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engine

Pure-Go Onigmo-lineage regex engine; stdlib-regexp-shaped API with lookaround & backrefs. CGO=0.

A regular-expression engine with a public API shaped like the standard library's regexp — Compile/MustCompile, the Find*/FindAll* family, ReplaceAll*, MatchString, SubexpNames — that additionally supports lookahead, lookbehind, backreferences, atomic groups and \g<> subexpression calls. Package onigmo.

Highlights

  • CGO_ENABLED=0, zero third-party dependencies.
  • Lookahead (?=…)/(?!…), lookbehind (?<=…)/(?<!…), backreferences — none expressible in RE2.
  • Standard-library-shaped API: Compile/MustCompile, Find*/FindAll*, ReplaceAll* (with $1/${name} expansion), MatchBounds, WithTimeout.
  • Backtracking VM for the full feature set; linear-time lazy-NFA/DFA accelerator for the RE2-compatible subset; step/time budget bounds pathological patterns.
  • 100% statement coverage; CI across amd64/arm64 + ppc64le/s390x/riscv64/loong64 (qemu) + wasm.

Example

re := onigmo.MustCompile(`v\d+\.\d+\.\d+(?=["<])`)
got := re.FindAllString(`a v1.2.3" b v4.5.6< c v9.9.9 d`, -1)
// got == []string{"v1.2.3", "v4.5.6"}   // v9.9.9 excluded by the lookahead

Install

go get github.com/go-regexp/engine

Requires Go 1.26.4 or newer.