rqrcode — go-ruby-rqrcode

A pure-Go (no cgo) reimplementation of Ruby's rqrcode_core and rqrcode gems (MRI 4.0.5). It generates the QR-code module matrix deterministically — modes, error-correction levels, versions 1–40 with auto-selection, Reed–Solomon ECC, all eight mask patterns with penalty scoring, finder / alignment / timing patterns and format / version info — and renders it (SVG, ANSI, HTML, PNG) module-for-module and byte-for-byte as the gems do, without any Ruby runtime or a C QR library.

It is a QR backend for go-embedded-ruby, but is a standalone, reusable module — a sibling of go-ruby-regexp, go-ruby-erb and go-ruby-yaml.

What it is — and isn't. Building the QR matrix (segment encoding, RS error correction, mask selection, module layout) is fully deterministic and needs no interpreter, so it lives here as pure Go, matching the gems exactly. Binding RQRCode::QRCode to live Ruby objects is the host's job; this library hands back a plain [][]bool matrix and the renderers.

Features

Faithful port of rqrcode_core + rqrcode, validated against the gems on every supported platform:

• All encoding modes — numeric, alphanumeric, byte (8-bit), plus multi-segment codes — with the gems' automatic mode detection.
• All four EC levels — :l / :m / :q / :h (default :h, as in the gem).
• Versions 1–40 with the gem's smallest-that-fits auto-selection, or an explicit WithSize.
• Reed–Solomon ECC over GF(256), block interleaving, and the exact QRMAXBITS / RS_BLOCK_TABLE capacity tables.
• Mask selection — all eight mask predicates and the four-part penalty (get_lost_points) scoring, choosing the same mask as the gem.
• Function patterns — finder + separators, alignment, timing, dark module, 15-bit BCH format info and 18-bit BCH version info (v ≥ 7).
• Renderers — AsSVG (both <rect> and the size-optimised <path>), AsANSI, AsHTML, ToString, and a pure-Go AsPNG (stdlib image/png, still CGO-free).

CGO-free, dependency-free, 100% test coverage, gofmt + go vet clean, and green across the six 64-bit Go targets (amd64, arm64, riscv64, loong64, ppc64le, s390x) and three OSes.

Install

go get github.com/go-ruby-rqrcode/rqrcode

Usage

package main

import (
	"fmt"

	"github.com/go-ruby-rqrcode/rqrcode"
)

func main() {
	// RQRCode::QRCode.new("hello world", level: :h)
	qr, err := rqrcode.New("hello world", rqrcode.WithLevelSymbol("h"))
	if err != nil {
		panic(err)
	}

	fmt.Println(qr.Version)     // 2  (auto-selected smallest version)
	fmt.Println(qr.ModuleCount) // 25

	// The boolean module matrix (qr.Modules[row][col] == qrcode.modules).
	dark, _ := qr.Checked(0, 0)
	fmt.Println(dark) // true — top-left finder pattern

	fmt.Println(qr.String())                    // to_s
	fmt.Println(qr.AsSVG(rqrcode.SVGOptions{}))  // as_svg
	fmt.Println(qr.AsANSIDefault())              // as_ansi
	fmt.Println(qr.AsHTML())                     // as_html

	png, _ := qr.AsPNG(rqrcode.PNGOptions{})     // as_png (pure-Go image/png)
	_ = png
}

Multi-segment codes mirror passing an array of {data:, mode:} hashes:

qr, _ := rqrcode.NewMulti([]rqrcode.Segment{
	rqrcode.Seg("foo", rqrcode.ModeByte8bit),
	rqrcode.Seg("1234", rqrcode.ModeNumeric),
})

API

// New builds a QR code from a string (RQRCode::QRCode.new). Default level :h.
func New(data string, opts ...Option) (*QRCode, error)

// NewMulti builds a multi-segment code (array of {data:, mode:} hashes).
func NewMulti(segs []Segment, opts ...Option) (*QRCode, error)

type QRCode struct {
	Modules     [][]bool // dark/light matrix; Modules[row][col]
	ModuleCount int
	Version     int
	// ...
}
func (q *QRCode) Checked(row, col int) (bool, error) // checked?
func (q *QRCode) Mode() Mode
func (q *QRCode) ErrorCorrectionLevel() Level
func (q *QRCode) String() string                        // to_s (default x / space)
func (q *QRCode) ToString(opts StringOptions) string    // to_s(dark:, light:, quiet_zone_size:)
func (q *QRCode) AsSVG(opts SVGOptions) string          // as_svg (rect + path)
func (q *QRCode) AsANSI(opts ANSIOptions) string        // as_ansi
func (q *QRCode) AsANSIDefault() string                 // as_ansi with gem defaults
func (q *QRCode) AsHTML() string                        // as_html
func (q *QRCode) AsPNG(opts PNGOptions) ([]byte, error) // as_png (pure-Go)

// Options mirror the gems' keyword arguments.
func WithSize(v int) Option        // :size (QR version 1..40; 0 = auto)
func WithMaxSize(v int) Option     // :max_size
func WithLevel(l Level) Option     // :level (typed)
func WithLevelSymbol(s string) Option // :level as "l"/"m"/"q"/"h"
func WithMode(m Mode) Option       // :mode (typed)
func WithModeSymbol(s string) Option  // :mode as "number"/"alphanumeric"/"byte_8bit"

type Level int  // LevelL, LevelM, LevelQ, LevelH (values match QRERRORCORRECTLEVEL)
type Mode  int  // ModeNumeric, ModeAlphanumeric, ModeByte8bit

Tests & coverage

The suite pairs deterministic, gem-free golden tests (which alone hold coverage at 100%, so the qemu cross-arch and Windows lanes pass the gate) with a differential MRI oracle: a corpus of numeric / alphanumeric / byte payloads across every level and a spread of versions is generated here and compared — module-for-module and byte-for-byte — against the rqrcode_core / rqrcode gems run through the system ruby (matrix, to_s, as_svg rect + path, as_ansi, as_html). The oracle skips itself where the gems are absent.

COVERPKG=$(go list ./... | paste -sd, -)
go test -race -coverpkg="$COVERPKG" -coverprofile=cover.out ./...
go tool cover -func=cover.out | tail -1   # 100.0%

License

BSD-3-Clause — see LICENSE. Copyright the go-ruby-rqrcode/rqrcode authors.

WebAssembly

Being pure Go (CGO=0), this library also compiles to WebAssembly — both GOOS=js GOARCH=wasm (browser / Node.js) and GOOS=wasip1 GOARCH=wasm (WASI). CI builds both targets on every push, alongside the six 64-bit native/qemu arches.

GOOS=js     GOARCH=wasm go build ./...   # browser / Node
GOOS=wasip1 GOARCH=wasm go build ./...   # WASI (wasmtime, wasmer, wasmedge, …)