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/*-
 * 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)ftell.c     8.1 (Berkeley) 6/4/93";
#endif
static const char rcsid[] =
                "$\Id: ftell.c,v 1.5 1996/06/22 10:33:25 jraynard Exp $";
#endif /* LIBC_SCCS and not lint */

#include <stdio.h>
#include <errno.h>
#include "local.h"
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
#endif

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

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

#ifdef _THREAD_SAFE
        _thread_flockfile(fp, __FILE__, __LINE__);
#endif
        /*
         * 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) {
#ifdef _THREAD_SAFE
                        _thread_funlockfile(fp);
#endif
                        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;
        }
#ifdef _THREAD_SAFE
        _thread_funlockfile(fp);
#endif
        return (pos);
}