1 files changed, 108 insertions, 0 deletions
diff --git a/src/runtime/pprof/label.go b/src/runtime/pprof/label.go
new file mode 100644
index 0000000..b614f12
--- /dev/null
+++ b/src/runtime/pprof/label.go
@@ -0,0 +1,108 @@
+// 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 (
+	"context"
+	"fmt"
+	"sort"
+	"strings"
+)
+
+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(ctx context.Context) labelMap {
+	labels, _ := ctx.Value(labelContextKey{}).(*labelMap)
+	if labels == nil {
+		return labelMap(nil)
+	}
+	return *labels
+}
+
+// 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 (l *labelMap) String() string {
+	if l == nil {
+		return ""
+	}
+	keyVals := make([]string, 0, len(*l))
+
+	for k, v := range *l {
+		keyVals = append(keyVals, fmt.Sprintf("%q:%q", k, v))
+	}
+
+	sort.Strings(keyVals)
+
+	return "{" + strings.Join(keyVals, ", ") + "}"
+}
+
+// WithLabels returns a new context.Context with the given labels added.
+// A label overwrites a prior label with the same key.
+func WithLabels(ctx context.Context, labels LabelSet) context.Context {
+	childLabels := make(labelMap)
+	parentLabels := labelValue(ctx)
+	// TODO(matloob): replace the map implementation with something
+	// more efficient so creating a child context WithLabels doesn't need
+	// to clone the map.
+	for k, v := range parentLabels {
+		childLabels[k] = v
+	}
+	for _, label := range labels.list {
+		childLabels[label.key] = label.value
+	}
+	return context.WithValue(ctx, labelContextKey{}, &childLabels)
+}
+
+// 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 Labels(args ...string) LabelSet {
+	if len(args)%2 != 0 {
+		panic("uneven number of arguments to pprof.Labels")
+	}
+	list := make([]label, 0, len(args)/2)
+	for i := 0; i+1 < len(args); i += 2 {
+		list = append(list, label{key: args[i], value: args[i+1]})
+	}
+	return LabelSet{list: list}
+}
+
+// Label returns the value of the label with the given key on ctx, and a boolean indicating
+// whether that label exists.
+func Label(ctx context.Context, key string) (string, bool) {
+	ctxLabels := labelValue(ctx)
+	v, ok := ctxLabels[key]
+	return v, ok
+}
+
+// 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 ForLabels(ctx context.Context, f func(key, value string) bool) {
+	ctxLabels := labelValue(ctx)
+	for k, v := range ctxLabels {
+		if !f(k, v) {
+			break
+		}
+	}
+}