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// Copyright 2015 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.
package expfmt
import (
"fmt"
"io"
"net/http"
"github.com/golang/protobuf/proto"
"github.com/matttproud/golang_protobuf_extensions/pbutil"
"github.com/prometheus/common/internal/bitbucket.org/ww/goautoneg"
dto "github.com/prometheus/client_model/go"
)
// Encoder types encode metric families into an underlying wire protocol.
type Encoder interface {
Encode(*dto.MetricFamily) error
}
type encoder func(*dto.MetricFamily) error
func (e encoder) Encode(v *dto.MetricFamily) error {
return e(v)
}
// Negotiate returns the Content-Type based on the given Accept header.
// If no appropriate accepted type is found, FmtText is returned.
func Negotiate(h http.Header) Format {
for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {
// Check for protocol buffer
if ac.Type+"/"+ac.SubType == ProtoType && ac.Params["proto"] == ProtoProtocol {
switch ac.Params["encoding"] {
case "delimited":
return FmtProtoDelim
case "text":
return FmtProtoText
case "compact-text":
return FmtProtoCompact
}
}
// Check for text format.
ver := ac.Params["version"]
if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {
return FmtText
}
}
return FmtText
}
// NewEncoder returns a new encoder based on content type negotiation.
func NewEncoder(w io.Writer, format Format) Encoder {
switch format {
case FmtProtoDelim:
return encoder(func(v *dto.MetricFamily) error {
_, err := pbutil.WriteDelimited(w, v)
return err
})
case FmtProtoCompact:
return encoder(func(v *dto.MetricFamily) error {
_, err := fmt.Fprintln(w, v.String())
return err
})
case FmtProtoText:
return encoder(func(v *dto.MetricFamily) error {
_, err := fmt.Fprintln(w, proto.MarshalTextString(v))
return err
})
case FmtText:
return encoder(func(v *dto.MetricFamily) error {
_, err := MetricFamilyToText(w, v)
return err
})
}
panic("expfmt.NewEncoder: unknown format")
}
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