util: Add a UInt64Slice and associated sorting functionality.

This adds an easy to sort slice of uint64's and associated functionality
to sort a list of strings by their associated order in a map indexed by
uint64's.

util/util.go

@@ -455,3 +455,41 @@ func (obj PathSlice) Less(i, j int) bool {
 	}
 	return true
 }
+
+// UInt64Slice attaches the methods of sort.Interface to []uint64, sorting in
+// increasing order.
+type UInt64Slice []uint64
+
+// Len returns the length of the slice of uint64's.
+func (obj UInt64Slice) Len() int { return len(obj) }
+
+// Less returns the smaller element in the sort order.
+func (obj UInt64Slice) Less(i, j int) bool { return obj[i] < obj[j] }
+
+// Swap swaps two elements in the slice.
+func (obj UInt64Slice) Swap(i, j int) { obj[i], obj[j] = obj[j], obj[i] }
+
+// Sort is a convenience method.
+func (obj UInt64Slice) Sort() { sort.Sort(obj) }
+
+// SortMapStringValuesByUInt64Keys builds a list of strings, sorted by the
+// corresponding key that is associated with that value.
+// TODO: add some tests
+func SortMapStringValuesByUInt64Keys(m map[uint64]string) []string {
+	//if m == nil { // no need to special case this, range handles it safely
+	//	return []string{}
+	//}
+	keys := []uint64{}
+	for i := range m {
+		keys = append(keys, i)
+	}
+	sort.Sort(UInt64Slice(keys))
+
+	result := []string{}
+	for _, key := range keys {
+		s := m[key]
+		result = append(result, s)
+	}
+
+	return result
+}

util/util_test.go

@@ -905,3 +905,53 @@ func TestPathSliceSort(t *testing.T) {
 		}
 	}
 }
+
+func TestSortUInt64Slice(t *testing.T) {
+	slice0 := []uint64{42, 13, 0}
+	sort.Sort(UInt64Slice(slice0))
+	if slice0[0] != 0 || slice0[1] != 13 || slice0[2] != 42 {
+		t.Errorf("input slice reordered to: %v", slice0)
+	}
+
+	slice1 := []uint64{99, 12, 13}
+	sort.Sort(UInt64Slice(slice1))
+	if slice1[0] != 12 || slice1[1] != 13 || slice1[2] != 99 {
+		t.Errorf("input slice reordered to: %v", slice1)
+	}
+}
+
+func TestSortMapStringValuesByUInt64Keys(t *testing.T) {
+	if x := len(SortMapStringValuesByUInt64Keys(nil)); x != 0 {
+		t.Errorf("input map of nil caused a: %d", x)
+	}
+
+	map0 := map[uint64]string{
+		42: "world",
+		34: "there",
+		13: "hello",
+	}
+	slice0 := SortMapStringValuesByUInt64Keys(map0)
+	if slice0[0] != "hello" || slice0[1] != "there" || slice0[2] != "world" {
+		t.Errorf("input slice reordered to: %v", slice0)
+	}
+
+	map1 := map[uint64]string{
+		99: "a",
+		12: "c",
+		13: "b",
+	}
+	slice1 := SortMapStringValuesByUInt64Keys(map1)
+	if slice1[0] != "c" || slice1[1] != "b" || slice1[2] != "a" {
+		t.Errorf("input slice reordered to: %v", slice1)
+	}
+
+	map2 := map[uint64]string{
+		12:    "c",
+		0:     "d",
+		44442: "b",
+	}
+	slice2 := SortMapStringValuesByUInt64Keys(map2)
+	if slice2[0] != "d" || slice2[1] != "c" || slice2[2] != "b" {
+		t.Errorf("input slice reordered to: %v", slice2)
+	}
+}