games/tetris/input.c

   1 /*      $OpenBSD: input.c,v 1.19 2017/08/13 02:12:16 tedu Exp $ */
   2 /*    $NetBSD: input.c,v 1.3 1996/02/06 22:47:33 jtc Exp $    */
   3
   4 /*-
   5  * Copyright (c) 1992, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * This code is derived from software contributed to Berkeley by
   9  * Chris Torek and Darren F. Provine.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  *      @(#)input.c     8.1 (Berkeley) 5/31/93
  36  */
  37
  38 /*
  39  * Tetris input.
  40  */
  41
  42 #include <sys/time.h>
  43
  44 #include <errno.h>
  45 #include <poll.h>
  46 #include <time.h>
  47 #include <unistd.h>
  48
  49 #include "input.h"
  50 #include "tetris.h"
  51
  52 /* return true iff the given timespec is positive */
  53 #define TS_POS(ts) \
  54         ((ts)->tv_sec > 0 || ((ts)->tv_sec == 0 && (ts)->tv_nsec > 0))
  55
  56 /*
  57  * Do a `read wait': poll for reading from stdin, with timeout *limit.
  58  * On return, subtract the time spent waiting from *limit.
  59  * It will be positive only if input appeared before the time ran out;
  60  * otherwise it will be zero or perhaps negative.
  61  *
  62  * If limit is NULL, wait forever, but return if poll is interrupted.
  63  *
  64  * Return 0 => no input, 1 => can read() from stdin, -1 => interrupted
  65  */
  66 int
  67 rwait(struct timespec *limit)
  68 {
  69         struct timespec start, end, elapsed;
  70         struct pollfd pfd[1];
  71
  72         pfd[0].fd = STDIN_FILENO;
  73         pfd[0].events = POLLIN;
  74
  75         if (limit != NULL)
  76                 clock_gettime(CLOCK_MONOTONIC, &start);
  77 again:
  78         switch (ppoll(pfd, 1, limit, NULL)) {
  79         case -1:
  80                 if (limit == NULL)
  81                         return (-1);
  82                 if (errno == EINTR)
  83                         goto again;
  84                 stop("poll failed, help");
  85         case 0: /* timed out */
  86                 timespecclear(limit);
  87                 return (0);
  88         }
  89         if (limit != NULL) {
  90                 /* we have input, so subtract the elapsed time from *limit */
  91                 clock_gettime(CLOCK_MONOTONIC, &end);
  92                 timespecsub(&end, &start, &elapsed);
  93                 timespecsub(limit, &elapsed, limit);
  94         }
  95         return (1);
  96 }
  97
  98 /*
  99  * `sleep' for the current turn time and eat any
 100  * input that becomes available.
 101  */
 102 void
 103 tsleep(void)
 104 {
 105         struct timespec ts;
 106         char c;
 107
 108         ts.tv_sec = 0;
 109         ts.tv_nsec = fallrate;
 110         while (TS_POS(&ts))
 111                 if (rwait(&ts) && read(STDIN_FILENO, &c, 1) != 1)
 112                         break;
 113 }
 114
 115 /*
 116  * getchar with timeout.
 117  */
 118 int
 119 tgetchar(void)
 120 {
 121         static struct timespec timeleft;
 122         char c;
 123
 124         /*
 125          * Reset timeleft to fallrate whenever it is not positive.
 126          * In any case, wait to see if there is any input.  If so,
 127          * take it, and update timeleft so that the next call to
 128          * tgetchar() will not wait as long.  If there is no input,
 129          * make timeleft zero or negative, and return -1.
 130          *
 131          * Most of the hard work is done by rwait().
 132          */
 133         if (!TS_POS(&timeleft)) {
 134                 faster();       /* go faster */
 135                 timeleft.tv_sec = 0;
 136                 timeleft.tv_nsec = fallrate;
 137         }
 138         if (!rwait(&timeleft))
 139                 return (-1);
 140         if (read(STDIN_FILENO, &c, 1) != 1)
 141                 stop("end of file, help");
 142         return ((int)(unsigned char)c);
 143 }