Lokad.Utf8Regex.Pcre2 0.3.0

Lokad.Utf8Regex.Pcre2

Lokad.Utf8Regex.Pcre2 is a net10.0, UTF-8-first managed companion to Lokad.Utf8Regex. Utf8Pcre2Regex implements the repository's selected PCRE2 10.47 standard-matcher profile over ReadOnlySpan<byte> and Span<byte>. Utf8Regex remains exclusively the .NET 10 Regex profile.

The package does not bind to native PCRE2. Its only non-BCL implementation dependency is Lokad.Utf8Regex; there is no P/Invoke, native loader, RID payload, or external matcher executable.

Release notes for the core and companion packages are tracked in the repository changelog.

Supported profile

The generic PCRE2 compiler/runtime covers the admitted literal, character, branching, repetition, capture, backreference, assertion, scoped-option, branch-reset, duplicate-name, recursion/subroutine, conditional, atomic, backtracking-control, \K, Unicode, and opted-in \C families. Normal operations include IsMatch, Match, MatchDetailed, Count, EnumerateMatches, MatchMany, and PCRE2 substitution.

Probe implements a curated partial-match profile and rejects unsupported partial shapes explicitly. The DFA matcher, invalid-UTF subject mode, callouts, split, full capture history, and substitution forms outside the selected profile are not included. The executable corpus and backlog ledgers are the authoritative capability boundary; support is never inferred from similarity to .NET behavior.

Patterns and subjects must be well-formed UTF-8. Public start positions and raw match ranges use byte offsets. UTF-16 coordinates are exposed only when the reported range is exactly projectable. Opted-in \C can return a byte slice that splits a scalar, and opted-in lookaround \K can report a non-monotone range; affected operations follow the explicit dispositions in SPEC-PCRE2.md.

Example

using System.Text;
using Lokad.Utf8Regex.Pcre2;

var regex = new Utf8Pcre2Regex(
    @"(?<scheme>https?)://(?<host>[A-Za-z0-9.-]+)",
    Pcre2CompileOptions.None);

ReadOnlySpan<byte> input = Encoding.UTF8.GetBytes(
    "Visit https://example.com and http://localhost.");

foreach (var match in regex.EnumerateMatches(input))
{
    if (match.Success && match.IsByteAligned)
    {
        Console.WriteLine(
            Encoding.UTF8.GetString(input.Slice(match.IndexInBytes, match.LengthInBytes)));
    }
}

byte[] redacted = regex.Replace(input, "<$host>");

Replacement strings use PCRE2 substitution syntax, not .NET replacement syntax. The API also exposes UTF-8 replacement patterns, callback replacement, TryReplace, ReplaceToString, detailed numeric-slot/name-table results, and explicit compile and execution settings.

Contract and development evidence

The public surface uses explicit overloads rather than default-valued parameters. Its exact frozen form is PublicApi.Shipped.txt. The package contract is SPEC-PCRE2.md, internal ownership is described in ARCHITECTURE.md, and release evidence is recorded in QUALIFICATION.md. The generated BENCHMARKS.md page keeps the PCRE2-specific performance snapshot, native PCRE2 baseline, dependency review, and scaling evidence local to this companion.

Run ./test-packaged-pcre2.ps1 -Configuration Release from the repository root to pack a version-coherent core/companion pair, reject native or RID assets, replace the PCRE2 test project's sibling references with package references, and execute the complete PCRE2 suite from an isolated NuGet cache.

• Project: Lokad.Utf8Regex.Pcre2.csproj
• Facade: Utf8Pcre2Regex.cs
• Result types: Utf8Pcre2CoreTypes.cs