extimer.c from Allegro game programming library at Krugle

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/*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program demonstrates how to use the timer routines.
 *    These can be a bit of a pain, because you have to be sure you lock 
 *    all the memory that is used inside your interrupt handlers.
 */


#include "allegro.h"



/* these must be declared volatile so the optimiser doesn't mess up */
volatile int x = 0;
volatile int y = 0;
volatile int z = 0;



/* timer interrupt handler */
void inc_x(void)
{
   x++;
}

AL_END_OF_FUNCTION(inc_x);



/* timer interrupt handler */
void inc_y(void)
{
   y++;
}

AL_END_OF_FUNCTION(inc_y);



/* timer interrupt handler */
void inc_z(void)
{
   z++;
}

AL_END_OF_FUNCTION(inc_z);



int main()
{
   int c;

   allegro_init();
   al_install_keyboard(); 
   al_install_timer();
   if (al_set_gfx_mode(AL_GFX_SAFE, 320, 200, 0, 0) != 0) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Unable to set any graphic mode\n%s\n", al_error);
      return 1;
   }
   al_set_palette(al_desktop_palette);
   al_clear_to_color(al_screen, al_make_color(255, 255, 255));
   al_text_mode(al_make_color(255, 255, 255));

   al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, 8, al_make_color(0, 0, 0),"Driver: %s", timer_driver->name);

   /* use al_rest() to delay for a specified number of milliseconds */
   al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, 48, al_make_color(0, 0, 0),"Timing five seconds:");

   for (c=1; c<=5; c++) {
      al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, 62+c*10, al_make_color(0, 0, 0),"%d", c);
      al_rest(1000);
   }

   al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, 142, al_make_color(0, 0, 0),"Press a al_key to set up interrupts");
   al_read_key();

   /* all variables and code used inside interrupt handlers must be locked */
   LOCK_VARIABLE(x);
   LOCK_VARIABLE(y);
   LOCK_VARIABLE(z);
   LOCK_FUNCTION(inc_x);
   LOCK_FUNCTION(inc_y);
   LOCK_FUNCTION(inc_z);

   /* the speed can be specified in milliseconds (this is once a second) */
   al_create_timer(inc_x, MSEC_TO_TIMER(1000));

   /* or in beats per second (this is 10 ticks a second) */
   al_create_timer(inc_y, BPS_TO_TIMER(10));

   /* or in seconds (this is 10 ticks a second) */
   al_create_timer(inc_z, SECS_TO_TIMER(10));

   /* the interrupts are now active... */
   while (!al_key_pressed())
      al_printf_text_centre(al_screen, al_font_8x8, AL_SCREEN_W/2, 176, al_make_color(0, 0, 0),"x=%d, y=%d, z=%d", x, y, z);

   return 0;
}

AL_END_OF_MAIN();
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