CFile多线程读文件

Question

Cfile多线程读的时候是线程安全的吗？

怎么使用CFile多线程读文件呢，为什么我这么写报错

 

const CString path = "C:\\test.t";
UINT ExecutingFunction(LPVOID pParam)
{
CString name = (char*)pParam;
CFile c1;
c1.Open(path, CFile::modeRead | CFile::bufferRead | CFile::shareDenyRead);
bool b= true;
while(true)
{
char ptrResult8[8];
if (b)
{
c1.SeekToBegin();
b = false;
}
else
{
c1.Seek(8,CFile::begin);
b = true;
}
c1.Read(ptrResult8,8);
double d1 = *(double*)ptrResult8;
char fu[10];
gcvt(d1,5,fu);
CString trace = name + " : " + fu + "\r\n";   
TRACE(trace);
Sleep(1000);
}
return 0;
}

main()
{
  CFile cfile;
cfile.Open(path, CFile::modeReadWrite | CFile::modeCreate);
double a = 20.2;
double b = 30.3;
cfile.Write((char*)&a,8);
cfile.Write((char*)&b,8);
cfile.Close();

AfxBeginThread(ExecutingFunction,"thread1");
AfxBeginThread(ExecutingFunction,"thread2");
}

我希望两个线程同时读一个硬盘上的文件，怎么写呢？

Answer 1

给你个例子程序，Win32 console application , support MFC

#include "stdafx.h"
#include <afxmt.h>

const CString path(_T("F:\\test.txt"));
CCriticalSection cs;
UINT ExecutingFunction(LPVOID pParam)
{
 LPCTSTR buf = (LPCTSTR)pParam;
 cs.Lock();
 _tprintf(_T("%s write file.\n"), buf);
 try
 {
  CFile file;
  file.Open(path, CFile::modeCreate|CFile::modeWrite|CFile::modeNoTruncate);
  file.SeekToEnd();
  file.Write(buf, _tcslen(buf)*sizeof(TCHAR));
  file.Close();
 }
 catch (CException* e)
 {
  e->ReportError();
  e->Delete();
 }
 cs.Unlock();
 return 0;
}

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
 HANDLE hThread[2] = {0};
 
 CWinThread* pThread1 = AfxBeginThread(ExecutingFunction, (LPVOID)(_T("Thread1")), THREAD_PRIORITY_NORMAL, 0, CREATE_SUSPENDED, NULL);
 CWinThread* pThread2 = AfxBeginThread(ExecutingFunction, (LPVOID)(_T("Thread2")), THREAD_PRIORITY_NORMAL, 0, CREATE_SUSPENDED, NULL);
 
 pThread1->m_bAutoDelete = FALSE;
 pThread2->m_bAutoDelete = FALSE;

 hThread[0] = pThread1->m_hThread;
 hThread[1] = pThread2->m_hThread;

 pThread1->ResumeThread();
 pThread2->ResumeThread();
 WaitForMultipleObjects(sizeof(hThread)/sizeof(hThread[0]), hThread, TRUE, INFINITE);
 for(int i=0; i<sizeof(hThread)/sizeof(hThread[0]); i++)
 {
  CloseHandle(hThread[i]);
 }

 delete pThread1;
 pThread1 = NULL;
 delete pThread2;
 pThread2 = NULL;

 return 0;
}

---

Visual C++ enthusiast, like network programming and driver development. At present is being engaged in the WinCE/Windows Mobile platform embedded development.

Answer 2

谢谢你  ！

Answer 3

最主要的问题是：

 CFile::shareDenyRead

禁止并发访问。