Manage shared variable in multithreading application

I designed one sample multithreaded application in which I read one file in one thread using circular buffer with checking isfull or not, also write same buffer to output file with checking buffer isEmpty or not.

My problem is that first thread complete its execution first so that second thread gets remaining data in buffer, so output is wrong.

Code:

 /* Circular Queues */ //#include<mutex.h> #include <iostream> using namespace std; #include<windows.h> const int chunk = 512; //buffer read data const int MAX = 2*chunk ; //queue size unsigned int Size ; FILE *fpOut; FILE *fp=fopen("Test_1K.txt","rb"); //class queue class cqueue { public : static int front,rear; static char *a; cqueue() { front=rear=-1; a=new char[MAX]; } ~cqueue() { delete[] a; } }; int cqueue::front; int cqueue::rear; char* cqueue::a; DWORD WINAPI Thread1(LPVOID param) { int i; fseek(fp,0,SEEK_END); Size=ftell(fp); //Read file size cout<<"\nsize is"<<Size; rewind(fp); for(i=0;i<Size;i+=chunk) //read data in chunk as buffer half size { while((cqueue::rear==MAX-1)); //wait until buffer is full? if((cqueue::rear>MAX-1)) cqueue::rear=0; else{ fread(cqueue::a,1,chunk,fp); //read data from in buffer cqueue::rear+=chunk; //increment rear pointer of queue to indicate buffer is filled up with data if((cqueue::front==-1)) cqueue::front=0; //update front pointer value to read data from buffer in Thread2 } } fclose(fp); cout<<"\nQueue write completed\n"; return 0; } DWORD WINAPI Thread2(LPVOID param) { for(int j=0;j<Size;j+=chunk) { while((cqueue::front==-1)); //wait until buffer is empty cqueue::front+=chunk; //update front pointer after read data from queue fwrite(cqueue::a,1,chunk,fpOut); //write data file if((cqueue::front==MAX-1)) cqueue::front=0; //update queue front pointer when it reads upto queue Max size } fclose(fpOut); cout<<"\nQueue read completed\n"; return 0; } void startThreads() { DWORD threadIDs[2]; HANDLE threads[2]; fpOut=fopen("V-1.7OutFile.txt","wb"); threads[0] = CreateThread(NULL,0,Thread1,NULL,0,&threadIDs[0]); threads[1] = CreateThread(NULL,0,Thread2,NULL,0,&threadIDs[1]); if(threads[0] && threads[1]) { printf("Threads Created.(IDs %d and %d)",threadIDs[0],threadIDs[1]); } } void main() { cqueue c1; startThreads(); system("pause"); } 

Please suggest any solution for shared buffer accessing.