Previously, case-insensitive regex matching used ASCII-only case
conversion (to_ascii_lowercase) even for Unicode characters.
Now we implement Canonicalize abstract operation, so we can case-fold
Unicode characters properly during case-insensitive matching.
This commit implements the regexp-modifiers proposal. It allows us to
use modification of i,m,s flags within groups using
`(?flags:subpattern)` and `(?flags-flags:subpattern)` syntax.
Step 2.b of the RepeatMatcher states that once minimum repetitions
are satisfied, empty matches should not be considered for further
repetitions. This was not being enforced for optional quantifiers
like `?`, so we had extra capture group matches.
This introduces a new mechanism for evaluating lookbehind assertions by
adding four new bytecode opcodes: SetStepBack, IncStepBack,
CheckStepBack, and CheckSavedPosition.
These opcodes replace the previous GoBack-based approach and enables
correct handling of variable-length lookbehind patterns,
where the match length cannot be known statically.
Track lookbehind greediness in the parser and propagate it to bytecode
generation. Allow controlled backtracking in lookbehind bodies while
avoiding incorrect captures during step-back execution.
Partially fix issue: #3459
Fixes handling of backreferences when the referenced capture group is
undefined or hasn't participated in the match.
CharacterCompareType::NamedReference is added to distinguish numbered
(\1) from named (\k<name>) backreferences. Numbered backreferences use
exact group lookup. Named backreferences search for participating
groups among duplicates.
When building with REGEX_DEBUG or ENABLE_ALL_THE_DEBUG_MACROS there are
two issues with linking of bin/TestRegex
- Libraries/LibRegex/RegexDebug.h:76 with undefined reference
regex::OpCode_Compare::variable_arguments_to_byte_string(
AK::Optional<regex::MatchInput const&>) const
- Libraries/LibRegex/RegexByteCode.h:672 with undefined reference
regex::OpCode::name(regex::OpCodeId)
Add REGEX_API on regex::OpCode and regex::OptCode_Compare to allow
access to the classes in bin/TestRegex
The opcode may have last been accessed by
block_satisfies_atomic_rewrite_precondition, which would set it to a
state that no longer exists.
Set the state to the correct one unconditionally to ensure we're looking
at the right value.
Fixes#5145.
This also moves the next_serial class static into a file scope static.
The public class static was causing visibility issues with certain Linux
builds when hidden visibility was enabled. However, the current design
makes more sense anyway :^).
This removes another Match member that required destruction. The "API"
for accessing the strings is definitely a bit awkward. We'll think of
something nicer eventually.
clang trunk with -std=c++20 doesn't seem to properly look for an
aggregate initializer here when the type being constructed is a simple
aggregate (e.g. `struct Thing { int a; int b; };`). This template fails
to compile in a usage added 12/16/2020 in `AK/Trie.h`.
Both forms of initialization are supposed to call the
aggregate-initializers but direct-list-initialization delegating to
aggregate initializers is a new addition in c++20 that might not be
implemented yet.
To allow storing unicode ranges compactly; this is not utilised at the
moment, but changing this later would've been significantly more
difficult.
Also fixes a few debug logs.
This commit is a mix of several commits, squashed into one because the
commits before 'Move regex to own Library and fix all the broken stuff'
were not fixable in any elegant way.
The commits are listed below for "historical" purposes:
- AK: Add options/flags and Errors for regular expressions
Flags can be provided for any possible flavour by adding a new scoped enum.
Handling of flags is done by templated Options class and the overloaded
'|' and '&' operators.
- AK: Add Lexer for regular expressions
The lexer parses the input and extracts tokens needed to parse a regular
expression.
- AK: Add regex Parser and PosixExtendedParser
This patchset adds a abstract parser class that can be derived to implement
different parsers. A parser produces bytecode to be executed within the
regex matcher.
- AK: Add regex matcher
This patchset adds an regex matcher based on the principles of the T-REX VM.
The bytecode pruduced by the respective Parser is put into the matcher and
the VM will recursively execute the bytecode according to the available OpCodes.
Possible improvement: the recursion could be replaced by multi threading capabilities.
To match a Regular expression, e.g. for the Posix standard regular expression matcher
use the following API:
```
Pattern<PosixExtendedParser> pattern("^.*$");
auto result = pattern.match("Well, hello friends!\nHello World!"); // Match whole needle
EXPECT(result.count == 1);
EXPECT(result.matches.at(0).view.starts_with("Well"));
EXPECT(result.matches.at(0).view.end() == "!");
result = pattern.match("Well, hello friends!\nHello World!", PosixFlags::Multiline); // Match line by line
EXPECT(result.count == 2);
EXPECT(result.matches.at(0).view == "Well, hello friends!");
EXPECT(result.matches.at(1).view == "Hello World!");
EXPECT(pattern.has_match("Well,....")); // Just check if match without a result, which saves some resources.
```
- AK: Rework regex to work with opcodes objects
This patchsets reworks the matcher to work on a more structured base.
For that an abstract OpCode class and derived classes for the specific
OpCodes have been added. The respective opcode logic is contained in
each respective execute() method.
- AK: Add benchmark for regex
- AK: Some optimization in regex for runtime and memory
- LibRegex: Move regex to own Library and fix all the broken stuff
Now regex works again and grep utility is also in place for testing.
This commit also fixes the use of regex.h in C by making `regex_t`
an opaque (-ish) type, which makes its behaviour consistent between
C and C++ compilers.
Previously, <regex.h> would've blown C compilers up, and even if it
didn't, would've caused a leak in C code, and not in C++ code (due to
the existence of `OwnPtr` inside the struct).
To make this whole ordeal easier to deal with (for now), this pulls the
definitions of `reg*()` into LibRegex.
pros:
- The circular dependency between LibC and LibRegex is broken
- Eaiser to test (without accidentally pulling in the host's libc!)
cons:
- Using any of the regex.h functions will require the user to link -lregex
- The symbols will be missing from libc, which will be a big surprise
down the line (especially with shared libs).
Co-Authored-By: Ali Mohammad Pur <ali.mpfard@gmail.com>
