Create multiple files using multi threading in C++ using Win32 API - c++

Question

I am trying to create files in a pen drive. If the pen drive is not present, threads should suspend. When it is inserted it should resume. Here is the code I tried but it's not working properly. Can any one help me?
#include "stdafx.h"
#include <Windows.h>
#include <Strsafe.h>
#include <WinBase.h>
LPCTSTR Disk=L"E:\";
LPTSTR drive_Name=L"E:\\demo";
CRITICAL_SECTION section;
#define BUFFER_SIZE 1024
#define count 10
HANDLE Write_Handle[10],Open_Handle[10],read_Handle[10] ;
DWORD WINAPI check_Thread(LPVOID lpParameter)
{
int *nThreadNo = (int*)lpParameter;
while(1)
{
if(GetDiskFreeSpaceExW(Disk,NULL,NULL,NULL))
{
ResumeThread(Write_Handle[*nThreadNo]);
ResumeThread(read_Handle[*nThreadNo]);
}
else
{
SuspendThread(Write_Handle[*nThreadNo]);
SuspendThread(read_Handle[*nThreadNo]);
}
}
}
DWORD WINAPI Write_Thread(LPVOID lpParameter)
{
DWORD g_tid = GetCurrentThreadId();
_tprintf(_T(" write thread id %d\n"),g_tid);
LPCWSTR filename=(LPCWSTR)lpParameter;
HANDLE ofile;
EnterCriticalSection(&section);
ofile=CreateFileW(filename,GENERIC_WRITE,FILE_SHARE_READ,NULL,OPEN_ALWAYS,NULL, NULL);
int d;
d=GetLastError();
if(ERROR_SUCCESS!=GetLastError())
{
_tprintf(_T("error values in open thread %d \n"),GetLastError());
_tprintf(_T("filename %s \n"),filename);
}
const int filesizeinKB = 1024;
BOOL bError;
DWORD dwBytesWritten=0;
WCHAR ReadBuffer[BUFFER_SIZE] = {0};
int i;
for(i = 0; i <= BUFFER_SIZE; i++)
{
ReadBuffer[i] = (char)(i%26 + 'a');
}
for (i = 0; i <= filesizeinKB; i++)
{
SetLastError(0);
bError= WriteFile(ofile, ReadBuffer-1, BUFFER_SIZE,&dwBytesWritten, NULL);
bError=GetLastError();
if (ERROR_SUCCESS!=GetLastError())
{ _tprintf(_T("error value in write %d\n"),GetLastError());
_tprintf(_T(" Write Error...\n"));
return 1;
}
}
SetLastError(0);
CloseHandle(ofile);
_tprintf(_T("write close error values %d\n"),GetLastError());
LeaveCriticalSection(&section);
return 1;
}
DWORD WINAPI Read_Thread(LPVOID lpParameter)
{
HANDLE ofile;
DWORD g_tid = GetCurrentThreadId();
_tprintf(_T(" write thread id %d\n"),g_tid);
LPCWSTR filename=(LPCWSTR)lpParameter;
EnterCriticalSection(&section);
ofile=CreateFileW(filename,GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_ALWAYS,NULL, NULL);
int d;
d=GetLastError();
if(ERROR_SUCCESS!=GetLastError())
{
_tprintf(_T("error values in open thread %d \n"),GetLastError());
_tprintf(_T("filename %s \n"),filename);
}
DWORD dwBytesRead=0;
WCHAR ReadBuffer[BUFFER_SIZE] = {0};
_tprintf(_T(" read thread \n"));
SetLastError(0);
int err;
ReadFile(ofile, ReadBuffer, (BUFFER_SIZE-1), &dwBytesRead, NULL);
err=GetLastError();
_tprintf(_T("read error values %d \n"),GetLastError());
if(ERROR_SUCCESS!=GetLastError())
{
_tprintf(L"reading failed \n");
return 0;
}
SetLastError(0);
CloseHandle(ofile);
err=GetLastError();
_tprintf(_T("close error values %d\n"),GetLastError());
LeaveCriticalSection(&section);
return 1;
}
int _tmain(int argc, _TCHAR* argv[])
{
unsigned int myCounter = 0;
DWORD WritethreadID,OpenThreadID,ReadthreadID;
HANDLE check_Handle;
DWORD exThread;
TCHAR filename[100];
HANDLE hfile;
INT bsize=100;
int i=0;
InitializeCriticalSection (&section);
CreateDirectory(drive_Name,NULL);
for(i=0;i<5;i++)
{
SetLastError(0);
StringCchPrintf(filename,bsize, TEXT("%s\\file_%d.txt"),drive_Name,i );
hfile=CreateFileW(filename,GENERIC_WRITE|GENERIC_READ,NULL,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
if (hfile == INVALID_HANDLE_VALUE)
{
_tprintf(_T("invalid handle \n" ));
}
_tprintf(_T("file created %s\n"),filename);
CloseHandle(hfile);
Write_Handle[i] =CreateThread(0, 0, Write_Thread, filename, CREATE_SUSPENDED, &WritethreadID);
SetThreadPriority(Write_Handle[i],2);
_tprintf(_T("write thread id is %d\n"),WritethreadID);
read_Handle[i]=CreateThread(0, 0, Read_Thread, filename, CREATE_SUSPENDED, &ReadthreadID);
SetThreadPriority(read_Handle[i],1);
_tprintf(_T("read thread id is %d\n "),ReadthreadID);
check_Handle =CreateThread(0, 0, check_Thread,(void*)&i ,0,&OpenThreadID);
}
for (i=0; i<count; ++i)
{
WaitForSingleObject(Write_Handle[i],INFINITE);
if ( !GetExitCodeThread(Write_Handle, &exThread) )
{
_tprintf(_T("close thread %08X\n"),GetLastError());
}
SetLastError(0);
CloseHandle(Write_Handle[i]);
_tprintf(_T("close thread %08X\n"),GetLastError());
WaitForSingleObject(read_Handle[i],INFINITE);
if ( !GetExitCodeThread(read_Handle, &exThread) )
{
_tprintf(_T("GetExitCodeThread %08X\n"),GetLastError());
}
SetLastError(0);
CloseHandle(read_Handle[i]);
_tprintf(_T("GetExitCodeThread %08X\n"),GetLastError());
CloseHandle(check_Thread);
}
DeleteCriticalSection(&section);
return 1;
}

Answer 1

If you have open file handles to a USB drive when that drive is removed, those file handles will become invalid. Reinserting the USB drive will not reconstitute those handles in such a way that you can continue after resuming a thread.
You will need to:
detect when the device is removed, and close those now-broken handles
when the device is inserted, open the files again and continue whatever you were doing

Answer 2

Your error handlers are returning without calling LeaveCriticalSection, leaving the CS locked and blocking the other threads indefinitely. From the EnterCriticalSection docs:
If a thread terminates while it has ownership of a critical section,
the state of the critical section is undefined.
Those cases also leave the file handles open.