+++ /dev/null
-# encoding: utf8
-u"""
-Handles reading and encryption/decryption of Pokémon save file data.
-
-See: http://projectpokemon.org/wiki/Pokemon_NDS_Structure
-
-Kudos to LordLandon for his pkmlib.py, from which this module was originally
-derived.
-"""
-
-import struct
-from pokedex.util import permutations
-
-def pokemon_prng(seed):
- u"""Creates a generator that simulates the main Pokémon PRNG."""
- while True:
- seed = 0x41C64E6D * seed + 0x6073
- seed &= 0xFFFFFFFF
- yield seed >> 16
-
-
-class PokemonSave(object):
- u"""Represents an individual Pokémon, from the game's point of view.
-
- Handles translating between the on-disk encrypted form, the in-RAM blob
- (also used by pokesav), and something vaguely intelligible.
-
- XXX: Okay, well, right now it's just encryption and decryption. But, you
- know.
- """
-
- def __init__(self, blob, encrypted=False):
- u"""Wraps a Pokémon save struct in a friendly object.
-
- If `encrypted` is True, the blob will be decrypted as though it were an
- on-disk save. Otherwise, the blob is taken to be already decrypted and
- is left alone.
- """
-
- # XXX Sometime this should have an abstract internal representation.
- # For now, just store the decrypted version
-
- if encrypted:
- # Decrypt it.
- # Interpret as one word (pid), followed by a bunch of shorts
- struct_def = "I" + "H" * ((len(blob) - 4) / 2)
- shuffled = list( struct.unpack(struct_def, blob) )
-
- # Apply standard Pokémon decryption, undo the block shuffling, and
- # done
- self.reciprocal_crypt(shuffled)
- words = self.shuffle_chunks(shuffled, reverse=True)
- self.blob = struct.pack(struct_def, *words)
-
- else:
- # Already decrypted
- self.blob = blob
-
-
- @property
- def as_struct(self):
- u"""Returns a decrypted struct, aka .pkm file."""
- return self.blob
-
- @property
- def as_encrypted(self):
- u"""Returns an encrypted struct the game expects in a save file."""
-
- # Interpret as one word (pid), followed by a bunch of shorts
- struct_def = "I" + "H" * ((len(self.blob) - 4) / 2)
- words = list( struct.unpack(struct_def, self.blob) )
-
- # Apply the block shuffle and standard Pokémon encryption
- shuffled = self.shuffle_chunks(words)
- self.reciprocal_crypt(shuffled)
-
- # Stuff back into a string, and done
- return struct.pack(struct_def, *shuffled)
-
-
- ### Utility methods
-
- shuffle_orders = list( permutations(range(4)) )
-
- @classmethod
- def shuffle_chunks(cls, words, reverse=False):
- """The main 128 encrypted bytes (or 64 words) in a save block are split
- into four chunks and shuffled around in some order, based on
- personality. The actual order of shuffling is a permutation of four
- items in order, indexed by the shuffle index. That is, 0 yields 0123,
- 1 yields 0132, 2 yields 0213, etc.
-
- Given a list of words (the first of which should be the pid), this
- function returns the words in shuffled order. Pass reverse=True to
- unshuffle instead.
- """
-
- pid = words[0]
- shuffle_index = (pid >> 0xD & 0x1F) % 24
-
- shuffle_order = cls.shuffle_orders[shuffle_index]
- if reverse:
- # Decoding requires going the other way; invert the order
- shuffle_order = [shuffle_order.index(i) for i in range(4)]
-
- shuffled = words[:3] # skip the unencrypted stuff
- for chunk in shuffle_order:
- shuffled += words[ chunk * 16 + 3 : chunk * 16 + 19 ]
- shuffled += words[67:] # extra bytes are also left alone
-
- return shuffled
-
- @classmethod
- def reciprocal_crypt(cls, words):
- u"""Applies the reciprocal Pokémon save file cipher to the provided
- list of words.
-
- Returns nothing; the list is changed in-place.
- """
- # Apply regular Pokémon "encryption": xor everything with the output of
- # the PRNG. First three items are pid/unused/checksum and are not
- # encrypted.
-
- # Main data is encrypted using the checksum as a seed
- prng = pokemon_prng(words[2])
- for i in range(3, 67):
- words[i] ^= next(prng)
-
- if len(words) > 67:
- # Extra bytes are encrypted using the pid as a seed
- prng = pokemon_prng(words[0])
- for i in range(67, len(words)):
- words[i] ^= next(prng)
-
- return
projects / zzz-pokedex.git / blobdiff