/*----------------------------------------------------------------------*
 * unpacker.c Convert data from "cmpByteRun1" run compression. 11/15/85
 *
 * By Jerry Morrison and Steve Shaw, Electronic Arts.
 * This software is in the public domain.
 *
 *      control bytes:
 *       [0..127]   : followed by n+1 bytes of data.
 *       [-1..-127] : followed by byte to be repeated (-n)+1 times.
 *       -128       : NOOP.
 *
 * This version for the Commodore-Amiga computer.
 *----------------------------------------------------------------------*/
 
#include "df1:packer.h"
 
 
/*----------- UnPackRow ------------------------------------------------*/
 
#define UGetByte()      (*source++)
#define UPutByte(c)     (*dest++ = (c))
 
/* Given POINTERS to POINTER variables, unpacks one row, updating the source
 * and destination pointers until it produces dstBytes bytes. */
 
BOOL UnPackRow(pSource, pDest, srcBytes0, dstBytes0)
BYTE **pSource, **pDest;
WORD srcBytes0, dstBytes0;
{
    register BYTE *source = *pSource;
    register BYTE *dest   = *pDest;
    register WORD n;
    register BYTE c;
    register WORD srcBytes = srcBytes0, dstBytes = dstBytes0;
    BOOL error = TRUE;  /* assume error until we make it through the loop */
    WORD minus128 = -128;  /* get the compiler to generate a CMP.W */
 
    while( dstBytes > 0 )  {
        if ( (srcBytes -= 1) < 0 )  goto ErrorExit;
        n = UGetByte();
 
        if (n >= 0) {
            n += 1;
            if ( (srcBytes -= n) < 0 )  goto ErrorExit;
            if ( (dstBytes -= n) < 0 )  goto ErrorExit;
            do {  UPutByte(UGetByte());  } while (--n > 0);
            }
 
        else if (n != minus128) {
            n = -n + 1;
            if ( (srcBytes -= 1) < 0 )  goto ErrorExit;
            if ( (dstBytes -= n) < 0 )  goto ErrorExit;
            c = UGetByte();
            do {  UPutByte(c);  } while (--n > 0);
            }
        }
    error = FALSE;      /* success! */
 
  ErrorExit:
    *pSource = source;  *pDest = dest;
    return(error);
}