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Fix bug that leads to ~23.3% miss rate on kernel32.dll (among others) #71

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Fix bug that leads to ~23.3% miss rate on kernel32.dll (among others) #71

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393e47d
Fix bug that lead to ~23.3% miss rate on kernel32.dll (among others)
cyb3rjerry Apr 7, 2025
5fe9ec4
Merge branch 'OALabs:main' into fix-murmur2_lummas_v3.py
cyb3rjerry Jun 4, 2025
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68 changes: 20 additions & 48 deletions algorithms/murmur2_lummas_v3.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,53 +13,25 @@


def hash(data):
fun_len = len(data)
seed = 0x20
new_index = 0
i = 0
seeded_len = (fun_len ^ seed)
if fun_len > 4:
shifted_len = fun_len >> 2 & 0xFFFFFFFF
fun_len = fun_len - (4 * (fun_len >> 2)) & 0xFFFFFFFF
for i in range(0, len(data), 4):
if shifted_len != 0:
shifted_len = shifted_len - 1
seeded_len = (seeded_len * 0x5BD1E995) & 0xFFFFFFFF
ecx = ((((((data[i+3] << 8) | data[i+2]) << 8) | data[i+1]) << 8 | data[i]) * 0x5BD1E995) & 0xFFFFFFFF
eax = ecx
eax = eax >> 0x18 & 0xFFFFFFFF
eax = (eax ^ ecx) & 0xFFFFFFFF
ecx = (eax * 0x5BD1E995) & 0xFFFFFFFF
seeded_len = (seeded_len ^ ecx) & 0xFFFFFFFF
new_index = i
if (fun_len - 1) == 0:
eax = (data[new_index] ^ seeded_len) & 0xFFFFFFFF
seeded_len = (eax * 0x5BD1E995) & 0xFFFFFFFF
return eax
elif (fun_len - 2) == 0:
eax = (data[new_index+1] << 8) & 0xFFFFFFFF
seeded_len = seeded_len ^ eax
eax = data[new_index]
eax = eax ^ seeded_len
seeded_len = (eax * 0x5BD1E995) & 0xFFFFFFFF
l = len(data)
m = 0x5bd1e995
h = seed ^ l

elif (fun_len - 3) != 0:
pass
else:
eax = data[new_index+2]
eax = eax << 0x10 & 0xFFFFFFFF
seeded_len = (seeded_len ^ eax) & 0xFFFFFFFF
eax = data[new_index+1]
eax = (eax << 8) & 0xFFFFFFFF
seeded_len = (seeded_len ^ eax) & 0xFFFFFFFF
eax = data[new_index]
eax = eax ^ seeded_len
seeded_len = (eax * 0x5BD1E995) & 0xFFFFFFFF
eax = seeded_len
eax = eax >> 0xD & 0xFFFFFFFF
eax = eax ^ seeded_len
ecx = (eax * 0x5BD1E995) & 0xFFFFFFFF
eax = ecx
eax = (eax >> 0xF) & 0xFFFFFFFF
eax = eax ^ ecx
return eax
x = l % 4
o = l - x

for i in range(0, o, 4):
k = (data[i + 3] << 24) | (data[i + 2] << 16) | (data[i + 1] << 8) | data[i]
k = (k * m) & 0xFFFFFFFF
h = (((k ^ (k >> 24)) * m) ^ (h * m)) & 0xFFFFFFFF

if x > 0:
if x > 2:
h ^= data[o + 2] << 16
if x > 1:
h ^= data[o + 1] << 8
h = ((h ^ data[o]) * m) & 0xFFFFFFFF

h = ((h ^ (h >> 13)) * m) & 0xFFFFFFFF
return (h ^ (h >> 15)) & 0xFFFFFFFF