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// Copyright (c) 2017 Uber Technologies, Inc.
//
// 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 rpcmetrics
// NameNormalizer is used to convert the endpoint names to strings
// that can be safely used as tags in the metrics.
type NameNormalizer interface {
Normalize(name string) string
}
// DefaultNameNormalizer converts endpoint names so that they contain only characters
// from the safe charset [a-zA-Z0-9-./_]. All other characters are replaced with '-'.
var DefaultNameNormalizer = &SimpleNameNormalizer{
SafeSets: []SafeCharacterSet{
&Range{From: 'a', To: 'z'},
&Range{From: 'A', To: 'Z'},
&Range{From: '0', To: '9'},
&Char{'-'},
&Char{'_'},
&Char{'/'},
&Char{'.'},
},
Replacement: '-',
}
// SimpleNameNormalizer uses a set of safe character sets.
type SimpleNameNormalizer struct {
SafeSets []SafeCharacterSet
Replacement byte
}
// SafeCharacterSet determines if the given character is "safe"
type SafeCharacterSet interface {
IsSafe(c byte) bool
}
// Range implements SafeCharacterSet
type Range struct {
From, To byte
}
// IsSafe implements SafeCharacterSet
func (r *Range) IsSafe(c byte) bool {
return c >= r.From && c <= r.To
}
// Char implements SafeCharacterSet
type Char struct {
Val byte
}
// IsSafe implements SafeCharacterSet
func (ch *Char) IsSafe(c byte) bool {
return c == ch.Val
}
// Normalize checks each character in the string against SafeSets,
// and if it's not safe substitutes it with Replacement.
func (n *SimpleNameNormalizer) Normalize(name string) string {
var retMe []byte
nameBytes := []byte(name)
for i, b := range nameBytes {
if n.safeByte(b) {
if retMe != nil {
retMe[i] = b
}
} else {
if retMe == nil {
retMe = make([]byte, len(nameBytes))
copy(retMe[0:i], nameBytes[0:i])
}
retMe[i] = n.Replacement
}
}
if retMe == nil {
return name
}
return string(retMe)
}
// safeByte checks if b against all safe charsets.
func (n *SimpleNameNormalizer) safeByte(b byte) bool {
for i := range n.SafeSets {
if n.SafeSets[i].IsSafe(b) {
return true
}
}
return false
}
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