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  1. /*
  2.     SDL - Simple DirectMedia Layer
  3.     Copyright (C) 1997-2009 Sam Lantinga
  4.  
  5.     This library is free software; you can redistribute it and/or
  6.     modify it under the terms of the GNU Lesser General Public
  7.     License as published by the Free Software Foundation; either
  8.     version 2.1 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.     Lesser General Public License for more details.
  14.  
  15.     You should have received a copy of the GNU Lesser General Public
  16.     License along with this library; if not, write to the Free Software
  17.     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18.  
  19.     Sam Lantinga
  20.     slouken@libsdl.org
  21. */
  22.  
  23. #ifndef _SDL_timer_h
  24. #define _SDL_timer_h
  25.  
  26. /** @file SDL_timer.h
  27.  *  Header for the SDL time management routines
  28.  */
  29.  
  30. #include "SDL_stdinc.h"
  31. #include "SDL_error.h"
  32.  
  33. #include "begin_code.h"
  34. /* Set up for C function definitions, even when using C++ */
  35. #ifdef __cplusplus
  36. extern "C" {
  37. #endif
  38.  
  39. /** This is the OS scheduler timeslice, in milliseconds */
  40. #define SDL_TIMESLICE           10
  41.  
  42. /** This is the maximum resolution of the SDL timer on all platforms */
  43. #define TIMER_RESOLUTION        10      /**< Experimentally determined */
  44.  
  45. /**
  46.  * Get the number of milliseconds since the SDL library initialization.
  47.  * Note that this value wraps if the program runs for more than ~49 days.
  48.  */
  49. extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
  50.  
  51. /** Wait a specified number of milliseconds before returning */
  52. extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
  53.  
  54. /** Function prototype for the timer callback function */
  55. typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
  56.  
  57. /**
  58.  * Set a callback to run after the specified number of milliseconds has
  59.  * elapsed. The callback function is passed the current timer interval
  60.  * and returns the next timer interval.  If the returned value is the
  61.  * same as the one passed in, the periodic alarm continues, otherwise a
  62.  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
  63.  * is cancelled.
  64.  *
  65.  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
  66.  *
  67.  * The timer callback function may run in a different thread than your
  68.  * main code, and so shouldn't call any functions from within itself.
  69.  *
  70.  * The maximum resolution of this timer is 10 ms, which means that if
  71.  * you request a 16 ms timer, your callback will run approximately 20 ms
  72.  * later on an unloaded system.  If you wanted to set a flag signaling
  73.  * a frame update at 30 frames per second (every 33 ms), you might set a
  74.  * timer for 30 ms:
  75.  *   @code SDL_SetTimer((33/10)*10, flag_update); @endcode
  76.  *
  77.  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
  78.  *
  79.  * Under UNIX, you should not use raise or use SIGALRM and this function
  80.  * in the same program, as it is implemented using setitimer().  You also
  81.  * should not use this function in multi-threaded applications as signals
  82.  * to multi-threaded apps have undefined behavior in some implementations.
  83.  *
  84.  * This function returns 0 if successful, or -1 if there was an error.
  85.  */
  86. extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
  87.  
  88. /** @name New timer API
  89.  * New timer API, supports multiple timers
  90.  * Written by Stephane Peter <megastep@lokigames.com>
  91.  */
  92. /*@{*/
  93.  
  94. /**
  95.  * Function prototype for the new timer callback function.
  96.  * The callback function is passed the current timer interval and returns
  97.  * the next timer interval.  If the returned value is the same as the one
  98.  * passed in, the periodic alarm continues, otherwise a new alarm is
  99.  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
  100.  */
  101. typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
  102.  
  103. /** Definition of the timer ID type */
  104. typedef struct _SDL_TimerID *SDL_TimerID;
  105.  
  106. /** Add a new timer to the pool of timers already running.
  107.  *  Returns a timer ID, or NULL when an error occurs.
  108.  */
  109. extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
  110.  
  111. /**
  112.  * Remove one of the multiple timers knowing its ID.
  113.  * Returns a boolean value indicating success.
  114.  */
  115. extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
  116.  
  117. /*@}*/
  118.  
  119. /* Ends C function definitions when using C++ */
  120. #ifdef __cplusplus
  121. }
  122. #endif
  123. #include "close_code.h"
  124.  
  125. #endif /* _SDL_timer_h */
  126.