CODEWITHSUNDEEP
c++windowsvisual-studiousbthermal-printer
Bruno
Bruno

Reputation: 139

How to setup timeout reading USB port in C++ (VS2010)?

I am opening and reading a port from a USB device (thermal printer):

HANDLE hUsb = CreateFile(symbolicName,
      GENERIC_READ | GENERIC_WRITE, 
      0, 
      NULL, 
      OPEN_EXISTING, 
      0, 
      NULL);

ReadFile(hUsb, buffer, bytes, &read, NULL);

I need to setup timeout to read, but it's an USB port, not a COM port, so I can't use the function SetCommTimeouts.

Is there any function that I can use and has the same effect of SetCommTimeouts?

If there's a simply way, I prefer to not use thread.

I am using Visual Studio 2010 with Windows 10.

Grateful.

Upvotes: 1

Views: 714

Answers (1)

RbMm
RbMm

Reputation: 33744

first of all any Visual Studio here absolute unrelated.

general solution - use asynchronous io, which never block. and you can yourself cancel io operation by some timeout. good way of course set timer (via CreateTimerQueueTimer) and cancel io in timer callback. or if io will complete before this - cancel timer. but if want simplest implementation, which do synchronous io in place - possible do next:

    inline ULONG BOOL_TO_ERROR(BOOL f)
    {
        return f ? NOERROR : GetLastError();
    }

    //------------------------------------------------------------------------

    HANDLE hFile = CreateFileW(symbolicName, FILE_GENERIC_READ, FILE_SHARE_READ, 0, OPEN_EXISTING,
        FILE_FLAG_OVERLAPPED, 0);

    if (hFile != INVALID_HANDLE_VALUE)
    {
        OVERLAPPED ov = {};
        if (ov.hEvent = CreateEventW(0, 0, 0, 0))
        {
            char buf[16];
            ULONG NumberOfBytesRead = 0;
            ULONG err = BOOL_TO_ERROR(ReadFile(hFile, buf, sizeof(buf), 0, &ov));

            switch (err)
            {
            case ERROR_IO_PENDING:
                if (WaitForSingleObject(ov.hEvent, timeout) != WAIT_OBJECT_0)
                {
                    CancelIo(hFile);
                }
            case NOERROR:
                err = BOOL_TO_ERROR(GetOverlappedResult(hFile, &ov, &NumberOfBytesRead, TRUE));
                break;
            }

            CloseHandle(ov.hEvent);
        }
        CloseHandle(hFile);
    }

Upvotes: 1

Related Questions