types/wgkey: use value receiver with MarshalJSON

josharian · josharian · commit 8febefe01258 · 2021-04-29T13:54:10.000-07:00
Pointer receivers used with MarshalJSON are code rakes. golang/go#22967 dominikh/go-tools#911 I just stepped on one, and it hurt. Turn it over. While we're here, optimize the code a bit. name old time/op new time/op delta MarshalJSON-8 184ns ± 0% 44ns ± 0% -76.03% (p=0.000 n=20+19) name old alloc/op new alloc/op delta MarshalJSON-8 184B ± 0% 80B ± 0% -56.52% (p=0.000 n=20+20) name old allocs/op new allocs/op delta MarshalJSON-8 4.00 ± 0% 1.00 ± 0% -75.00% (p=0.000 n=20+20) Signed-off-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/types/wgkey/key.go b/types/wgkey/key.go
@@ -91,9 +91,11 @@ func (k *Key) IsZero() bool {
 }
 
 func (k Key) MarshalJSON() ([]byte, error) {
-	buf := new(bytes.Buffer)
-	fmt.Fprintf(buf, `"%x"`, k[:])
-	return buf.Bytes(), nil
+	buf := make([]byte, 2+len(k)*2)
+	buf[0] = '"'
+	hex.Encode(buf[1:], k[:])
+	buf[len(buf)-1] = '"'
+	return buf, nil
 }
 
 func (k *Key) UnmarshalJSON(b []byte) error {
diff --git a/types/wgkey/key_test.go b/types/wgkey/key_test.go
@@ -6,6 +6,7 @@ package wgkey
 
 import (
 	"bytes"
+	"encoding/json"
 	"testing"
 )
 
@@ -20,7 +21,7 @@ func TestKeyBasics(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	t.Run("JSON round-trip", func(t *testing.T) {
+	t.Run("JSON round-trip (pointer)", func(t *testing.T) {
 		// should preserve the keys
 		k2 := new(Key)
 		if err := k2.UnmarshalJSON(b); err != nil {
@@ -55,6 +56,27 @@ func TestKeyBasics(t *testing.T) {
 			t.Fatalf("base64-encoded keys match: %s, %s", b1, b2)
 		}
 	})
+
+	t.Run("JSON round-trip (value)", func(t *testing.T) {
+		type T struct {
+			K Key
+		}
+		v := T{K: *k1}
+		b, err := json.Marshal(v)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var u T
+		if err := json.Unmarshal(b, &u); err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(v.K[:], u.K[:]) {
+			t.Fatalf("v.K %v != u.K %v", v.K[:], u.K[:])
+		}
+		if b1, b2 := v.K.String(), u.K.String(); b1 != b2 {
+			t.Fatalf("base64-encoded keys do not match: %s, %s", b1, b2)
+		}
+	})
 }
 func TestPrivateKeyBasics(t *testing.T) {
 	pri, err := NewPrivate()
@@ -109,3 +131,17 @@ func TestPrivateKeyBasics(t *testing.T) {
 		}
 	})
 }
+
+var sink []byte
+
+func BenchmarkMarshalJSON(b *testing.B) {
+	b.ReportAllocs()
+	var k Key
+	for i := 0; i < b.N; i++ {
+		var err error
+		sink, err = k.MarshalJSON()
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}

Original file line number	Diff line number	Diff line change
`@@ -91,9 +91,11 @@ func (k *Key) IsZero() bool {`
`91`	`91`	`}`
`92`	`92`
`93`	`93`	`func (k Key) MarshalJSON() ([]byte, error) {`
`94`		`- buf := new(bytes.Buffer)`
`95`		- fmt.Fprintf(buf, `"%x"`, k[:])
`96`		`- return buf.Bytes(), nil`
	`94`	`+ buf := make([]byte, 2+len(k)*2)`
	`95`	`+ buf[0] = '"'`
	`96`	`+ hex.Encode(buf[1:], k[:])`
	`97`	`+ buf[len(buf)-1] = '"'`
	`98`	`+ return buf, nil`
`97`	`99`	`}`
`98`	`100`
`99`	`101`	`func (k *Key) UnmarshalJSON(b []byte) error {`