[C/C++] Process和Thread

前言

作業系統作業要求使用Process和Thread來完成輸出1到10的任務。

Process

在Windows底下得使用CreateProcess，假設輸出是照順序的。

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

void _tmain( int argc, TCHAR *argv[] )
{

	STARTUPINFO si;
	PROCESS_INFORMATION pi;

	ZeroMemory( &si, sizeof(si) );
	si.cb = sizeof(si);
	ZeroMemory( &pi, sizeof(pi) );

	char *link = argv[0] ;
	LPTSTR szCmdline = _tcsdup(TEXT(link));	
	LPTSTR szParam ;	

	int i = 0 ;
	if ( argc == 1 ){ 	
		strcat(link," 0") ;
		szParam = _tcsdup(TEXT(link)) ;
	} else {	
		char buffer[100] ;
		i = atoi(argv[1]) + 1 ;
		itoa(i,buffer,10) ;
		strcat(link," ") ;
		strcat(link,buffer) ;
		szParam = _tcsdup(TEXT(link)) ;
	}

	if ( i < 10 ){
		if( !CreateProcess(szCmdline,szParam,NULL,NULL,FALSE,0,NULL,NULL,&si,&pi ) ) {
			printf( "CreateProcess failed (%d).\n", GetLastError() );
			return;
		}
		printf("id = %d , output i = %d\n", GetCurrentProcessId() , i );
	}

	WaitForSingleObject( pi.hProcess, INFINITE );

	CloseHandle( pi.hProcess );
	CloseHandle( pi.hThread );
}

Thread

假設輸出要求照順序，需要互斥鎖來避免Race Condition。

#include <stdio.h>
#include <stdlib.h>
#include <process.h>
#include <windows.h>

int i ;
int flag[2] = {0,0} ;
int turn ;

void printOutput(int n)
{
	do {
		flag[n] = 1 ;
		turn = 1 - n ;
		while ( flag[1-n] == 1 && turn == 1-n ) ;
		if ( i >= 10 )
			return ;
		printf("thread %d , output i = %d\n", n + 1 , i);
		i ++ ;
		flag[n] = 0 ;
	} while ( i < 10 );
}

int main()
{
	i = 0 ;
	HANDLE hThread , hThread2;
	unsigned threadID , threadID2;
	hThread = (HANDLE)_beginthreadex(NULL, 0, &printOutput, 0 , 0, &threadID);
	hThread2 = (HANDLE)_beginthreadex(NULL, 0, &printOutput, 1 , 0, &threadID2);

	WaitForSingleObject(hThread, INFINITE);
	WaitForSingleObject(hThread2, INFINITE);
	CloseHandle(hThread2);
	CloseHandle(hThread);
}