include/SDL_timer.h

   1 /*
   2     SDL - Simple DirectMedia Layer
   3     Copyright (C) 1997-2006 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 /* Header for the SDL time management routines */
  27
  28 #include "SDL_stdinc.h"
  29 #include "SDL_error.h"
  30
  31 #include "begin_code.h"
  32 /* Set up for C function definitions, even when using C++ */
  33 #ifdef __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 /* This is the OS scheduler timeslice, in milliseconds */
  38 #define SDL_TIMESLICE           10
  39
  40 /* This is the maximum resolution of the SDL timer on all platforms */
  41 #define TIMER_RESOLUTION        10      /* Experimentally determined */
  42
  43 /* Get the number of milliseconds since the SDL library initialization.
  44  * Note that this value wraps if the program runs for more than ~49 days.
  45  */
  46 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
  47
  48 /* Wait a specified number of milliseconds before returning */
  49 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
  50
  51 /* Function prototype for the timer callback function */
  52 typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
  53
  54 /* Set a callback to run after the specified number of milliseconds has
  55  * elapsed. The callback function is passed the current timer interval
  56  * and returns the next timer interval.  If the returned value is the
  57  * same as the one passed in, the periodic alarm continues, otherwise a
  58  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
  59  * is cancelled.
  60  *
  61  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
  62  *
  63  * The timer callback function may run in a different thread than your
  64  * main code, and so shouldn't call any functions from within itself.
  65  *
  66  * The maximum resolution of this timer is 10 ms, which means that if
  67  * you request a 16 ms timer, your callback will run approximately 20 ms
  68  * later on an unloaded system.  If you wanted to set a flag signaling
  69  * a frame update at 30 frames per second (every 33 ms), you might set a
  70  * timer for 30 ms:
  71  *   SDL_SetTimer((33/10)*10, flag_update);
  72  *
  73  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
  74  *
  75  * Under UNIX, you should not use raise or use SIGALRM and this function
  76  * in the same program, as it is implemented using setitimer().  You also
  77  * should not use this function in multi-threaded applications as signals
  78  * to multi-threaded apps have undefined behavior in some implementations.
  79  *
  80  * This function returns 0 if successful, or -1 if there was an error.
  81  */
  82 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
  83
  84 /* New timer API, supports multiple timers
  85  * Written by Stephane Peter <megastep@lokigames.com>
  86  */
  87
  88 /* Function prototype for the new timer callback function.
  89  * The callback function is passed the current timer interval and returns
  90  * the next timer interval.  If the returned value is the same as the one
  91  * passed in, the periodic alarm continues, otherwise a new alarm is
  92  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
  93  */
  94 typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
  95
  96 /* Definition of the timer ID type */
  97 typedef struct _SDL_TimerID *SDL_TimerID;
  98
  99 /* Add a new timer to the pool of timers already running.
 100    Returns a timer ID, or NULL when an error occurs.
 101  */
 102 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
 103
 104 /* Remove one of the multiple timers knowing its ID.
 105  * Returns a boolean value indicating success.
 106  */
 107 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
 108
 109 /* Ends C function definitions when using C++ */
 110 #ifdef __cplusplus
 111 }
 112 #endif
 113 #include "close_code.h"
 114
 115 #endif /* _SDL_timer_h */