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feat(http): make interceptingWriter reimplement common interfaces #1212

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merged 1 commit into from
Jan 31, 2022
Merged

feat(http): make interceptingWriter reimplement common interfaces #1212

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257 changes: 257 additions & 0 deletions transport/http/intercepting_writer.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,257 @@
package http

import (
"io"
"net/http"
)

type interceptingWriter struct {
http.ResponseWriter
code int
written int64
}

// WriteHeader may not be explicitly called, so care must be taken to
// initialize w.code to its default value of http.StatusOK.
func (w *interceptingWriter) WriteHeader(code int) {
w.code = code
w.ResponseWriter.WriteHeader(code)
}

func (w *interceptingWriter) Write(p []byte) (int, error) {
n, err := w.ResponseWriter.Write(p)
w.written += int64(n)
return n, err
}

// reimplementInterfaces returns a wrapped version of the embedded ResponseWriter
// and selectively implements the same combination of additional interfaces as
// the wrapped one. The interfaces it may implement are: http.Hijacker,
// http.CloseNotifier, http.Pusher, http.Flusher and io.ReaderFrom. The standard
// library is known to assert the existence of these interfaces and behaves
// differently. This implementation is derived from
// https://github.com/felixge/httpsnoop.
func (w *interceptingWriter) reimplementInterfaces() http.ResponseWriter {
var (
hj, i0 = w.ResponseWriter.(http.Hijacker)
cn, i1 = w.ResponseWriter.(http.CloseNotifier)
pu, i2 = w.ResponseWriter.(http.Pusher)
fl, i3 = w.ResponseWriter.(http.Flusher)
rf, i4 = w.ResponseWriter.(io.ReaderFrom)
)

switch {
case !i0 && !i1 && !i2 && !i3 && !i4:
return struct {
http.ResponseWriter
}{w}
case !i0 && !i1 && !i2 && !i3 && i4:
return struct {
http.ResponseWriter
io.ReaderFrom
}{w, rf}
case !i0 && !i1 && !i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Flusher
}{w, fl}
case !i0 && !i1 && !i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Flusher
io.ReaderFrom
}{w, fl, rf}
case !i0 && !i1 && i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.Pusher
}{w, pu}
case !i0 && !i1 && i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.Pusher
io.ReaderFrom
}{w, pu, rf}
case !i0 && !i1 && i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Pusher
http.Flusher
}{w, pu, fl}
case !i0 && !i1 && i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Pusher
http.Flusher
io.ReaderFrom
}{w, pu, fl, rf}
case !i0 && i1 && !i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.CloseNotifier
}{w, cn}
case !i0 && i1 && !i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.CloseNotifier
io.ReaderFrom
}{w, cn, rf}
case !i0 && i1 && !i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Flusher
}{w, cn, fl}
case !i0 && i1 && !i2 && i3 && i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Flusher
io.ReaderFrom
}{w, cn, fl, rf}
case !i0 && i1 && i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Pusher
}{w, cn, pu}
case !i0 && i1 && i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Pusher
io.ReaderFrom
}{w, cn, pu, rf}
case !i0 && i1 && i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Pusher
http.Flusher
}{w, cn, pu, fl}
case !i0 && i1 && i2 && i3 && i4:
return struct {
http.ResponseWriter
http.CloseNotifier
http.Pusher
http.Flusher
io.ReaderFrom
}{w, cn, pu, fl, rf}
case i0 && !i1 && !i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
}{w, hj}
case i0 && !i1 && !i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
io.ReaderFrom
}{w, hj, rf}
case i0 && !i1 && !i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Flusher
}{w, hj, fl}
case i0 && !i1 && !i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Flusher
io.ReaderFrom
}{w, hj, fl, rf}
case i0 && !i1 && i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Pusher
}{w, hj, pu}
case i0 && !i1 && i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Pusher
io.ReaderFrom
}{w, hj, pu, rf}
case i0 && !i1 && i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Pusher
http.Flusher
}{w, hj, pu, fl}
case i0 && !i1 && i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.Pusher
http.Flusher
io.ReaderFrom
}{w, hj, pu, fl, rf}
case i0 && i1 && !i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
}{w, hj, cn}
case i0 && i1 && !i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
io.ReaderFrom
}{w, hj, cn, rf}
case i0 && i1 && !i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Flusher
}{w, hj, cn, fl}
case i0 && i1 && !i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Flusher
io.ReaderFrom
}{w, hj, cn, fl, rf}
case i0 && i1 && i2 && !i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Pusher
}{w, hj, cn, pu}
case i0 && i1 && i2 && !i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Pusher
io.ReaderFrom
}{w, hj, cn, pu, rf}
case i0 && i1 && i2 && i3 && !i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Pusher
http.Flusher
}{w, hj, cn, pu, fl}
case i0 && i1 && i2 && i3 && i4:
return struct {
http.ResponseWriter
http.Hijacker
http.CloseNotifier
http.Pusher
http.Flusher
io.ReaderFrom
}{w, hj, cn, pu, fl, rf}
default:
return struct {
http.ResponseWriter
}{w}
}
}