sdl_timer.h

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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    [e-mail]
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

#ifndef _SDL_timer_h
#define _SDL_timer_h

/* Header for the SDL time management routines */

#include "SDL_main.h"
#include "SDL_types.h"

#include "begin_code.h"
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
extern "C" {
#endif

/* This is the OS scheduler timeslice, in milliseconds */
#define SDL_TIMESLICE		10

/* This is the maximum resolution of the SDL timer on all platforms */
#define TIMER_RESOLUTION	10	/* Experimentally determined */

/* Get the number of milliseconds since the SDL library initialization.
 * Note that this value wraps if the program runs for more than ~49 days.
 */ 
extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);

/* Wait a specified number of milliseconds before returning */
extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);

/* Function prototype for the timer callback function */
typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);

/* Set a callback to run after the specified number of milliseconds has
 * elapsed. The callback function is passed the current timer interval
 * and returns the next timer interval.  If the returned value is the 
 * same as the one passed in, the periodic alarm continues, otherwise a
 * new alarm is scheduled.  If the callback returns 0, the periodic alarm
 * is cancelled.
 *
 * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
 *
 * The timer callback function may run in a different thread than your
 * main code, and so shouldn't call any functions from within itself.
 *
 * The maximum resolution of this timer is 10 ms, which means that if
 * you request a 16 ms timer, your callback will run approximately 20 ms
 * later on an unloaded system.  If you wanted to set a flag signaling
 * a frame update at 30 frames per second (every 33 ms), you might set a 
 * timer for 30 ms:
 *   SDL_SetTimer((33/10)*10, flag_update);
 *
 * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
 *
 * Under UNIX, you should not use raise or use SIGALRM and this function
 * in the same program, as it is implemented using setitimer().  You also
 * should not use this function in multi-threaded applications as signals
 * to multi-threaded apps have undefined behavior in some implementations.
 */
extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);

/* New timer API, supports multiple timers
 * Written by Stephane Peter <[e-mail]>
 */

/* Function prototype for the new timer callback function.
 * The callback function is passed the current timer interval and returns
 * the next timer interval.  If the returned value is the same as the one
 * passed in, the periodic alarm continues, otherwise a new alarm is
 * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
 */
typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);

/* Definition of the timer ID type */
typedef struct _SDL_TimerID *SDL_TimerID;

/* Add a new timer to the pool of timers already running.
   Returns a timer ID, or NULL when an error occurs.
 */
extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);

/* Remove one of the multiple timers knowing its ID.
 * Returns a boolean value indicating success.
 */
extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);

/* Ends C function definitions when using C++ */
#ifdef __cplusplus
}
#endif
#include "close_code.h"

#endif /* _SDL_timer_h */