Atlas - SDL_systimer.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2025 Sam Lantinga <[email protected]>
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#include "SDL_internal.h"
22
23#ifdef SDL_TIMER_UNIX
24
25#include <stdio.h>
26#include <sys/time.h>
27#include <unistd.h>
28#include <errno.h>
29
30#include "../SDL_timer_c.h"
31
32#ifdef SDL_PLATFORM_EMSCRIPTEN
33#include <emscripten.h>
34#endif
35
36/* The clock_gettime provides monotonous time, so we should use it if
37   it's available. The clock_gettime function is behind ifdef
38   for __USE_POSIX199309
39   Tommi Kyntola ([email protected]) 27/09/2005
40*/
41/* Reworked monotonic clock to not assume the current system has one
42   as not all linux kernels provide a monotonic clock (yeah recent ones
43   probably do)
44   Also added macOS Monotonic clock support
45   Based on work in https://github.com/ThomasHabets/monotonic_clock
46 */
47#if defined(HAVE_NANOSLEEP) || defined(HAVE_CLOCK_GETTIME)
48#include <time.h>
49#endif
50#ifdef SDL_PLATFORM_APPLE
51#include <mach/mach_time.h>
52#endif
53
54// Use CLOCK_MONOTONIC_RAW, if available, which is not subject to adjustment by NTP
55#ifdef HAVE_CLOCK_GETTIME
56// Older Android phones have a buggy CLOCK_MONOTONIC_RAW, use CLOCK_MONOTONIC
57// See fix: https://github.com/torvalds/linux/commit/dbb236c1ceb697a559e0694ac4c9e7b9131d0b16
58#if defined(CLOCK_MONOTONIC_RAW) && !defined(__ANDROID__)
59#define SDL_MONOTONIC_CLOCK CLOCK_MONOTONIC_RAW
60#else
61#define SDL_MONOTONIC_CLOCK CLOCK_MONOTONIC
62#endif
63#endif
64
65// The first ticks value of the application
66#if !defined(HAVE_CLOCK_GETTIME) && defined(SDL_PLATFORM_APPLE)
67mach_timebase_info_data_t mach_base_info;
68#endif
69static bool checked_monotonic_time = false;
70static bool has_monotonic_time = false;
71
72static void CheckMonotonicTime(void)
73{
74#ifdef HAVE_CLOCK_GETTIME
75    struct timespec value;
76    if (clock_gettime(SDL_MONOTONIC_CLOCK, &value) == 0) {
77        has_monotonic_time = true;
78    }
79#elif defined(SDL_PLATFORM_APPLE)
80    if (mach_timebase_info(&mach_base_info) == 0) {
81        has_monotonic_time = true;
82    }
83#endif
84    checked_monotonic_time = true;
85}
86
87Uint64 SDL_GetPerformanceCounter(void)
88{
89    Uint64 ticks;
90
91    if (!checked_monotonic_time) {
92        CheckMonotonicTime();
93    }
94
95    if (has_monotonic_time) {
96#ifdef HAVE_CLOCK_GETTIME
97        struct timespec now;
98
99        clock_gettime(SDL_MONOTONIC_CLOCK, &now);
100        ticks = now.tv_sec;
101        ticks *= SDL_NS_PER_SECOND;
102        ticks += now.tv_nsec;
103#elif defined(SDL_PLATFORM_APPLE)
104        ticks = mach_absolute_time();
105#else
106        SDL_assert(false);
107        ticks = 0;
108#endif
109    } else {
110        struct timeval now;
111
112        gettimeofday(&now, NULL);
113        ticks = now.tv_sec;
114        ticks *= SDL_US_PER_SECOND;
115        ticks += now.tv_usec;
116    }
117    return ticks;
118}
119
120Uint64 SDL_GetPerformanceFrequency(void)
121{
122    if (!checked_monotonic_time) {
123        CheckMonotonicTime();
124    }
125
126    if (has_monotonic_time) {
127#ifdef HAVE_CLOCK_GETTIME
128        return SDL_NS_PER_SECOND;
129#elif defined(SDL_PLATFORM_APPLE)
130        Uint64 freq = mach_base_info.denom;
131        freq *= SDL_NS_PER_SECOND;
132        freq /= mach_base_info.numer;
133        return freq;
134#endif
135    }
136
137    return SDL_US_PER_SECOND;
138}
139
140void SDL_SYS_DelayNS(Uint64 ns)
141{
142    int was_error;
143
144#ifdef HAVE_NANOSLEEP
145    struct timespec tv, remaining;
146#else
147    struct timeval tv;
148    Uint64 then, now, elapsed;
149#endif
150
151#ifdef SDL_PLATFORM_EMSCRIPTEN
152    if (emscripten_has_asyncify() && SDL_GetHintBoolean(SDL_HINT_EMSCRIPTEN_ASYNCIFY, true)) {
153        // pseudo-synchronous pause, used directly or through e.g. SDL_WaitEvent
154        emscripten_sleep(ns / SDL_NS_PER_MS);
155        return;
156    }
157#endif
158
159    // Set the timeout interval
160#ifdef HAVE_NANOSLEEP
161    remaining.tv_sec = (time_t)(ns / SDL_NS_PER_SECOND);
162    remaining.tv_nsec = (long)(ns % SDL_NS_PER_SECOND);
163#else
164    then = SDL_GetTicksNS();
165#endif
166    do {
167        errno = 0;
168
169#ifdef HAVE_NANOSLEEP
170        tv.tv_sec = remaining.tv_sec;
171        tv.tv_nsec = remaining.tv_nsec;
172        was_error = nanosleep(&tv, &remaining);
173#else
174        // Calculate the time interval left (in case of interrupt)
175        now = SDL_GetTicksNS();
176        elapsed = (now - then);
177        then = now;
178        if (elapsed >= ns) {
179            break;
180        }
181        ns -= elapsed;
182        tv.tv_sec = (ns / SDL_NS_PER_SECOND);
183        tv.tv_usec = SDL_NS_TO_US(ns % SDL_NS_PER_SECOND);
184
185        was_error = select(0, NULL, NULL, NULL, &tv);
186#endif // HAVE_NANOSLEEP
187    } while (was_error && (errno == EINTR));
188}
189
190#endif // SDL_TIMER_UNIX
191
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