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Replace bytes_xor with much faster numpy based version #15

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Replace bytes_xor with much faster numpy based version #15

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17 changes: 13 additions & 4 deletions makeelf/utils.py
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Original file line number Diff line number Diff line change
@@ -1,8 +1,17 @@
#!/usr/bin/env python3
## \file utils.py
# \brief Utility functions

# Old code was quite slow on large files (e.g., several seconds on a 32MB ELF).
# Most of this was xor. Large speedup from this SO answer:
#https://stackoverflow.com/questions/2119761/simple-python-challenge-fastest-bitwise-xor-on-data-buffers
#
# Although, this does add numpy as a dependency, so perhaps this should be checked at runtime?
Comment on lines +5 to +9
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This is perfect information for commit message, but serves no purpose inline, as whoever reads this does not see previous version.

from numpy import frombuffer, bitwise_xor, byte

def bytes_xor(lhs, rhs):
res = []
for a, b in zip(lhs, rhs):
res.append(a ^ b)
return bytes(res)
a = frombuffer(lhs, dtype=byte)
b = frombuffer(rhs, dtype=byte)
c = bitwise_xor(a, b)
r = c.tostring()
return bytes(r)