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Timer.cpp
资源名称：tanksrc.zip　[点击查看]
上传用户：royluo
上传日期：2007-01-05
资源大小：1584k
文件大小：5k
源码类别：

游戏

开发平台：

Visual C++

Timer.cpp：源码内容
  1. /*****************************************************************************
  2. *                                                                             
  3. *   Timer.cpp                                                            
  4. *                                                                             
  5. *   Electrical Engineering Faculty - Software Lab                             
  6. *   Spring semester 1998                                                      
  7. *                                                                             
  8. *   Tanks game                                                                
  9. *                                                                             
  10. *   Module description: Calculates the time delta between the local time and 
  11. *                       the host machine local time.
  12. *                       
  13. *                                                                             
  14. *   Authors: Eran Yariv - 28484475                                           
  15. *            Moshe Zur  - 24070856                                           
  16. *                                                                            
  17. *                                                                            
  18. *   Date: 23/09/98                                                           
  19. *                                                                            
  20. ******************************************************************************/
  21. #include <stdafx.h>
  22. #include <Timer.h>
  23. #include <math.h>
  25. /****************** CTimer **********************/
  27. CTimer::CTimer (BOOL bForceLowResTimers) : m_bFirstSample (TRUE)
  28. {
  29.     LARGE_INTEGER   liFreq;
  30.     if (!bForceLowResTimers && QueryPerformanceFrequency( &liFreq ))
  31.     {   // User didn't force us to use low resoultion timer and 
  32.         // the high res timer is supported by the system
  33.         ASSERT (liFreq.QuadPart > 0);
  34.         m_llFreq = liFreq.QuadPart / LONGLONG (1000);
  35.         m_pActualSampleFunction = this->SampleLocalTimeWithPerfCounters;
  36.     }
  37.     else
  38.     {
  39.         m_pActualSampleFunction = GetTickCount;
  40.     }
  41. }
  43. DWORD CALLBACK
  44. CTimer::SampleLocalTimeWithPerfCounters()
  45. {
  46.     LARGE_INTEGER li;    
  47.     QueryPerformanceCounter (&li);
  48.     return DWORD (li.QuadPart / m_llFreq);
  49. }
  51. LONGLONG CTimer::m_llFreq;
  53. /****************** CVanJacobsonTimer **********************/
  55. /*------------------------------------------------------------------------------
  57.   Function: UpdateDelta
  59.   Purpose:  Updates the delta between the local timer (on this machine) and the 
  60.             host machine timer, using the Van-Jacobson algo. (used in TCP protocol)
  61.             based on former samples. This algo. gives more damped results than the
  62.             smoothed average algo..
  64.   Input:    dwRemoteTime - a new delta sample calculated from last message.
  66.   Output:   Returns last sample of local time.
  68.   Remarks:  
  70. ------------------------------------------------------------------------------*/
  71. DWORD
  72. CVanJacobsonTimer::UpdateDelta (DWORD dwRemoteTime)
  73. {
  74.     DWORD dwCurLocalTime = GetLocalTime ();
  75.     LONG lCurDelta = LONG(dwCurLocalTime) - LONG (dwRemoteTime);
  77.     if (m_bFirstSample)
  78.     {
  79.         m_lLastDelta = lCurDelta;
  80.         m_dPrevSRTT = double(lCurDelta);
  81.         m_dPrevSDEV = 0.0;
  82.     }
  83.     else
  84.     {
  85.         double dSRTT = (1.0 - VJ_g) * double(m_dPrevSRTT) + VJ_g * double(lCurDelta);
  86.         double dERR  = double(lCurDelta) - double(m_dPrevSRTT);
  87.         double dSDEV = (1.0 - VJ_h) * m_dPrevSDEV + VJ_h * fabs(dERR);
  88.         double dRTO  = dSRTT + VJ_f * dSDEV;
  90.         m_lLastDelta = LONG(dRTO);
  92.         // Update previous values:
  93.         m_dPrevSRTT = dSRTT;
  94.         m_dPrevSDEV = dSDEV;
  95.     }
  96.     return dwCurLocalTime;   // Return sampled local time
  97. }
  99. /****************** CSmoothedAverageTimer **********************/
  101. CSmoothedAverageTimer::CSmoothedAverageTimer  (BOOL bForceLowResTimers) :
  102.     CTimer (bForceLowResTimers),
  103.     m_dPrevDelta (0.0)
  104. {}
  106. /*------------------------------------------------------------------------------
  108.   Function: UpdateDelta
  110.   Purpose:  Updates the delta between the local timer (on this machine) and the 
  111.             host machine timer, using the smoothed average algo..
  113.   Input:    dwRemoteTime - a new delta sample calculated from last message.
  115.   Output:   Returns last sample of local time.
  117.   Remarks:  
  119. ------------------------------------------------------------------------------*/
  120. DWORD
  121. CSmoothedAverageTimer::UpdateDelta (DWORD dwRemoteTime)
  122. // Returns last sample of local time, updates m_lLastDelta 
  123. {
  124.     DWORD dwCurLocalTime = GetLocalTime ();
  125.     LONG lCurDelta = LONG(dwCurLocalTime) - LONG (dwRemoteTime);
  127.     if (!m_bFirstSample)
  128.     {   // Not first time we get a sample
  129.         m_dPrevDelta = ALPHA * m_dPrevDelta + ONE_MINUS_ALPHA * double(lCurDelta);
  130.     }
  131.     else 
  132.     {   // First time we get a sample
  133.         m_bFirstSample = FALSE; // Turn it off
  134.         m_dPrevDelta = lCurDelta;
  135.     }
  137.     m_lLastDelta = LONG (m_dPrevDelta);
  138.     return dwCurLocalTime;   // Return sampled local time
  139. }