1 /*
2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "webrtc/system_wrappers/include/clock.h"
12
13 #if defined(_WIN32)
14 // Windows needs to be included before mmsystem.h
15 #include "webrtc/base/win32.h"
16 #include <MMSystem.h>
17 #elif ((defined WEBRTC_LINUX) || (defined WEBRTC_MAC))
18 #include <sys/time.h>
19 #include <time.h>
20 #endif
21
22 #include "webrtc/base/criticalsection.h"
23 #include "webrtc/system_wrappers/include/rw_lock_wrapper.h"
24 #include "webrtc/system_wrappers/include/tick_util.h"
25
26 namespace webrtc {
27
28 const double kNtpFracPerMs = 4.294967296E6;
29
NtpToMs(uint32_t ntp_secs,uint32_t ntp_frac)30 int64_t Clock::NtpToMs(uint32_t ntp_secs, uint32_t ntp_frac) {
31 const double ntp_frac_ms = static_cast<double>(ntp_frac) / kNtpFracPerMs;
32 return 1000 * static_cast<int64_t>(ntp_secs) +
33 static_cast<int64_t>(ntp_frac_ms + 0.5);
34 }
35
36 class RealTimeClock : public Clock {
37 // Return a timestamp in milliseconds relative to some arbitrary source; the
38 // source is fixed for this clock.
TimeInMilliseconds() const39 int64_t TimeInMilliseconds() const override {
40 return TickTime::MillisecondTimestamp();
41 }
42
43 // Return a timestamp in microseconds relative to some arbitrary source; the
44 // source is fixed for this clock.
TimeInMicroseconds() const45 int64_t TimeInMicroseconds() const override {
46 return TickTime::MicrosecondTimestamp();
47 }
48
49 // Retrieve an NTP absolute timestamp in seconds and fractions of a second.
CurrentNtp(uint32_t & seconds,uint32_t & fractions) const50 void CurrentNtp(uint32_t& seconds, uint32_t& fractions) const override {
51 timeval tv = CurrentTimeVal();
52 double microseconds_in_seconds;
53 Adjust(tv, &seconds, µseconds_in_seconds);
54 fractions = static_cast<uint32_t>(
55 microseconds_in_seconds * kMagicNtpFractionalUnit + 0.5);
56 }
57
58 // Retrieve an NTP absolute timestamp in milliseconds.
CurrentNtpInMilliseconds() const59 int64_t CurrentNtpInMilliseconds() const override {
60 timeval tv = CurrentTimeVal();
61 uint32_t seconds;
62 double microseconds_in_seconds;
63 Adjust(tv, &seconds, µseconds_in_seconds);
64 return 1000 * static_cast<int64_t>(seconds) +
65 static_cast<int64_t>(1000.0 * microseconds_in_seconds + 0.5);
66 }
67
68 protected:
69 virtual timeval CurrentTimeVal() const = 0;
70
Adjust(const timeval & tv,uint32_t * adjusted_s,double * adjusted_us_in_s)71 static void Adjust(const timeval& tv, uint32_t* adjusted_s,
72 double* adjusted_us_in_s) {
73 *adjusted_s = tv.tv_sec + kNtpJan1970;
74 *adjusted_us_in_s = tv.tv_usec / 1e6;
75
76 if (*adjusted_us_in_s >= 1) {
77 *adjusted_us_in_s -= 1;
78 ++*adjusted_s;
79 } else if (*adjusted_us_in_s < -1) {
80 *adjusted_us_in_s += 1;
81 --*adjusted_s;
82 }
83 }
84 };
85
86 #if defined(_WIN32)
87 // TODO(pbos): Consider modifying the implementation to synchronize itself
88 // against system time (update ref_point_, make it non-const) periodically to
89 // prevent clock drift.
90 class WindowsRealTimeClock : public RealTimeClock {
91 public:
WindowsRealTimeClock()92 WindowsRealTimeClock()
93 : last_time_ms_(0),
94 num_timer_wraps_(0),
95 ref_point_(GetSystemReferencePoint()) {}
96
~WindowsRealTimeClock()97 virtual ~WindowsRealTimeClock() {}
98
99 protected:
100 struct ReferencePoint {
101 FILETIME file_time;
102 LARGE_INTEGER counter_ms;
103 };
104
CurrentTimeVal() const105 timeval CurrentTimeVal() const override {
106 const uint64_t FILETIME_1970 = 0x019db1ded53e8000;
107
108 FILETIME StartTime;
109 uint64_t Time;
110 struct timeval tv;
111
112 // We can't use query performance counter since they can change depending on
113 // speed stepping.
114 GetTime(&StartTime);
115
116 Time = (((uint64_t) StartTime.dwHighDateTime) << 32) +
117 (uint64_t) StartTime.dwLowDateTime;
118
119 // Convert the hecto-nano second time to tv format.
120 Time -= FILETIME_1970;
121
122 tv.tv_sec = (uint32_t)(Time / (uint64_t)10000000);
123 tv.tv_usec = (uint32_t)((Time % (uint64_t)10000000) / 10);
124 return tv;
125 }
126
GetTime(FILETIME * current_time) const127 void GetTime(FILETIME* current_time) const {
128 DWORD t;
129 LARGE_INTEGER elapsed_ms;
130 {
131 rtc::CritScope lock(&crit_);
132 // time MUST be fetched inside the critical section to avoid non-monotonic
133 // last_time_ms_ values that'll register as incorrect wraparounds due to
134 // concurrent calls to GetTime.
135 t = timeGetTime();
136 if (t < last_time_ms_)
137 num_timer_wraps_++;
138 last_time_ms_ = t;
139 elapsed_ms.HighPart = num_timer_wraps_;
140 }
141 elapsed_ms.LowPart = t;
142 elapsed_ms.QuadPart = elapsed_ms.QuadPart - ref_point_.counter_ms.QuadPart;
143
144 // Translate to 100-nanoseconds intervals (FILETIME resolution)
145 // and add to reference FILETIME to get current FILETIME.
146 ULARGE_INTEGER filetime_ref_as_ul;
147 filetime_ref_as_ul.HighPart = ref_point_.file_time.dwHighDateTime;
148 filetime_ref_as_ul.LowPart = ref_point_.file_time.dwLowDateTime;
149 filetime_ref_as_ul.QuadPart +=
150 static_cast<ULONGLONG>((elapsed_ms.QuadPart) * 1000 * 10);
151
152 // Copy to result
153 current_time->dwHighDateTime = filetime_ref_as_ul.HighPart;
154 current_time->dwLowDateTime = filetime_ref_as_ul.LowPart;
155 }
156
GetSystemReferencePoint()157 static ReferencePoint GetSystemReferencePoint() {
158 ReferencePoint ref = {};
159 FILETIME ft0 = {};
160 FILETIME ft1 = {};
161 // Spin waiting for a change in system time. As soon as this change happens,
162 // get the matching call for timeGetTime() as soon as possible. This is
163 // assumed to be the most accurate offset that we can get between
164 // timeGetTime() and system time.
165
166 // Set timer accuracy to 1 ms.
167 timeBeginPeriod(1);
168 GetSystemTimeAsFileTime(&ft0);
169 do {
170 GetSystemTimeAsFileTime(&ft1);
171
172 ref.counter_ms.QuadPart = timeGetTime();
173 Sleep(0);
174 } while ((ft0.dwHighDateTime == ft1.dwHighDateTime) &&
175 (ft0.dwLowDateTime == ft1.dwLowDateTime));
176 ref.file_time = ft1;
177 timeEndPeriod(1);
178 return ref;
179 }
180
181 // mutable as time-accessing functions are const.
182 mutable rtc::CriticalSection crit_;
183 mutable DWORD last_time_ms_;
184 mutable LONG num_timer_wraps_;
185 const ReferencePoint ref_point_;
186 };
187
188 #elif ((defined WEBRTC_LINUX) || (defined WEBRTC_MAC))
189 class UnixRealTimeClock : public RealTimeClock {
190 public:
UnixRealTimeClock()191 UnixRealTimeClock() {}
192
~UnixRealTimeClock()193 ~UnixRealTimeClock() override {}
194
195 protected:
CurrentTimeVal() const196 timeval CurrentTimeVal() const override {
197 struct timeval tv;
198 struct timezone tz;
199 tz.tz_minuteswest = 0;
200 tz.tz_dsttime = 0;
201 gettimeofday(&tv, &tz);
202 return tv;
203 }
204 };
205 #endif
206
207 #if defined(_WIN32)
208 static WindowsRealTimeClock* volatile g_shared_clock = nullptr;
209 #endif
GetRealTimeClock()210 Clock* Clock::GetRealTimeClock() {
211 #if defined(_WIN32)
212 // This read relies on volatile read being atomic-load-acquire. This is
213 // true in MSVC since at least 2005:
214 // "A read of a volatile object (volatile read) has Acquire semantics"
215 if (g_shared_clock != nullptr)
216 return g_shared_clock;
217 WindowsRealTimeClock* clock = new WindowsRealTimeClock;
218 if (InterlockedCompareExchangePointer(
219 reinterpret_cast<void* volatile*>(&g_shared_clock), clock, nullptr) !=
220 nullptr) {
221 // g_shared_clock was assigned while we constructed/tried to assign our
222 // instance, delete our instance and use the existing one.
223 delete clock;
224 }
225 return g_shared_clock;
226 #elif defined(WEBRTC_LINUX) || defined(WEBRTC_MAC)
227 static UnixRealTimeClock clock;
228 return &clock;
229 #else
230 return NULL;
231 #endif
232 }
233
SimulatedClock(int64_t initial_time_us)234 SimulatedClock::SimulatedClock(int64_t initial_time_us)
235 : time_us_(initial_time_us), lock_(RWLockWrapper::CreateRWLock()) {
236 }
237
~SimulatedClock()238 SimulatedClock::~SimulatedClock() {
239 }
240
TimeInMilliseconds() const241 int64_t SimulatedClock::TimeInMilliseconds() const {
242 ReadLockScoped synchronize(*lock_);
243 return (time_us_ + 500) / 1000;
244 }
245
TimeInMicroseconds() const246 int64_t SimulatedClock::TimeInMicroseconds() const {
247 ReadLockScoped synchronize(*lock_);
248 return time_us_;
249 }
250
CurrentNtp(uint32_t & seconds,uint32_t & fractions) const251 void SimulatedClock::CurrentNtp(uint32_t& seconds, uint32_t& fractions) const {
252 int64_t now_ms = TimeInMilliseconds();
253 seconds = (now_ms / 1000) + kNtpJan1970;
254 fractions =
255 static_cast<uint32_t>((now_ms % 1000) * kMagicNtpFractionalUnit / 1000);
256 }
257
CurrentNtpInMilliseconds() const258 int64_t SimulatedClock::CurrentNtpInMilliseconds() const {
259 return TimeInMilliseconds() + 1000 * static_cast<int64_t>(kNtpJan1970);
260 }
261
AdvanceTimeMilliseconds(int64_t milliseconds)262 void SimulatedClock::AdvanceTimeMilliseconds(int64_t milliseconds) {
263 AdvanceTimeMicroseconds(1000 * milliseconds);
264 }
265
AdvanceTimeMicroseconds(int64_t microseconds)266 void SimulatedClock::AdvanceTimeMicroseconds(int64_t microseconds) {
267 WriteLockScoped synchronize(*lock_);
268 time_us_ += microseconds;
269 }
270
271 }; // namespace webrtc
272