void frameController::capFps(){  if(targetFps == 0) return; //do nothing if fps is uncapped  while(true){    //find the current tick of the high resolution timer    QueryPerformanceCounter(&hpt);    //if done waiting    if(hpt.QuadPart >= frameStartTicks + maxTicksPerFrame)      break; //exit the while loop    //Sleep(1); //yield to cpu  }}

#include <cstdlib>#include <iostream>#include <Windows.h>using namespace std;//very basic abs functionint abs(int in){  if(in < 0){    return -in;  }  return in;}class frameController{  private:    LARGE_INTEGER hpt; //64 bit result holder for the high performance timer    LONGLONG ticksPerSecond, //resolution of the high performance timer    frameStartTicks, //ticks at the start of the previous frame    frameNowTicks, //ticks at the time step is called    initTicks, //ticks when the frame controller was initialised    ticksForFrame, //ticks that the frame took to process    totalFrameTicks, //ticks the frame took including capped idle time    maxTicksPerFrame; //maximum number of ticks a frame should take        //calculates the animation factor    void calcAnimFactor();    //calculates how many ticks the frame took to compute    void calcTicksForFrame();    //calculates the fps    void calcFps();    //caps the frame rate    void capFps();      public:    unsigned long frameCount; //frame counter    int targetFps, //desired frame rate    fps; //current frame rate    float animFactor, //animation scale    timeScale, //time scale    floatFps; //float version of the frame rate        //constructor    frameController(){      QueryPerformanceFrequency(&hpt); //gather timer resolution      ticksPerSecond = hpt.QuadPart; //store resolution (will not change)      cout << "ticksPerSecond: " << ticksPerSecond << endl;      QueryPerformanceCounter(&hpt); //gather tick count      initTicks = hpt.QuadPart; //store tick count at init      cout << "initTicks: " << initTicks << endl;      timeScale = 1; //default timescale is 1    }        //called at the start of every frame to process the frame control    void step();        //setters    //target frame rate    void setTargetFps(unsigned int sTargetFps);    //frame start ticks    void setFrameStartTicks(LONGLONG sFrameStartTicks);};void frameController::setTargetFps(unsigned int sTargetFps = 0){  targetFps = sTargetFps; //set the target fps  cout << "targetFps: " << targetFps << endl;    //calculate ticks per frame at the desired frame rate  if(targetFps != 0)    maxTicksPerFrame = ticksPerSecond / targetFps;  cout << "maxTicksPerFrame: " << maxTicksPerFrame << endl;}void frameController::setFrameStartTicks(LONGLONG sFrameStartTicks){  frameStartTicks = sFrameStartTicks;}void frameController::step(){  //find the current tick of the high resolution timer  QueryPerformanceCounter(&hpt);  //extract current tick count  frameNowTicks = hpt.QuadPart;  //calculate how many ticks the frame took  calcTicksForFrame();  //increment frame counter  frameCount ++;  //cap the fps  capFps();  //calculate the fps  calcFps();  //calculate animation factor  //calcAnimFactor();  //find the current tick of the high resolution timer  QueryPerformanceCounter(&hpt);  //remember the tick count  frameStartTicks = hpt.QuadPart;}void frameController::calcTicksForFrame(){  ticksForFrame = frameNowTicks - frameStartTicks;  //clamp results incase the hpt returned an erroneous value  if(ticksForFrame < 1){    //clamp to 1    ticksForFrame = 1;    //if the frame took too long  } else if(ticksForFrame > maxTicksPerFrame * 3){    //clamp it to maxTicksPerFrame    ticksForFrame = maxTicksPerFrame;  }}void frameController::calcFps(){  //find the current tick of the high resolution timer  QueryPerformanceCounter(&hpt);  //record the entire number of ticks which passed for the whole frame  totalFrameTicks = hpt.QuadPart - frameStartTicks;  //calculate the float fps  floatFps = float(ticksPerSecond/totalFrameTicks);  //calculate the integer fps  fps = int(floatFps);}void frameController::calcAnimFactor(){  //calculate the animation factor  animFactor = totalFrameTicks/double(ticksPerSecond/floatFps);  cout << "animFactor: " << animFactor << endl;  //don't let the animation factor be too low  if(animFactor <= 0)    //smallest possible positive value for 32 bit float    animFactor = 1.175494351e-38F;  //apply time scale to animation factor  //animFactor *= timeScale;}void frameController::capFps(){  if(targetFps == 0) return; //do nothing if fps is uncapped  while(true){    //find the current tick of the high resolution timer    QueryPerformanceCounter(&hpt);    //if done waiting    if(hpt.QuadPart >= frameStartTicks + maxTicksPerFrame)      break; //exit the while loop    Sleep(0); //yield to cpu  }}//make a frame control objectframeController fpsHandler;//application entry pointint main(){  //remain on a single core for timing (QueryPerformanceCounter)  SetThreadAffinityMask(GetCurrentThread(),1);    //high performance timer (hpt2 to avoid confusion with frameController member)  LARGE_INTEGER hpt2;    QueryPerformanceFrequency(&hpt2); //gather timer resolution  LONGLONG hptFreq = hpt2.QuadPart, //hpt resolution  startSec, //tick to start counting a second from  nowTime; //current tick at a point in the logic    int frameOffset, //offset frame gap between seconds (shows inaccuracies)  lastFrameOffset, //offset in the previous frame  fpsDifference, //gap between actual fps and intended fps  syncInRow = 0, //how many offsets have been the same in a row (big = accurate)  frameProc, //processing as an integer count, to do each frame  baseFrameProc = 200000, //base amount of processing each frame  lastFrameProc, //processing done in the previous frame  secondsRun = 0; //how many seconds have been passed  float procDeviation = 0.1; //multiple of baseFrameProc to add as random load    fpsHandler.setTargetFps(100); //choose the target frame rate  cout << "targetFps: " << fpsHandler.targetFps << endl;    cout << "Frame loop will begin in 1 second\n";  Sleep(1000); //wait a bit before proceeding      //keep running  bool run = true;  //print frame information spam  bool printFrameInfo = false;  //do any extra frame load processing  bool doFrameProc = true;    if(doFrameProc){    //make a starting value so the first frame isn't wrongly considered abnormal    lastFrameProc = baseFrameProc + rand()%int(baseFrameProc*procDeviation);  }    //find the current tick of the high resolution timer (just before main loop)  QueryPerformanceCounter(&hpt2);     startSec = hpt2.QuadPart; //remember when to start counting the second  fpsHandler.setFrameStartTicks(startSec);    while(run){ //main loop      fpsHandler.step(); //step the frame rate controller first      //other engine singletons etc            if(printFrameInfo){        //cout << "frameProc: " << frameProc << endl;        cout << "frame: " << fpsHandler.frameCount << endl;        cout << "fps: " << fpsHandler.fps << endl;      }            //find the current tick of the high resolution timer      QueryPerformanceCounter(&hpt2);      nowTime = hpt2.QuadPart; //the current tick      //if a second has passed      if(nowTime >= startSec + hptFreq){        secondsRun ++;        system("CLS");        cout << "run for " << secondsRun << "s\n";                startSec = nowTime; //remember when to start counting the second                //if fps is capped at a value        if(fpsHandler.targetFps != 0){          //find the offset of the frame from the intended fps          frameOffset = fpsHandler.frameCount % fpsHandler.targetFps;                    //if this frame offset is the same as the last          if(frameOffset == lastFrameOffset){            //since last second, frames have been in sync            syncInRow ++; //note that another frame has been in sync            cout << "frames are in sync\n";            cout << "syncInRow: " << syncInRow << endl;          } else {            syncInRow = 0; //reset frames in sync in a row            cout << "frames are out of sync!\n";            cout << "frameOffset: " << frameOffset << endl;            cout << "lastFrameOffset: " << lastFrameOffset << endl;          }          lastFrameOffset = frameOffset; //remember the frame offset                    //find the difference between target and actual fps          fpsDifference = abs(fpsHandler.fps - fpsHandler.targetFps);          //if the fps is the target fps          if(fpsDifference == 0){            cout << "fps is on target: " << fpsHandler.targetFps << endl;          } else {            cout << "fps is " << fpsDifference << " away from target\n";          }        } else {          //show the fps          cout << "fps: " << fpsHandler.fps << endl;        }      }            //if frame process loading is on      if(doFrameProc){        //10% deviation in frame load        frameProc = baseFrameProc + rand()%int(baseFrameProc*procDeviation);        //if the deviation was more than deviation expectation        if(abs(frameProc - lastFrameProc) > baseFrameProc*procDeviation){                    cout << "frameProc: " << frameProc << endl;          cout << "lastFrameProc: " << lastFrameProc << endl;        }        lastFrameProc = frameProc;        for(int i = 0;i < frameProc; i ++){} //busy up the cpu to test fps      }      //handle other threads: AI, physics input, networking, rendering etc            //any particular frame-end specific logic (endStep events possibly)  }    //correctly exit the application  system("PAUSE");  return EXIT_SUCCESS;}