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 <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "local.h"

int

ungetc(c, fp)

        int c;

        FILE *fp;

{

        if (c == EOF)

                return (EOF);

        if (!__sdidinit)

                __sinit();

        if ((fp->_flags & __SRD) == 0) {

                /*

                 * Not already reading: no good unless reading-and-writing.

                 * Otherwise, flush any current write stuff.

                 */

                if ((fp->_flags & __SRW) == 0)

                        return (EOF);

                if (fp->_flags & __SWR) {

                        if (__sflush(fp))

                                return (EOF);

                        fp->_flags &= ~__SWR;

                        fp->_w = 0;

                }

                fp->_flags |= __SRD;

        }

        c = (unsigned char)c;

        /*

         * If we are in the middle of ungetc'ing, just continue.

         */

        if (HASUB(fp)) {

                if (fp->_r >= fp->_ub._size)

                        return (EOF);

                *--fp->_p = c;

                fp->_r++;

                return (c);

        }

        fp->_flags &= ~__SEOF;

        /*

         * If we can handle this by simply backing up, do so,

         * but never replace the original character.

         * (This makes sscanf() work when scanning `const' data.)

         */

        if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&

            fp->_p[-1] == c) {

                fp->_p--;

                fp->_r++;

                return (c);

        }

        /*

         * Create an ungetc buffer.

         * we will use the `reserve' buffer.

         */

        fp->_ur = fp->_r;

        fp->_up = fp->_p;

        fp->_ub._base = fp->_ubuf;

        fp->_ub._size = sizeof(fp->_ubuf);

        fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;

        fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];

        fp->_r = 1;

        return (c);

}