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base_encode/base_decode: performance improvement

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For example, for 50 KB of random data, and base 43,
previously,
- base_encode took ~38 seconds
- base_decode took ~270 seconds
now,
- base_encode takes ~7.5 seconds
- base_decode takes ~6 seconds
This commit is contained in:
SomberNight 2019-12-08 06:07:01 +01:00
parent 369d972aed
commit 01f94fcf58
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GPG key ID: B33B5F232C6271E9
1 changed files with 10 additions and 4 deletions
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14
electrum/bitcoin.py
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@ -455,8 +455,11 @@ def base_encode(v: bytes, base: int) -> str:
if base == 43: if base == 43:
chars = __b43chars chars = __b43chars
long_value = 0 long_value = 0
for (i, c) in enumerate(v[::-1]): power_of_base = 1
long_value += (256**i) * c for c in v[::-1]:
# naive but slow variant: long_value += (256**i) * c
long_value += power_of_base * c
power_of_base <<= 8
result = bytearray() result = bytearray()
while long_value >= base: while long_value >= base:
div, mod = divmod(long_value, base) div, mod = divmod(long_value, base)
@ -486,11 +489,14 @@ def base_decode(v: Union[bytes, str], length: Optional[int], base: int) -> Optio
if base == 43: if base == 43:
chars = __b43chars chars = __b43chars
long_value = 0 long_value = 0
for (i, c) in enumerate(v[::-1]): power_of_base = 1
for c in v[::-1]:
digit = chars.find(bytes([c])) digit = chars.find(bytes([c]))
if digit == -1: if digit == -1:
raise ValueError('Forbidden character {} for base {}'.format(c, base)) raise ValueError('Forbidden character {} for base {}'.format(c, base))
long_value += digit * (base**i) # naive but slow variant: long_value += digit * (base**i)
long_value += digit * power_of_base
power_of_base *= base
result = bytearray() result = bytearray()
while long_value >= 256: while long_value >= 256:
div, mod = divmod(long_value, 256) div, mod = divmod(long_value, 256)