/*

native_midi: Hardware Midi support for the SDL_mixer library

Copyright (C) 2000,2001 Florian 'Proff' Schulze

This library is free software; you can redistribute it and/or

modify it under the terms of the GNU Library General Public

License as published by the Free Software Foundation; either

version 2 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

Library General Public License for more details.

You should have received a copy of the GNU Library General Public

License along with this library; if not, write to the Free

Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

Florian 'Proff' Schulze

florian.proff.schulze@gmx.net

*/

#include "native_midi_common.h"

#else

#define Mix_SetError(X)

#endif

#include <stdlib.h>

#include <string.h>

#include <limits.h>

/* The maximum number of midi tracks that we can handle */

#define MIDI_TRACKS 32

/* A single midi track as read from the midi file */

typedef struct

{

Uint8 *data; /* MIDI message stream */

int len; /* length of the track data */

} MIDITrack;

/* A midi file, stripped down to the absolute minimum - divison & track data */

typedef struct

{

int division; /* number of pulses per quarter note (ppqn) */

MIDITrack track[MIDI_TRACKS];

} MIDIFile;

/* Some macros that help us stay endianess-independant */

#if SDL_BYTEORDER == SDL_BIG_ENDIAN

#define BE_SHORT(x) (x)

#define BE_LONG(x) (x)

#else

#define BE_SHORT(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))

#define BE_LONG(x) ((((x)&0x0000FF)<<24) | \

(((x)&0x00FF00)<<8) | \

(((x)&0xFF0000)>>8) | \

(((x)>>24)&0xFF))

#endif

/* Get Variable Length Quantity */

static int GetVLQ(MIDITrack *track, int *currentPos)

{

int l = 0;

Uint8 c;

while(1)

{

c = track->data[*currentPos];

(*currentPos)++;

l += (c & 0x7f);

if (!(c & 0x80))

return l;

l <<= 7;

}

}

/* Create a single MIDIEvent */

static MIDIEvent *CreateEvent(Uint32 time, Uint8 event, Uint8 a, Uint8 b)

{

MIDIEvent *newEvent;

newEvent = calloc(1, sizeof(MIDIEvent));

if (newEvent)

{

newEvent->time = time;

newEvent->status = event;

newEvent->data[0] = a;

newEvent->data[1] = b;

}

else

Mix_SetError("Out of memory");

return newEvent;

}

/* Convert a single midi track to a list of MIDIEvents */

static MIDIEvent *MIDITracktoStream(MIDITrack *track)

{

Uint32 atime = 0;

Uint32 len = 0;

Uint8 laststatus = 0;

Uint8 lastchan = 0;

int currentPos = 0;

int end = 0;

MIDIEvent *head = CreateEvent(0,0,0,0); /* dummy event to make handling the list easier */

MIDIEvent *currentEvent = head;

while (!end)

{

if (currentPos >= track->len)

break; /* End of data stream reached */

atime += GetVLQ(track, &currentPos);

event = track->data[currentPos++];

/* Handle SysEx seperatly */

if (((event>>4) & 0x0F) == MIDI_STATUS_SYSEX)

{

if (event == 0xFF)

{

type = track->data[currentPos];

currentPos++;

switch(type)

{

case 0x2f: /* End of data marker */

end = 1;

case 0x51: /* Tempo change */

/*

a=track->data[currentPos];

b=track->data[currentPos+1];

c=track->data[currentPos+2];

AddEvent(song, atime, MEVT_TEMPO, c, b, a);

*/

break;

}

}

else

type = 0;

len = GetVLQ(track, &currentPos);

/* Create an event and attach the extra data, if any */

currentEvent->next = CreateEvent(atime, event, type, 0);

currentEvent = currentEvent->next;

if (NULL == currentEvent)

{

FreeMIDIEventList(head);

return NULL;

}

if (len)

{

currentEvent->extraLen = len;

currentEvent->extraData = malloc(len);

memcpy(currentEvent->extraData, &(track->data[currentPos]), len);

currentPos += len;

}

}

else

{

a = event;

if (a & 0x80) /* It's a status byte */

{

/* Extract channel and status information */

lastchan = a & 0x0F;

laststatus = (a>>4) & 0x0F;

/* Read the next byte which should always be a data byte */

a = track->data[currentPos++] & 0x7F;

}

switch(laststatus)

{

case MIDI_STATUS_NOTE_OFF:

case MIDI_STATUS_NOTE_ON: /* Note on */

case MIDI_STATUS_AFTERTOUCH: /* Key Pressure */

case MIDI_STATUS_CONTROLLER: /* Control change */

case MIDI_STATUS_PITCH_WHEEL: /* Pitch wheel */

b = track->data[currentPos++] & 0x7F;

currentEvent->next = CreateEvent(atime, (Uint8)((laststatus<<4)+lastchan), a, b);

currentEvent = currentEvent->next;

if (NULL == currentEvent)

{

FreeMIDIEventList(head);

return NULL;

}

break;

case MIDI_STATUS_PROG_CHANGE: /* Program change */

case MIDI_STATUS_PRESSURE: /* Channel pressure */

a &= 0x7f;

currentEvent->next = CreateEvent(atime, (Uint8)((laststatus<<4)+lastchan), a, 0);

currentEvent = currentEvent->next;

if (NULL == currentEvent)

{

FreeMIDIEventList(head);

return NULL;

}

break;

default: /* Sysex already handled above */

break;

}

}

}

currentEvent = head->next;

free(head); /* release the dummy head event */

return currentEvent;

}

/*

* Convert a midi song, consisting of up to 32 tracks, to a list of MIDIEvents.

* To do so, first convert the tracks seperatly, then interweave the resulting

* MIDIEvent-Lists to one big list.

*/

static MIDIEvent *MIDItoStream(MIDIFile *mididata)

{

MIDIEvent *track[MIDI_TRACKS];

MIDIEvent *head = CreateEvent(0,0,0,0); /* dummy event to make handling the list easier */

MIDIEvent *currentEvent = head;

int trackID;

if (NULL == head)

return NULL;

/* First, convert all tracks to MIDIEvent lists */

for (trackID = 0; trackID < MIDI_TRACKS; trackID++)

track[trackID] = MIDITracktoStream(&mididata->track[trackID]);

/* Now, merge the lists. */

/* TODO */

while(1)

{

int currentTrackID = -1;

/* Find the next event */

for (trackID = 0; trackID < MIDI_TRACKS; trackID++)

{

if (track[trackID] && (track[trackID]->time < lowestTime))

{

currentTrackID = trackID;

lowestTime = track[currentTrackID]->time;

}

}

/* Check if we processes all events */

if (currentTrackID == -1)

break;

currentEvent->next = track[currentTrackID];

track[currentTrackID] = track[currentTrackID]->next;

currentEvent = currentEvent->next;

lowestTime = 0;

}

/* Make sure the list is properly terminated */

currentEvent->next = 0;

currentEvent = head->next;

free(head); /* release the dummy head event */

return currentEvent;

}

static int ReadMIDIFile(MIDIFile *mididata, FILE *fp)

{

int i = 0;

Uint32 ID;

Uint32 size;

Uint16 format;

Uint16 tracks;

Uint16 division;

if (!mididata)

return 0;

if (!fp)

return 0;

/* Make sure this is really a MIDI file */

fread(&ID, 1, 4, fp);

if (BE_LONG(ID) != 'MThd')

return 0;

/* Header size must be 6 */

fread(&size, 1, 4, fp);

size = BE_LONG(size);

if (size != 6)

return 0;

/* We only support format 0 and 1, but not 2 */

fread(&format, 1, 2, fp);

format = BE_SHORT(format);

if (format != 0 && format != 1)

return 0;

fread(&tracks, 1, 2, fp);

tracks = BE_SHORT(tracks);

/* Retrieve the PPQN value, needed for playback */

fread(&division, 1, 2, fp);

mididata->division = BE_SHORT(division);

for (i=0; i<tracks; i++)

{

fread(&ID, 1, 4, fp); /* We might want to verify this is MTrk... */

fread(&size, 1, 4, fp);

size = BE_LONG(size);

mididata->track[i].len = size;

mididata->track[i].data = malloc(size);

if (NULL == mididata->track[i].data)

{

Mix_SetError("Out of memory");

goto bail;

}

fread(mididata->track[i].data, 1, size, fp);

}

return 1;

bail:

for(;i >= 0; i--)

{

if (mididata->track[i].data)

free(mididata->track[i].data);

}

return 0;

}

MIDIEvent *CreateMIDIEventList(char *midifile, Uint16 *division)

{

FILE *fp = NULL;

MIDIFile *mididata = NULL;

MIDIEvent *eventList;

int trackID;

mididata = calloc(1, sizeof(MIDIFile));

if (!mididata)

return NULL;

/* Open the file */

fp = fopen(midifile, "rb");

if ( fp != NULL )

{

/* Read in the data */

if ( ! ReadMIDIFile(mididata, fp))

{

free(mididata);

fclose(fp);

return NULL;

}

fclose(fp);

}

else

{

free(mididata);

return NULL;

}

if (division)

*division = mididata->division;

eventList = MIDItoStream(mididata);

for(trackID = 0; trackID < MIDI_TRACKS; trackID++)

{

if (mididata->track[trackID].data)

free(mididata->track[trackID].data);

}

free(mididata);

return eventList;

}

void FreeMIDIEventList(MIDIEvent *head)

{

MIDIEvent *cur, *next;

cur = head;

while (cur)

{

next = cur->next;

if (cur->extraData)

free (cur->extraData);

free (cur);

cur = next;

}

}