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/* sdltimer.c: Game timing functions.
*
* Copyright (C) 2001-2006 by Brian Raiter, under the GNU General Public
* License. No warranty. See COPYING for details.
*/
#include <stdlib.h>
#include "SDL.h"
#include "sdlgen.h"
/* By default, a second of game time lasts for 1000 milliseconds of
* real time.
*/
static int mspertick = 1000 / TICKS_PER_SECOND;
/* The tick counter.
*/
static int utick = 0;
/* The time of the next tick.
*/
static int nexttickat = 0;
/* A histogram of how many milliseconds the program spends sleeping
* per tick.
*/
static int showhistogram = FALSE;
static unsigned hist[100];
/* Set the length (in real time) of a second of game time. A value of
* zero selects the default length of one second.
*/
void settimersecond(int ms)
{
mspertick = (ms ? ms : 1000) / TICKS_PER_SECOND;
}
/* Change the current timer setting. If action is positive, the timer
* is started (or resumed). If action is negative, the timer is
* stopped if it is running and the counter is reset to zero. If
* action is zero, the timer is stopped if it is running, and the
* counter remains at its current setting.
*/
void settimer(int action)
{
if (action < 0) {
nexttickat = 0;
utick = 0;
} else if (action > 0) {
if (nexttickat < 0)
nexttickat = SDL_GetTicks() - nexttickat;
else
nexttickat = SDL_GetTicks() + mspertick;
} else {
if (nexttickat > 0)
nexttickat = SDL_GetTicks() - nexttickat;
}
}
/* Return the number of ticks since the timer was last reset.
*/
int gettickcount(void)
{
return (int)utick;
}
/* Put the program to sleep until the next timer tick. If we've
* already missed a timer tick, then wait for the next one.
*/
int waitfortick(void)
{
int ms;
ms = nexttickat - SDL_GetTicks();
if (showhistogram)
if (ms < (int)(sizeof hist / sizeof *hist))
++hist[ms >= 0 ? ms + 1 : 0];
if (ms <= 0) {
++utick;
nexttickat += mspertick;
return FALSE;
}
while (ms < 0)
ms += mspertick;
SDL_Delay(ms);
++utick;
nexttickat += mspertick;
return TRUE;
}
/* Move to the next timer tick without waiting.
*/
int advancetick(void)
{
return ++utick;
}
/* At shutdown time, display the histogram data on stdout.
*/
static void shutdown(void)
{
unsigned long n;
int i;
settimer(-1);
if (showhistogram) {
n = 0;
for (i = 0 ; i < (int)(sizeof hist / sizeof *hist) ; ++i)
n += hist[i];
if (n) {
printf("Histogram of idle time (ms/tick)\n");
if (hist[0])
printf("NEG: %.1f%%\n", (hist[0] * 100.0) / n);
for (i = 1 ; i < (int)(sizeof hist / sizeof *hist) ; ++i)
if (hist[i])
printf("%3d: %.1f%%\n", i - 1, (hist[i] * 100.0) / n);
}
}
}
/* Initialize and reset the timer.
*/
int _sdltimerinitialize(int _showhistogram)
{
showhistogram = _showhistogram;
atexit(shutdown);
settimer(-1);
return TRUE;
}
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