109 lines
2.9 KiB
Go
109 lines
2.9 KiB
Go
// Copyright (C) 2014-2020 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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// Package assets hold utilities for serving static assets.
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//
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// The actual assets live in auto subpackages instead of here,
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// because the set of assets varies per program.
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package assets
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import (
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"compress/gzip"
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"fmt"
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"io"
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"mime"
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"net/http"
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"path/filepath"
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"strconv"
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"strings"
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"time"
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)
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// An Asset is an embedded file to be served over HTTP.
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type Asset struct {
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Content string // Contents of asset, possibly gzipped.
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Gzipped bool
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Length int // Length of (decompressed) Content.
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Filename string // Original filename, determines Content-Type.
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Modified time.Time // Determines ETag and Last-Modified.
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}
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// Serve writes a gzipped asset to w.
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func Serve(w http.ResponseWriter, r *http.Request, asset Asset) {
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header := w.Header()
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mtype := MimeTypeForFile(asset.Filename)
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if mtype != "" {
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header.Set("Content-Type", mtype)
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}
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etag := fmt.Sprintf(`"%x"`, asset.Modified.Unix())
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header.Set("ETag", etag)
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header.Set("Last-Modified", asset.Modified.Format(http.TimeFormat))
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t, err := http.ParseTime(r.Header.Get("If-Modified-Since"))
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if err == nil && !asset.Modified.After(t) {
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w.WriteHeader(http.StatusNotModified)
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return
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}
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if r.Header.Get("If-None-Match") == etag {
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w.WriteHeader(http.StatusNotModified)
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return
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}
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switch {
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case !asset.Gzipped:
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header.Set("Content-Length", strconv.Itoa(len(asset.Content)))
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io.WriteString(w, asset.Content)
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case strings.Contains(r.Header.Get("Accept-Encoding"), "gzip"):
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header.Set("Content-Encoding", "gzip")
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header.Set("Content-Length", strconv.Itoa(len(asset.Content)))
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io.WriteString(w, asset.Content)
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default:
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header.Set("Content-Length", strconv.Itoa(asset.Length))
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// gunzip for browsers that don't want gzip.
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var gr *gzip.Reader
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gr, _ = gzip.NewReader(strings.NewReader(asset.Content))
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io.Copy(w, gr)
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gr.Close()
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}
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}
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// MimeTypeForFile returns the appropriate MIME type for an asset,
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// based on the filename.
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//
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// We use a built in table of the common types since the system
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// TypeByExtension might be unreliable. But if we don't know, we delegate
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// to the system. All our text files are in UTF-8.
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func MimeTypeForFile(file string) string {
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ext := filepath.Ext(file)
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switch ext {
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case ".htm", ".html":
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return "text/html; charset=utf-8"
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case ".css":
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return "text/css; charset=utf-8"
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case ".eot":
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return "application/vnd.ms-fontobject"
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case ".js":
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return "application/javascript; charset=utf-8"
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case ".json":
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return "application/json; charset=utf-8"
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case ".png":
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return "image/png"
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case ".svg":
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return "image/svg+xml; charset=utf-8"
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case ".ttf":
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return "font/ttf"
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case ".woff":
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return "font/woff"
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case ".woff2":
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return "font/woff2"
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default:
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return mime.TypeByExtension(ext)
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}
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}
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