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