MIDIReader.cxx

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/*
 * Copyright (c) 2001-2004 MUSIC TECHNOLOGY GROUP (MTG)
 * UNIVERSITAT POMPEU FABRA
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * MIDIFileReader C++ classes
 * This code is part of the CLAM library, but also usable stand-alone.
 * Maarten de Boer <mdeboer@iua.upf.es>
 *
 */
#include "MIDIReader.hxx"
#include "MIDISong.hxx"
#include "MIDITrack.hxx"

namespace MIDI
{

        void Reader::Read(Song& s)
  /* ToDo: document and explain this function */
        {
                static int nbytesPerChnMsg[7] =
                { 3,3,3,3,2,3,3 };

                ChunkType chnkType = GetChunkType();
                unsigned int length;
                unsigned short format,ntrcks;
                
                if (chnkType!="MThd") throw Error("Expected a header chunk\n");

                length = GetInt();
                if (length!=6)
                        throw Error("Unexpected header chunk length\n");

                format = GetShort();
                if (format!=0 && format!=1)
                        throw Error("Unsupported MIDI file format\n");

                ntrcks = GetShort();

                s.SetTicksPerQ(GetShort());

                for (int i=0;i<ntrcks;i++)
                {
                        chnkType = GetChunkType();
                        if (chnkType!="MTrk") throw Error("Expected a track chunk\n");

                        int chnkLength = GetInt();

                        Byte runningStatus = 0;
                        Ticks t = 0;
                        Track *track = new Track;
                        s.AddTrack(track);

                        mCnt = 0;

                        while (mCnt!=chnkLength)
                        {
                                unsigned int dt = GetVarLength();
                                t += dt;
                                Byte b = GetByte();
                                if (b & 0x80)
                                {
                                        int type = ((b&0xF0)>>4)-8;
                                        if (type==7)
                                        {
                                                if (b == 0xFF)
                                                {
                                                        Byte metaType = GetByte();
                                                        unsigned int length = GetVarLength();
                                                        if (metaType!=0x2F) // don't add end-of-track events
                                                        {
                                                                MetaEvent* ev = new MetaEvent(Message(b,metaType),t,length);

                                                                track->Add(ev);

                                                                for (unsigned int i=0;i<length;i++)
                                                                        ev->mData[i] = GetByte();

                                                                if (metaType == 3) // sequence/track name
                                                                {
                                                                        track->Name(ev->mData,length);
                                                                }
                                                        }
                                                }
                                                else if (b == 0xF0 || b==0xF7)
                                                {
                                                        /* TODO: For now, we'll just skip SysEx events */
                                                        int length = GetVarLength();
                                                        while (--length)
                                                        {
                                                                GetByte();
                                                        }
                                                        if (GetByte()!=0xF7)
                                                        {
                                                                throw Error("SysEx message did not terminate with 0xF7");
                                                        }
                                                }
                                                else
                                                {
                                                        throw Error("Encountered a message that I don't know how to handle");
                                                }
                                                runningStatus = 0;
                                        }else{
                                                if (nbytesPerChnMsg[type]==2)
                                                {
                                                        Byte b1 = GetByte();
                                                        track->Add(new Event(Message(b,b1),t));
                                                }
                                                else
                                                {
                                                        Byte b1 = GetByte();
                                                        Byte b2 = GetByte();
                                                        track->Add(new Event(Message(b,b1,b2),t));
                                                }
                                                runningStatus = b;
                                        }
                                }else{
                                        int type = ((runningStatus&0xF0)>>4)-8;
                                        if (nbytesPerChnMsg[type]==2)
                                        {
                                                track->Add(new Event(Message(runningStatus,b),t));
                                        }
                                        else
                                        {
                                                Byte b2 = GetByte();
                                                track->Add(new Event(Message(runningStatus,b,b2),t));
                                        }
                                }
                        }
                }       
        }

}

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