/*                                                                        *
*  gmext.c                                                               *
*                                                                        *
*  gm.cat MIDI sequence extractor                                        *
*                                                                        */

/*
* Originally created by cirdan
* Published on: http://www.tt-forums.net/viewtopic.php?f=31&t=31293&hilit=music+gm
*
* Modified by Lck for MSVC 2008 compatibility
*/

//#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

typedef int uint32_t;

#define RUNNING_MODE

/*inline*/ long read_delta (const unsigned char* *p)
{
	long delta = **p & 0x7F;
	while ( *(*p)++ & 0x80 )
	{
		delta <<= 7;
		delta += **p & 0x7F;
	}
	return delta;
}

void write_delta (FILE *f, long delta)
{
	unsigned char c [4] = { 0, 0x80, 0x80, 0x80 };
	int i = 0;
	while ( delta > 0x7F )
	{
		c[i++] |= delta & 0x7F;
		delta >>= 7;
	}
	c[i++] |= delta;
	while ( i )
		fwrite (c + --i, 1, 1, f);
}

struct seq
{
	uint32_t size;
	unsigned char *data;
};

unsigned char volume [0x80] = {
	100,100,100,100,100, 90, 100,100,100,100,100, 90, 100,100,100,100,100,100,
	85, 100,100,100,100,100,100,100,100,100, 90,90, 110, 80, 100,100,100,
	90, 70, 100,100,100,100,100,100,100,100,100,100,100,100,100, 90,
	100,100,100,100,100,100, 120, 100,100,100, 120, 100, 127, 100,100, 90,
	100,100,100,100,100,100, 95,
	100,100,100,100,100,100,100,100,100,100,100,100,100, 115,
	100,100,100,100,100,100,100,100,100,100,
	100,100,100,100,100,100,100,100,100,100,
	100,100,100,100,100,100,100,100,100,100,
	100,100,100,100,100,100,100,100,100,100
};

long tseq (FILE *f, unsigned nsubs, const struct seq *subs, char channel,
		   const struct seq *seq, unsigned char *patch, long delta0)
{
	long delta = delta0;
	unsigned char output, command = 0x80;
	unsigned char data1, data2;
	const unsigned char *data = seq->data;
	const unsigned char *dataend = seq->data + seq->size;
	while ( data < dataend )
	{
		delta += read_delta (&data);
		if ( *data & 0x80 )  command = *data++;
		switch ( command )
		{
		case 0xFF:
		case 0xFD:  return delta;
		case 0xFE:  /* insert subsequence */
			if ( *data >= nsubs )
			{
				puts ("invalid subsequence");
				return 0;
			}
			delta = tseq (f, nsubs, subs, channel, &subs[*data++],
				patch, delta);
			continue;
		}
		command &= 0xF0;
		data1 = *data++;
		switch ( command )
		{
		case 0x80:  case 0x90:
			data2 = *data++;
			write_delta (f, delta);
			delta = 0;
#ifdef RUNNING_MODE
			if ( output != (command|channel) )
#endif
			{
				output = command | channel;
				fwrite (&output, 1, 1, f);
			}
			fwrite (&data1, 1, 1, f);
			if ( data2 )
				data2 = (unsigned) data2 *
				(channel==9 ? 80 : volume[*patch]) >> 7;
			fwrite (&data2, 1, 1, f);
			break;
		case 0xC0:
			if ( data1 == 0x7E )  return delta;
			*patch = data1;
			write_delta (f, delta);
			delta = 0;
#ifdef RUNNING_MODE
			if ( output != (0xC0|channel) )
#endif
			{
				output = 0xC0 | channel;
				fwrite (&output, 1, 1, f);
			}
			if ( (data1==0x57) || (data1==0x3F) )  data1 = 0x3E;
			fwrite (&data1, 1, 1, f);
			break;
		case 0xB0:
			data2 = *data++;
			if ( (data1==0x7E) || (!data1 && !data2) )  continue;
			write_delta (f, delta);
			delta = 0;
			if ( !data1 )
			{
				uint32_t x;
				char xdata [3];
				output = 0xFF;
				fwrite (&output, 1, 1, f);
				data1 = 0x51;
				fwrite (&data1, 1, 1, f);
				data1 = 3;
				fwrite (&data1, 1, 1, f);
				x = (740*163840) * data2;
				xdata[0] = x>>16;
				xdata[1] = x>>8;
				xdata[2] = x;
				fwrite (&xdata, 1, 3, f);
			}
#ifdef RUNNING_MODE
			if ( output != (0xB0|channel) )
#endif
			{
				output = 0xB0 | channel;
				fwrite (&output, 1, 1, f);
			}
			fwrite (&data1, 1, 1, f);
			if ( data1 == 0x5B )  data2 = 0x1E;
			fwrite (&data2, 1, 1, f);
			break;
		case 0xE0:
			data2 = *data++;
			write_delta (f, delta);
			delta = 0;
#ifdef RUNNING_MODE
			if ( output != (0xE0|channel) )
#endif
			{
				output = 0xE0 | channel;
				fwrite (&output, 1, 1, f);
			}
			fwrite (&data1, 1, 1, f);
			fwrite (&data2, 1, 1, f);
			break;
		}
	}
	return 0;
}

void midi_header (FILE *f, unsigned ntracks)
{
	static const char header [10] = { 'M','T','h','d',0,0,0,6,0,1 };
	static const char delta [2] = { 0,24 };
	char ntr [2];
	fwrite (header, 1, 10, f);
	ntr[0] = ntracks>>8;
	ntr[1] = ntracks;
	fwrite (ntr, 1, 2, f);
	fwrite (delta, 1, 2, f);
}

static const char midi_track_start [8] = { 'M','T','r','k',0,0,0,0 };
static const char midi_track_end [4] = { 0, 0xFF, 0x2F, 0 };

void midi_track0 (FILE *f, unsigned tempo, unsigned namelen,
				  const char *name)
{
	static const char set_tempo [4] = { 0, 0xFF, 0x51, 3 };
	static const char text_event [3] = { 0, 0xFF, 1 };
	char data [4];
	unsigned tsize;
	fwrite (midi_track_start, 1, 4, f);
	tsize = namelen + 15;
	data[0] = tsize>>24;
	data[1] = tsize>>16;
	data[2] = tsize>>8;
	data[3] = tsize;
	fwrite (data, 1, 4, f);
	fwrite (set_tempo, 1, 4, f);
	tempo = (370*163840) / tempo;
	data[0] = tempo>>16;
	data[1] = tempo>>8;
	data[2] = tempo;
	fwrite (data, 1, 3, f);
	fwrite (text_event, 1, 3, f);
	fwrite (&namelen, 1, 1, f);
	fwrite (name, 1, namelen, f);
	fwrite (midi_track_end, 1, 4, f);
}

void midi_track (FILE *f, unsigned nsubs, const struct seq *subs,
				 char channel, const struct seq *seq)
{
	static char midi_track_begin [10] =
	{ 0, 0xB0, 0x78, 0, 0, 0x79, 0, 0, 0x7B, 0 };
	long foffset, length;
	char data [4];
	unsigned char patch = 0;
	fwrite (midi_track_start, 1, 8, f);
	foffset = ftell (f);
	midi_track_begin[1] = 0xB0 | channel;
	fwrite (midi_track_begin, 1, 10, f);
	write_delta (f, tseq (f, nsubs, subs, channel, seq, &patch, 0));
	fwrite (midi_track_end+1, 1, 3, f);
	length = ftell(f) - foffset;
	fseek (f, foffset-4, SEEK_SET);
	data[0] = length>>24;
	data[1] = length>>16;
	data[2] = length>>8;
	data[3] = length;
	fwrite (data, 1, 4, f);
	fseek (f, 0, SEEK_END);
}

int gmext_song (FILE *f, uint32_t n)
{
	uint32_t offset, length;
	unsigned char namelength, tempo, nsubs, ntracks;
	char name [256];
	struct seq subs [256];
	char channels [256];
	struct seq tracks [256];
	unsigned namelen, i;
	char out [256];
	FILE *fout;
	/* read in offset and length of song */
	if ( fseek (f, 8*n, SEEK_SET) == -1 )     return -1;
	if ( fread (&offset, 4, 1, f) != 1 )      return -1;
	if ( fread (&length, 4, 1, f) != 1 )      return -1;
	if ( fseek (f, offset, SEEK_SET) == -1 )  return -1;
	/* read in song name */
	if ( fread (&namelength, 1, 1, f) != 1 )  return -1;
	if ( fread (name, 1, namelength, f) != namelength )  return -1;
	if ( namelength && !name[namelength-1] )
		namelen = namelength-1;
	else name[namelen=namelength] = 0;
	printf ("Extracting song #%u %s\n", n, name);
	/* read in tempo */
	if ( fread (&tempo, 1, 1, f) != 1 )  return -1;
	/* read in subs */
	if ( fread (&nsubs, 1, 1, f) != 1 )  return -1;
	for (i=0; i<nsubs; i++)
	{
		/* do not bother free()ing memory on failure, */
		/* since we are going to abort                */
		if ( fread (&subs[i].size, 4, 1, f) != 1 )  return -1;
		if ( subs[i].size < 4 )
		{
			puts ("invalid data length");
			return -2;
		}
		subs[i].size -= 4;
		subs[i].data = malloc (subs[i].size);
		if ( !subs[i].data )
		{
			perror (0);
			return -2;
		}
		if ( fread (subs[i].data, 1, subs[i].size, f) != subs[i].size )
			return -1;
	}
	/* read in tracks */
	if ( fread (&ntracks, 1, 1, f) != 1 )  return -1;
	for (i=0; i<ntracks; i++)
	{
		if ( fread (&channels[i], 1, 1, f) != 1 )     return -1;
		if ( fread (&tracks[i].size, 4, 1, f) != 1 )  return -1;
		if ( tracks[i].size < 4 )
		{
			puts ("invalid data length");
			return -2;
		}
		tracks[i].size -= 4;
		tracks[i].data = malloc (tracks[i].size);
		if ( !tracks[i].data )
		{
			perror (0);
			return -2;
		}
		if ( fread (tracks[i].data, 1, tracks[i].size, f) != tracks[i].size )
			return -1;
	}
	/* check current offset */
	if ( ftell(f) != (offset+length+namelength+1) )
	{
		puts ("offset mismatch");
		return -2;
	}
	/* write output file */
	sprintf (out, "gm_tt%02d.gm", n);
	printf ("Output file: %s\n", out);
	fout = fopen (out, "wb");
	if ( !fout )
	{
		perror (out);
		return -2;
	}
	midi_header (fout, ntracks+1);
	midi_track0 (fout, tempo, namelen, name);
	for (i=0; i<ntracks; i++)
		midi_track (fout, nsubs, subs, channels[i], &tracks[i]);
	/* clean up */
	fclose (fout);
	for (i=0; i<nsubs; i++)    free (subs[i].data);
	for (i=0; i<ntracks; i++)  free (tracks[i].data);
	return 0;
}

int gmext (const char *filename)
{
	FILE *f;
	uint32_t nsongs, i;
	printf ("Reading file %s\n", filename);
	f = fopen (filename, "rb");
	if ( !f )
	{
		perror (filename);
		return 1;
	}
	/* compute the number of songs, knowing that the */
	/* first song starts right after the index table */
	if ( fread (&nsongs, 4, 1, f) != 1 )    /* file format is little-endian */
	{
		perror (filename);
		return 1;
	}
	nsongs /= 8;
	printf ("There are %u songs in %s\n", nsongs, filename);
	/* read songs one by one */
	for (i=0; i<nsongs; i++)
		switch ( gmext_song (f, i) )
	{
		case -1:
			perror (filename);
		case -2:
			fclose (f);
			return 1;
	}
	fclose (f);
	return 0;
}

int main (int nargs, char* *args)
{
	return gmext (nargs>1 ? args[1] : "gm.cat");
}