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comparison include/SDL_timer.h @ 5113:481dabb098ef

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Improved timer implementation The new timer model is formalized as using a separate thread to handle timer callbacks. This was the case on almost every platform before, but it's now a requirement, and simplifies the implementation and makes it perform consistently across platforms. Goals: * Minimize timer thread blocking * Dispatch timers as accurately as possible * SDL_AddTimer() and SDL_RemoveTimer() are completely threadsafe * SDL_RemoveTimer() doesn't crash with a timer that's expired or removed
author Sam Lantinga <slouken@libsdl.org>
date Thu, 27 Jan 2011 14:45:06 -0800
parents f7b03b6838cb
children b530ef003506
comparison
equal deleted inserted replaced
5112:0846f18eb625 5113:481dabb098ef
39 extern "C" { 39 extern "C" {
40 /* *INDENT-ON* */ 40 /* *INDENT-ON* */
41 #endif 41 #endif
42 42
43 /** 43 /**
44 * This is the OS scheduler timeslice, in milliseconds. 44 * \brief Get the number of milliseconds since the SDL library initialization.
45 */
46 #define SDL_TIMESLICE 10
47
48 /**
49 * This is the maximum resolution of the SDL timer on all platforms.
50 */
51 #define TIMER_RESOLUTION 10 /**< Experimentally determined */
52
53 /**
54 * Get the number of milliseconds since the SDL library initialization.
55 * 45 *
56 * Note that this value wraps if the program runs for more than ~49 days. 46 * \note This value wraps if the program runs for more than ~49 days.
57 */ 47 */
58 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void); 48 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
59 49
60 /** 50 /**
61 * Wait a specified number of milliseconds before returning. 51 * \brief Wait a specified number of milliseconds before returning.
62 */ 52 */
63 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms); 53 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
64 54
65 /** 55 /**
66 * Function prototype for the timer callback function. 56 * Function prototype for the timer callback function.
67 */
68 typedef Uint32(SDLCALL * SDL_TimerCallback) (Uint32 interval);
69
70 /**
71 * Set a callback to run after the specified number of milliseconds has
72 * elapsed. The callback function is passed the current timer interval
73 * and returns the next timer interval. If the returned value is the
74 * same as the one passed in, the periodic alarm continues, otherwise a
75 * new alarm is scheduled. If the callback returns 0, the periodic alarm
76 * is cancelled.
77 *
78 * To cancel a currently running timer, call
79 * \code SDL_SetTimer(0, NULL); \endcode
80 *
81 * The timer callback function may run in a different thread than your
82 * main code, and so shouldn't call any functions from within itself.
83 *
84 * The maximum resolution of this timer is 10 ms, which means that if
85 * you request a 16 ms timer, your callback will run approximately 20 ms
86 * later on an unloaded system. If you wanted to set a flag signaling
87 * a frame update at 30 frames per second (every 33 ms), you might set a
88 * timer for 30 ms:
89 * \code
90 * SDL_SetTimer((33/10)*10, flag_update);
91 * \endcode
92 *
93 * If you use this function, you need to pass ::SDL_INIT_TIMER to SDL_Init().
94 *
95 * Under UNIX, you should not use raise or use SIGALRM and this function
96 * in the same program, as it is implemented using setitimer(). You also
97 * should not use this function in multi-threaded applications as signals
98 * to multi-threaded apps have undefined behavior in some implementations.
99 *
100 * \return 0 if successful, or -1 if there was an error.
101 */
102 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval,
103 SDL_TimerCallback callback);
104
105 /**
106 * \name Peter timers
107 * New timer API, supports multiple timers
108 * Written by Stephane Peter <megastep@lokigames.com>
109 */
110 /*@{*/
111
112 /**
113 * Function prototype for the new timer callback function.
114 * 57 *
115 * The callback function is passed the current timer interval and returns 58 * The callback function is passed the current timer interval and returns
116 * the next timer interval. If the returned value is the same as the one 59 * the next timer interval. If the returned value is the same as the one
117 * passed in, the periodic alarm continues, otherwise a new alarm is 60 * passed in, the periodic alarm continues, otherwise a new alarm is
118 * scheduled. If the callback returns 0, the periodic alarm is cancelled. 61 * scheduled. If the callback returns 0, the periodic alarm is cancelled.
119 */ 62 */
120 typedef Uint32(SDLCALL * SDL_NewTimerCallback) (Uint32 interval, void *param); 63 typedef Uint32 (SDLCALL * SDL_TimerCallback) (Uint32 interval, void *param);
121 64
122 /** 65 /**
123 * Definition of the timer ID type. 66 * Definition of the timer ID type.
124 */ 67 */
125 typedef struct _SDL_TimerID *SDL_TimerID; 68 typedef int SDL_TimerID;
126 69
127 /** 70 /**
128 * Add a new timer to the pool of timers already running. 71 * \brief Add a new timer to the pool of timers already running.
129 * \return A timer ID, or NULL when an error occurs. 72 *
73 * \return A timer ID, or NULL when an error occurs.
130 */ 74 */
131 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, 75 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval,
132 SDL_NewTimerCallback 76 SDL_TimerCallback callback,
133 callback, void *param); 77 void *param);
134 78
135 /** 79 /**
136 * Remove one of the multiple timers knowing its ID. 80 * \brief Remove a timer knowing its ID.
137 * \return A boolean value indicating success or failure. 81 *
82 * \return A boolean value indicating success or failure.
83 *
84 * \warning It is not safe to remove a timer multiple times.
138 */ 85 */
139 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t); 86 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
140 87
141 /*@}*//*Peter timers*/
142 88
143 /* Ends C function definitions when using C++ */ 89 /* Ends C function definitions when using C++ */
144 #ifdef __cplusplus 90 #ifdef __cplusplus
145 /* *INDENT-OFF* */ 91 /* *INDENT-OFF* */
146 } 92 }