go-lolhtml

Go bindings for the Rust crate cloudflare/lol-html, the Low Output Latency streaming HTML rewriter/parser with CSS-selector based API, talking via cgo.

Status:

All abilities provided by lol_html's c-api are available, except for customized user data in handlers. The original tests included in c-api package have also been translated to examine this binding's functionality.

The code is at its early stage and breaking changes might be introduced. If you have any ideas on how the public API can be better structured, feel free to open a PR or an issue.

go-lolhtml

Installation

For Linux/macOS/Windows x86_64 platform users, installation is as simple as a single go get command:

$ go get github.com/coolspring8/go-lolhtml

Installing Rust is not a necessary step. That's because lol-html could be prebuilt into static libraries, stored and shipped in /build folder, so that cgo can handle other compilation matters naturally and smoothly, without intervention.

For other platforms, you will have to compile it yourself.

Features

Fast: A Go (cgo) wrapper built around the highly-optimized Rust HTML parsing crate lol_html.
Easy to use: Utilizing Go's idiomatic I/O methods, lolhtml.Writer implements io.Writer interface.

Getting Started

Now let's initialize a project and create main.go:

package main

import (
	"bytes"
	"io"
	"log"
	"os"

	"github.com/coolspring8/go-lolhtml"
)

func main() {
	chunk := []byte("Hello, <span>World</span>!")
	r := bytes.NewReader(chunk)
	w, err := lolhtml.NewWriter(
		// output to stdout
		os.Stdout,
		&lolhtml.Handlers{
			ElementContentHandler: []lolhtml.ElementContentHandler{
				{
					Selector: "span",
					ElementHandler: func(e *lolhtml.Element) lolhtml.RewriterDirective {
						err := e.SetInnerContentAsText("LOL-HTML")
						if err != nil {
							log.Fatal(err)
						}
						return lolhtml.Continue
					},
				},
			},
		},
	)
	if err != nil {
		log.Fatal(err)
	}

	// copy from the bytes reader to lolhtml writer
	_, err = io.Copy(w, r)
	if err != nil {
		log.Fatal(err)
	}

	// explicitly close the writer and flush the remaining content
	err = w.Close()
	if err != nil {
		log.Fatal(err)
	}
	// Output: Hello, <span>LOL-HTML</span>!
}

The above program creates a new Writer configured to rewrite all texts in span tags to "LOL-HTML". It takes the chunk Hello, <span>World</span>! as input, and prints the result to standard output.

And the result is Hello, <span>LOL-HTML</span>! .

Examples

example_test.go contains two examples.

For more detailed examples, please visit the /examples subdirectory.

defer-scripts

Usage: curl -NL https://git.io/JeOSZ | go run main.go
mixed-content-rewriter

Usage: curl -NL https://git.io/JeOSZ | go run main.go
web-scraper

A ported Go version of https://web.scraper.workers.dev/.

Documentation

Available at pkg.go.dev.

Other Bindings

Rust (native), C, JavaScript - cloudflare/lol-html
Lua - jdesgats/lua-lolhtml

Versioning

This package does not really follow Semantic Versioning. The current strategy is to follow lol_html's major and minor version, and the patch version number is reserved for this binding's updates, for Go Modul to upgrade correctly.

Help Wanted!

There are a few interesting things at Projects panel that I have considered but is not yet implemented. Other contributions and suggestions are also welcome!

License

BSD 3-Clause "New" or "Revised" License

Disclaimer

This is an unofficial binding.

Cloudflare is a registered trademark of Cloudflare, Inc. Cloudflare names used in this project are for identification purposes only. The project is not associated in any way with Cloudflare Inc.

CoolSpring8/go-lolhtml