// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package pprof

import (
	
	
	
	
)

type label struct {
	key   string
	value string
}

// LabelSet is a set of labels.
type LabelSet struct {
	list []label
}

// labelContextKey is the type of contextKeys used for profiler labels.
type labelContextKey struct{}

func labelValue( context.Context) labelMap {
	,  := .Value(labelContextKey{}).(*labelMap)
	if  == nil {
		return labelMap(nil)
	}
	return *
}

// labelMap is the representation of the label set held in the context type.
// This is an initial implementation, but it will be replaced with something
// that admits incremental immutable modification more efficiently.
type labelMap map[string]string

// String statisfies Stringer and returns key, value pairs in a consistent
// order.
func ( *labelMap) () string {
	if  == nil {
		return ""
	}
	 := make([]string, 0, len(*))

	for ,  := range * {
		 = append(, fmt.Sprintf("%q:%q", , ))
	}

	sort.Strings()

	return "{" + strings.Join(, ", ") + "}"
}

// WithLabels returns a new context.Context with the given labels added.
// A label overwrites a prior label with the same key.
func ( context.Context,  LabelSet) context.Context {
	 := make(labelMap)
	 := labelValue()
	// TODO(matloob): replace the map implementation with something
	// more efficient so creating a child context WithLabels doesn't need
	// to clone the map.
	for ,  := range  {
		[] = 
	}
	for ,  := range .list {
		[.key] = .value
	}
	return context.WithValue(, labelContextKey{}, &)
}

// Labels takes an even number of strings representing key-value pairs
// and makes a LabelSet containing them.
// A label overwrites a prior label with the same key.
// Currently only the CPU and goroutine profiles utilize any labels
// information.
// See https://golang.org/issue/23458 for details.
func ( ...string) LabelSet {
	if len()%2 != 0 {
		panic("uneven number of arguments to pprof.Labels")
	}
	 := make([]label, 0, len()/2)
	for  := 0; +1 < len();  += 2 {
		 = append(, label{key: [], value: [+1]})
	}
	return LabelSet{list: }
}

// Label returns the value of the label with the given key on ctx, and a boolean indicating
// whether that label exists.
func ( context.Context,  string) (string, bool) {
	 := labelValue()
	,  := []
	return , 
}

// ForLabels invokes f with each label set on the context.
// The function f should return true to continue iteration or false to stop iteration early.
func ( context.Context,  func(,  string) bool) {
	 := labelValue()
	for ,  := range  {
		if !(, ) {
			break
		}
	}
}