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tailscale/util/precompress/precompress.go

131 lines
3.3 KiB
Go

// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package precompress provides build- and serving-time support for
// precompressed static resources, to avoid the cost of repeatedly compressing
// unchanging resources.
package precompress
import (
"bytes"
"compress/gzip"
"io"
"io/fs"
"net/http"
"os"
"path"
"path/filepath"
"github.com/andybalholm/brotli"
"golang.org/x/sync/errgroup"
"tailscale.com/tsweb"
)
// PrecompressDir compresses static assets in dirPath using Gzip and Brotli, so
// that they can be later served with OpenPrecompressedFile.
func PrecompressDir(dirPath string, options Options) error {
var eg errgroup.Group
err := fs.WalkDir(os.DirFS(dirPath), ".", func(p string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if d.IsDir() {
return nil
}
if !compressibleExtensions[filepath.Ext(p)] {
return nil
}
p = path.Join(dirPath, p)
if options.ProgressFn != nil {
options.ProgressFn(p)
}
eg.Go(func() error {
return Precompress(p, options)
})
return nil
})
if err != nil {
return err
}
return eg.Wait()
}
type Options struct {
// FastCompression controls whether compression should be optimized for
// speed rather than size.
FastCompression bool
// ProgressFn, if non-nil, is invoked when a file in the directory is about
// to be compressed.
ProgressFn func(path string)
}
// OpenPrecompressedFile opens a file from fs, preferring compressed versions
// generated by PrecompressDir if possible.
func OpenPrecompressedFile(w http.ResponseWriter, r *http.Request, path string, fs fs.FS) (fs.File, error) {
if tsweb.AcceptsEncoding(r, "br") {
if f, err := fs.Open(path + ".br"); err == nil {
w.Header().Set("Content-Encoding", "br")
return f, nil
}
}
if tsweb.AcceptsEncoding(r, "gzip") {
if f, err := fs.Open(path + ".gz"); err == nil {
w.Header().Set("Content-Encoding", "gzip")
return f, nil
}
}
return fs.Open(path)
}
var compressibleExtensions = map[string]bool{
".js": true,
".css": true,
}
func Precompress(path string, options Options) error {
contents, err := os.ReadFile(path)
if err != nil {
return err
}
fi, err := os.Lstat(path)
if err != nil {
return err
}
gzipLevel := gzip.BestCompression
if options.FastCompression {
gzipLevel = gzip.BestSpeed
}
err = writeCompressed(contents, func(w io.Writer) (io.WriteCloser, error) {
return gzip.NewWriterLevel(w, gzipLevel)
}, path+".gz", fi.Mode())
if err != nil {
return err
}
brotliLevel := brotli.BestCompression
if options.FastCompression {
brotliLevel = brotli.BestSpeed
}
return writeCompressed(contents, func(w io.Writer) (io.WriteCloser, error) {
return brotli.NewWriterLevel(w, brotliLevel), nil
}, path+".br", fi.Mode())
}
func writeCompressed(contents []byte, compressedWriterCreator func(io.Writer) (io.WriteCloser, error), outputPath string, outputMode fs.FileMode) error {
var buf bytes.Buffer
compressedWriter, err := compressedWriterCreator(&buf)
if err != nil {
return err
}
if _, err := compressedWriter.Write(contents); err != nil {
return err
}
if err := compressedWriter.Close(); err != nil {
return err
}
return os.WriteFile(outputPath, buf.Bytes(), outputMode)
}