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Club Amiga de Montreal - CAM
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SimGen_Src
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unpacker.c
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C/C++ Source or Header
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1989-07-26
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/*----------------------------------------------------------------------*
* 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 "iff/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);
}