The MIM_LONGDATA message is sent to a MIDI input callback function when a system-exclusive buffer has been filled with data and is being returned to the application.
MIM_LONGDATA
dwParam1 = (DWORD) lpMidiHdr
dwParam2 = dwTimestamp
This message does not return a value.
The returned buffer might not be full. To determine the number of bytes recorded into the returned buffer, use the dwBytesRecorded member of the MIDIHDR structure specified by lpMidiHdr.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in mmsystem.h.
Musical Instrument Digital Interface (MIDI) Overview, MIDI Messages, midiInStart, MIDIHDR