Moves string slice sorting, copying and shuffling into pkg/util/slice

pkg/util/slice/slice.go

@@ -0,0 +1,49 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+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 slice provides utility methods for common operations on slices.
+package slice
+
+import (
+	"math/rand"
+	"sort"
+)
+
+// CopyStrings copies the contents of the specified string slice
+// into a new slice.
+func CopyStrings(s []string) []string {
+	c := make([]string, len(s))
+	copy(c, s)
+	return c
+}
+
+// SortStrings sorts the specified string slice in place. It returns the same
+// slice that was provided in order to facilitate method chaining.
+func SortStrings(s []string) []string {
+	sort.Strings(s)
+	return s
+}
+
+// ShuffleStrings copies strings from the specified slice into a copy in random
+// order. It returns a new slice.
+func ShuffleStrings(s []string) []string {
+	shuffled := make([]string, len(s))
+	perm := rand.Perm(len(s))
+	for i, j := range perm {
+		shuffled[j] = s[i]
+	}
+	return shuffled
+}

pkg/util/slice/slice_test.go

@@ -0,0 +1,56 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+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 slice
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestCopyStrings(t *testing.T) {
+	src := []string{"a", "c", "b"}
+	dest := CopyStrings(src)
+
+	if !reflect.DeepEqual(src, dest) {
+		t.Errorf("%v and %v are not equal", src, dest)
+	}
+
+	src[0] = "A"
+	if reflect.DeepEqual(src, dest) {
+		t.Errorf("CopyStrings didn't make a copy")
+	}
+}
+
+func TestSortStrings(t *testing.T) {
+	src := []string{"a", "c", "b"}
+	dest := SortStrings(src)
+	expected := []string{"a", "b", "c"}
+
+	if !reflect.DeepEqual(dest, expected) {
+		t.Errorf("SortString didn't sort the strings")
+	}
+}
+
+func TestSortStringsSortsInPlace(t *testing.T) {
+	src := []string{"a", "c", "b"}
+	_ = SortStrings(src)
+	expected := []string{"a", "b", "c"}
+
+	if !reflect.DeepEqual(src, expected) {
+		t.Errorf("SortString didn't sort in place")
+	}
+}