Improve performance by preallocating the output buffer

cobs.go

@@ -35,7 +35,9 @@ func TrimNull(p []byte) []byte {
 }
 
 // Encode a null-terminated slice of bytes to a cobs frame
-func Encode(p []byte) (b []byte) {
+func Encode(p []byte) []byte {
+	// preallocate output buffer with estimated size
+	b := make([]byte, 0, EncodedSize(len(p)))
 	var x [0xff]byte
 	x[0] = 1
 	for _, v := range p {
@@ -58,7 +60,9 @@ func Encode(p []byte) (b []byte) {
 }
 
 // Decode a cobs frame to a null-terminated slice of bytes
-func Decode(p []byte) (b []byte) {
+func Decode(p []byte) []byte {
+	// preallocate output buffer, data will be smaller than input
+	b := make([]byte, 0, len(p))
 	for len(p) > 0 {
 		n, data := p[0], p[1:]
 		// invalid frame, abort

cobs_test.go

@@ -388,3 +388,42 @@ func ExampleEncode() {
 	// Hello: [6 72 101 108 108 111]
 	// [6 72 101 108 108 111]: Hello
 }
+
+func benchmarkEncode(i int, b *testing.B) {
+	data := make([]byte, i)
+	for i := range data {
+		data[i] = byte(i % 255)
+	}
+	data[len(data)-1] = 0 // zero-terminate input
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Encode(data)
+	}
+}
+
+func benchmarkDecode(i int, b *testing.B) {
+	data := make([]byte, i)
+	for i := range data {
+		data[i] = byte(i % 255)
+	}
+	data[len(data)-1] = 0 // zero-terminate input
+	enc := Encode(data)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Decode(enc)
+	}
+}
+
+func BenchmarkCobs(b *testing.B) {
+	cases := []int{32, 256, 1024, 4096}
+	for _, c := range cases {
+		b.Run(fmt.Sprintf("%d/Encode", c), func(b *testing.B) {
+			benchmarkEncode(c, b)
+		})
+		b.Run(fmt.Sprintf("%d/Decode", c), func(b *testing.B) {
+			benchmarkDecode(c, b)
+		})
+	}
+}