Colony » Colony Scout » Colony Scout OS

/*-

 * 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 <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include "local.h"

#define        POS_ERR        (-(fpos_t)1)

/*

 * Seek the given file to the given offset.

 * `Whence' must be one of the three SEEK_* macros.

 */

int

fseek(fp, offset, whence)

        FILE *fp;

        long offset;

        int whence;

{

        fpos_t curoff;

        int havepos;

        /* make sure stdio is set up */

        if (!__sdidinit)

                __sinit();

        /*

         * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.

         * After this, whence is either SEEK_SET or SEEK_END.

         */

        switch (whence) {

        case SEEK_CUR:

                /*

                 * In order to seek relative to the current stream offset,

                 * we have to first find the current stream offset a la

                 * ftell (see ftell for details).

                 */

                curoff = __sseek(fp, (fpos_t)0, SEEK_CUR);

                if (curoff == POS_ERR)

                        return (EOF);

                if (fp->_flags & __SRD) {

                        curoff -= fp->_r;

                        if (HASUB(fp))

                                curoff -= fp->_ur;

                } else if (fp->_flags & __SWR && fp->_p != NULL)

                        curoff += fp->_p - fp->_bf._base;

                offset += curoff;

                whence = SEEK_SET;

                havepos = 1;

                break;

        case SEEK_SET:

        case SEEK_END:

                curoff = 0;                /* XXX just to keep gcc quiet */

                havepos = 0;

                break;

        default:

                errno = EINVAL;

                return (EOF);

        }

        if (fp->_bf._base == NULL)

                __smakebuf(fp);

        if (__sflush(fp) ||

            __sseek(fp, (fpos_t)offset, whence) == POS_ERR) {

                return (EOF);

        }

        /* success: clear EOF indicator and discard ungetc() data */

        if (HASUB(fp))

                FREEUB(fp);

        fp->_p = fp->_bf._base;

        fp->_r = 0;

        /* fp->_w = 0; */        /* unnecessary (I think...) */

        fp->_flags &= ~__SEOF;

        return (0);

}