Windows下的高精度定时器实现及精确时刻获取

原帖地址 http://blog.csdn.net/akumas/article/details/5703366

感谢作者 akumas

    通讯、VOIP、视频等领域的很多核心技术对时间精度的要求非常高，比如数据采集、时间同步、媒体流平滑控制、拥塞算法等等，很多技术都是以毫秒为单位来进行计算和控制的。但是Windows设计之初并不是以实时系统为目标的，所以Windows系统的时间精度一直不高，实际最小单位是15ms左右，导致的结果就是所有Windows的时间、线程相关的操作都无法以1ms来实现精确控制。

 

受影响的操作包括Sleep、GetTickCount、_ftime等等。比如你调用Sleep(2)，期待2ms之后线程自动唤醒，但是实际结果可能是15ms甚至2x ms的时候才会唤醒，对于简单应用来说影响不大，但是对于精度要求非常高的系统来说，这样的问题就是非常致命的了。

 

代码思路如下：

1、高精度定时器。使用Singleton模式挂起请求Sleep的线程并统一管理，后台使用Windows MultiMedia SDK的定期回调函数不断检测并回复到时的线程，超时时间与当前时间采用QueryPerformanceCounter/QueryPerformanceFrequency的高精度计时，确保整体功能可靠性。

2、精确时刻获取。由于可以获取到毫秒级别的_ftime与GetTickCount都受到Windows系统时间精度影响，最小单位只有15ms，所以需要借助QueryPerformanceCounter/QueryPerformanceFrequency进行准确计时。代码首先根据_ftime获取起始时刻的精确刻度，然后根据差量计算当前的精确时刻。

 

代码中的Singleton模式可以找到很多实现，因此本文不进行详述

代码（VS2005 c++编译）

1、高精度定时器

 

 

[c-sharp] view plaincopyprint?

1. #pragma once  
2.  
3. #include <Windows.h>  
4. #include <list>  
5. #include <akumaslab/system/singleton.hpp>  
6.   
7. namespace akumaslab{  
8.     namespace time{  
9.         using std::list;  
10.   
11.         class PreciseTimerProvider  
12.         {  
13.             struct WaitedHandle{  
14.                 HANDLE threadHandle;  
15.                 LONGLONG elapsed;//超时时间  
16.             } ;  
17.             typedef list< WaitedHandle > handle_list_type;  
18.             typedef akumaslab::system::Singleton< PreciseTimerProvider > timer_type;  
19.         public:  
20.             PreciseTimerProvider(void):highResolutionAvailable(false), timerID(0)  
21.             {  
22.                 InitializeCriticalSection(&critical);  
23.                 static LARGE_INTEGER systemFrequency;  
24.                 if(0 != QueryPerformanceFrequency(&systemFrequency))  
25.                 {  
26.                     timeBeginPeriod(callbackInterval);  
27.                     highResolutionAvailable = true;  
28.                     countPerMilliSecond = systemFrequency.QuadPart/1000;  
29.                     timerID = timeSetEvent(callbackInterval, 0, &PreciseTimerProvider::TimerFunc, NULL, TIME_PERIODIC);  
30.                 }  
31.             }  
32.             //挂起当前线程   
33.             //@milliSecond:超时时间，单位：毫秒  
34.             bool suspendCurrentThread(int milliSecond)  
35.             {  
36.                 if(milliSecond <= 0)return false;  
37.                 if (!highResolutionAvailable)return false;  
38.                 HANDLE currentThreadHandle = GetCurrentThread();  
39.                 HANDLE currentProcessHandle = GetCurrentProcess();  
40.                 HANDLE realThreadHandle(0);  
41.                 DuplicateHandle(currentProcessHandle, currentThreadHandle, currentProcessHandle, &realThreadHandle, 0, FALSE, DUPLICATE_SAME_ACCESS);  
42.                 WaitedHandle item;  
43.                 item.threadHandle = realThreadHandle;  
44.                 LARGE_INTEGER now;  
45.                 QueryPerformanceCounter(&now);  
46.                 now.QuadPart += milliSecond * countPerMilliSecond;  
47.                 item.elapsed = now.QuadPart;  
48.                 EnterCriticalSection(&critical);  
49.                 waitList.push_back(item);  
50.                 LeaveCriticalSection(&critical);  
51.                 //挂起线程   
52.                 SuspendThread(realThreadHandle);  
53.                 CloseHandle(realThreadHandle);  
54.                 return true;  
55.             }  
56.             //恢复超时线程   
57.             void resumeTimeoutThread()  
58.             {  
59.                 if (!highResolutionAvailable)return;  
60.                 LARGE_INTEGER now;  
61.                 QueryPerformanceCounter(&now);  
62.                 EnterCriticalSection(&critical);  
63.                 for (handle_list_type::iterator ir = waitList.begin(); ir != waitList.end(); )  
64.                 {  
65.                     WaitedHandle& waited = *ir;  
66.                     if (now.QuadPart >= waited.elapsed)  
67.                     {  
68.                         ResumeThread(waited.threadHandle);  
69.                         ir = waitList.erase(ir);  
70.                         continue;  
71.                     }  
72.                     ir++;  
73.                 }                                 
74.                 LeaveCriticalSection(&critical);  
75.             }  
76.             ~PreciseTimerProvider(){  
77.                 if (0 != timerID)  
78.                 {  
79.                     timeKillEvent(timerID);  
80.                     timerID = 0;  
81.                     timeEndPeriod(callbackInterval);  
82.                 }  
83.                 DeleteCriticalSection(&critical);  
84.             }  
85.         private:  
86.   
87.             static void CALLBACK TimerFunc(UINT uID, UINT uMsg, DWORD dwUser, DWORD dw1, DWORD dw2)  
88.             {  
89.                 static bool initialed = false;  
90.                 if (!initialed)  
91.                 {  
92.                     if (initialWorkThread())  
93.                     {  
94.                         initialed = true;  
95.                     }  
96.                     else{  
97.                         return;  
98.                     }  
99.                 }  
100.                 timer_type::getRef().resumeTimeoutThread();  
101.             }  
102.             //调整定时器工作线程优先级   
103.             static bool initialWorkThread()  
104.             {  
105.                 HANDLE realProcessHandle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, _getpid());  
106.                 if (NULL == realProcessHandle)  
107.                 {  
108.                     return false;  
109.                 }  
110.                 if (0 == SetPriorityClass(realProcessHandle, REALTIME_PRIORITY_CLASS))  
111.                 {  
112.                     CloseHandle(realProcessHandle);  
113.                     return false;  
114.                 }  
115.                 HANDLE currentThreadHandle = GetCurrentThread();  
116.                 HANDLE currentProcessHandle = GetCurrentProcess();  
117.                 HANDLE realThreadHandle(0);  
118.                 DuplicateHandle(currentProcessHandle, currentThreadHandle, currentProcessHandle, &realThreadHandle, 0, FALSE, DUPLICATE_SAME_ACCESS);  
119.                 SetThreadPriority(realThreadHandle, THREAD_PRIORITY_TIME_CRITICAL);  
120.                 //必须关闭复制句柄   
121.                 CloseHandle(realThreadHandle);  
122.                 CloseHandle(realProcessHandle);  
123.                 return true;  
124.             }  
125.         private:  
126.             const static int callbackInterval = 1;  
127.             CRITICAL_SECTION critical;  
128.             MMRESULT timerID;  
129.             LONGLONG countPerMilliSecond;  
130.             bool highResolutionAvailable;  
131.             handle_list_type waitList;  
132.         };  
133.         class PreciseTimer  
134.         {  
135.             typedef akumaslab::system::Singleton< PreciseTimerProvider > timer_type;  
136.         public:  
137.             static bool wait(int milliSecond)  
138.             {  
139.                 //static PreciseTimerProvider timer;  
140.                 return timer_type::getRef().suspendCurrentThread(milliSecond);  
141.             }  
142.         };  
143.     }  
144. }  

#pragma once#include <Windows.h>#include <list>#include <akumaslab/system/singleton.hpp>namespace akumaslab{namespace time{using std::list;class PreciseTimerProvider{struct WaitedHandle{HANDLE threadHandle;LONGLONG elapsed;//超时时间} ;typedef list< WaitedHandle > handle_list_type;typedef akumaslab::system::Singleton< PreciseTimerProvider > timer_type;public:PreciseTimerProvider(void):highResolutionAvailable(false), timerID(0){InitializeCriticalSection(&critical);static LARGE_INTEGER systemFrequency;if(0 != QueryPerformanceFrequency(&systemFrequency)){timeBeginPeriod(callbackInterval);highResolutionAvailable = true;countPerMilliSecond = systemFrequency.QuadPart/1000;timerID = timeSetEvent(callbackInterval, 0, &PreciseTimerProvider::TimerFunc, NULL, TIME_PERIODIC);}}//挂起当前线程//@milliSecond:超时时间，单位：毫秒bool suspendCurrentThread(int milliSecond){if(milliSecond <= 0)return false;if (!highResolutionAvailable)return false;HANDLE currentThreadHandle = GetCurrentThread();HANDLE currentProcessHandle = GetCurrentProcess();HANDLE realThreadHandle(0);DuplicateHandle(currentProcessHandle, currentThreadHandle, currentProcessHandle, &realThreadHandle, 0, FALSE, DUPLICATE_SAME_ACCESS);WaitedHandle item;item.threadHandle = realThreadHandle;LARGE_INTEGER now;QueryPerformanceCounter(&now);now.QuadPart += milliSecond * countPerMilliSecond;item.elapsed = now.QuadPart;EnterCriticalSection(&critical);waitList.push_back(item);LeaveCriticalSection(&critical);//挂起线程SuspendThread(realThreadHandle);CloseHandle(realThreadHandle);return true;}//恢复超时线程void resumeTimeoutThread(){if (!highResolutionAvailable)return;LARGE_INTEGER now;QueryPerformanceCounter(&now);EnterCriticalSection(&critical);for (handle_list_type::iterator ir = waitList.begin(); ir != waitList.end(); ){WaitedHandle& waited = *ir;if (now.QuadPart >= waited.elapsed){ResumeThread(waited.threadHandle);ir = waitList.erase(ir);continue;}ir++;}LeaveCriticalSection(&critical);}~PreciseTimerProvider(){if (0 != timerID){timeKillEvent(timerID);timerID = 0;timeEndPeriod(callbackInterval);}DeleteCriticalSection(&critical);}private:static void CALLBACK TimerFunc(UINT uID, UINT uMsg, DWORD dwUser, DWORD dw1, DWORD dw2){static bool initialed = false;if (!initialed){if (initialWorkThread()){initialed = true;}else{return;}}timer_type::getRef().resumeTimeoutThread();}//调整定时器工作线程优先级static bool initialWorkThread(){HANDLE realProcessHandle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, _getpid());if (NULL == realProcessHandle){return false;}if (0 == SetPriorityClass(realProcessHandle, REALTIME_PRIORITY_CLASS)){CloseHandle(realProcessHandle);return false;}HANDLE currentThreadHandle = GetCurrentThread();HANDLE currentProcessHandle = GetCurrentProcess();HANDLE realThreadHandle(0);DuplicateHandle(currentProcessHandle, currentThreadHandle, currentProcessHandle, &realThreadHandle, 0, FALSE, DUPLICATE_SAME_ACCESS);SetThreadPriority(realThreadHandle, THREAD_PRIORITY_TIME_CRITICAL);//必须关闭复制句柄CloseHandle(realThreadHandle);CloseHandle(realProcessHandle);return true;}private:const static int callbackInterval = 1;CRITICAL_SECTION critical;MMRESULT timerID;LONGLONG countPerMilliSecond;bool highResolutionAvailable;handle_list_type waitList;};class PreciseTimer{typedef akumaslab::system::Singleton< PreciseTimerProvider > timer_type;public:static bool wait(int milliSecond){//static PreciseTimerProvider timer;return timer_type::getRef().suspendCurrentThread(milliSecond);}};}} 

DEMO

[cpp] view plaincopyprint?

1. int interval = 1;  
2. int repeatCount = 50;  
3. cout << getCurrentTime() << "test begin" << endl;  
4. unit.reset();  
5. for (int i = 0; i < repeatCount; i++)  
6. {  
7.     akumaslab::time::PreciseTimer::wait(interval);  
8.     cout << getCurrentTime() << "/" << getNewTime() << " used " << unit.getPreciseElapsedTime() << " ms" << endl;  
9.     unit.reset();  
10. }  

int interval = 1;int repeatCount = 50;cout << getCurrentTime() << "test begin" << endl;unit.reset();for (int i = 0; i < repeatCount; i++){akumaslab::time::PreciseTimer::wait(interval);cout << getCurrentTime() << "/" << getNewTime() << " used " << unit.getPreciseElapsedTime() << " ms" << endl;unit.reset();}

 

2、精确时刻获取

[cpp:firstline[1]] view plaincopyprint?

1. #pragma once   
2.   
3. #include <sys/timeb.h>   
4. #include <time.h>   
5. #include <Windows.h>   
6. #include <akumaslab/system/singleton.hpp>  
7.   
8. namespace akumaslab{  
9.     namespace time{  
10.         struct HighResolutionTime  
11.         {  
12.             int year;  
13.             int month;  
14.             int day;  
15.             int hour;  
16.             int min;  
17.             int second;  
18.             int millisecond;  
19.         };  
20.         class CurrentTimeProvider  
21.         {  
22.         public:  
23.             CurrentTimeProvider():highResolutionAvailable(false), countPerMilliSecond(0), beginCount(0)  
24.             {  
25.                 static LARGE_INTEGER systemFrequency;  
26.                 if(0 != QueryPerformanceFrequency(&systemFrequency))  
27.                 {  
28.                     highResolutionAvailable = true;  
29.                     countPerMilliSecond = systemFrequency.QuadPart/1000;  
30.                     _timeb tb;  
31.                     _ftime_s(&tb);  
32.                     unsigned short currentMilli = tb.millitm;  
33.                     LARGE_INTEGER now;  
34.                     QueryPerformanceCounter(&now);  
35.                     beginCount = now.QuadPart - (currentMilli*countPerMilliSecond);  
36.                 }  
37.             };  
38.             bool getCurrentTime(HighResolutionTime& _time)  
39.             {  
40.                 time_t tt;  
41.                 ::time(&tt);  
42.                 tm now;  
43.                 localtime_s(&now, &tt);  
44.                 _time.year = now.tm_year + 1900;  
45.                 _time.month = now.tm_mon + 1;  
46.                 _time.day = now.tm_mday + 1;  
47.                 _time.hour = now.tm_hour;  
48.                 _time.min = now.tm_min;  
49.                 _time.second = now.tm_sec;  
50.                 if (!highResolutionAvailable)  
51.                 {  
52.                     _time.millisecond = 0;  
53.                 }  
54.                 else{  
55.                     LARGE_INTEGER qfc;  
56.                     QueryPerformanceCounter(&qfc);  
57.                     _time.millisecond = (int)((qfc.QuadPart - beginCount)/countPerMilliSecond)%1000;  
58.                 }  
59.                 return true;  
60.             }  
61.         private:  
62.             bool highResolutionAvailable;  
63.             LONGLONG countPerMilliSecond;  
64.             LONGLONG beginCount;  
65.         };  
66.         class CurrentTime  
67.         {  
68.         public:  
69.             static bool get(HighResolutionTime& _time)  
70.             {  
71.                 return akumaslab::system::Singleton< CurrentTimeProvider >::getRef().getCurrentTime(_time);  
72.             }  
73.         };  
74.     }  
75. }  

#pragma once#include <sys/timeb.h>#include <time.h>#include <Windows.h>#include <akumaslab/system/singleton.hpp>namespace akumaslab{namespace time{struct HighResolutionTime{int year;int month;int day;int hour;int min;int second;int millisecond;};class CurrentTimeProvider{public:CurrentTimeProvider():highResolutionAvailable(false), countPerMilliSecond(0), beginCount(0){static LARGE_INTEGER systemFrequency;if(0 != QueryPerformanceFrequency(&systemFrequency)){highResolutionAvailable = true;countPerMilliSecond = systemFrequency.QuadPart/1000;_timeb tb;_ftime_s(&tb);unsigned short currentMilli = tb.millitm;LARGE_INTEGER now;QueryPerformanceCounter(&now);beginCount = now.QuadPart - (currentMilli*countPerMilliSecond);}};bool getCurrentTime(HighResolutionTime& _time){time_t tt;::time(&tt);tm now;localtime_s(&now, &tt);_time.year = now.tm_year + 1900;_time.month = now.tm_mon + 1;_time.day = now.tm_mday + 1;_time.hour = now.tm_hour;_time.min = now.tm_min;_time.second = now.tm_sec;if (!highResolutionAvailable){_time.millisecond = 0;}else{LARGE_INTEGER qfc;QueryPerformanceCounter(&qfc);_time.millisecond = (int)((qfc.QuadPart - beginCount)/countPerMilliSecond)%1000;}return true;}private:bool highResolutionAvailable;LONGLONG countPerMilliSecond;LONGLONG beginCount;};class CurrentTime{public:static bool get(HighResolutionTime& _time){return akumaslab::system::Singleton< CurrentTimeProvider >::getRef().getCurrentTime(_time);}};}}

DEMO：

[cpp] view plaincopyprint?

1. HighResolutionTime time;  
2. CurrentTime::get(time);  
3. const int size = 20;  
4. char buf[size] = {0};  
5. _snprintf_s(buf, size, size, "%02d:%02d %02d:%02d:%02d.%03d ", time.month, time.day, time.hour, time.min, time.second, time.millisecond);  

HighResolutionTime time;CurrentTime::get(time);const int size = 20;char buf[size] = {0};_snprintf_s(buf, size, size, "%02d:%02d %02d:%02d:%02d.%03d ", time.month, time.day, time.hour, time.min, time.second, time.millisecond);

 

测试结果如下，下图是高精度计时器按1ms进行Sleep的结果，左侧为使用_ftime计时，右侧为使用精确时刻计时，总体来说，虽然无法达到100%可靠，但是相对原来的15ms已经有较大提升，期望Windows能够尽快提供真正的高精度时间管理技术