xref: /illumos-gate/usr/src/lib/libc/port/stdio/ftell.c (revision cf3ec608)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1988 AT&T	*/
/*	  All Rights Reserved	*/

/*
 * Return file offset.
 * Coordinates with buffering.
 */
#pragma weak _ftell = ftell

#include "lint.h"
#include "file64.h"
#include "mtlib.h"
#include <fcntl.h>
#include <stdio.h>
#include <thread.h>
#include <synch.h>
#include <errno.h>
#include <unistd.h>
#include <stddef.h>
#include <limits.h>
#include <sys/types.h>
#include "stdiom.h"

off64_t
ftell_common(FILE *iop)
{
	ptrdiff_t adjust;
	off64_t	tres;
	rmutex_t *lk;

	FLOCKFILE(lk, iop);

	/*
	 * If we're dealing with a memory stream, we need to flush the internal
	 * state before we try and determine the location. This is especially
	 * important for open_wmemstream() as it will have buffered bytes, but
	 * we need to convert that to wide characters before we proceed. If we
	 * have no file descriptor, then the units that the backing store are in
	 * can be arbitrary.
	 */
	if (_get_fd(iop) == -1) {
		(void) _fflush_u(iop);
	}

	if (iop->_cnt < 0)
		iop->_cnt = 0;
	if (iop->_flag & _IOREAD) {
		adjust = (ptrdiff_t)-iop->_cnt;
	} else if (iop->_flag & (_IOWRT | _IORW)) {
		adjust = 0;
		if (((iop->_flag & (_IOWRT | _IONBF)) == _IOWRT) &&
		    (iop->_base != 0)) {
			adjust = iop->_ptr - iop->_base;
		} else if ((iop->_flag & _IORW) && (iop->_base != 0)) {
			adjust = (ptrdiff_t)-iop->_cnt;
		}
	} else {
		errno = EBADF;	/* file descriptor refers to no open file */
		FUNLOCKFILE(lk);
		return (EOF);
	}

	tres = _xseek64(iop, 0, SEEK_CUR);
	if (tres >= 0)
		tres += adjust;

	FUNLOCKFILE(lk);
	return (tres);
}

long
ftell(FILE *iop)
{
	off64_t	tres;

	tres = ftell_common(iop);
	if (tres > LONG_MAX) {
		errno = EOVERFLOW;
		return (EOF);
	}

	return ((long)tres);
}