C++高精度定时器

1. ///////////////////////////////////////////////////////////////////////////////
2. //KTimer.h
3. //
4. //WindowsGraphicsProgrammingWin32GDIandDirectDraw®
5. //FengYuan
6. //Publisher:PrenticeHallPTR
7. //FirstEditionDecember01,2000
8. //
9. //高精度纳秒计时器,最后修改:
10. //[e-mail]
11. ///////////////////////////////////////////////////////////////////////////////
12. /*Usage:
14. intmain()
15. {
16. KTimerkt;
17. unsignedintcpu_speed=kt.CPUSpeedMHz();
19. kt.Start();
21. Sleep(1234);
23. unsignedintelapsed_cyc=(unsignedint)kt.Stop();
25. printf("CPUSpeed:%.2fGhz.Elapsed%ldCPUCycles(%ldNanosecond)/n",
26. cpu_speed/1000.f,
27. elapsed_cyc,
28. KTimer::CyclesToNanos(elapsed_cyc,cpu_speed));
29. }
30. */
31. #pragmaonce
33. #ifndefSTRICT
34. #defineSTRICT
35. #endif
37. #ifndefWIN32_LEAN_AND_MEAN
38. #defineWIN32_LEAN_AND_MEAN
39. #endif
41. #include<windows.h>
43. inlineunsigned__int64GetCycleCount(void)
44. {
45. _asm_emit0x0F
46. _asm_emit0x31
47. }
49. classKTimer
50. {
51. unsigned__int64m_startcycle;
53. public:
55. unsigned__int64m_overhead;//ClockCycles
57. KTimer(void)
58. {
59. m_overhead=0;
60. Start();
61. m_overhead=Stop();
62. }
64. //启动CPU时钟
65. voidStart(void)
66. {
67. m_startcycle=GetCycleCount();
68. }
70. //停止CPU时钟,返回自上一次启动的时钟周期数
71. unsigned__int64Stop(void)
72. {
73. returnGetCycleCount()-m_startcycle-m_overhead;
74. }
76. //把以CPU周期数转为纳秒
77. unsigned__int64staticCyclesToNanos(unsigned__int64time_cycles,unsignedintspeed_mhz)
78. {
79. returntime_cycles*1000/speed_mhz;
80. }
82. //把以CPU周期数转为毫秒
83. unsigned__int64staticCyclesToMillis(unsigned__int64time_cycles,unsignedintspeed_mhz)
84. {
85. returntime_cycles/speed_mhz/1000;
86. }
88. //1GHz=1000MHz
89. unsignedintCPUSpeedMHz()
90. {
91. Start();
92. Sleep(1000);
93. unsigned__int64cputime=Stop();
95. return(unsignedint)(cputime/1000000);
96. }
97. };