/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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. 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 "namespace.h"
#include <sys/types.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include "un-namespace.h"
#include "local.h"
#include "libc_private.h"

/*
 * standard ftell function.
 */
long
ftell(FILE *fp)
{
        off_t rv;

        rv = ftello(fp);
        if (rv > LONG_MAX) {
                errno = EOVERFLOW;
                return (-1);
        }
        return (rv);
}

/*
 * ftello: return current offset.
 */
off_t
ftello(FILE *fp)
{
        fpos_t rv;
        int ret;

        FLOCKFILE(fp);
        ret = _ftello(fp, &rv);
        FUNLOCKFILE(fp);
        if (ret)
                return (-1);
        if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
                errno = ESPIPE;
                return (-1);
        }
        return (rv);
}

int
_ftello(FILE *fp, fpos_t *offset)
{
        fpos_t pos;
        size_t n;

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

        /*
         * Find offset of underlying I/O object, then
         * adjust for buffered bytes.
         */
        if (!(fp->_flags & __SRD) && (fp->_flags & __SWR) &&
            fp->_p != NULL && fp->_p - fp->_bf._base > 0 &&
            ((fp->_flags & __SAPP) || (fp->_flags2 & __S2OAP))) {
                pos = _sseek(fp, (fpos_t)0, SEEK_END);
                if (pos == -1)
                        return (1);
        } else if (fp->_flags & __SOFF)
                pos = fp->_offset;
        else {
                pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
                if (pos == -1)
                        return (1);
        }
        if (fp->_flags & __SRD) {
                /*
                 * Reading.  Any unread characters (including
                 * those from ungetc) cause the position to be
                 * smaller than that in the underlying object.
                 */
                if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
                        fp->_flags |= __SERR;
                        errno = EIO;
                        return (1);
                }
                if (HASUB(fp))
                        pos -= fp->_r;  /* Can be negative at this point. */
        } else if ((fp->_flags & __SWR) && fp->_p != NULL &&
            (n = fp->_p - fp->_bf._base) > 0) {
                /*
                 * Writing.  Any buffered characters cause the
                 * position to be greater than that in the
                 * underlying object.
                 */
                if (pos > OFF_MAX - n) {
                        errno = EOVERFLOW;
                        return (1);
                }
                pos += n;
        }
        *offset = pos;
        return (0);
}