fix: prevent heap overflow in ByteLevel bulk path with overlapping sp… - #62
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…lits The bulk fast path (use_regex=false, add_prefix_space=false) reserved output capacity once from the input length, then encoded each split with an unchecked helper whose soundness assumed splits form a non-overlapping partition. Since PreTokenizedString::new accepts arbitrary caller-supplied splits, overlapping ranges make total encoded output exceed the reservation, so Vec::set_len runs past capacity — an out-of-bounds heap write reachable from safe code (CWE-787). Use the capacity-checked encode_bytes_into (reserves per split) instead of encode_bytes_into_unchecked. The initial with_capacity still covers the common non-overlapping case, so reserve is a no-op there — no perf change — but overlapping splits can no longer overflow. Remove the now-unused unchecked helper and add a regression test. Fixes #61 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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…lits
The bulk fast path (use_regex=false, add_prefix_space=false) reserved output capacity once from the input length, then encoded each split with an unchecked helper whose soundness assumed splits form a non-overlapping partition. Since PreTokenizedString::new accepts arbitrary caller-supplied splits, overlapping ranges make total encoded output exceed the reservation, so Vec::set_len runs past capacity — an out-of-bounds heap write reachable from safe code (CWE-787).
Use the capacity-checked encode_bytes_into (reserves per split) instead of encode_bytes_into_unchecked. The initial with_capacity still covers the common non-overlapping case, so reserve is a no-op there — no perf change — but overlapping splits can no longer overflow. Remove the now-unused unchecked helper and add a regression test.
Fixes #61