Libc-262.tar.gz

[apple/libc.git] / stdio / ftell.c

/*
 * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include <sys/types.h>
#include <stdio.h>
#include <errno.h>
#include "local.h"

/*
 * ftello: return current offset.
 */
off_t
ftello(fp)
	register FILE *fp;
{
	register fpos_t pos;

	if (fp->_seek == NULL) {
		errno = ESPIPE;			/* historic practice */
		return (-1L);
	}

	/* FLOCKFILE(fp); */
	/*
	 * Find offset of underlying I/O object, then
	 * adjust for buffered bytes.
	 */
	if (fp->_flags & __SOFF)
		pos = fp->_offset;
	else {
		pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
		if (pos == -1) {
		        /* FUNLOCKFILE(fp); */
			return (pos);
		}
	}
	if (fp->_flags & __SRD) {
		/*
		 * Reading.  Any unread characters (including
		 * those from ungetc) cause the position to be
		 * smaller than that in the underlying object.
		 */
		pos -= fp->_r;
		if (HASUB(fp))
			pos -= fp->_ur;
	} else if (fp->_flags & __SWR && fp->_p != NULL) {
		/*
		 * Writing.  Any buffered characters cause the
		 * position to be greater than that in the
		 * underlying object.
		 */
		pos += fp->_p - fp->_bf._base;
	}
	/* FUNLOCKFILE(fp); */
	return (pos);
}

/*
 * standard ftell function.
 */
long
ftell(fp)
        register FILE *fp;
{
        register off_t rv;
        rv = ftello(fp);
        if ((long)rv != rv) {
                errno = EOVERFLOW;
                return (-1);
        }
        return (rv);
}