device: avoid hex allocations in IpcGet

benchmark               old ns/op     new ns/op     delta
BenchmarkUAPIGet-16     2872          2157          -24.90%

benchmark               old allocs     new allocs     delta
BenchmarkUAPIGet-16     30             18             -40.00%

benchmark               old bytes     new bytes     delta
BenchmarkUAPIGet-16     737           256           -65.26%

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 14 insertions, 15 deletions

diff --git a/device/noise-types.go b/device/noise-types.go
index 90108d4..3688f7d 100644
--- a/device/noise-types.go
+++ b/device/noise-types.go
@@ -60,18 +60,10 @@ func (key *NoisePrivateKey) FromMaybeZeroHex(src string) (err error) {
 	return
 }
 
-func (key NoisePrivateKey) ToHex() string {
-	return hex.EncodeToString(key[:])
-}
-
 func (key *NoisePublicKey) FromHex(src string) error {
 	return loadExactHex(key[:], src)
 }
 
-func (key NoisePublicKey) ToHex() string {
-	return hex.EncodeToString(key[:])
-}
-
 func (key NoisePublicKey) IsZero() bool {
 	var zero NoisePublicKey
 	return key.Equals(zero)
@@ -84,7 +76,3 @@ func (key NoisePublicKey) Equals(tar NoisePublicKey) bool {
 func (key *NoisePresharedKey) FromHex(src string) error {
 	return loadExactHex(key[:], src)
 }
-
-func (key NoisePresharedKey) ToHex() string {
-	return hex.EncodeToString(key[:])
-}
diff --git a/device/uapi.go b/device/uapi.go
index bfef877..6f7fb2a 100644
--- a/device/uapi.go
+++ b/device/uapi.go
@@ -57,6 +57,17 @@ func (device *Device) IpcGetOperation(w io.Writer) error {
 		fmt.Fprintf(buf, format, args...)
 		buf.WriteByte('\n')
 	}
+	keyf := func(prefix string, key *[32]byte) {
+		buf.Grow(len(key)*2 + 2 + len(prefix))
+		buf.WriteString(prefix)
+		buf.WriteByte('=')
+		const hex = "0123456789abcdef"
+		for i := 0; i < len(key); i++ {
+			buf.WriteByte(hex[key[i]>>4])
+			buf.WriteByte(hex[key[i]&0xf])
+		}
+		buf.WriteByte('\n')
+	}
 
 	func() {
 
@@ -74,7 +85,7 @@ func (device *Device) IpcGetOperation(w io.Writer) error {
 		// serialize device related values
 
 		if !device.staticIdentity.privateKey.IsZero() {
-			sendf("private_key=%s", device.staticIdentity.privateKey.ToHex())
+			keyf("private_key", (*[32]byte)(&device.staticIdentity.privateKey))
 		}
 
 		if device.net.port != 0 {
@@ -91,8 +102,8 @@ func (device *Device) IpcGetOperation(w io.Writer) error {
 			peer.RLock()
 			defer peer.RUnlock()
 
-			sendf("public_key=%s", peer.handshake.remoteStatic.ToHex())
-			sendf("preshared_key=%s", peer.handshake.presharedKey.ToHex())
+			keyf("public_key", (*[32]byte)(&peer.handshake.remoteStatic))
+			keyf("preshared_key", (*[32]byte)(&peer.handshake.presharedKey))
 			sendf("protocol_version=1")
 			if peer.endpoint != nil {
 				sendf("endpoint=%s", peer.endpoint.DstToString())