130 lines
3.2 KiB
Go
130 lines
3.2 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package precompress provides build- and serving-time support for
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// precompressed static resources, to avoid the cost of repeatedly compressing
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// unchanging resources.
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package precompress
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import (
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"bytes"
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"compress/gzip"
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"io"
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"io/fs"
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"net/http"
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"os"
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"path"
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"path/filepath"
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"github.com/andybalholm/brotli"
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"golang.org/x/sync/errgroup"
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"tailscale.com/tsweb"
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)
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// PrecompressDir compresses static assets in dirPath using Gzip and Brotli, so
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// that they can be later served with OpenPrecompressedFile.
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func PrecompressDir(dirPath string, options Options) error {
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var eg errgroup.Group
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err := fs.WalkDir(os.DirFS(dirPath), ".", func(p string, d fs.DirEntry, err error) error {
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if err != nil {
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return err
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}
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if d.IsDir() {
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return nil
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}
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if !compressibleExtensions[filepath.Ext(p)] {
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return nil
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}
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p = path.Join(dirPath, p)
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if options.ProgressFn != nil {
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options.ProgressFn(p)
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}
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eg.Go(func() error {
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return Precompress(p, options)
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})
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return nil
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})
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if err != nil {
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return err
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}
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return eg.Wait()
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}
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type Options struct {
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// FastCompression controls whether compression should be optimized for
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// speed rather than size.
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FastCompression bool
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// ProgressFn, if non-nil, is invoked when a file in the directory is about
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// to be compressed.
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ProgressFn func(path string)
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}
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// OpenPrecompressedFile opens a file from fs, preferring compressed versions
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// generated by PrecompressDir if possible.
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func OpenPrecompressedFile(w http.ResponseWriter, r *http.Request, path string, fs fs.FS) (fs.File, error) {
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if tsweb.AcceptsEncoding(r, "br") {
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if f, err := fs.Open(path + ".br"); err == nil {
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w.Header().Set("Content-Encoding", "br")
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return f, nil
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}
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}
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if tsweb.AcceptsEncoding(r, "gzip") {
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if f, err := fs.Open(path + ".gz"); err == nil {
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w.Header().Set("Content-Encoding", "gzip")
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return f, nil
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}
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}
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return fs.Open(path)
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}
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var compressibleExtensions = map[string]bool{
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".js": true,
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".css": true,
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}
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func Precompress(path string, options Options) error {
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contents, err := os.ReadFile(path)
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if err != nil {
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return err
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}
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fi, err := os.Lstat(path)
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if err != nil {
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return err
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}
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gzipLevel := gzip.BestCompression
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if options.FastCompression {
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gzipLevel = gzip.BestSpeed
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}
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err = writeCompressed(contents, func(w io.Writer) (io.WriteCloser, error) {
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return gzip.NewWriterLevel(w, gzipLevel)
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}, path+".gz", fi.Mode())
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if err != nil {
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return err
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}
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brotliLevel := brotli.BestCompression
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if options.FastCompression {
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brotliLevel = brotli.BestSpeed
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}
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return writeCompressed(contents, func(w io.Writer) (io.WriteCloser, error) {
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return brotli.NewWriterLevel(w, brotliLevel), nil
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}, path+".br", fi.Mode())
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}
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func writeCompressed(contents []byte, compressedWriterCreator func(io.Writer) (io.WriteCloser, error), outputPath string, outputMode fs.FileMode) error {
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var buf bytes.Buffer
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compressedWriter, err := compressedWriterCreator(&buf)
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if err != nil {
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return err
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}
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if _, err := compressedWriter.Write(contents); err != nil {
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return err
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}
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if err := compressedWriter.Close(); err != nil {
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return err
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}
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return os.WriteFile(outputPath, buf.Bytes(), outputMode)
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}
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