114 lines
3.5 KiB
C
114 lines
3.5 KiB
C
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/* callback.c - Contains the low-level MIDI input callback function for
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* MIDIMon. This module also contains the LibMain() and WEP()
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* DLL routines, and other functions accessed by the callback.
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*
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* Because this module contains a low-level callback function,
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* this entire module must reside in a FIXED code segment in a DLL.
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* The data segment must be FIXED as well, since it accessed by
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* the callback.
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*/
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#include <windows.h>
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#include <mmsystem.h>
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#include "midimon.h"
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#include "circbuf.h"
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#include "instdata.h"
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#include "callback.h"
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static EVENT event;
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/* midiInputHandler - Low-level callback function to handle MIDI input.
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* Installed by midiInOpen(). The input handler takes incoming
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* MIDI events and places them in the circular input buffer. It then
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* notifies the application by posting a MM_MIDIINPUT message.
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*
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* This function is accessed at interrupt time, so it should be as
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* fast and efficient as possible. You can't make any
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* Windows calls here, except PostMessage(). The only Multimedia
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* Windows call you can make are timeGetSystemTime(), midiOutShortMsg().
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*
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*
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* Param: hMidiIn - Handle for the associated input device.
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* wMsg - One of the MIM_***** messages.
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* dwInstance - Points to CALLBACKINSTANCEDATA structure.
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* dwParam1 - MIDI data.
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* dwParam2 - Timestamp (in milliseconds)
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*
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* Return: void
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*/
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void FAR PASCAL midiInputHandler(
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HMIDIIN hMidiIn,
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WORD wMsg,
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DWORD dwInstance,
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DWORD dwParam1,
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DWORD dwParam2)
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{
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UNREFERENCED_PARAMETER(hMidiIn);
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switch(wMsg)
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{
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case MIM_OPEN:
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break;
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/* The only error possible is invalid MIDI data, so just pass
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* the invalid data on so we'll see it.
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*/
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case MIM_ERROR:
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case MIM_DATA:
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event.dwDevice = ((LPCALLBACKINSTANCEDATA)dwInstance)->dwDevice;
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event.data = dwParam1;
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event.timestamp = dwParam2;
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/* Send the MIDI event to the MIDI Mapper, put it in the
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* circular input buffer, and notify the application that
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* data was received.
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*/
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if(((LPCALLBACKINSTANCEDATA)dwInstance)->hMapper)
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midiOutShortMsg(
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((LPCALLBACKINSTANCEDATA)dwInstance)->hMapper,
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dwParam1);
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PutEvent(((LPCALLBACKINSTANCEDATA)dwInstance)->lpBuf,
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(LPEVENT) &event);
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PostMessage(((LPCALLBACKINSTANCEDATA)dwInstance)->hWnd,
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MM_MIDIINPUT, 0, 0L);
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break;
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default:
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break;
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}
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}
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/* PutEvent - Puts an EVENT in a CIRCULARBUFFER. If the buffer is full,
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* it sets the wError element of the CIRCULARBUFFER structure
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* to be non-zero.
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*
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* Params: lpBuf - Points to the CIRCULARBUFFER.
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* lpEvent - Points to the EVENT.
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*
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* Return: void
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*/
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void FAR PASCAL PutEvent(LPCIRCULARBUFFER lpBuf, LPEVENT lpEvent)
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{
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/* If the buffer is full, set an error and return.
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*/
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if(lpBuf->dwCount >= lpBuf->dwSize){
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lpBuf->wError = 1;
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return;
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}
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/* Put the event in the buffer, bump the head pointer and the byte count.
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*/
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*lpBuf->lpHead = *lpEvent;
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++lpBuf->lpHead;
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++lpBuf->dwCount;
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/* Wrap the head pointer, if necessary.
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*/
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if(lpBuf->lpHead >= lpBuf->lpEnd)
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lpBuf->lpHead = lpBuf->lpStart;
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}
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