- 1 year ago
Is it possible to use Windows Overlapped IO to wait for another process to write to a file?
Yes, it is possible to use Windows Overlapped I/O to wait for another process to write to a file. Overlapped I/O is a mechanism in Windows that allows you to perform asynchronous I/O operations, including waiting for certain events to occur, without blocking the calling thread.
To achieve your goal of waiting for another process to write to a file, you can follow these steps:
Create an Event Object:
Create an event object using theCreateEvent
function. This event will be used to signal when the write operation by the other process is completed.Initialize the Overlapped Structure:
Initialize anOVERLAPPED
structure with the event object and other required parameters. You'll pass this structure to the asynchronous write operation.Start the Asynchronous Write Operation:
Use theWriteFile
function with the overlapped structure to start the asynchronous write operation by the other process.Wait for the Event:
Use theWaitForSingleObject
orWaitForMultipleObjects
function to wait for the event object to be signaled. This will indicate that the write operation by the other process is completed.Check the Result:
After the event is signaled, you can check the result of the asynchronous write operation using theGetOverlappedResult
function to see if the write was successful.
Here's a simplified example in C++:
cpp#include <Windows.h>
int main() {
HANDLE hEvent = CreateEvent(nullptr, TRUE, FALSE, nullptr);
OVERLAPPED overlapped;
overlapped.hEvent = hEvent;
HANDLE hFile = CreateFile(
L"C:\\path\\to\\file.txt",
GENERIC_WRITE,
FILE_SHARE_READ,
nullptr,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
nullptr
);
if (hFile != INVALID_HANDLE_VALUE) {
char buffer[] = "Data written by another process";
DWORD bytesWritten = 0;
WriteFile(hFile, buffer, sizeof(buffer), nullptr, &overlapped);
WaitForSingleObject(hEvent, INFINITE);
DWORD result = 0;
GetOverlappedResult(hFile, &overlapped, &bytesWritten, TRUE);
CloseHandle(hFile);
}
CloseHandle(hEvent);
return 0;
}
Keep in mind that coordinating file access between processes can be complex and might require careful synchronization. It's important to consider potential race conditions, data integrity, and proper error handling.