LibRegex: Add a regular expression library

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>

1 files changed, 102 insertions, 0 deletions

diff --git a/Libraries/LibRegex/RegexError.h b/Libraries/LibRegex/RegexError.h
new file mode 100644
index 0000000000..90d6a71eca
--- /dev/null
+++ b/Libraries/LibRegex/RegexError.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2020, Emanuel Sprung <emanuel.sprung@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Types.h>
+#ifdef __serenity__
+#    include <regex.h>
+#else
+#    include <LibC/regex.h>
+#endif
+
+namespace regex {
+
+enum class Error : u8 {
+    NoError = __Regex_NoError,
+    InvalidPattern = __Regex_InvalidPattern,                         // Invalid regular expression.
+    InvalidCollationElement = __Regex_InvalidCollationElement,       // Invalid collating element referenced.
+    InvalidCharacterClass = __Regex_InvalidCharacterClass,           // Invalid character class type referenced.
+    InvalidTrailingEscape = __Regex_InvalidTrailingEscape,           // Trailing \ in pattern.
+    InvalidNumber = __Regex_InvalidNumber,                           // Number in \digit invalid or in error.
+    MismatchingBracket = __Regex_MismatchingBracket,                 // [ ] imbalance.
+    MismatchingParen = __Regex_MismatchingParen,                     // ( ) imbalance.
+    MismatchingBrace = __Regex_MismatchingBrace,                     // { } imbalance.
+    InvalidBraceContent = __Regex_InvalidBraceContent,               // Content of {} invalid: not a number, number too large, more than two numbers, first larger than second.
+    InvalidBracketContent = __Regex_InvalidBracketContent,           // Content of [] invalid.
+    InvalidRange = __Regex_InvalidRange,                             // Invalid endpoint in range expression.
+    InvalidRepetitionMarker = __Regex_InvalidRepetitionMarker,       // ?, * or + not preceded by valid regular expression.
+    ReachedMaxRecursion = __Regex_ReachedMaxRecursion,               // MaximumRecursion has been reached.
+    EmptySubExpression = __Regex_EmptySubExpression,                 // Sub expression has empty content.
+    InvalidCaptureGroup = __Regex_InvalidCaptureGroup,               // Content of capture group is invalid.
+    InvalidNameForCaptureGroup = __Regex_InvalidNameForCaptureGroup, // Name of capture group is invalid.
+};
+
+inline String get_error_string(Error error)
+{
+    switch (error) {
+    case Error::NoError:
+        return "No error";
+    case Error::InvalidPattern:
+        return "Invalid regular expression.";
+    case Error::InvalidCollationElement:
+        return "Invalid collating element referenced.";
+    case Error::InvalidCharacterClass:
+        return "Invalid character class type referenced.";
+    case Error::InvalidTrailingEscape:
+        return "Trailing \\ in pattern.";
+    case Error::InvalidNumber:
+        return "Number in \\digit invalid or in error.";
+    case Error::MismatchingBracket:
+        return "[ ] imbalance.";
+    case Error::MismatchingParen:
+        return "( ) imbalance.";
+    case Error::MismatchingBrace:
+        return "{ } imbalance.";
+    case Error::InvalidBraceContent:
+        return "Content of {} invalid: not a number, number too large, more than two numbers, first larger than second.";
+    case Error::InvalidBracketContent:
+        return "Content of [] invalid.";
+    case Error::InvalidRange:
+        return "Invalid endpoint in range expression.";
+    case Error::InvalidRepetitionMarker:
+        return "?, * or + not preceded by valid regular expression.";
+    case Error::ReachedMaxRecursion:
+        return "Maximum recursion has been reached.";
+    case Error::EmptySubExpression:
+        return "Sub expression has empty content.";
+    case Error::InvalidCaptureGroup:
+        return "Content of capture group is invalid.";
+    case Error::InvalidNameForCaptureGroup:
+        return "Name of capture group is invalid.";
+    }
+    return "Undefined error.";
+}
+}
+
+using regex::Error;
+using regex::get_error_string;