SinSynthWithMidi.cpp

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/*
	This is a subclass of SinSynth that demonstrates how to use the midi output properties kAudioUnitProperty_MIDIOutputCallbackInfo, and kAudioUnitProperty_MIDIOutputCallback
	defined in AudioUnitProperties.h. Using these properties, the SinSynthWithMidi simply passes through the midi data it receives. Use of these properties requires host support.
	
	To build a version of the SinSynth with this functionality, activate the "SinSynth with MIDI Output" target in Xcode.
*/

#include "SinSynth.h"
#include <vector>

typedef struct MIDIMessageInfoStruct {
	UInt8	status;
	UInt8	channel;
	UInt8	data1;
	UInt8	data2;
	UInt32	startFrame;
} MIDIMessageInfoStruct;


class MIDIOutputCallbackHelper {
public:
							MIDIOutputCallbackHelper() {mMIDIMessageList.reserve (16); mMIDICallbackStruct.midiOutputCallback = NULL;}
	virtual					~MIDIOutputCallbackHelper() {};
	
	void					SetCallbackInfo(AUMIDIOutputCallback callback, void *userData) {mMIDICallbackStruct.midiOutputCallback = callback; mMIDICallbackStruct.userData = userData;}
	
	void					AddEvent(	UInt8	status,
										UInt8	channel,
										UInt8	data1,
										UInt8	data2, 
										UInt32	inStartFrame );
							
	void					FireAtTimeStamp(const AudioTimeStamp &inTimeStamp);

protected:
	typedef std::vector<MIDIMessageInfoStruct> MIDIMessageList;
	
private:
	MIDIPacketList		  * PacketList() {return (MIDIPacketList *)mBuffersAllocated; }
	Byte					mBuffersAllocated[1024];
	
	AUMIDIOutputCallbackStruct	mMIDICallbackStruct;

	MIDIMessageList			mMIDIMessageList;
};

class SinSynthWithMidi : public SinSynth {
public:
								SinSynthWithMidi(ComponentInstance inComponentInstance);
	virtual						~SinSynthWithMidi();
	
	virtual OSStatus			GetPropertyInfo(		AudioUnitPropertyID				inID,
														AudioUnitScope					inScope,
														AudioUnitElement				inElement,
														UInt32 &						outDataSize,
														Boolean &						outWritable);
	
	virtual OSStatus			GetProperty(			AudioUnitPropertyID				inID,
														AudioUnitScope					inScope,
														AudioUnitElement				inElement,
														void *							outData);
														
	virtual OSStatus			SetProperty(			AudioUnitPropertyID 			inID,
														AudioUnitScope 					inScope,
														AudioUnitElement 				inElement,
														const void *					inData,
														UInt32 							inDataSize);
														
			OSStatus			HandleMidiEvent(		UInt8							status, 
														UInt8							channel, 
														UInt8							data1, 
														UInt8							data2, 
														UInt32							inStartFrame);
	
			OSStatus			Render(					AudioUnitRenderActionFlags &	ioActionFlags,
														const AudioTimeStamp &			inTimeStamp,
														UInt32							inNumberFrames);

private:
	MIDIOutputCallbackHelper mCallbackHelper;
	
	TestNote mTestNotes[kNumNotes];
};

#pragma mark MIDIOutputCallbackHelper Methods

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//	MIDIOutputCallbackHelper::AddEvent
//
// 
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
void MIDIOutputCallbackHelper::AddEvent(UInt8 status, UInt8 channel,
										UInt8 data1, UInt8 data2, 
										UInt32 inStartFrame) {
	MIDIMessageInfoStruct info = {status, channel, data1, data2, inStartFrame};	
	mMIDIMessageList.push_back(info);
}

void MIDIOutputCallbackHelper::FireAtTimeStamp(const AudioTimeStamp &inTimeStamp) {
	if (!mMIDIMessageList.empty() && mMIDICallbackStruct.midiOutputCallback != 0) {
		// synthesize the packet list and call the MIDIOutputCallback
		// iterate through the vector and get each item
				
		std::vector<MIDIMessageInfoStruct>::iterator myIterator;
		MIDIPacketList *pktlist = PacketList();

		for (myIterator = mMIDIMessageList.begin(); myIterator != mMIDIMessageList.end(); myIterator++) {
			MIDIMessageInfoStruct item = *myIterator;
			
			MIDIPacket *pkt = MIDIPacketListInit(pktlist);
			bool tooBig = false;
			
			Byte midiStatusByte = (item.status << 4) | item.channel;
			Byte data[3] = { midiStatusByte, item.data1, item.data2 };
			if ((pkt = MIDIPacketListAdd(pktlist, sizeof(mBuffersAllocated), pkt, item.startFrame, 4, const_cast<Byte*>(data))) == NULL)
				tooBig = true;
				
			if (tooBig) {	// send what we have and then clear the buffer and send again
				// issue the callback with what we got
				OSStatus result = mMIDICallbackStruct.midiOutputCallback(mMIDICallbackStruct.userData, &inTimeStamp, 0, pktlist);
				if (result != noErr)
					printf("error calling output callback: %d", (int) result);
				
				// clear stuff we've already processed, and fire again
				mMIDIMessageList.erase(mMIDIMessageList.begin(), myIterator);
				this->FireAtTimeStamp(inTimeStamp);
				return;
			}
		}
		
		// fire callback
		OSStatus result = mMIDICallbackStruct.midiOutputCallback(mMIDICallbackStruct.userData, &inTimeStamp, 0, pktlist);
		if (result != noErr)
			printf("error calling output callback: %d", (int) result);

		mMIDIMessageList.clear();
	}
}

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#pragma mark SinSynthWithMidi Methods

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

COMPONENT_ENTRY(SinSynthWithMidi)

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//	SinSynthWithMidi::SinSynthWithMidi
//
// This synth has No inputs, One output
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SinSynthWithMidi::SinSynthWithMidi(ComponentInstance inComponentInstance)
	: SinSynth(inComponentInstance)
{
}

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//	SinSynthWithMidi::~SinSynthWithMidi
//
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SinSynthWithMidi::~SinSynthWithMidi()
{}

OSStatus			SinSynthWithMidi::GetPropertyInfo(		AudioUnitPropertyID				inID,
													AudioUnitScope					inScope,
													AudioUnitElement				inElement,
													UInt32 &						outDataSize,
													Boolean &						outWritable)
{
	if (inScope == kAudioUnitScope_Global) {
		if (inID == kAudioUnitProperty_MIDIOutputCallbackInfo) {
			outDataSize = sizeof(CFArrayRef);
			outWritable = false;
			return noErr;
		} else if (inID == kAudioUnitProperty_MIDIOutputCallback) {
			outDataSize = sizeof(AUMIDIOutputCallbackStruct);
			outWritable = true;
			return noErr;
		}
	}
	return SinSynth::GetPropertyInfo (inID, inScope, inElement, outDataSize, outWritable);
}

OSStatus			SinSynthWithMidi::GetProperty(	AudioUnitPropertyID		inID,
											AudioUnitScope			inScope,
											AudioUnitElement		inElement,
											void *					outData)
{
	if (inScope == kAudioUnitScope_Global) {
		if (inID == kAudioUnitProperty_MIDIOutputCallbackInfo) {
			CFStringRef strs[1];
			strs[0] = CFSTR("MIDI Callback");
			
			CFArrayRef callbackArray = CFArrayCreate(NULL, (const void **)strs, 1, &kCFTypeArrayCallBacks);
			*(CFArrayRef *)outData = callbackArray;
			return noErr;
		}
	}
	return SinSynth::GetProperty (inID, inScope, inElement, outData);
}

OSStatus			SinSynthWithMidi::SetProperty(	AudioUnitPropertyID 			inID,
													AudioUnitScope 					inScope,
													AudioUnitElement 				inElement,
													const void *					inData,
													UInt32 							inDataSize)
{
	if (inScope == kAudioUnitScope_Global) {
		if (inID == kAudioUnitProperty_MIDIOutputCallback) {
			if (inDataSize < sizeof(AUMIDIOutputCallbackStruct)) return kAudioUnitErr_InvalidPropertyValue;
			
			AUMIDIOutputCallbackStruct *callbackStruct = (AUMIDIOutputCallbackStruct *)inData;
			mCallbackHelper.SetCallbackInfo(callbackStruct->midiOutputCallback, callbackStruct->userData);
			return noErr;
		}
	}
	return SinSynth::SetProperty(inID, inScope, inElement, inData, inDataSize);
}

OSStatus 	SinSynthWithMidi::HandleMidiEvent(UInt8 status, UInt8 channel, UInt8 data1, UInt8 data2, UInt32 inStartFrame) {
	// snag the midi event and then store it in a vector
	
	mCallbackHelper.AddEvent(status, channel, data1, data2, inStartFrame);
	
	return AUMIDIBase::HandleMidiEvent(status, channel, data1, data2, inStartFrame);
}

OSStatus	SinSynthWithMidi::Render(   AudioUnitRenderActionFlags &		ioActionFlags,
												const AudioTimeStamp &		inTimeStamp,
												UInt32						inNumberFrames) {
	OSStatus result = AUInstrumentBase::Render(ioActionFlags, inTimeStamp, inNumberFrames);
	if (result == noErr) {
		mCallbackHelper.FireAtTimeStamp(inTimeStamp);
	} 
	return result;
}