Add UnmarshalString

Before
'''
2512 B/op       83 allocs/op
'''

After
'''
2016 B/op         47 allocs/op
'''

base_lexer.go

@@ -25,12 +25,12 @@ func (e syntaxError) Error() string {
 }
 
 type baseLexer struct {
-	value []byte
+	value string
 	pos   int
 }
 
 func (l baseLexer) syntaxError() error {
-	return syntaxError{s: string(l.value), i: l.pos - 1}
+	return syntaxError{s: l.value, i: l.pos - 1}
 }
 
 func (l *baseLexer) unreadByte() error {
@@ -157,7 +157,7 @@ func (l *baseLexer) readField() (string, error) {
 			break
 		}
 	}
-	return string(l.value[start:stop]), nil
+	return l.value[start:stop], nil
 }
 
 // Returns symbols until line end
@@ -173,7 +173,7 @@ func (l *baseLexer) readLine() (string, error) {
 			trim++
 		}
 		if ch == '\n' {
-			return string(l.value[start : l.pos-trim]), nil
+			return l.value[start : l.pos-trim], nil
 		}
 	}
 }

base_lexer_test.go

@@ -16,7 +16,7 @@ func TestLexer(t *testing.T) {
 			"with linebreak":   "aaa \n",
 			"with linebreak 2": "aaa \r\n",
 		} {
-			l := &baseLexer{value: []byte(value)}
+			l := &baseLexer{value: value}
 			field, err := l.readField()
 			if err != nil {
 				t.Fatal(err)
@@ -28,7 +28,7 @@ func TestLexer(t *testing.T) {
 	})
 
 	t.Run("syntax error", func(t *testing.T) {
-		l := &baseLexer{value: []byte("12NaN")}
+		l := &baseLexer{value: "12NaN"}
 		_, err := l.readUint64Field()
 		if err != nil {
 			fmt.Println("error message:", err.Error())
@@ -38,7 +38,7 @@ func TestLexer(t *testing.T) {
 	})
 
 	t.Run("many fields", func(t *testing.T) {
-		l := &baseLexer{value: []byte("aaa  123\nf1 f2\nlast")}
+		l := &baseLexer{value: "aaa  123\nf1 f2\nlast"}
 
 		t.Run("first line", func(t *testing.T) {
 			field, err := l.readField()

fuzz_test.go

@@ -6,12 +6,12 @@ package sdp
 import "testing"
 
 func FuzzUnmarshal(f *testing.F) {
-	f.Add([]byte{})
-	f.Add([]byte(CanonicalUnmarshalSDP))
-	f.Fuzz(func(t *testing.T, data []byte) {
+	f.Add("")
+	f.Add(CanonicalUnmarshalSDP)
+	f.Fuzz(func(t *testing.T, data string) {
 		// Check that unmarshalling any byte slice does not panic.
 		var sd SessionDescription
-		if err := sd.Unmarshal(data); err != nil {
+		if err := sd.UnmarshalString(data); err != nil {
 			return
 		}
 		// Check that we can marshal anything we unmarshalled.

marshal_test.go

@@ -177,7 +177,7 @@ func TestMarshalCanonical(t *testing.T) {
 func BenchmarkMarshal(b *testing.B) {
 	b.ReportAllocs()
 	var sd SessionDescription
-	err := sd.Unmarshal([]byte(CanonicalUnmarshalSDP))
+	err := sd.UnmarshalString(CanonicalUnmarshalSDP)
 	if err != nil {
 		b.Fatal(err)
 	}

unmarshal.go

@@ -18,7 +18,7 @@ var (
 	errSDPInvalidPortValue    = errors.New("sdp: invalid port value")
 )
 
-// Unmarshal is the primary function that deserializes the session description
+// UnmarshalString is the primary function that deserializes the session description
 // message and stores it inside of a structured SessionDescription object.
 //
 // The States Transition Table describes the computation flow between functions
@@ -99,7 +99,7 @@ var (
 // |   s15  |    |    14 |    |     | 15 |     |   |    | 12 |   |   |     |   |   |    |   |    |
 // |   s16  |    |    14 |    |     |    |  15 |   |    | 12 |   |   |     |   |   |    |   |    |
 // +--------+----+-------+----+-----+----+-----+---+----+----+---+---+-----+---+---+----+---+----+
-func (s *SessionDescription) Unmarshal(value []byte) error {
+func (s *SessionDescription) UnmarshalString(value string) error {
 	l := new(lexer)
 	l.desc = s
 	l.value = value
@@ -113,6 +113,12 @@ func (s *SessionDescription) Unmarshal(value []byte) error {
 	return nil
 }
 
+// Unmarshal converts the value into a []byte and then calls UnmarshalString.
+// Callers should use the more performant UnmarshalString
+func (s *SessionDescription) Unmarshal(value []byte) error {
+	return s.UnmarshalString(string(value))
+}
+
 func s1(l *lexer) (stateFn, error) {
 	return l.handleType(func(key byte) stateFn {
 		if key == 'v' {

unmarshal_test.go

@@ -303,7 +303,7 @@ func TestRoundTrip(t *testing.T) {
 		t.Run(test.Name, func(t *testing.T) {
 			sd := &SessionDescription{}
 
-			err := sd.Unmarshal([]byte(test.SDP))
+			err := sd.UnmarshalString(test.SDP)
 			if got, want := err, error(nil); !errors.Is(got, want) {
 				t.Fatalf("Unmarshal:\nerr=%v\nwant=%v", got, want)
 			}
@@ -327,7 +327,7 @@ func TestRoundTrip(t *testing.T) {
 
 func TestUnmarshalRepeatTimes(t *testing.T) {
 	sd := &SessionDescription{}
-	if err := sd.Unmarshal([]byte(RepeatTimesSDP)); err != nil {
+	if err := sd.UnmarshalString(RepeatTimesSDP); err != nil {
 		t.Errorf("error: %v", err)
 	}
 
@@ -339,15 +339,15 @@ func TestUnmarshalRepeatTimes(t *testing.T) {
 		t.Errorf("error:\n\nEXPECTED:\n%v\nACTUAL:\n%v", RepeatTimesSDPExpected, string(actual))
 	}
 
-	err = sd.Unmarshal([]byte(TimingSDP + "r=\r\n"))
+	err = sd.UnmarshalString(TimingSDP + "r=\r\n")
 	if got, want := err, errSDPInvalidValue; !errors.Is(got, want) {
 		t.Fatalf("Marshal(): err=%v, want %v", got, want)
 	}
 }
 
 func TestUnmarshalTimeZones(t *testing.T) {
 	sd := &SessionDescription{}
-	if err := sd.Unmarshal([]byte(TimeZonesSDP)); err != nil {
+	if err := sd.UnmarshalString(TimeZonesSDP); err != nil {
 		t.Errorf("error: %v", err)
 	}
 
@@ -363,7 +363,7 @@ func TestUnmarshalTimeZones(t *testing.T) {
 func TestUnmarshalNonNilAddress(t *testing.T) {
 	in := "v=0\r\no=0 0 0 IN IP4 0\r\ns=0\r\nc=IN IP4\r\nt=0 0\r\n"
 	var sd SessionDescription
-	err := sd.Unmarshal([]byte(in))
+	err := sd.UnmarshalString(in)
 	if err != nil {
 		t.Fatalf("failed to unmarshal %q", in)
 	}
@@ -378,10 +378,9 @@ func TestUnmarshalNonNilAddress(t *testing.T) {
 
 func BenchmarkUnmarshal(b *testing.B) {
 	b.ReportAllocs()
-	raw := []byte(CanonicalUnmarshalSDP)
 	for i := 0; i < b.N; i++ {
 		var sd SessionDescription
-		err := sd.Unmarshal(raw)
+		err := sd.UnmarshalString(CanonicalUnmarshalSDP)
 		if err != nil {
 			b.Fatal(err)
 		}