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⚡ Use frozenset for printable chars to enable O(1) membership checks in string detection loops #29

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r0ny123 wants to merge 1 commit into from
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⚡ Use frozenset for printable chars to enable O(1) membership checks in string detection loops #29

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8 changes: 6 additions & 2 deletions smda/utility/StringExtractor.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,10 @@
# ported back from our PR to capa v4.0.0
# https://github.com/mandiant/capa/blob/v4.0.0/capa/features/extractors/smda/insn.py

# Precomputed set of printable characters for O(1) membership checks
# (string.printable is a string, so `in` does a linear scan; a set is O(1))
_PRINTABLE_CHARS = frozenset(string.printable)


def read_bytes(smda_report, va, num_bytes=None):
"""
Expand Down Expand Up @@ -64,7 +68,7 @@ def detect_ascii_len(smda_report, offset, maxlen=None):
char = smda_report.buffer[rva]
while (
char < 127
and chr(char) in string.printable
and chr(char) in _PRINTABLE_CHARS

@gemini-code-assist gemini-code-assist Bot May 6, 2026

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medium

The char < 127 check on the preceding line is redundant. All characters in _PRINTABLE_CHARS have an ordinal value less than 127 (the maximum is ord('~') which is 126). Removing this redundant check would simplify the code and provide a minor performance improvement in this tight loop, which is consistent with the goals of this PR.

and (maxlen is None or ascii_len < maxlen)
and rva + 1 < len(smda_report.buffer)
):
Expand All @@ -87,7 +91,7 @@ def detect_unicode_len(smda_report, offset, maxlen=None):
second_char = smda_report.buffer[rva + 1]
while (
char < 127
and chr(char) in string.printable
and chr(char) in _PRINTABLE_CHARS

@gemini-code-assist gemini-code-assist Bot May 6, 2026

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medium

Similar to detect_ascii_len, the char < 127 check on the preceding line is redundant here as well. All characters in _PRINTABLE_CHARS have an ordinal value less than 127. Removing this check would be a good follow-up optimization.

and second_char == 0
and (maxlen is None or unicode_len < 2 * maxlen)
and rva + 3 < len(smda_report.buffer)
Expand Down
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