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 .