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// +build !go1.8
package mutil
import (
"bufio"
"io"
"net"
"net/http"
)
// WriterProxy is a proxy around an http.ResponseWriter that allows you to hook
// into various parts of the response process.
type WriterProxy interface {
http.ResponseWriter
// Status returns the HTTP status of the request, or 0 if one has not
// yet been sent.
Status() int
// BytesWritten returns the total number of bytes sent to the client.
BytesWritten() int
// Tee causes the response body to be written to the given io.Writer in
// addition to proxying the writes through. Only one io.Writer can be
// tee'd to at once: setting a second one will overwrite the first.
// Writes will be sent to the proxy before being written to this
// io.Writer. It is illegal for the tee'd writer to be modified
// concurrently with writes.
Tee(io.Writer)
// Unwrap returns the original proxied target.
Unwrap() http.ResponseWriter
}
// WrapWriter wraps an http.ResponseWriter, returning a proxy that allows you to
// hook into various parts of the response process.
func WrapWriter(w http.ResponseWriter) WriterProxy {
_, cn := w.(http.CloseNotifier)
_, fl := w.(http.Flusher)
_, hj := w.(http.Hijacker)
_, rf := w.(io.ReaderFrom)
bw := basicWriter{ResponseWriter: w}
if cn && fl && hj && rf {
return &fancyWriter{bw}
}
if fl {
return &flushWriter{bw}
}
return &bw
}
// basicWriter wraps a http.ResponseWriter that implements the minimal
// http.ResponseWriter interface.
type basicWriter struct {
http.ResponseWriter
wroteHeader bool
code int
bytes int
tee io.Writer
}
func (b *basicWriter) WriteHeader(code int) {
if !b.wroteHeader {
b.code = code
b.wroteHeader = true
b.ResponseWriter.WriteHeader(code)
}
}
func (b *basicWriter) Write(buf []byte) (int, error) {
b.WriteHeader(http.StatusOK)
n, err := b.ResponseWriter.Write(buf)
if b.tee != nil {
_, err2 := b.tee.Write(buf[:n])
// Prefer errors generated by the proxied writer.
if err == nil {
err = err2
}
}
b.bytes += n
return n, err
}
func (b *basicWriter) maybeWriteHeader() {
if !b.wroteHeader {
b.WriteHeader(http.StatusOK)
}
}
func (b *basicWriter) Status() int {
return b.code
}
func (b *basicWriter) BytesWritten() int {
return b.bytes
}
func (b *basicWriter) Tee(w io.Writer) {
b.tee = w
}
func (b *basicWriter) Unwrap() http.ResponseWriter {
return b.ResponseWriter
}
// fancyWriter is a writer that additionally satisfies http.CloseNotifier,
// http.Flusher, http.Hijacker, and io.ReaderFrom. It exists for the common case
// of wrapping the http.ResponseWriter that package http gives you, in order to
// make the proxied object support the full method set of the proxied object.
type fancyWriter struct {
basicWriter
}
func (f *fancyWriter) CloseNotify() <-chan bool {
cn := f.basicWriter.ResponseWriter.(http.CloseNotifier)
return cn.CloseNotify()
}
func (f *fancyWriter) Flush() {
fl := f.basicWriter.ResponseWriter.(http.Flusher)
fl.Flush()
}
func (f *fancyWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
hj := f.basicWriter.ResponseWriter.(http.Hijacker)
return hj.Hijack()
}
func (f *fancyWriter) ReadFrom(r io.Reader) (int64, error) {
if f.basicWriter.tee != nil {
return io.Copy(&f.basicWriter, r)
}
rf := f.basicWriter.ResponseWriter.(io.ReaderFrom)
f.basicWriter.maybeWriteHeader()
return rf.ReadFrom(r)
}
type flushWriter struct {
basicWriter
}
func (f *flushWriter) Flush() {
fl := f.basicWriter.ResponseWriter.(http.Flusher)
fl.Flush()
}
var (
_ http.CloseNotifier = &fancyWriter{}
_ http.Flusher = &fancyWriter{}
_ http.Hijacker = &fancyWriter{}
_ io.ReaderFrom = &fancyWriter{}
_ http.Flusher = &flushWriter{}
)
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