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// Copyright 2015 Light Code Labs, LLC
//
// 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 gzip provides a middleware layer that performs
// gzip compression on the response.
package gzip
import (
"compress/gzip"
"io"
"net/http"
"strings"
"github.com/mholt/caddy"
"github.com/mholt/caddy/caddyhttp/httpserver"
)
func init() {
caddy.RegisterPlugin("gzip", caddy.Plugin{
ServerType: "http",
Action: setup,
})
initWriterPool()
}
// Gzip is a middleware type which gzips HTTP responses. It is
// imperative that any handler which writes to a gzipped response
// specifies the Content-Type, otherwise some clients will assume
// application/x-gzip and try to download a file.
type Gzip struct {
Next httpserver.Handler
Configs []Config
}
// Config holds the configuration for Gzip middleware
type Config struct {
RequestFilters []RequestFilter
ResponseFilters []ResponseFilter
Level int // Compression level
}
// ServeHTTP serves a gzipped response if the client supports it.
func (g Gzip) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
return g.Next.ServeHTTP(w, r)
}
outer:
for _, c := range g.Configs {
// Check request filters to determine if gzipping is permitted for this request
for _, filter := range c.RequestFilters {
if !filter.ShouldCompress(r) {
continue outer
}
}
// In order to avoid unused memory allocation, gzip.putWriter only be called when gzip compression happened.
// see https://github.com/mholt/caddy/issues/2395
gz := &gzipResponseWriter{
ResponseWriterWrapper: &httpserver.ResponseWriterWrapper{ResponseWriter: w},
newWriter: func() io.Writer {
// gzipWriter modifies underlying writer at init,
// use a discard writer instead to leave ResponseWriter in
// original form.
return getWriter(c.Level)
},
}
defer func() {
if gzWriter, ok := gz.internalWriter.(*gzip.Writer); ok {
putWriter(c.Level, gzWriter)
}
}()
var rw http.ResponseWriter
// if no response filter is used
if len(c.ResponseFilters) == 0 {
// replace discard writer with ResponseWriter
if gzWriter, ok := gz.Writer().(*gzip.Writer); ok {
gzWriter.Reset(w)
}
rw = gz
} else {
// wrap gzip writer with ResponseFilterWriter
rw = NewResponseFilterWriter(c.ResponseFilters, gz)
}
// Any response in forward middleware will now be compressed
status, err := g.Next.ServeHTTP(rw, r)
// If there was an error that remained unhandled, we need
// to send something back before gzipWriter gets closed at
// the return of this method!
if status >= 400 {
httpserver.DefaultErrorFunc(w, r, status)
return 0, err
}
return status, err
}
// no matching filter
return g.Next.ServeHTTP(w, r)
}
// gzipResponseWriter wraps the underlying Write method
// with a gzip.Writer to compress the output.
type gzipResponseWriter struct {
internalWriter io.Writer
*httpserver.ResponseWriterWrapper
statusCodeWritten bool
newWriter func() io.Writer
}
// WriteHeader wraps the underlying WriteHeader method to prevent
// problems with conflicting headers from proxied backends. For
// example, a backend system that calculates Content-Length would
// be wrong because it doesn't know it's being gzipped.
func (w *gzipResponseWriter) WriteHeader(code int) {
w.Header().Del("Content-Length")
w.Header().Set("Content-Encoding", "gzip")
w.Header().Add("Vary", "Accept-Encoding")
originalEtag := w.Header().Get("ETag")
if originalEtag != "" && !strings.HasPrefix(originalEtag, "W/") {
w.Header().Set("ETag", "W/"+originalEtag)
}
w.ResponseWriterWrapper.WriteHeader(code)
w.statusCodeWritten = true
}
// Write wraps the underlying Write method to do compression.
func (w *gzipResponseWriter) Write(b []byte) (int, error) {
if w.Header().Get("Content-Type") == "" {
w.Header().Set("Content-Type", http.DetectContentType(b))
}
if !w.statusCodeWritten {
w.WriteHeader(http.StatusOK)
}
n, err := w.Writer().Write(b)
return n, err
}
//Writer use a lazy way to initialize Writer
func (w *gzipResponseWriter) Writer() io.Writer {
if w.internalWriter == nil {
w.internalWriter = w.newWriter()
}
return w.internalWriter
}
// Interface guards
var _ httpserver.HTTPInterfaces = (*gzipResponseWriter)(nil)
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