Mercurial > touhou
changeset 179:3c2a9e28198c
Make rand_uint16 slighty easier to understand, and add a rewind function for debugging purposes.
| author | Thibaut Girka <thib@sitedethib.com> |
|---|---|
| date | Sun, 23 Oct 2011 21:00:53 +0200 |
| parents | 0bd5e5f19a73 |
| children | 5a1533677a9a |
| files | pytouhou/utils/random.py |
| diffstat | 1 files changed, 14 insertions(+), 4 deletions(-) [+] |
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--- a/pytouhou/utils/random.py +++ b/pytouhou/utils/random.py @@ -20,7 +20,7 @@ It is the only truly reverse-engineered as it is needed in order to retain compatibility with replay files produced by the offical game code. -It has been reverse engineered from 102h.exe@0x41e780.""" +It has been reverse engineered from 102h.exe.""" #TODO: maybe some post-processing is missing @@ -41,12 +41,22 @@ class Random(object): self.counter = 0 + def rewind(self): + """Rewind the PRNG by 1 step. This is the reverse of rand_uint16. + Might be useful for debugging purposes. + """ + x = self.seed + x = (x >> 2) | ((x & 3) << 14) + self.seed = ((x + 0x6553) & 0xffff) ^ 0x9630 + self.counter -= 1 + return self.seed + + def rand_uint16(self): - # Further reverse engineering might be needed. + # 102h.exe@0x41e780 x = ((self.seed ^ 0x9630) - 0x6553) & 0xffff - self.seed = (((x & 0x0c000) >> 0xe) | (x << 2)) & 0xffff + self.seed = (((x & 0xc000) >> 14) | (x << 2)) & 0xffff self.counter += 1 - self.counter &= 0xffff return self.seed