Pre-allocate visited array and thread lists at compile time and
reuse them across re_exec calls. A cache_in_use flag detects
re-entrancy and falls back to malloc when needed.
Eliminates 3 malloc + 3 free per NFA execution for the common
non-re-entrant case. Combined with the literal fast path, brings
literal match? from 4.7x to 2.5x vs CRuby.
Co-authored-by: Claude <noreply@anthropic.com>
Pure literal patterns (/hello/, /abc/) are detected at compile
time and matched using memchr+memcmp directly, completely
bypassing Pike VM setup (no malloc, no visited array, no thread
lists). Engine-only time drops from ~400ns to ~80ns.
Co-authored-by: Claude <noreply@anthropic.com>
Compute a 128-bit bitmap of bytes that could start a match.
For patterns like /cat|dog|fox/ the bitmap contains only {b,c,d,f},
skipping positions where no alternative can match. For /\d+/ only
{'0'-'9'} are set.
Used when no literal prefix is available (alternation, character
class patterns). Falls back gracefully when too many bytes match.
Key improvements vs CRuby ratio:
alternation miss: 9.5x -> 3.6x
\d+ medium string: 3.0x -> 1.4x
Co-authored-by: Claude <noreply@anthropic.com>
Extract the leading literal bytes from compiled bytecode and use
memchr + memcmp to skip positions where the prefix cannot match.
Both Pike VM and backtracking engine benefit.
For /needle/ in a 2006-char string: 29x faster (1.97s -> 0.07s),
now on par with CRuby/Oniguruma.
Co-authored-by: Claude <noreply@anthropic.com>
The flag is set not only for non-greedy quantifiers but also for
lookahead, lookbehind, and backreferences. The new name accurately
reflects its purpose: indicating that the backtracking engine is
required instead of the Pike VM.
Co-authored-by: Claude <noreply@anthropic.com>
Add (?<=...) positive and (?<!...) negative lookbehind support.
The sub-pattern must have a fixed byte length (no quantifiers or
alternation), computed at compile time and stored in the instruction.
At execution time, the engine backs up by that many bytes and runs
the sub-pattern forward. Maximum lookbehind length is 255 bytes.
Co-authored-by: Claude <noreply@anthropic.com>
The x flag ignores unescaped whitespace and #comments in patterns,
making complex regexps more readable. Whitespace inside character
classes [...] remains literal. Implemented as a preprocessing step
that strips whitespace/comments before compilation.
Co-authored-by: Claude <noreply@anthropic.com>
implement positive and negative lookahead in the backtracking engine:
- (?=pattern): succeeds if pattern matches at current position
without consuming characters
- (?!pattern): succeeds if pattern does NOT match at current position
new bytecodes RE_LOOKAHEAD and RE_NEG_LOOKAHEAD implemented in
the backtracking engine via nested bt_match calls.
Co-authored-by: Claude <noreply@anthropic.com>
support named capture groups in patterns:
- compiler parses (?<name>...) syntax and builds name table
- MatchData#[:name] and MatchData#["name"] access by name
- MatchData#named_captures returns {name => value} hash
- Regexp#named_captures returns {name => group_number} hash
- named captures stored in mrb_regexp_pattern for GC safety
Co-authored-by: Claude <noreply@anthropic.com>
non-greedy patterns now correctly match the shortest possible
string. patterns with non-greedy quantifiers are dispatched to
the backtracking engine which naturally handles non-greedy
semantics.
the Pike VM continues to be used for purely greedy patterns
(O(n*m) guarantee).
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto