gziphandler.go

// Copyright 2015 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package handler

import (
	"compress/gzip"
	"io"
	"net/http"
	"strings"
)

type gzipResponseWriter struct {
	io.Writer
	http.ResponseWriter
}

// Use the Writer part of gzipResponseWriter to write the output.
func (w gzipResponseWriter) Write(b []byte) (int, error) {
	return w.Writer.Write(b)
}

// MakeGzipHandler adds support for gzip compression for given handler
func MakeGzipHandler(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Check if the client can accept the gzip encoding.
		if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
			handler.ServeHTTP(w, r)
			return
		}

		// Set the HTTP header indicating encoding.
		w.Header().Set("Content-Encoding", "gzip")
		gz := gzip.NewWriter(w)
		defer gz.Close()
		gzw := gzipResponseWriter{Writer: gz, ResponseWriter: w}
		handler.ServeHTTP(gzw, r)
	})
}