From 751302c4d84f8e51b8cbec8200646fc88afd5179 Mon Sep 17 00:00:00 2001
From: Charles Iliya Krempeaux <iamreiver@gmail.com>
Date: Mon, 2 Jul 2018 11:03:47 -0700
Subject: [PATCH] utf8s.Len()

---
 len.go      | 22 +++++++++++++++++++++
 len_test.go | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 len.go
 create mode 100644 len_test.go

diff --git a/len.go b/len.go
new file mode 100644
index 0000000..c6635d5
--- /dev/null
+++ b/len.go
@@ -0,0 +1,22 @@
+package utf8s
+
+// Len returns the number of bytes in a UTF-8 encoding of this Unicode code point.
+func Len(r rune) int {
+
+	switch {
+	case 127 > r:
+		return 1
+
+	case 0x7FF >= r:
+		return 2
+
+	case 0xFFFF >= r:
+		return 3
+
+	case 0x10FFFF >= r:
+		return 4
+
+	default:
+		return 0
+	}
+}
diff --git a/len_test.go b/len_test.go
new file mode 100644
index 0000000..1d2eed1
--- /dev/null
+++ b/len_test.go
@@ -0,0 +1,56 @@
+package utf8s
+
+import (
+	"testing"
+)
+
+func TestLen(t *testing.T) {
+
+	tests := []struct{
+		Datum rune
+		Expected int
+	}{
+		{
+			Datum:   'A',
+			Expected: 1,
+		},
+		{
+			Datum:   'r',
+			Expected: 1,
+		},
+		{
+			Datum:   '¡',
+			Expected: 2,
+		},
+		{
+			Datum:   '۵',
+			Expected: 2,
+		},
+		{
+			Datum:   '‱',
+			Expected: 3,
+		},
+		{
+			Datum:   '≡',
+			Expected: 3,
+		},
+		{
+			Datum:   '𐏕',
+			Expected: 4,
+		},
+		{
+			Datum:   '🙂',
+			Expected: 4,
+		},
+	}
+
+
+	for testNumber, test := range tests {
+
+		actual := Len(test.Datum)
+		if expected := test.Expected; expected != actual {
+			t.Errorf("For test #%d, expected %d, but actually got %d.", testNumber, expected, actual)
+			continue
+		}
+	}
+}