1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2021 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 * \returns an unsigned 32-bit value representing the number of milliseconds
46 * since the SDL library initialized.
47 *
48 * \sa SDL_TICKS_PASSED
49 */
50extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
51
52/**
53 * Compare SDL ticks values, and return true if `A` has passed `B`.
54 *
55 * For example, if you want to wait 100 ms, you could do this:
56 *
57 * ```c++
58 * Uint32 timeout = SDL_GetTicks() + 100;
59 * while (!SDL_TICKS_PASSED(SDL_GetTicks(), timeout)) {
60 * // ... do work until timeout has elapsed
61 * }
62 * ```
63 */
64#define SDL_TICKS_PASSED(A, B) ((Sint32)((B) - (A)) <= 0)
65
66/**
67 * Get the current value of the high resolution counter.
68 *
69 * This function is typically used for profiling.
70 *
71 * The counter values are only meaningful relative to each other. Differences
72 * between values can be converted to times by using
73 * SDL_GetPerformanceFrequency().
74 *
75 * \returns the current counter value.
76 *
77 * \sa SDL_GetPerformanceFrequency
78 */
79extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceCounter(void);
80
81/**
82 * Get the count per second of the high resolution counter.
83 *
84 * \returns a platform-specific count per second.
85 *
86 * \since This function is available since SDL 2.0.0.
87 *
88 * \sa SDL_GetPerformanceCounter
89 */
90extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceFrequency(void);
91
92/**
93 * Wait a specified number of milliseconds before returning.
94 *
95 * This function waits a specified number of milliseconds before returning. It
96 * waits at least the specified time, but possibly longer due to OS
97 * scheduling.
98 *
99 * \param ms the number of milliseconds to delay
100 */
101extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
102
103/**
104 * Function prototype for the timer callback function.
105 *
106 * The callback function is passed the current timer interval and returns
107 * the next timer interval. If the returned value is the same as the one
108 * passed in, the periodic alarm continues, otherwise a new alarm is
109 * scheduled. If the callback returns 0, the periodic alarm is cancelled.
110 */
111typedef Uint32 (SDLCALL * SDL_TimerCallback) (Uint32 interval, void *param);
112
113/**
114 * Definition of the timer ID type.
115 */
116typedef int SDL_TimerID;
117
118/**
119 * Call a callback function at a future time.
120 *
121 * If you use this function, you must pass `SDL_INIT_TIMER` to SDL_Init().
122 *
123 * The callback function is passed the current timer interval and the user
124 * supplied parameter from the SDL_AddTimer() call and should return the next
125 * timer interval. If the value returned from the callback is 0, the timer is
126 * canceled.
127 *
128 * The callback is run on a separate thread.
129 *
130 * Timers take into account the amount of time it took to execute the
131 * callback. For example, if the callback took 250 ms to execute and returned
132 * 1000 (ms), the timer would only wait another 750 ms before its next
133 * iteration.
134 *
135 * Timing may be inexact due to OS scheduling. Be sure to note the current
136 * time with SDL_GetTicks() or SDL_GetPerformanceCounter() in case your
137 * callback needs to adjust for variances.
138 *
139 * \param interval the timer delay, in milliseconds, passed to `callback`
140 * \param callback the SDL_TimerCallback function to call when the specified
141 * `interval` elapses
142 * \param param a pointer that is passed to `callback`
143 * \returns a timer ID or 0 if an error occurs; call SDL_GetError() for more
144 * information.
145 *
146 * \sa SDL_RemoveTimer
147 */
148extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval,
149 SDL_TimerCallback callback,
150 void *param);
151
152/**
153 * Remove a timer created with SDL_AddTimer().
154 *
155 * \param id the ID of the timer to remove
156 * \returns SDL_TRUE if the timer is removed or SDL_FALSE if the timer wasn't
157 * found.
158 *
159 * \sa SDL_AddTimer
160 */
161extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID id);
162
163
164/* Ends C function definitions when using C++ */
165#ifdef __cplusplus
166}
167#endif
168#include "close_code.h"
169
170#endif /* SDL_timer_h_ */
171
172/* vi: set ts=4 sw=4 expandtab: */
173