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  1. /*
  2.     SDL - Simple DirectMedia Layer
  3.     Copyright (C) 1997-2004 Sam Lantinga
  4.  
  5.     This library is free software; you can redistribute it and/or
  6.     modify it under the terms of the GNU Library General Public
  7.     License as published by the Free Software Foundation; either
  8.     version 2 of the License, or (at your option) any later version.
  9.  
  10.     This library is distributed in the hope that it will be useful,
  11.     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12.     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13.     Library General Public License for more details.
  14.  
  15.     You should have received a copy of the GNU Library General Public
  16.     License along with this library; if not, write to the Free
  17.     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18.  
  19.     Sam Lantinga
  20.     slouken@libsdl.org
  21. */
  22.  
  23. #ifdef SAVE_RCSID
  24. static char rcsid =
  25.  "@(#) $Id: SDL_timer.h,v 1.6 2004/01/04 16:49:08 slouken Exp $";
  26. #endif
  27.  
  28. #ifndef _SDL_timer_h
  29. #define _SDL_timer_h
  30.  
  31. /* Header for the SDL time management routines */
  32.  
  33. #include "SDL_main.h"
  34. #include "SDL_types.h"
  35.  
  36. #include "begin_code.h"
  37. /* Set up for C function definitions, even when using C++ */
  38. #ifdef __cplusplus
  39. extern "C" {
  40. #endif
  41.  
  42. /* This is the OS scheduler timeslice, in milliseconds */
  43. #define SDL_TIMESLICE           10
  44.  
  45. /* This is the maximum resolution of the SDL timer on all platforms */
  46. #define TIMER_RESOLUTION        10      /* Experimentally determined */
  47.  
  48. /* Get the number of milliseconds since the SDL library initialization.
  49.  * Note that this value wraps if the program runs for more than ~49 days.
  50.  */
  51. extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
  52.  
  53. /* Wait a specified number of milliseconds before returning */
  54. extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
  55.  
  56. /* Function prototype for the timer callback function */
  57. typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
  58.  
  59. /* Set a callback to run after the specified number of milliseconds has
  60.  * elapsed. The callback function is passed the current timer interval
  61.  * and returns the next timer interval.  If the returned value is the
  62.  * same as the one passed in, the periodic alarm continues, otherwise a
  63.  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
  64.  * is cancelled.
  65.  *
  66.  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
  67.  *
  68.  * The timer callback function may run in a different thread than your
  69.  * main code, and so shouldn't call any functions from within itself.
  70.  *
  71.  * The maximum resolution of this timer is 10 ms, which means that if
  72.  * you request a 16 ms timer, your callback will run approximately 20 ms
  73.  * later on an unloaded system.  If you wanted to set a flag signaling
  74.  * a frame update at 30 frames per second (every 33 ms), you might set a
  75.  * timer for 30 ms:
  76.  *   SDL_SetTimer((33/10)*10, flag_update);
  77.  *
  78.  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
  79.  *
  80.  * Under UNIX, you should not use raise or use SIGALRM and this function
  81.  * in the same program, as it is implemented using setitimer().  You also
  82.  * should not use this function in multi-threaded applications as signals
  83.  * to multi-threaded apps have undefined behavior in some implementations.
  84.  */
  85. extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
  86.  
  87. /* New timer API, supports multiple timers
  88.  * Written by Stephane Peter <megastep@lokigames.com>
  89.  */
  90.  
  91. /* Function prototype for the new timer callback function.
  92.  * The callback function is passed the current timer interval and returns
  93.  * the next timer interval.  If the returned value is the same as the one
  94.  * passed in, the periodic alarm continues, otherwise a new alarm is
  95.  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
  96.  */
  97. typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
  98.  
  99. /* Definition of the timer ID type */
  100. typedef struct _SDL_TimerID *SDL_TimerID;
  101.  
  102. /* Add a new timer to the pool of timers already running.
  103.    Returns a timer ID, or NULL when an error occurs.
  104.  */
  105. extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
  106.  
  107. /* Remove one of the multiple timers knowing its ID.
  108.  * Returns a boolean value indicating success.
  109.  */
  110. extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
  111.  
  112. /* Ends C function definitions when using C++ */
  113. #ifdef __cplusplus
  114. }
  115. #endif
  116. #include "close_code.h"
  117.  
  118. #endif /* _SDL_timer_h */
  119.