port/stdio/ftell.c

/*
 * 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   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * 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"

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

    FLOCKFILE(lk, 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 = lseek64(FILENO(iop), 0, SEEK_CUR);
    if (tres >= 0)
        tres += adjust;

    if (tres > LONG_MAX) {
        errno = EOVERFLOW;
        FUNLOCKFILE(lk);
        return (EOF);
    }

    FUNLOCKFILE(lk);
    return ((long)tres);
}