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base64: optimize b16decode #157310

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methane merged 2 commits into from
Sep 11, 2026
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base64: optimize b16decode #157310

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c6fdc28
Optimize b16decode for empty ignorechars
methane Sep 11, 2026
4298ee9
Skip b16decode translation when ignorechars is empty
methane Sep 11, 2026
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3 changes: 2 additions & 1 deletion Lib/base64.py
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Original file line number Diff line number Diff line change
Expand Up @@ -304,7 +304,8 @@ def b16decode(s, casefold=False, *, ignorechars=b''):
for b in b'abcdef':
if b in s and b not in ignorechars:
raise binascii.Error('Non-base16 digit found')
s = s.translate(None, delete=b'abcdef')
if ignorechars:

@chatgpt-codex-connector chatgpt-codex-connector Bot Sep 11, 2026

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P2 Badge Check the actual byte length before skipping translation

When ignorechars is a nonempty bytes subclass whose __bool__ returns false, this condition skips the translation even though the lowercase characters must be removed. For example, with such a subclass containing b'a', b16decode(b'aB', ignorechars=...) now decodes the lowercase a as a hex digit and returns b'\xab'; previously a was ignored and the remaining odd digit raised binascii.Error. Normalize bytes subclasses or otherwise test the underlying buffer's emptiness without invoking overridable truthiness.

AGENTS.md reference: AGENTS.md:L16-L16

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s = s.translate(None, delete=b'abcdef')
return binascii.unhexlify(s, ignorechars=ignorechars)

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