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// Copyright 2017 The Prometheus Authors
// 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.
// +build go1.8
package promhttp
import (
"io"
"net/http"
)
// newDelegator handles the four different methods of upgrading a
// http.ResponseWriter to delegator.
func newDelegator(w http.ResponseWriter) delegator {
d := &responseWriterDelegator{ResponseWriter: w}
_, cn := w.(http.CloseNotifier)
_, fl := w.(http.Flusher)
_, hj := w.(http.Hijacker)
_, ps := w.(http.Pusher)
_, rf := w.(io.ReaderFrom)
// Check for the four most common combination of interfaces a
// http.ResponseWriter might implement.
switch {
case cn && fl && hj && rf && ps:
// All interfaces.
return &fancyPushDelegator{
fancyDelegator: &fancyDelegator{d},
p: &pushDelegator{d},
}
case cn && fl && hj && rf:
// All interfaces, except http.Pusher.
return &fancyDelegator{d}
case ps:
// Just http.Pusher.
return &pushDelegator{d}
}
return d
}
type fancyPushDelegator struct {
p *pushDelegator
*fancyDelegator
}
func (f *fancyPushDelegator) Push(target string, opts *http.PushOptions) error {
return f.p.Push(target, opts)
}
type pushDelegator struct {
*responseWriterDelegator
}
func (f *pushDelegator) Push(target string, opts *http.PushOptions) error {
return f.ResponseWriter.(http.Pusher).Push(target, opts)
}
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