1 /*
2 * This software is licensed under the terms of the MIT License.
3 * See COPYING for further information.
4 * ---
5 * Copyright (c) 2011-2019, Lukas Weber <laochailan@web.de>.
6 * Copyright (c) 2012-2019, Andrei Alexeyev <akari@taisei-project.org>.
7 */
8
9 #include "taisei.h"
10
11 #include "util.h"
12 #include "hirestime.h"
13
14 static bool use_hires;
15 static hrtime_t time_current;
16 static hrtime_t time_offset;
17 static uint64_t prev_hires_time;
18 static uint64_t prev_hires_freq;
19 static uint64_t fast_path_mul;
20
set_freq(uint64_t freq)21 INLINE void set_freq(uint64_t freq) {
22 prev_hires_freq = freq;
23 lldiv_t d = lldiv(HRTIME_RESOLUTION, freq);
24 fast_path_mul = d.quot * (d.rem == 0);
25 }
26
time_update(void)27 static void time_update(void) {
28 bool retry;
29
30 do {
31 retry = false;
32
33 uint64_t freq = SDL_GetPerformanceFrequency();
34 uint64_t cntr = SDL_GetPerformanceCounter();
35
36 if(freq != prev_hires_freq) {
37 log_debug("High resolution timer frequency changed: was %"PRIu64", now %"PRIu64". Saved time offset: %"PRIuTIME"", prev_hires_freq, freq, time_offset);
38 time_offset = time_current;
39 set_freq(freq);
40 prev_hires_time = SDL_GetPerformanceCounter();
41 retry = true;
42 continue;
43 }
44
45 hrtime_t time_new;
46
47 if(fast_path_mul) {
48 time_new = time_offset + (cntr - prev_hires_time) * fast_path_mul;
49 } else {
50 time_new = time_offset + umuldiv64(cntr - prev_hires_time, HRTIME_RESOLUTION, freq);
51 }
52
53 if(time_new < time_current) {
54 log_warn("BUG: time went backwards. Was %"PRIuTIME", now %"PRIuTIME". Possible cause: your OS sucks spherical objects. Attempting to correct this...", time_current, time_new);
55 time_offset = time_current;
56 time_current = 0;
57 prev_hires_time = SDL_GetPerformanceCounter();
58 retry = true;
59 } else {
60 time_current = time_new;
61 }
62 } while(retry);
63 }
64
time_init(void)65 void time_init(void) {
66 use_hires = env_get("TAISEI_HIRES_TIMER", 1);
67
68 if(use_hires) {
69 log_info("Using the system high resolution timer");
70 prev_hires_time = SDL_GetPerformanceCounter();
71 set_freq(SDL_GetPerformanceFrequency());
72 } else {
73 log_info("Not using the system high resolution timer: disabled by environment");
74 return;
75 }
76 }
77
time_shutdown(void)78 void time_shutdown(void) {
79
80 }
81
time_get(void)82 hrtime_t time_get(void) {
83 if(use_hires) {
84 assert(is_main_thread());
85 time_update();
86 return time_current;
87 }
88
89 return SDL_GetTicks() * (HRTIME_RESOLUTION / 1000);
90 }
91