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go/src/infra/libs/infra_util/stringSet.go

Index: go/src/infra/libs/infra_util/stringSet.go
diff --git a/go/src/infra/libs/infra_util/stringSet.go b/go/src/infra/libs/infra_util/stringSet.go
new file mode 100644
index 0000000000000000000000000000000000000000..2b417edb1d50a4cc84c86d7a3bde54d7f1aa32d4
--- /dev/null
+++ b/go/src/infra/libs/infra_util/stringSet.go
@@ -0,0 +1,60 @@
+// Copyright 2014 The Chromium 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 infra_util
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type StringSet map[string]struct{}
+
+func StringSetFrom(elems ...string) StringSet {
+	ret := make(StringSet, len(elems))
+	ret.Add(elems...)
+	return ret
+}
+
+func (s StringSet) Cardinality() int { return len(s) }
+
+func (s StringSet) Add(elems ...string) (ret int) {
+	for _, e := range elems {
+		if !s.Has(e) {
+			ret++
+			s[e] = struct{}{}
+		}
+	}
+	return
+}
+
+func (s StringSet) Remove(elems ...string) (ret int) {
+	for _, e := range elems {
+		if s.Has(e) {
+			delete(s, e)
+			ret++
+		}
+	}
+	return
+}
+
+func (s StringSet) Has(elem string) bool {
+	_, has := s[elem]
+	return has
+}
+
+func (s StringSet) String() string {
+	buf := &bytes.Buffer{}
+	fmt.Fprintf(buf, "set(")
+	first := true
+	for e := range s {
+		if !first {
+			fmt.Fprint(buf, ",")
+		}
+		first = false
+		fmt.Fprintf(buf, "%#v", e)
+	}
+	fmt.Fprintf(buf, ")")
+	return buf.String()
+}