe8fb19SBen Gras  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
302fe8fb19SBen Gras  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
312fe8fb19SBen Gras  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
322fe8fb19SBen Gras  * SUCH DAMAGE.
33b7061124SArun Thomas  */
342fe8fb19SBen Gras 
352fe8fb19SBen Gras #include <sys/cdefs.h>
362fe8fb19SBen Gras #if defined(LIBC_SCCS) && !defined(lint)
372fe8fb19SBen Gras #if 0
382fe8fb19SBen Gras static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
392fe8fb19SBen Gras #else
40*f14fb602SLionel Sambuc __RCSID("$NetBSD: ftell.c,v 1.20 2012/03/27 15:05:42 christos Exp $");
412fe8fb19SBen Gras #endif
422fe8fb19SBen Gras #endif /* LIBC_SCCS and not lint */
43b7061124SArun Thomas 
44551374c2SErik van der Kouwe #include <assert.h>
452fe8fb19SBen Gras #include <errno.h>
46b7061124SArun Thomas #include <stdio.h>
472fe8fb19SBen Gras #include "reentrant.h"
482fe8fb19SBen Gras #include "local.h"
49b7061124SArun Thomas 
502fe8fb19SBen Gras /*
512fe8fb19SBen Gras  * ftell: return current offset.
522fe8fb19SBen Gras  */
532fe8fb19SBen Gras long
ftell(FILE * fp)54*f14fb602SLionel Sambuc ftell(FILE *fp)
55b7061124SArun Thomas {
56*f14fb602SLionel Sambuc 	off_t pos;
572fe8fb19SBen Gras 
582fe8fb19SBen Gras 
592fe8fb19SBen Gras 	FLOCKFILE(fp);
602fe8fb19SBen Gras 
612fe8fb19SBen Gras 	if (fp->_seek == NULL) {
622fe8fb19SBen Gras 		FUNLOCKFILE(fp);
632fe8fb19SBen Gras 		errno = ESPIPE;			/* historic practice */
642fe8fb19SBen Gras 		return -1L;
65551374c2SErik van der Kouwe 	}
66551374c2SErik van der Kouwe 
672fe8fb19SBen Gras 	/*
682fe8fb19SBen Gras 	 * Find offset of underlying I/O object, then
692fe8fb19SBen Gras 	 * adjust for buffered bytes.
702fe8fb19SBen Gras 	 */
71*f14fb602SLionel Sambuc 	(void)__sflush(fp); /* may adjust seek offset on append stream */
722fe8fb19SBen Gras 	if (fp->_flags & __SOFF)
732fe8fb19SBen Gras 		pos = fp->_offset;
742fe8fb19SBen Gras 	else {
75*f14fb602SLionel Sambuc 		pos = (*fp->_seek)(fp->_cookie, (off_t)0, SEEK_CUR);
762fe8fb19SBen Gras 		if (pos == -1L) {
772fe8fb19SBen Gras 			FUNLOCKFILE(fp);
78*f14fb602SLionel Sambuc 			return (long)pos;
792fe8fb19SBen Gras 		}
802fe8fb19SBen Gras 	}
812fe8fb19SBen Gras 	if (fp->_flags & __SRD) {
822fe8fb19SBen Gras 		/*
832fe8fb19SBen Gras 		 * Reading.  Any unread characters (including
842fe8fb19SBen Gras 		 * those from ungetc) cause the position to be
852fe8fb19SBen Gras 		 * smaller than that in the underlying object.
862fe8fb19SBen Gras 		 */
872fe8fb19SBen Gras 		pos -= fp->_r;
882fe8fb19SBen Gras 		if (HASUB(fp))
892fe8fb19SBen Gras 			pos -= fp->_ur;
902fe8fb19SBen Gras 	} else if (fp->_flags & __SWR && fp->_p != NULL) {
912fe8fb19SBen Gras 		/*
922fe8fb19SBen Gras 		 * Writing.  Any buffered characters cause the
932fe8fb19SBen Gras 		 * position to be greater than that in the
942fe8fb19SBen Gras 		 * underlying object.
952fe8fb19SBen Gras 		 */
962fe8fb19SBen Gras 		pos += fp->_p - fp->_bf._base;
972fe8fb19SBen Gras 	}
982fe8fb19SBen Gras 	FUNLOCKFILE(fp);
99b7061124SArun Thomas 
100*f14fb602SLionel Sambuc 	if (__long_overflow(pos)) {
1012fe8fb19SBen Gras 		errno = EOVERFLOW;
1022fe8fb19SBen Gras 		return -1L;
1032fe8fb19SBen Gras 	}
104b7061124SArun Thomas 
105*f14fb602SLionel Sambuc 	return (long)pos;
106b7061124SArun Thomas }
107