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pcre2

NOTE: This release is graded alpha and is likely to experience API changes up until the 1.0 release.

Overview

A V library module for processing Perl Compatible Regular Expressions (PCRE) using the PCRE2 library.

• The pcre2 module is a wrapper for the PCRE2 8-bit runtime library.
• Regex find_* methods search a subject string for regular expression matches.
• Regex replace_* methods return a string in which matches in the subject string are replaced by a replacement string or the result of a replacement function.
• Regex *_all_* methods process all matches; *_one_* methods process the first match.
• The Regex replace_*_extended methods support the PCRE2 extended replacements string syntax (see PCRE2_SUBSTITUTE_EXTENDED in the pcre2api man page).
• Currently there are no extraction methods for named subpatterns.
• The pcre module (which uses the older PCRE library) was the inspiration and starting point for this project; the Go regex package also influenced the project.

Documentation

• pcre2 module documentation.
• PCRE regular expressions syntax.
• Github repository

Examples

import srackham.pcre2

fn main() {
	// Match words starting with `d` or `n`.
	r := pcre2.must_compile(r'\b([dn].*?)\b')

	subject := 'Lorem nisi dis diam a cras placerat natoque'

	// Extract array of all matched strings.
	a := r.find_all(subject)
	println(a) // ['nisi', 'dis', 'diam', 'natoque']

	// Quote matched words.
	s1 := r.replace_all(subject, '"$1"')
	println(s1) // 'Lorem "nisi" "dis" "diam" a cras placerat "natoque"'

	// Replace all matched strings with upper case.
	s2 := r.replace_all_fn(subject, fn (m string) string {
		return m.to_upper()
	})
	println(s2) // 'Lorem NISI DIS DIAM a cras placerat NATOQUE'

	// Replace all matched strings with upper case (PCRE2 extended replacement syntax).
	s3 := r.replace_all_extended(subject, r'\U$1')
	println(s3) // 'Lorem NISI DIS DIAM a cras placerat NATOQUE'
}

For more examples see inside the examples directory and take a look at the module tests.

Dependencies

Install the PCRE2 library:

Arch Linux and Manjaro: pacman -S pcre2

Debian and Ubuntu: apt install libpcre2-dev

Fedora: yum install pcre2-devel

macOS: brew install pcre2

Windows †: pacman.exe -S mingw-w64-x86_64-pcre2

† Uses the MSYS2 package management tools.

Installation

v install srackham.pcre2

Test the installation by running:

v test $HOME/.vmodules/srackham/pcre2

Example installation and test workflows for Ubuntu, macOS and Windows can be found in the Github Actions workflow file.

Performance

Complex patterns can cause PCRE2 resource exhaustion. find_* library functions respond to such errors by raising a panic. The solution is to simplify the offending pattern. Unlike, for example, the Go regexp package, PCRE2 does not have linear-time performance and while they may not trigger a panic, pathalogical patterns can exhibit slow performance. See the PCRE2 pcre2perform man page.