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comparison pytouhou/utils/random.pyx @ 509:292fea5c584e

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Some more type optimisations.
author Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
date Mon, 25 Nov 2013 19:12:56 +0100
parents pytouhou/utils/random.py@3c2a9e28198c
children 4ce3ef053a25
comparison
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508:1bc014f9d572 509:292fea5c584e
1 # -*- encoding: utf-8 -*-
2 ##
3 ## Copyright (C) 2011 Thibaut Girka <thib@sitedethib.com>
4 ##
5 ## This program is free software; you can redistribute it and/or modify
6 ## it under the terms of the GNU General Public License as published
7 ## by the Free Software Foundation; version 3 only.
8 ##
9 ## This program is distributed in the hope that it will be useful,
10 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
11 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 ## GNU General Public License for more details.
13 ##
14
15
16 """
17 This file provides a pseudo-random number generator identical to the one used in
18 Touhou 6: The Embodiment of Scarlet Devil.
19 It is the only truly reverse-engineered piece of code of this project,
20 as it is needed in order to retain compatibility with replay files produced by
21 the offical game code.
22
23 It has been reverse engineered from 102h.exe."""
24
25
26 #TODO: maybe some post-processing is missing
27
28
29 from time import time
30
31 cdef class Random:
32 def __init__(self, long seed=-1):
33 if seed < 0:
34 seed = time()
35 self.set_seed(<unsigned short>(seed & 65535))
36
37
38 cdef void set_seed(self, unsigned short seed) nogil:
39 self.seed = seed
40 self.counter = 0
41
42
43 cdef unsigned short rewind(self) nogil:
44 """Rewind the PRNG by 1 step. This is the reverse of rand_uint16.
45 Might be useful for debugging purposes.
46 """
47 x = self.seed
48 x = (x >> 2) | ((x & 3) << 14)
49 self.seed = ((x + 0x6553) & 0xffff) ^ 0x9630
50 self.counter -= 1
51 return self.seed
52
53
54 cpdef unsigned short rand_uint16(self):
55 # 102h.exe@0x41e780
56 x = ((self.seed ^ 0x9630) - 0x6553) & 0xffff
57 self.seed = (((x & 0xc000) >> 14) | (x << 2)) & 0xffff
58 self.counter += 1
59 return self.seed
60
61
62 cpdef unsigned int rand_uint32(self):
63 # 102h.exe@0x41e7f0
64 a = self.rand_uint16() << 16
65 a |= self.rand_uint16()
66 return a
67
68
69 cpdef double rand_double(self):
70 # 102h.exe@0x41e820
71 return self.rand_uint32() / <double>0x100000000