/*

	UNITRK.C

	All routines dealing with the manipulation of UNITRK(tm) streams

*/

#include <malloc.h>
#include <string.h>
#include "munitrk.h"


#define BUFPAGE  128            // smallest unibuffer size
#define TRESHOLD 16

/* unibuffer is increased by BUFPAGE
  bytes when unipc reaches unimax-TRESHOLD */



/*
	Ok.. I'll try to explain the new internal module format.. so here it goes:


	The UNITRK(tm) Format:
	======================

	A UNITRK stream is an array of bytes representing a single track
	of a pattern. It's made up of 'repeat/length' bytes, opcodes and
	operands (sort of a assembly language):

	rrrlllll
	[REP/LEN][OPCODE][OPERAND][OPCODE][OPERAND] [REP/LEN][OPCODE][OPERAND]..
	^                                         ^ ^
	|-------ROWS 0 - 0+REP of a track---------| |-------ROWS xx - xx+REP of a track...


	The rep/len byte contains the number of bytes in the current row,
	_including_ the length byte itself (So the LENGTH byte of row 0 in the
	previous example would have a value of 5). This makes it easy to search
	through a stream for a particular row. A track is concluded by a 0-value
	length byte.

	The upper 3 bits of the rep/len byte contain the number of times -1 this
	row is repeated for this track. (so a value of 7 means this row is repeated
	8 times)

	Opcodes can range from 1 to 255 but currently only opcodes 1 to 19 are
	being used. Each opcode can have a different number of operands. You can
	find the number of operands to a particular opcode by using the opcode
	as an index into the 'unioperands' table.

*/



UWORD unioperands[256]={
	0,              // not used
	1,              // UNI_NOTE
	1,              // UNI_INSTRUMENT
	1,              // UNI_PTEFFECT0
	1,              // UNI_PTEFFECT1
	1,              // UNI_PTEFFECT2
	1,              // UNI_PTEFFECT3
	1,              // UNI_PTEFFECT4
	1,              // UNI_PTEFFECT5
	1,              // UNI_PTEFFECT6
	1,              // UNI_PTEFFECT7
	1,              // UNI_PTEFFECT8
	1,              // UNI_PTEFFECT9
	1,              // UNI_PTEFFECTA
	1,              // UNI_PTEFFECTB
	1,              // UNI_PTEFFECTC
	1,              // UNI_PTEFFECTD
	1,              // UNI_PTEFFECTE
	1,              // UNI_PTEFFECTF
	1,				// UNI_S3MEFFECTA
	1,              // UNI_S3MEFFECTD
	1,              // UNI_S3MEFFECTE
	1,              // UNI_S3MEFFECTF
	1,              // UNI_S3MEFFECTI
	1,              // UNI_S3MEFFECTQ
	1,				// UNI_S3MEFFECTT
};


UBYTE *unibuf;		// pointer to the temporary unitrk buffer
UWORD unimax;		// maximum number of bytes to be written to this buffer

UWORD unipc;		// index in the buffer where next opcode will be written
UWORD unitt;        // holds index of the rep/len byte of a row
UWORD lastp;		// holds index to the previous row (needed for compressing)

UBYTE *rowstart;	// startadress of a row
UBYTE *rowend;      // endaddress of a row (exclusive)
UBYTE *rowpc;       // current unimod(tm) programcounter


void UniSetRow(UBYTE *t)
{
	rowstart=t;
	rowpc=rowstart;
	rowend=rowstart+(*(rowpc++)&0x1f);
}


UBYTE UniGetByte(void)
{
	return (rowpc<rowend) ? *(rowpc++) : 0;
}


void UniSkipOpcode(UBYTE op)
{
	UWORD t=unioperands[op];
	while(t--) UniGetByte();
}



UBYTE *UniFindRow(UBYTE *t,UWORD row)
/*
	Finds the address of row number 'row' in the UniMod(tm) stream 't'

	returns NULL if the row can't be found.
*/
{
	UBYTE c,l;

	while(1){

		c=*t;					// get rep/len byte

		if(!c) return NULL;		// zero ? -> end of track..

		l=(c>>5)+1;				// extract repeat value

		if(l>row) break;		// reached wanted row? -> return pointer

		row-=l;					// havn't reached row yet.. update row
		t+=c&0x1f;				// point t to the next row
	}

	return t;
}



void UniReset(void)
/*
	Resets index-pointers to create a new track.
*/
{
	unitt=0;		// reset index to rep/len byte
	unipc=1;		// first opcode will be written to index 1
	lastp=0;		// no previous row yet
	unibuf[0]=0;	// clear rep/len byte
}



void UniWrite(UBYTE data)
/*
	Appends one byte of data to the current row of a track.
*/
{
	// write byte to current position and update

	unibuf[unipc++]=data;

	// Check if we've reached the end of the buffer

	if(unipc>(unimax-TRESHOLD)){

		UBYTE *newbuf;

		/* We've reached the end of the buffer, so expand
		   the buffer by BUFPAGE bytes */

		newbuf=realloc(unibuf,unimax+BUFPAGE);

		// Check if realloc succeeded

		if(newbuf!=NULL){
			unibuf=newbuf;
			unimax+=BUFPAGE;
		}
		else{
			/* realloc failed, so decrease unipc so we won't write beyond
			   the end of the buffer.. I don't report the out-of-memory
			   here; the UniDup() will fail anyway so that's where the
			   loader sees that something went wrong */

			unipc--;
		}
	}
}



void UniInstrument(UBYTE ins)
/*
	Appends UNI_INSTRUMENT opcode to the unitrk stream.
*/
{
	UniWrite(UNI_INSTRUMENT);
	UniWrite(ins);
}



void UniNote(UBYTE note)
/*
	Appends UNI_NOTE opcode to the unitrk stream.
*/
{
	UniWrite(UNI_NOTE);
	UniWrite(note);
}


void UniPTEffect(UBYTE eff,UBYTE dat)
/*
	Appends UNI_PTEFFECTX opcode to the unitrk stream.
*/
{
	if(eff!=0 || dat!=0){				// don't write empty effect
		UniWrite(UNI_PTEFFECT0+eff);
		UniWrite(dat);
	}
}



BOOL MyCmp(UBYTE *a,UBYTE *b,UWORD l)
{
	UWORD t;

	for(t=0;t<l;t++){
		if(*(a++)!=*(b++)) return 0;
	}
	return 1;
}



void UniNewline(void)
/*
	Closes the current row of a unitrk stream (updates the rep/len byte)
	and sets pointers to start a new row.
*/
{
	UWORD n,l,len;

	n=(unibuf[lastp]>>5)+1;		// repeat of previous row
	l=(unibuf[lastp]&0x1f);		// length of previous row

	len=unipc-unitt;			// length of current row

	/* Now, check if the previous and the current row are identical..
	   when they are, just increase the repeat field of the previous row */

	if(n<8 && len==l && MyCmp(&unibuf[lastp+1],&unibuf[unitt+1],len-1)){
		unibuf[lastp]+=0x20;
		unipc=unitt+1;
	}
	else{
		// current and previous row aren't equal.. so just update the pointers

		unibuf[unitt]=len;
		lastp=unitt;
		unitt=unipc;
		unipc++;
	}
}




UBYTE *UniDup(void)
/*
	Terminates the current unitrk stream and returns a pointer
	to a copy of the stream.
*/
{
	UBYTE *d;

	unibuf[unitt]=0;

	if((d=malloc(unipc))==NULL){
		myerr=ERROR_ALLOC_STRUCT;
		return NULL;
	}
	memcpy(d,unibuf,unipc);

	return d;
}



UWORD TrkLen(UBYTE *t)
/*
	Determines the length (in rows) of a unitrk stream 't'
*/
{
	UWORD len=0;
	UBYTE c;

	while(c=*t&0x1f){
		len+=c;
		t+=c;
	}
	len++;

	return len;
}



BOOL UniInit(void)
{
	unimax=BUFPAGE;

	if(!(unibuf=malloc(unimax))){
		myerr=ERROR_ALLOC_STRUCT;
		return 0;
	}
	return 1;
}



void UniCleanup(void)
{
	if(unibuf!=NULL) free(unibuf);
	unibuf=NULL;
}