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annotate pytouhou/utils/random.py @ 39:493b503c81e0

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Fix PRNG and add some methods to perform like EoSD
author Thibaut Girka <thib@sitedethib.com>
date Mon, 15 Aug 2011 00:38:19 +0200
parents 776453783743
children ab826bc29aa2
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776453783743 Add PRNG reverse-engineered from EoSD's 102h.exe.
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1 """
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2 This file provides a pseudo-random number generator identical to the one used in
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3 Touhou 6: The Embodiment of Scarlet Devil.
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4 It is the only truly reverse-engineered piece of code of this project,
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5 as it is needed in order to retain compatibility with replay files produced by
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6 the offical game code.
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8 It has been reverse engineered from 102h.exe@0x41e780."""
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11 #TODO: maybe some post-processing is missing
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14 from time import time
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16 class Random(object):
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17 def __init__(self, seed=None):
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18 if seed is None:
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493b503c81e0 Fix PRNG and add some methods to perform like EoSD
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19 seed = int(time() % 65536)
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20 self.seed = seed
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21 self.counter = 0
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24 def set_seed(self, seed):
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25 self.seed = seed
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26 self.counter = 0
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29 def rand_uint16(self):
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30 # Further reverse engineering might be needed.
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31 x = ((self.seed ^ 0x9630) - 0x6553) & 0xffff
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32 self.seed = (((x & 0x0c000) >> 0xe) + x*4) & 0xffff
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33 self.counter += 1
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34 self.counter &= 0xffff
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35 return self.seed
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38 def rand_uint32(self):
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39 # 102h.exe@0x41e7f0
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40 a = self.rand_uint16() << 16
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41 a |= self.rand_uint16()
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42 return a
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45 def rand_double(self):
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46 # 102h.exe@0x41e820
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47 return float(self.rand_uint32()) / 0x100000000
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