1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
4
5 This software is provided 'as-is', without any express or implied
6 warranty. In no event will the authors be held liable for any damages
7 arising from the use of this software.
8
9 Permission is granted to anyone to use this software for any purpose,
10 including commercial applications, and to alter it and redistribute it
11 freely, subject to the following restrictions:
12
13 1. The origin of this software must not be misrepresented; you must not
14 claim that you wrote the original software. If you use this software
15 in a product, an acknowledgment in the product documentation would be
16 appreciated but is not required.
17 2. Altered source versions must be plainly marked as such, and must not be
18 misrepresented as being the original software.
19 3. This notice may not be removed or altered from any source distribution.
20*/
21
22#ifndef SDL_timer_h_
23#define SDL_timer_h_
24
25/**
26 * \file SDL_timer.h
27 *
28 * Header for the SDL time management routines.
29 */
30
31#include "SDL_stdinc.h"
32#include "SDL_error.h"
33
34#include "begin_code.h"
35/* Set up for C function definitions, even when using C++ */
36#ifdef __cplusplus
37extern "C" {
38#endif
39
40/**
41 * Get the number of milliseconds since SDL library initialization.
42 *
43 * This value wraps if the program runs for more than ~49 days.
44 *
45 * This function is not recommended as of SDL 2.0.18; use SDL_GetTicks64()
46 * instead, where the value doesn't wrap every ~49 days. There are places in
47 * SDL where we provide a 32-bit timestamp that can not change without
48 * breaking binary compatibility, though, so this function isn't officially
49 * deprecated.
50 *
51 * \returns an unsigned 32-bit value representing the number of milliseconds
52 * since the SDL library initialized.
53 *
54 * \since This function is available since SDL 2.0.0.
55 *
56 * \sa SDL_TICKS_PASSED
57 */
58extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
59
60/**
61 * Get the number of milliseconds since SDL library initialization.
62 *
63 * Note that you should not use the SDL_TICKS_PASSED macro with values
64 * returned by this function, as that macro does clever math to compensate for
65 * the 32-bit overflow every ~49 days that SDL_GetTicks() suffers from. 64-bit
66 * values from this function can be safely compared directly.
67 *
68 * For example, if you want to wait 100 ms, you could do this:
69 *
70 * ```c
71 * const Uint64 timeout = SDL_GetTicks64() + 100;
72 * while (SDL_GetTicks64() < timeout) {
73 * // ... do work until timeout has elapsed
74 * }
75 * ```
76 *
77 * \returns an unsigned 64-bit value representing the number of milliseconds
78 * since the SDL library initialized.
79 *
80 * \since This function is available since SDL 2.0.18.
81 */
82extern DECLSPEC Uint64 SDLCALL SDL_GetTicks64(void);
83
84/**
85 * Compare 32-bit SDL ticks values, and return true if `A` has passed `B`.
86 *
87 * This should be used with results from SDL_GetTicks(), as this macro
88 * attempts to deal with the 32-bit counter wrapping back to zero every ~49
89 * days, but should _not_ be used with SDL_GetTicks64(), which does not have
90 * that problem.
91 *
92 * For example, with SDL_GetTicks(), if you want to wait 100 ms, you could
93 * do this:
94 *
95 * ```c
96 * const Uint32 timeout = SDL_GetTicks() + 100;
97 * while (!SDL_TICKS_PASSED(SDL_GetTicks(), timeout)) {
98 * // ... do work until timeout has elapsed
99 * }
100 * ```
101 *
102 * Note that this does not handle tick differences greater
103 * than 2^31 so take care when using the above kind of code
104 * with large timeout delays (tens of days).
105 */
106#define SDL_TICKS_PASSED(A, B) ((Sint32)((B) - (A)) <= 0)
107
108/**
109 * Get the current value of the high resolution counter.
110 *
111 * This function is typically used for profiling.
112 *
113 * The counter values are only meaningful relative to each other. Differences
114 * between values can be converted to times by using
115 * SDL_GetPerformanceFrequency().
116 *
117 * \returns the current counter value.
118 *
119 * \since This function is available since SDL 2.0.0.
120 *
121 * \sa SDL_GetPerformanceFrequency
122 */
123extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceCounter(void);
124
125/**
126 * Get the count per second of the high resolution counter.
127 *
128 * \returns a platform-specific count per second.
129 *
130 * \since This function is available since SDL 2.0.0.
131 *
132 * \sa SDL_GetPerformanceCounter
133 */
134extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceFrequency(void);
135
136/**
137 * Wait a specified number of milliseconds before returning.
138 *
139 * This function waits a specified number of milliseconds before returning. It
140 * waits at least the specified time, but possibly longer due to OS
141 * scheduling.
142 *
143 * \param ms the number of milliseconds to delay
144 *
145 * \since This function is available since SDL 2.0.0.
146 */
147extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
148
149/**
150 * Function prototype for the timer callback function.
151 *
152 * The callback function is passed the current timer interval and returns
153 * the next timer interval. If the returned value is the same as the one
154 * passed in, the periodic alarm continues, otherwise a new alarm is
155 * scheduled. If the callback returns 0, the periodic alarm is cancelled.
156 */
157typedef Uint32 (SDLCALL * SDL_TimerCallback) (Uint32 interval, void *param);
158
159/**
160 * Definition of the timer ID type.
161 */
162typedef int SDL_TimerID;
163
164/**
165 * Call a callback function at a future time.
166 *
167 * If you use this function, you must pass `SDL_INIT_TIMER` to SDL_Init().
168 *
169 * The callback function is passed the current timer interval and the user
170 * supplied parameter from the SDL_AddTimer() call and should return the next
171 * timer interval. If the value returned from the callback is 0, the timer is
172 * canceled.
173 *
174 * The callback is run on a separate thread.
175 *
176 * Timers take into account the amount of time it took to execute the
177 * callback. For example, if the callback took 250 ms to execute and returned
178 * 1000 (ms), the timer would only wait another 750 ms before its next
179 * iteration.
180 *
181 * Timing may be inexact due to OS scheduling. Be sure to note the current
182 * time with SDL_GetTicks() or SDL_GetPerformanceCounter() in case your
183 * callback needs to adjust for variances.
184 *
185 * \param interval the timer delay, in milliseconds, passed to `callback`
186 * \param callback the SDL_TimerCallback function to call when the specified
187 * `interval` elapses
188 * \param param a pointer that is passed to `callback`
189 * \returns a timer ID or 0 if an error occurs; call SDL_GetError() for more
190 * information.
191 *
192 * \since This function is available since SDL 2.0.0.
193 *
194 * \sa SDL_RemoveTimer
195 */
196extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval,
197 SDL_TimerCallback callback,
198 void *param);
199
200/**
201 * Remove a timer created with SDL_AddTimer().
202 *
203 * \param id the ID of the timer to remove
204 * \returns SDL_TRUE if the timer is removed or SDL_FALSE if the timer wasn't
205 * found.
206 *
207 * \since This function is available since SDL 2.0.0.
208 *
209 * \sa SDL_AddTimer
210 */
211extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID id);
212
213
214/* Ends C function definitions when using C++ */
215#ifdef __cplusplus
216}
217#endif
218#include "close_code.h"
219
220#endif /* SDL_timer_h_ */
221
222/* vi: set ts=4 sw=4 expandtab: */
223