I'm still having problems decompressing the LZS compressed files using the algorhythm Fice has give. I also do have a small 'update' to the documentation for it, LZOFFSET is 18 for the following reason 3 is your minimum length 18 is your maximum length. The makers of the format likely surmized that if you can't go back at LEAST your maximum length and read all that data you will end up trying to read from unwritten data on the output (a bad thing) so they put that in to alleviate potention errors.
If I find the background files I'll be happy (smirk) either they are MIM BSX or DAT my guess is DAT or MIM. Anyhow here is what I am using to decompress LZS (pardon the lack of commments).
#define LZLEN 3
#define LZOFFSET 18
AnsiString TMain::LZSDec(AnsiString FName)
{
fstream File;
fstream Out;
AnsiString Return;
char Ctrl;
short int CtrlBits;
unsigned short Ref;
int Offset, Len, DestLen, FileEnd;
int Pos, NewP, Result;
char OutB[64];
File.open(FName.c_str(), fstream::in | fstream::binary);
Return = "temp";
Out.open(Return.c_str(), fstream::out | fstream::in | fstream::binary);
if (File.is_open())
{
File.seekg(0, SEEK_END);
FileEnd = File.tellg();
File.seekg(0, SEEK_SET);
if (Out.is_open())
{
DestLen = 0;
CtrlBits = 0;
Ctrl = 0xFF;
while ((File.tellg() < FileEnd) && !File.eof())
{
if (CtrlBits == 0)
{ // read more control bits here
File.read(&Ctrl, 1);
CtrlBits = 8;
}
if ((Ctrl & 0x01) == 0)
{
File.read((char *)&Ref, 2);
Offset = (Ref & 0x00FF) << 4;
Offset+= (Ref & 0x0F000) >> 12;
Len = ((Ref & 0xF) >> 8) + LZLEN;
Pos = Out.tellg();
// the new position is
// the current position - 18 - Offset
NewP = Pos - LZOFFSET - Offset;
// and the result with 0xFFF
NewP &= 0x0FFF;
if (NewP == 0)
break;
// if the Offset position is <=
// the current Output position
if (NewP <= Pos)
{ int I;
Offset = Len / NewP;
// the resulting position is within the file
Out.seekg(Pos - NewP, SEEK_SET);
// the Length is greater than the offset
if (Offset > 0)
{ // read the New Position bytes
Out.read(OutB, NewP);
// now write the data (Length / Offset) times
for (I = 0; I < Offset; I++)
{ // write out data here :)
Out.write(OutB, NewP);
}
}
else
{ // read len bytes
Out.read(OutB, Len);
// move back to our position
Out.seekg(Pos, SEEK_SET);
// write len bytes
Out.write(OutB, Len);
}
}
else
{ // it's beyond the begining of the file
// so we just write out 0's
memset(OutB, 0, Len);
Out.write(OutB, Len);
}
DestLen += Len;
}
else
{ // copy the byte
File.read(OutB, 1);
Out.write(OutB, 1);
DestLen ++;
}
Ctrl >>=1;
CtrlBits--;
}
Out.close();
}
File.close();
}
return Return;
}
