93 lines
2.7 KiB
Go
93 lines
2.7 KiB
Go
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// Copyright 2013 Prometheus Team
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package web
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import (
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"compress/gzip"
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"compress/zlib"
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"io"
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"net/http"
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"strings"
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)
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const (
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acceptEncodingHeader = "Accept-Encoding"
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contentEncodingHeader = "Content-Encoding"
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gzipEncoding = "gzip"
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deflateEncoding = "deflate"
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)
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// Wrapper around http.Handler which adds suitable response compression based
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// on the client's Accept-Encoding headers.
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type compressedResponseWriter struct {
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http.ResponseWriter
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writer io.Writer
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}
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// Writes HTTP response content data.
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func (c *compressedResponseWriter) Write(p []byte) (int, error) {
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return c.writer.Write(p)
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}
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// Closes the compressedResponseWriter and ensures to flush all data before.
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func (c *compressedResponseWriter) Close() {
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if zlibWriter, ok := c.writer.(*zlib.Writer); ok {
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zlibWriter.Flush()
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}
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if gzipWriter, ok := c.writer.(*gzip.Writer); ok {
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gzipWriter.Flush()
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}
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if closer, ok := c.writer.(io.Closer); ok {
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defer closer.Close()
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}
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}
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// Constructs a new compressedResponseWriter based on client request headers.
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func newCompressedResponseWriter(writer http.ResponseWriter, req *http.Request) *compressedResponseWriter {
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encodings := strings.Split(req.Header.Get(acceptEncodingHeader), ",")
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for _, encoding := range encodings {
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switch strings.TrimSpace(encoding) {
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case gzipEncoding:
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writer.Header().Set(contentEncodingHeader, gzipEncoding)
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return &compressedResponseWriter{
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ResponseWriter: writer,
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writer: gzip.NewWriter(writer),
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}
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case deflateEncoding:
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writer.Header().Set(contentEncodingHeader, deflateEncoding)
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return &compressedResponseWriter{
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ResponseWriter: writer,
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writer: zlib.NewWriter(writer),
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}
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}
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}
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return &compressedResponseWriter{
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ResponseWriter: writer,
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writer: writer,
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}
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}
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// Wrapper around http.Handler which adds suitable response compression based
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// on the client's Accept-Encoding headers.
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type compressionHandler struct {
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handler http.Handler
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}
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// Adds compression to the original http.Handler's ServeHTTP() method.
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func (c compressionHandler) ServeHTTP(writer http.ResponseWriter, req *http.Request) {
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compWriter := newCompressedResponseWriter(writer, req)
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c.handler.ServeHTTP(compWriter, req)
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compWriter.Close()
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}
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