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 */