There are two processes: one written in C and the other written in C#.
Simply, C process will create a file name "test.dat", map the file to its memory, and keep on writing on it.
C# process on the other hand will open the file and read whenever there is a change on the memory.
The problem is that on the C# end, it does not let me open the file. (IOException saying the other process is in use"
Here is what I've tested.
//C
// Test create & open
void CTestDlg::OnBnClickedBtn1()
{
WCHAR wcsDebug[1024];
HANDLE hFile, hMapFile;
UINT size = sizeof(syncData);
hFile = CreateFile(L"C:\\Users\\test\\Documents\\2134\\test.dat", GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile != INVALID_HANDLE_VALUE)
{
hMapFile = CreateFileMapping(hFile, NULL, PAGE_READWRITE, 0, size, NULL);
if (hMapFile)
{
g_pb = (BYTE*)MapViewOfFile(hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, 0);
}
}
}
// Test Writing
void CLibTestDlg::OnBnClickedBtn2()
{
WCHAR sz[] = L"C:\\Users\\test\\Documents\\2134\\";
WCHAR wcsFilePath[MAX_PATH];
CString str;
GetDlgItemText(IDC_EDIT_FID, str);
if (str != L"\0")
{
swprintf_s(wcsFilePath, _countof(wcsFilePath), L"%s%s", sz, str.GetBuffer());
if (g_pb)
{
syncData sd;
sd.dwCurrent = nCurr;
sd.dwTotal = 15;
sd.eSyncType = TYPE_DOWNLOAD;
StringCchCopy(sd.wcsFileName, _countof(sd.wcsFileName), wcsFilePath);
sd.eReqType = TYPE_DOWNLOAD;
sd.ullTimeStamp = GetTickCount();
nCurr ;
memcpy(g_pb, &sd, sizeof(sd));
}
}
}
C# portion below:
private void Button_MouseUp(object sender, RoutedEventArgs e)
{
Console.WriteLine("Click");
FileStream fs = File.Open(@"C:\\Users\\test\\Documents\\2134\\test.dat", FileMode.Open, FileAccess.ReadWrite); // Error Here! IOException: The file is being used by another process.
using (var mmf = MemoryMappedFile.CreateFromFile(fs, "mmf", 0, MemoryMappedFileAccess.ReadWrite, HandleInheritability.None, true))
{
using (var accessor = mmf.CreateViewAccessor(0, 544))
{
DWORD dwCurrent;
accessor.Read(0, out dwCurrent);
Console.WriteLine("Hello" dwCurrent);
}
}
}
Any ideas on approaching the file sharing between the two processes?
CodePudding user response:
FileStream
defaults to only allowing read sharing which is not compatible with how you've opened your c file. You need to request write sharing too:
File.Open(@"...", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);