istio

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// Copyright Istio Authors
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//
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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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package path
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import (
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	"path/filepath"
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	"strings"
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)
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var (
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	// pathSeparator is the separator between path elements.
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	pathSeparator = "/"
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	// escapedPathSeparator is what to use when the path shouldn't separate
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	escapedPathSeparator = "\\" + pathSeparator
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)
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// Path is a path in slice form.
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type Path []string
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// FromString converts a string path of form a.b.c to a string slice representation.
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func FromString(path string) Path {
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	path = filepath.Clean(path)
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	path = strings.TrimPrefix(path, pathSeparator)
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	path = strings.TrimSuffix(path, pathSeparator)
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	pv := splitEscaped(path, []rune(pathSeparator)[0])
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	var r []string
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	for _, str := range pv {
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		if str != "" {
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			str = strings.ReplaceAll(str, escapedPathSeparator, pathSeparator)
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			// Is str of the form node[expr], convert to "node", "[expr]"?
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			nBracket := strings.IndexRune(str, '[')
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			if nBracket > 0 {
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				r = append(r, str[:nBracket], str[nBracket:])
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			} else {
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				// str is "[expr]" or "node"
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				r = append(r, str)
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			}
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		}
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	}
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	return r
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}
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// String converts a string slice path representation of form ["a", "b", "c"] to a string representation like "a.b.c".
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func (p Path) String() string {
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	return strings.Join(p, pathSeparator)
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}
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// splitEscaped splits a string using the rune r as a separator. It does not split on r if it's prefixed by \.
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func splitEscaped(s string, r rune) []string {
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	var prev rune
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	if len(s) == 0 {
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		return []string{}
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	}
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	prevIdx := 0
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	var out []string
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	for i, c := range s {
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		if c == r && (i == 0 || (i > 0 && prev != '\\')) {
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			out = append(out, s[prevIdx:i])
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			prevIdx = i + 1
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		}
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		prev = c
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	}
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	out = append(out, s[prevIdx:])
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	return out
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}
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