Vigilante8.py

#!/usr/bin/env python

#-------------------------------------------------------------------------------
# Decompression routine for Vigilante 8.

def dec(data):
     out = bytearray()
     ring = bytearray(0x800)
     src = iter(data[8:])
     sz = int.from_bytes(data[4:8], 'little')
     rp = 0
     c = next(src) | 0x100
     while len(out) < sz:
         if c > 0xFFFF:
             c = next(src) | 0x100
         if c & 0x80:
             out.append(next(src))
             ring[rp] = out[-1]
             rp += 1
             rp &= 0x7FF
         else:
             p = next(src)
             p |= next(src) << 8
             l = (p & 0x1F) + 2
             p >>= 5
             for i in range(p, p+l):
                 out.append(ring[i & 0x7FF])
                 ring[rp] = out[-1]
                 rp += 1
                 rp &= 0x7FF
         c <<= 1
     return bytes(out)