rockbox/apps/plugins/midi/midifile.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 *
 * Copyright (C) 2005 Stepan Moskovchenko
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/



extern struct plugin_api * rb;

struct Track * readTrack(int file);
int readID(int file);
void bail(const char *);

struct MIDIfile * loadFile(char * filename)
{
	struct MIDIfile * mf;
	int file = rb->open (filename, O_RDONLY);

	if(file==0)
	{
		bail("Could not open file\n");
	}

	mf = (struct MIDIfile*)allocate(sizeof(struct MIDIfile));

	if(mf==NULL)
	{
		rb->close(file);
		bail("Could not allocate memory for MIDIfile struct\n");
	}

	rb->memset(mf, 0, sizeof(struct MIDIfile));

	if(readID(file) != ID_MTHD)
	{
		rb->close(file);
		bail("Invalid file header chunk.");
	}

	if(readFourBytes(file)!=6)
	{
		rb->close(file);
		bail("Header chunk size invalid.");
	}

	if(readTwoBytes(file)==2)
	{
		rb->close(file);
		bail("MIDI file type not supported");
	}

	mf->numTracks = readTwoBytes(file);
	mf->div = readTwoBytes(file);

	int track=0;

	printf("\nnumTracks=%d  div=%d\nBegin reading track data\n", mf->numTracks, mf->div);

//	return;


	while(! eof(file) && track < mf->numTracks)
	{
		unsigned char id = readID(file);


		if(id == ID_EOF)
		{
			if(mf->numTracks != track)
			{
				printf("\nError: file claims to have %d tracks.\n       I only see %d here.\n", 	mf->numTracks, track);
				mf->numTracks = track;
			}
			return mf;
		}

		if(id == ID_MTRK)
		{
			mf->tracks[track] = readTrack(file);
			//exit(0);
			track++;
		} else
		{
			printf("\n SKIPPING TRACK");
			int len = readFourBytes(file);
			while(--len)
				readChar(file);
		}
	}
	return mf;

}


int rStatus = 0;

//Returns 0 if done, 1 if keep going
int readEvent(int file, void * dest)
{
	struct Event dummy;
	struct Event * ev = (struct Event *) dest;

	if(ev == NULL)
		ev = &dummy; //If we are just counting events instead of loading them

	ev->delta = readVarData(file);


	int t=readChar(file);

	if((t&0x80) == 0x80) //if not a running status event
	{
		ev->status = t;
		if(t == 0xFF)
		{
			ev->d1 = readChar(file);
			ev->len = readVarData(file);

			 //Allocate and read in the data block
			if(dest != NULL)
			{
				ev->evData = readData(file, ev->len);
				printf("\nDATA: <%s>", ev->evData);
			}
			else
			{
				//Don't allocate anything, just see how much it would tale
				//To make memory usage efficient

				int a=0;
				for(a=0; a<ev->len; a++)
					readChar(file); //Skip skip
			}

			if(ev->d1 == 0x2F)
			{
 				return 0; 	//Termination meta-event
			}
		} else             //If part of a running status event
		{
			rStatus = t;
			ev->status = t;
			ev->d1 = readChar(file);

			if (  ((t & 0xF0) != 0xD0) && ((t & 0xF0) != 0xC0) && ((t & 0xF0) > 0x40) )
			{
				ev->d2 = readChar(file);
			} else
				ev->d2 = 127;
		}
	} else  //Running Status
	{
		ev->status = rStatus;
		ev->d1 = t;
		if (  ((rStatus & 0xF0) != 0xD0) && ((rStatus & 0xF0) != 0xC0) && ((rStatus & 0xF0) > 0x40) )
		{
			ev->d2 = readChar(file);
		} else
			ev->d2 = 127;
	}
	return 1;
}



struct Track * readTrack(int file)
{
	struct Track * trk = (struct Track *)allocate(sizeof(struct Track));
	rb->memset(trk, 0, sizeof(struct Track));

	trk->size = readFourBytes(file);
	trk->pos = 0;
	trk->delta = 0;

	int len=0;
	int numEvents=0;

	int pos = rb->lseek(file, 0, SEEK_CUR);

	while(readEvent(file, NULL))	//Memory saving technique
		numEvents++;		//Attempt to read in events, count how many
					//THEN allocate memory and read them in
	rb->lseek(file, pos, SEEK_SET);

	int trackSize = (numEvents+1) * sizeof(struct Event);
	void * dataPtr = allocate(trackSize);
	trk->dataBlock = dataPtr;

	numEvents=0;

	while(readEvent(file, dataPtr))
	{
		if(trackSize < dataPtr-trk->dataBlock)
		{
			printf("\nTrack parser memory out of  bounds");
			exit(1);
		}
		dataPtr+=sizeof(struct Event);
		numEvents++;
	}
	trk->numEvents = numEvents;

	return trk;
}


int readID(int file)
{
	char id[5];
	id[4]=0;
	BYTE a;

	for(a=0; a<4; a++)
		id[a]=readChar(file);
	if(eof(file))
	{
		printf("\End of file reached.");
		return ID_EOF;
	}
	if(rb->strcmp(id, "MThd")==0)
		return ID_MTHD;
	if(rb->strcmp(id, "MTrk")==0)
		return ID_MTRK;
	return ID_UNKNOWN;
}


int readFourBytes(int file)
{
	int data=0;
	BYTE a=0;
	for(a=0; a<4; a++)
		data=(data<<8)+readChar(file);
	return data;
}

int readTwoBytes(int file)
{
	int data=(readChar(file)<<8)+readChar(file);
	return data;
}

//This came from the MIDI file format guide
int readVarData(int file)
{
    unsigned int value;
    char c;
    if ( (value = readChar(file)) & 0x80 )
    {
       value &= 0x7F;
       do
       {
         value = (value << 7) + ((c = readChar(file)) & 0x7F);
       } while (c & 0x80);
    }
    return(value);
}

//This function should not be needed because we
//can just release the whole memory buffer at once
void unloadFile(struct MIDIfile * mf)
{
	if(mf == NULL)
		return;
	int a=0;
	//Unload each track
	for(a=0; a<mf->numTracks; a++)
	{
		int b=0;

		if(mf->tracks[a] != NULL)
			for(b=0; b<mf->tracks[a]->numEvents; b++)
			{
				if(((struct Event*)((mf->tracks[a]->dataBlock)+b*sizeof(struct Event)))->evData!=NULL)
					free(((struct Event*)((mf->tracks[a]->dataBlock)+b*sizeof(struct Event)))->evData);
			}

		if(mf->tracks[a]!=NULL && mf->tracks[a]->dataBlock != NULL)
			free(mf->tracks[a]->dataBlock);	//Unload the event block

		if(mf->tracks[a]!=NULL)
			free(mf->tracks[a]);	//Unload the track structure itself
	}
	free(mf); 	//Unload the main struct
}

void bail(const char * err)
{
	printf("\nERROR: %s\n", err);
	exit(0);
}