Set the number of stars you have in Sky Force Reloaded

skyforcestars.py

#!/usr/bin/env python

"""
The game Sky Force Reloaded on Android stores how many in-game stars you've
collected in an obfuscated config file. This program was made by
reverse-engineering that obfuscation using a bunch of sample values.

Given the number of stars you want, it will generate a line to add to the
game's config file. Note that the game will treat invalid values as 0 so make a
backup of your config before modifying it.
"""

# Samples:
# 4A-10-1D-42-0B-70-4B-10 = 0191
# 4B-10-1D-42-0B-70-4B-10 = 1191
# 48-10-1D-42-0B-70-4B-10 = 2191
# 49-10-1D-42-0B-70-4B-10 = 3191
# 4E-10-1D-42-0B-70-4B-10 = 4191
# 4F-10-1D-42-0B-70-4B-10 = 5191
# 4C-10-1D-42-0B-70-4B-10 = 6191
# 4D-10-1D-42-0B-70-4B-10 = 7191
# 42-10-1D-42-0B-70-4B-10 = 8191
# 43-10-1D-42-0B-70-4B-10 = 9191
# 4B-10-1F-42-03-70-4F-10 = 1315
# 4E-10-1A-42-06-70-4F-10 = 4645
# 4B-10-1D-42-04-70-4F-10-1D-42 = 11651
# 43-10-1D-42-04-70-4F-10-1D-42 = 91651
# 43-10-1D-42-06-70-48-10-1A-42 = 91426
# 43-10-1E-42-06-70-48-10-1A-42 = 92426
# 43-10-14-42-06-70-48-10-1A-42 = 98426
# 43-10-15-42-06-70-48-10-1A-42 = 99426
# 43-10-15-42-07-70-48-10-1A-42 = 99526
# 43-10-15-42-03-70-48-10-1A-42 = 99126
# 43-10-15-42-0B-70-48-10-1A-42 = 99926
# 43-10-15-42-0B-70-48-10-15-42 = 99929
# 43-10-15-42-04-70-48-10-15-42 = 99629

# Each digit is represented by a single byte, separated by a filler value
# The translation of digit to byte depends on its position in the number mod 3

# Filler:
# c1 c2 c3
# ---------
# 10 42 70

# Digits:
# n: c1 c2 c3
# ------------
# 0: 4A 1C 02
# 1: 4B 1D 03
# 2: 48 1E 00
# 3: 49 1F 01
# 4: 4E 18 06
# 5: 4F 19 07
# 6: 4C 1A 04
# 7: 4D 1B 05
# 8: 42 14 0A
# 9: 43 15 0B
# extrapolation...
# A: 40 16 08
# B: 41 17 09
# C: 46 10 0E
# D: 47 11 0F
# E: 44 12 0C
# F: 45 13 0D

# The digit mappings can be generated by repeatly splitting a list of 1 - 16 in
# half and swapping (or not) the 2 halves


import argparse

STARS_KEY = "2A-10-40-42-53-70-03-10-49-42-40-70-22-10-7C-42"


def swap(lst, s):
    """Recursively swap list halves

    s is a bit array (0=leave, 1=swap) consumed from the right (0b100 = leave, leave, swap).
    Will stop swapping when s is 0
    """
    if not s:
        return lst
    m = len(lst) // 2
    if s & 1:
        lst[:m], lst[m:] = lst[m:], lst[:m]
    s >>= 1
    return swap(lst[:m], s) + swap(lst[m:], s)


# Filler values - static bytes that follow the actual data
FILLER = [0x10, 0x42, 0x70]

# Data bytes. The index is the value they represent
# ex: 5 = VALUES[x][5]
VALUES = [
    [0x40 + x for x in swap(list(range(0, 16)), 0b101)],
    [0x10 + x for x in swap(list(range(0, 16)), 0b11)],
    [0x00 + x for x in swap(list(range(0, 16)), 0b100)],
]


def encode(val):
    out = []
    # Add a byte representing each digit followed by the correct filler byte
    for i, x in enumerate(str(val)):
        out.append(VALUES[i % 3][int(x)])
        out.append(FILLER[i % 3])
    return "-".join("{:0>2X}".format(x) for x in out)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description="Set the number of stars in Sky Force Reloaded"
    )
    parser.add_argument("stars", type=int, help="Number of stars you want")
    args = parser.parse_args()

    val = encode(args.stars)
    print(
        "To apply the stars, edit:\n"
        "   /data/data/pl.idreams.SkyForceReloaded2016/shared_prefs/pl.idreams.SkyForceReloaded2016.v2.playerprefs.xml\n"
        "and add the following line just before the closing </map> tag:\n"
        '    <string name="{}">{}</string>'.format(STARS_KEY, val)
    )

Sample output:

$ ./skyforcestars.py 9999999
To apply the stars, edit:
   /data/data/pl.idreams.SkyForceReloaded2016/shared_prefs/pl.idreams.SkyForceReloaded2016.v2.playerprefs.xml
and add the following line just before the closing </map> tag:
    <string name="2A-10-40-42-53-70-03-10-49-42-40-70-22-10-7C-42">43-10-15-42-0B-70-43-10-15-42-0B-70-43-10</string>