Decode strings from some feelplus games

dec.py

# Translate feelplus packed strings
# Derived from examples at https://pastebin.com/UkfBaSga

import itertools
import struct

# Unknown char 39 is shown as "{39}"
charset1 = ['{%s}'%(i,) for i in range(40)]

for i in range(10):
    charset1[i + 1] = str(i)

for i, c in enumerate("ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
    charset1[11 + i] = c

charset1[37] = '_'
charset1[38] = '.'

def unpack(words, char_count):
    for v in words:
        x = v % char_count
        v = (v - x) // char_count
        if x == 0:
            return
        yield x

        y = v % char_count
        v = (v - y) // char_count
        if y == 0:
            return
        yield y

        z = v
        if z == 0:
            return
        yield z

def wswap(dw):
    return struct.unpack("<H", struct.pack(">H", dw))[0]

# decode
#
# skip_middle_repeat: Otherwise 9274e791 be96efee be96efee cd4a0000 decodes to
#                     BGM01_TITLE.TITLE.XWV
def decode(hex_code, charset = charset1, skip_middle_repeat = True, big_endian = True):
    # parse string as hex
    dwords = list(map(lambda x: int(x, base=16), hex_code.split()))

    # drop repeated middle dword
    if skip_middle_repeat and len(dwords) == 4 and dwords[1] == dwords[2]:
        dwords = dwords[0:2] + dwords[3:]

    # split into 16-bit words
    words = itertools.chain.from_iterable([dword >> 16, dword & 0xffff] for dword in dwords)

    # swap each word if little endian
    if not big_endian:
        words = [wswap(w) for w in words]

    # make string
    return ''.join(charset[c] for c in unpack(words, len(charset)))

# Moon Diver
print(decode("9274e791 be96efee be96efee cd4a0000"))

# Mind Jack
print(decode("b309b16d c02d4734 c02d4734 da870275"))
print(decode("be856373 31a0ebc9 31a0ebc9 8b4f69d7"))
print(decode("be856373 31a0ebc9 31a0ebc9 8b4f69d7", skip_middle_repeat = False))

# Lost Odyssey Demo
print(decode("62e96906 937cc8ef 937cc8ef 6a620000", big_endian = False))
print(decode("d5bab46c b6ba0f00 b6ba0f00 00000000", big_endian = False))