source: mainline/tetris/input.c@ 854387b

/*      $OpenBSD: input.c,v 1.12 2005/04/13 02:33:08 deraadt Exp $      */
/*    $NetBSD: input.c,v 1.3 1996/02/06 22:47:33 jtc Exp $    */

/*-
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek and Darren F. Provine.
 *
 * 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.
 *
 *      @(#)input.c     8.1 (Berkeley) 5/31/93
 */

/*
 * Tetris input.
 */

#include <sys/types.h>
#include <sys/time.h>

#include <errno.h>
#include <unistd.h>
#include <string.h>

#include "input.h"
#include "tetris.h"

/* return true iff the given timeval is positive */
#define TV_POS(tv) \
        ((tv)->tv_sec > 0 || ((tv)->tv_sec == 0 && (tv)->tv_usec > 0))

/* subtract timeval `sub' from `res' */
#define TV_SUB(res, sub) \
        (res)->tv_sec -= (sub)->tv_sec; \
        (res)->tv_usec -= (sub)->tv_usec; \
        if ((res)->tv_usec < 0) { \
                (res)->tv_usec += 1000000; \
                (res)->tv_sec--; \
        }

/*
 * Do a `read wait': select for reading from stdin, with timeout *tvp.
 * On return, modify *tvp to reflect the amount of time spent waiting.
 * It will be positive only if input appeared before the time ran out;
 * otherwise it will be zero or perhaps negative.
 *
 * If tvp is nil, wait forever, but return if select is interrupted.
 *
 * Return 0 => no input, 1 => can read() from stdin
 */
int
rwait(struct timeval *tvp)
{
        struct timeval starttv, endtv, *s;
        fd_set fds;

#define NILTZ ((struct timezone *)0)

        /*
         * Someday, select() will do this for us.
         * Just in case that day is now, and no one has
         * changed this, we use a temporary.
         */
        if (tvp) {
                (void) gettimeofday(&starttv, NILTZ);
                endtv = *tvp;
                s = &endtv;
        } else
                s = NULL;
again:
        FD_ZERO(&fds);
        FD_SET(STDIN_FILENO, &fds);
        switch (select(STDIN_FILENO + 1, &fds, (fd_set *)0, (fd_set *)0, s)) {

        case -1:
                if (tvp == 0)
                        return (-1);
                if (errno == EINTR)
                        goto again;
                stop("select failed, help");
                /* NOTREACHED */

        case 0: /* timed out */
                tvp->tv_sec = 0;
                tvp->tv_usec = 0;
                return (0);
        }
        if (tvp) {
                /* since there is input, we may not have timed out */
                (void) gettimeofday(&endtv, NILTZ);
                TV_SUB(&endtv, &starttv);
                TV_SUB(tvp, &endtv);    /* adjust *tvp by elapsed time */
        }
        return (1);
}

/*
 * `sleep' for the current turn time (using select).
 * Eat any input that might be available.
 */
void
tsleep(void)
{
        struct timeval tv;
        char c;

        tv.tv_sec = 0;
        tv.tv_usec = fallrate;
        while (TV_POS(&tv))
                if (rwait(&tv) && read(STDIN_FILENO, &c, 1) != 1)
                        break;
}

/*
 * getchar with timeout.
 */
int
tgetchar(void)
{
        static struct timeval timeleft;
        char c;

        /*
         * Reset timeleft to fallrate whenever it is not positive.
         * In any case, wait to see if there is any input.  If so,
         * take it, and update timeleft so that the next call to
         * tgetchar() will not wait as long.  If there is no input,
         * make timeleft zero or negative, and return -1.
         *
         * Most of the hard work is done by rwait().
         */
        if (!TV_POS(&timeleft)) {
                faster();       /* go faster */
                timeleft.tv_sec = 0;
                timeleft.tv_usec = fallrate;
        }
        if (!rwait(&timeleft))
                return (-1);
        if (read(STDIN_FILENO, &c, 1) != 1)
                stop("end of file, help");
        return ((int)(unsigned char)c);
}