PC Loisirs 18/cd.iso/sharewar/mikm202/source/munitrk.c

C/C++ Source or Header | 1995-09-18 | 6.9 KB | 342 lines

/*

    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
    1,                // UNI_XMEFFECTA
    1                // UNI_XMEFFECTP
};


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;
}