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1 /*
2     SDL - Simple DirectMedia Layer
3     Copyright (C) 1997-2012 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