utf8s.WriteRune()

writerune.go

@@ -0,0 +1,58 @@
+package utf8s
+
+import (
+	"io"
+)
+
+// WriteRune writes a single UTF-8 encoded Unicode character and returns the number of bytes written.
+func WriteRune(w io.Writer, r rune) (int, error) {
+
+
+	switch {
+	case 127 >= r:
+		var buffer [1]byte
+
+		buffer[0] = byte(r)
+
+		p := buffer[:]
+
+		return w.Write(p)
+
+	case 0x7FF >= r:
+		var buffer [2]byte
+
+		buffer[0] = 0xC0 | byte((0x000007C0 & r) >> 6)
+		buffer[1] = 0x80 | byte( 0x0000003F & r)
+
+		p := buffer[:]
+
+		return w.Write(p)
+
+	case 0xFFFF >= r:
+		var buffer [3]byte
+
+		buffer[0] = 0xE0 | byte((0x0000F000 & r) >> 12)
+		buffer[1] = 0x80 | byte((0x00000FC0 & r) >>  6)
+		buffer[2] = 0x80 | byte( 0x0000003F & r)
+
+		p := buffer[:]
+
+		return w.Write(p)
+
+	case 0x10FFFF >= r:
+		var buffer [4]byte
+
+		buffer[0] = 0xF0 | byte((0x001C0000 & r) >> 18)
+		buffer[1] = 0x80 | byte((0x0003F000 & r) >> 12)
+		buffer[2] = 0x80 | byte((0x00000FC0 & r) >>  6)
+		buffer[3] = 0x80 | byte( 0x0000003F & r)
+
+		p := buffer[:]
+
+		return w.Write(p)
+
+	default:
+		return 0, errInternalError
+	}
+
+}

writerune_test.go

@@ -0,0 +1,224 @@
+package utf8s
+
+import (
+	"bytes"
+
+	"testing"
+)
+
+func TestWriteRune(t *testing.T) {
+
+	tests := []struct{
+		Rune            rune
+		ExpectedInt     int
+		ExpectedBytes []byte
+	}{
+		{
+			Rune:         'a',
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{'a'},
+		},
+
+
+
+		{
+			Rune:         'b',
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{'b'},
+		},
+
+
+
+		{
+			Rune:         'c',
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{'c'},
+		},
+
+
+
+		{
+			Rune:         'A',
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{'A'},
+		},
+
+
+
+		{
+			Rune:         'r',
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{'r'},
+		},
+
+
+
+		{
+			Rune:         '¡',
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xC2, 0xA1},
+		},
+
+
+
+		{
+			Rune:         '۵',
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xDB, 0xB5},
+		},
+
+
+
+		{
+			Rune:         '‱',
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xe2, 0x80, 0xb1},
+		},
+
+
+
+		{
+			Rune:         '≡',
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xE2, 0x89, 0xA1},
+		},
+
+
+
+		{
+			Rune:         '𐏕',
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xf0, 0x90, 0x8f, 0x95},
+		},
+
+
+
+		{
+			Rune:         '🙂',
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xf0, 0x9f, 0x99, 0x82},
+		},
+
+
+
+		{
+			Rune        :  0x0000,
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{0x00},
+		},
+		{
+			Rune:          0x0001,
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{0x01},
+		},
+		{
+			Rune:          0x007e,
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{0x7e},
+		},
+		{
+			Rune:          0x007f,
+			ExpectedInt:   1,
+			ExpectedBytes: []byte{0x7f},
+		},
+
+
+
+		{
+			Rune:          0x0080,  // 0b0000,1000,0000
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xC2, 0x80}, // <<0b11000010 ; 0b1000,0000>>
+		},
+		{
+			Rune:          0x0081,  // 0b0000,1000,0000
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xC2, 0x81}, // <<0b11000010 ; 0b1000,0001>>
+		},
+		{
+			Rune:          0x07fe, // 0b0111,1111,1110
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xDF, 0xBE}, // <<0b1101,1111 ; 0b1011,1110>>
+		},
+		{
+			Rune:          0x07ff, // 0b0111,1111,1111
+			ExpectedInt:   2,
+			ExpectedBytes: []byte{0xDF, 0xBF}, // <<0b1101,1111 ; 0b1011,1111>>
+		},
+
+
+
+		{
+			Rune:          0x0800, // 0b1000,0000,0000
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xe0, 0xa0, 0x80}, // <<0b111,00000 ; 0b1010,0000 ; 0b1000,0000>>
+		},
+		{
+			Rune:          0x0801, // 0b1000,0000,0001
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xe0, 0xa0, 0x81}, // <<0b111,00000 ; 0b1010,0000 ; 0b1000,0001>>
+		},
+		{
+			Rune:          0xfffe, // 0b1111,1111,1111,1110
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xEF, 0xBF, 0xBE}, // <<0b11101111 ; 0b1011,1111 ; 0b1011,1110>>
+		},
+		{
+			Rune:          0xffff, // 0b1111,1111,1111,1111
+			ExpectedInt:   3,
+			ExpectedBytes: []byte{0xEF, 0xBF, 0xBF}, // <<0b11101111 ; 0b1011,1111 ; 0b1011,1111>>
+		},
+
+
+
+		{
+			Rune:          0x010000, // 0b0001,0000,0000,0000,0000
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xF0, 0x90, 0x80, 0x80}, // <<0b1111,0000 ; 0b10010000 ; 0b1000,0000 ; 0b1000,0000>>
+		},
+		{
+			Rune:          0x010001, // 0b0001,0000,0000,0000,0001
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xF0, 0x90, 0x80, 0x81}, // <<0b1111,0000 ; 0b10010000 ; 0b1000,0000 ; 0b1000,0001>>
+		},
+		{
+			Rune:          0x10fffe, // 0b0001,0000,1111,1111,1111,1110
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xF4, 0x8F, 0xBF, 0xBE}, // <<0b1111,0100 ; 0b10001111 ; 0b1011,1111 ; 0b1011,1110>>
+		},
+		{
+			Rune:          0x10ffff, // 0b0001,0000,1111,1111,1111,1111
+			ExpectedInt:   4,
+			ExpectedBytes: []byte{0xF4, 0x8F, 0xBF, 0xBF}, // <<0b1111,0100 ; 0b10001111 ; 0b1011,1111 ; 0b1011,1111>>
+		},
+	}
+
+
+	for testNumber, test := range tests {
+
+		var buffer bytes.Buffer
+
+		actualInt, err := WriteRune(&buffer, test.Rune)
+		if nil != err {
+			t.Errorf("For test #%d, did not expect an error, but actually got one: (%T) %q", testNumber, err, err)
+			t.Errorf("\trune = %q (%x)", test.Rune, test.Rune)
+			continue
+		}
+		if expected, actual := test.ExpectedInt, actualInt; expected != actual {
+			t.Errorf("For test #%d, expected %d, but actually got %d.", testNumber, expected, actual)
+			t.Errorf("\trune = %q (%x)", test.Rune, test.Rune)
+			continue
+		}
+		if expected, actual := test.ExpectedInt, buffer.Len(); expected != actual {
+			t.Errorf("For test #%d, expected %d, but actually got %d.", testNumber, expected, actual)
+			t.Errorf("\trune = %q (%x)", test.Rune, test.Rune)
+			continue
+		}
+		for byteNumber, expected := range test.ExpectedBytes {
+			if actual := buffer.Bytes()[byteNumber]; expected != actual {
+				t.Errorf("For test #%d and byte #%d, expected %q (%X), but actually got %q (%X).", testNumber, byteNumber, expected, expected, actual, actual)
+				t.Errorf("\trune = %q (%x)", test.Rune, test.Rune)
+				continue
+			}
+		}
+	}
+}