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go-ruby-strscan documentation

Ruby's StringScanner in pure Go — MRI-compatible, no cgo.

go-ruby-strscan/strscan is a faithful, pure-Go (zero cgo) reimplementation of Ruby's StringScanner, matching reference Ruby (MRI) byte-for-byte. The module path is github.com/go-ruby-strscan/strscan.

It was extracted from rbgo's prelude/internals into a reusable standalone library: the module is standalone and importable by any Go program, and it is the backend bound into go-embedded-ruby by rbgo as a native module — just like go-ruby-regexp and go-ruby-erb. The dependency runs the other way: this library has no dependency on the Ruby runtime.

Status: scanner complete — MRI byte-exact

Faithful port of MRI's strscan.c: the full method surface — scan / scan_until / skip, match? / check / check_until, peek / getch, pos / charpos, captures ([] / captures) and unscan — with pattern matching backed by go-ruby-regexp. Validated by a differential oracle against the system ruby — scan results compared byte-for-byte — at 100% coverage, gofmt + go vet clean, CI green across the six 64-bit Go targets and three OSes.

Quick taste

sc := strscan.New("3 + 41 = 44")
n, _  := sc.Scan(`\d+`)        // "3",  cursor after "3"
_      = sc.Skip(`\s*\+\s*`)   // skip " + "
m, _  := sc.Scan(`\d+`)        // "41"
rest  := sc.Peek(10)           // " = 44" without advancing
_      = n; _ = m; _ = rest

Repositories

Repo What it is
strscan the library — Ruby's StringScanner in pure Go
docs this documentation site (MkDocs Material, versioned with mike)
go-ruby-strscan.github.io the organization landing page (Hugo)
brand logo and brand assets

Principles

  • Pure Go, CGO_ENABLED=0 — trivial cross-compilation, a single static binary, no C toolchain.
  • MRI byte-exact. Output matches reference Ruby exactly, not approximately, validated by a differential oracle against the ruby binary.
  • Standalone & reusable. Extracted from rbgo's internals; no dependency on the Ruby runtime — the dependency runs the other way.
  • 100% test coverage is the target, enforced as a CI gate, across 6 arches and 3 OSes.

Where to go next

  • Why pure Go — why this slice of Ruby is deterministic enough to live as a standalone, interpreter-independent Go library.
  • Usage & API — the public surface and worked examples.
  • Roadmap — what is done and what is downstream by design.

Source lives at github.com/go-ruby-strscan/strscan.