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gzip.go
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gzip.go
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package responsewriter
import (
"bufio"
"compress/gzip"
"fmt"
"io"
"net"
"net/http"
"reflect"
"strings"
)
type wrapWriter struct {
gzipResponseWriter
code int
}
type gzipResponseWriter struct {
io.Writer
http.ResponseWriter
}
func (g gzipResponseWriter) Write(b []byte) (int, error) {
// Header logic is kept here in case the user does not use WriteHeader
g.Header().Set("Content-Encoding", "gzip")
g.Header().Del("Content-Length")
return g.Writer.Write(b)
}
// Close uses gzip to write gzip footer if message is gzip encoded
func (g gzipResponseWriter) Close(writer *gzip.Writer) {
if g.Header().Get("Content-Encoding") == "gzip" {
writer.Close()
}
}
// WriteHeader sets gzip encoding and removes length. Should always be used when using gzip writer.
func (g gzipResponseWriter) WriteHeader(statusCode int) {
g.Header().Set("Content-Encoding", "gzip")
g.Header().Del("Content-Length")
g.ResponseWriter.WriteHeader(statusCode)
}
// Gzip creates a gzip writer if gzip encoding is accepted.
func Gzip(handler http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
handler.ServeHTTP(w, r)
return
}
gz := gzip.NewWriter(w)
gzw := &wrapWriter{gzipResponseWriter{Writer: gz, ResponseWriter: w}, http.StatusOK}
defer gzw.Close(gz)
// Content encoding will be set once Write or WriteHeader is called, to avoid gzipping empty messages
handler.ServeHTTP(gzw, r)
})
}
// Hijack must be implemented to properly chain with handlers expecting a hijacker handler to be passed
func (g *gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
if hijacker, ok := g.ResponseWriter.(http.Hijacker); ok {
return hijacker.Hijack()
}
return nil, nil, fmt.Errorf("Upstream ResponseWriter of type %v does not implement http.Hijacker", reflect.TypeOf(g.ResponseWriter))
}