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Wrapper Library for Windows MIDI API

, 28 Jan 2008 MIT
A small library encapsulating the Windows MIDI API
mididevdemo.zip
MIDIDeviceDemo.exe
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MIDIDevDemo v2
MIDIDevDemo v2.clw
MIDIDevDemo v2.dsp
MIDIDevDemo v2.dsw
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MIDIDevDemo v2.opt
MIDIDevDemo v2.plg
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MIDIDevDemo v2.ico
midiwrapper.zip
MIDIDeviceDemo.zip
MIDIWrapperSrc.zip
midiwrappersource.zip
MIDIWrapper Source
midiwrapper_demo.zip
MIDIDevDemo v2.clw
MIDIDevDemo v2.dsp
MIDIDevDemo v2.dsw
MIDIDevDemo v2.ico
midiwrapper_source.zip
MIDIWrapper_Source
MIDIWrapper Source
midiwrapper_src.zip
/*******************************************************************************
 * MIDIInDevice.cpp - Implementation for CMIDIInDevice and related 
 *                    classes.
 *
 * Copyright (C) 2002 Leslie Sanford
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Contact: jabberdabber@hotmail.com
 *
 * Last modified: 09/02/2003
 ******************************************************************************/


//--------------------------------------------------------------------
// Dependencies
//--------------------------------------------------------------------


#include "MIDIInDevice.h"
#include "midi.h"


//--------------------------------------------------------------------
// Using declarations
//--------------------------------------------------------------------


using midi::CMIDIInDevice;
using midi::CMIDIReceiver;
using midi::CMIDIInException;


//--------------------------------------------------------------------
// CMIDIInHeader implementation
//--------------------------------------------------------------------


// Constructor
CMIDIInDevice::CMIDIInHeader::CMIDIInHeader(HMIDIIN DevHandle,
                                            LPSTR Buffer, 
                                            DWORD BufferLength) :
m_DevHandle(DevHandle)
{
    // Initialize header
    m_MIDIHdr.lpData         = Buffer;
    m_MIDIHdr.dwBufferLength = BufferLength;
    m_MIDIHdr.dwFlags        = 0;

    // Prepare header
    MMRESULT Result = ::midiInPrepareHeader(DevHandle, &m_MIDIHdr,
                                            sizeof m_MIDIHdr);

    // If an error occurred, throw exception
    if(Result != MMSYSERR_NOERROR)
    {
        throw CMIDIInException(Result);
    }
}


// Destructor
CMIDIInDevice::CMIDIInHeader::~CMIDIInHeader()
{
    ::midiInUnprepareHeader(m_DevHandle, &m_MIDIHdr, 
                            sizeof m_MIDIHdr);
}


// Add system exclusive buffer to queue
void CMIDIInDevice::CMIDIInHeader::AddSysExBuffer()
{
    MMRESULT Result = ::midiInAddBuffer(m_DevHandle, &m_MIDIHdr,
                                        sizeof m_MIDIHdr);

    // If an error occurred, throw exception
    if(Result != MMSYSERR_NOERROR)
    {
        throw CMIDIInException(Result);
    }
}


//--------------------------------------------------------------------
// CHeaderQueue implementation
//--------------------------------------------------------------------


// Constructor
CMIDIInDevice::CHeaderQueue::CHeaderQueue()
{
    ::InitializeCriticalSection(&m_CriticalSection);
}


// Destructor
CMIDIInDevice::CHeaderQueue::~CHeaderQueue()
{
    RemoveAll();

    ::DeleteCriticalSection(&m_CriticalSection);
}


// Add header to queue
void CMIDIInDevice::CHeaderQueue::AddHeader(
                                 CMIDIInDevice::CMIDIInHeader *Header)
{
    ::EnterCriticalSection(&m_CriticalSection);

    m_HdrQueue.push(Header);

    ::LeaveCriticalSection(&m_CriticalSection);
}


// Remove header from queue
void CMIDIInDevice::CHeaderQueue::RemoveHeader()
{
    ::EnterCriticalSection(&m_CriticalSection);

    if(!m_HdrQueue.empty())
    {
        delete m_HdrQueue.front();
        m_HdrQueue.pop();
    }

    ::LeaveCriticalSection(&m_CriticalSection);
}


// Empty header queue
void CMIDIInDevice::CHeaderQueue::RemoveAll()
{
    ::EnterCriticalSection(&m_CriticalSection);

    while(!m_HdrQueue.empty())
    {
        delete m_HdrQueue.front();
        m_HdrQueue.pop();
    }

    ::LeaveCriticalSection(&m_CriticalSection);
}


// Determines if the header queue is empty
bool CMIDIInDevice::CHeaderQueue::IsEmpty()
{
    bool Result;

    ::EnterCriticalSection(&m_CriticalSection);

    Result = m_HdrQueue.empty();

    ::LeaveCriticalSection(&m_CriticalSection);

    return Result;
}


//--------------------------------------------------------------------
// CMIDIInDevice implementation
//--------------------------------------------------------------------


// Constructs CMIDIInDevice object in an closed state
CMIDIInDevice::CMIDIInDevice() :
m_Receiver(0),
m_State(CLOSED)
{
    // If we are unable to create signalling event, throw exception
    if(!CreateEvent())
    {
        throw CMIDIInEventFailure();
    }
}


// Constructs CMIDIInDevice object in an closed state and initializes the 
// MIDI receiver
CMIDIInDevice::CMIDIInDevice(CMIDIReceiver &Receiver) :
m_Receiver(&Receiver),
m_State(CLOSED)
{
    // If we are unable to create signalling event, throw exception
    if(!CreateEvent())
    {
        throw CMIDIInEventFailure();
    }
}


// Constructs CMIDIInDevice object in an opened state
CMIDIInDevice::CMIDIInDevice(UINT DeviceId, CMIDIReceiver &Receiver) :
m_Receiver(&Receiver),
m_State(CLOSED)
{
    // Open device
    Open(DeviceId);

    // If we are unable to create signalling event, throw exception
    if(!CreateEvent())
    {
        Close();
        throw CMIDIInEventFailure();
    }
}


// Destruction
CMIDIInDevice::~CMIDIInDevice()
{
    // Close device
    Close();

    // Close handle to signalling event
    ::CloseHandle(m_Event);
}


// Opens the MIDI input device
void CMIDIInDevice::Open(UINT DeviceId)
{
    // Makes sure the previous device, if any, is closed before 
    // opening another one
    Close();

    // Open MIDI input device
    MMRESULT Result = ::midiInOpen(&m_DevHandle, DeviceId, 
                                  reinterpret_cast<DWORD>(MidiInProc),
                                  reinterpret_cast<DWORD>(this),
                                  CALLBACK_FUNCTION);

    // If we are able to open the device, change state
    if(Result == MMSYSERR_NOERROR)
    {
        m_State = OPENED;
    }
    // Else opening failed, throw exception
    else
    {
        throw CMIDIInException(Result);
    }
}


// Closes the MIDI input device
void CMIDIInDevice::Close()
{
    // If the device is recording, stop recording before closing the 
    // device
    if(m_State == RECORDING)
    {
        StopRecording();
    }

    // If the device is opened...
    if(m_State == OPENED)
    {
        // Close the device
        MMRESULT Result = ::midiInClose(m_DevHandle);

        // If a failure occurred, throw exception
        if(Result != MMSYSERR_NOERROR)
        {
            throw CMIDIInException(Result);
        }

        // Change state
        m_State = CLOSED;
    }
}


// Adds a buffer for receiving system exclusive messages
void CMIDIInDevice::AddSysExBuffer(LPSTR Buffer, DWORD BufferLength)
{
    CMIDIInHeader *Header;

    try
    {
        // Create new header
        Header = new CMIDIInHeader(m_DevHandle, Buffer, BufferLength);
    }
    // If memory allocation failed, throw exception
    catch(const std::bad_alloc &)
    {
        throw CMIDIInMemFailure();
    }
    // If preparation for the header failed, rethrow exception
    catch(const CMIDIInDevice &)
    {
        throw;
    }

    try
    {
        // Add header to queue
        Header->AddSysExBuffer();
        m_HdrQueue.AddHeader(Header);
    }
    // If we are unable to add the buffer to the queue, delete header
    // and throw exception
    catch(const CMIDIInDevice &)
    {
        delete Header;
        throw;
    }
}


// Starts the recording process
void CMIDIInDevice::StartRecording()
{
    // Only begin recording if the MIDI input device has been opened
    if(m_State == OPENED)
    { 
        // Change state
        m_State = RECORDING;

        m_Thread = ::AfxBeginThread((AFX_THREADPROC)HeaderProc, this);

        // Start recording
        MMRESULT Result = ::midiInStart(m_DevHandle);

        // If recording attempt failed...
        if(Result != MMSYSERR_NOERROR)
        {
            // Revert back to opened state
            m_State = OPENED;

            // Signal the worker thread to finish
            ::SetEvent(m_Event);

			::WaitForSingleObject(m_Thread->m_hThread, INFINITE);

            // Throw exception
            throw CMIDIInException(Result);
        }
    }
}


// Stops the recording process
void CMIDIInDevice::StopRecording()
{
    // If the device is in fact recording...
    if(m_State == RECORDING)
    {
        // Change state
        m_State = OPENED;

        // Signal the worker thread to finish
        ::SetEvent(m_Event);

		::WaitForSingleObject(m_Thread->m_hThread, INFINITE);

        // Reset the MIDI input device
        ::midiInReset(m_DevHandle);

        // Empty header queue
        m_HdrQueue.RemoveAll();
    }
}


// Registers the MIDI receiver. Returns the previous receiver.
CMIDIReceiver *CMIDIInDevice::SetReceiver(CMIDIReceiver &Receiver)
{
    CMIDIReceiver *PrevReceiver = m_Receiver;

    m_Receiver = &Receiver;

    return PrevReceiver;
}


// Determines if the MIDI input device is opened
bool CMIDIInDevice::IsOpen() const
{
    return ((m_State == OPENED) || (m_State == RECORDING));
}


// Determines if the MIDI input device is recording
bool CMIDIInDevice::IsRecording() const
{
    return (m_State == RECORDING);
}


// Gets Id for this device
UINT CMIDIInDevice::GetDevID() const
{
    UINT DeviceID;
    MMRESULT Result = ::midiInGetID(m_DevHandle, &DeviceID);

    if(Result != MMSYSERR_NOERROR)
    {
        throw CMIDIInException(Result);
    }

    return DeviceID;
}


// Gets the capabilities of a particular MIDI input device
void CMIDIInDevice::GetDevCaps(UINT DeviceId, MIDIINCAPS &Caps)
{
    MMRESULT Result = ::midiInGetDevCaps(DeviceId, &Caps, 
                                         sizeof Caps);

    // If we are not able to retrieve device capabilities, throw 
    // exception
    if(Result != MMSYSERR_NOERROR)
    {
        throw CMIDIInException(Result);
    }
}


// Creates event for signalling header thread
bool CMIDIInDevice::CreateEvent()
{
    bool Result = true;

    m_Event = ::CreateEvent(NULL, FALSE, FALSE, NULL);

    // If event creation failed, record failure
    if(m_Event == NULL)
    {
        Result = false;
    }

    return Result;
}


// Called by Windows when a MIDI input event occurs
void CALLBACK CMIDIInDevice::MidiInProc(HMIDIIN MidiIn, UINT Msg,
                                        DWORD Instance, DWORD Param1,
                                        DWORD Param2)
{
    CMIDIInDevice *Device;
    
    Device = reinterpret_cast<CMIDIInDevice *>(Instance);

    if(Device->m_Receiver != 0)
    {
        switch(Msg)
        {
        case MIM_DATA:      // Short message received
            Device->m_Receiver->ReceiveMsg(Param1, Param2);
            break;

        case MIM_ERROR:     // Invalid short message received
            Device->m_Receiver->OnError(Param1, Param2);
            break;

        case MIM_LONGDATA:  // System exclusive message received
            if(Device->m_State == RECORDING)
            {
                // Retrieve data, send it to receiver, and notify header
                // thread that we are done with the system exclusive 
                // message
                MIDIHDR *MidiHdr = reinterpret_cast<MIDIHDR *>(Param1);
                Device->m_Receiver->ReceiveMsg(MidiHdr->lpData, 
                                               MidiHdr->dwBytesRecorded, 
                                               Param2);
                ::SetEvent(Device->m_Event);
            }
            break;

        case MIM_LONGERROR: // Invalid system exclusive message received
            if(Device->m_State == RECORDING)
            {
                // Retrieve data, send it to receiver, and notify header
                // thread that we are done with the system exclusive 
                // message
                MIDIHDR *MidiHdr = reinterpret_cast<MIDIHDR *>(Param1);
                Device->m_Receiver->OnError(MidiHdr->lpData,
                                            MidiHdr->dwBytesRecorded,
                                            Param2);
                ::SetEvent(Device->m_Event);
            }
            break;
        }
    }
}


// Header worker thread
DWORD CMIDIInDevice::HeaderProc(LPVOID Parameter)
{
    CMIDIInDevice *Device; 
    
    Device = reinterpret_cast<CMIDIInDevice *>(Parameter);

    // Continue while the MIDI input device is recording
    while(Device->m_State == RECORDING)
    {
        ::WaitForSingleObject(Device->m_Event, INFINITE);

        // Make sure we are still recording
        if(Device->m_State == RECORDING)
        {
            // Remove the finished header
            Device->m_HdrQueue.RemoveHeader();
        }
    }

    return 0;
}

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This article, along with any associated source code and files, is licensed under The MIT License

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About the Author

Leslie Sanford

United States United States
Aside from dabbling in BASIC on his old Atari 1040ST years ago, Leslie's programming experience didn't really begin until he discovered the Internet in the late 90s. There he found a treasure trove of information about two of his favorite interests: MIDI and sound synthesis.
 
After spending a good deal of time calculating formulas he found on the Internet for creating new sounds by hand, he decided that an easier way would be to program the computer to do the work for him. This led him to learn C. He discovered that beyond using programming as a tool for synthesizing sound, he loved programming in and of itself.
 
Eventually he taught himself C++ and C#, and along the way he immersed himself in the ideas of object oriented programming. Like many of us, he gotten bitten by the design patterns bug and a copy of GOF is never far from his hands.
 
Now his primary interest is in creating a complete MIDI toolkit using the C# language. He hopes to create something that will become an indispensable tool for those wanting to write MIDI applications for the .NET framework.
 
Besides programming, his other interests are photography and playing his Les Paul guitars.

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