address: refactor common code into AddressSegWit

To avoid a lot of code duplication, we extract the common parts of the
AddressWitnessPubKeyHash and AddressWitnessScriptHash types into a
common base type called AddressSegWit.

address.go

@@ -506,25 +506,88 @@ func (a *AddressPubKey) PubKey() *btcec.PublicKey {
 	return a.pubKey
 }
 
+// AddressSegWit is the base address type for all SegWit addresses.
+type AddressSegWit struct {
+	hrp            string
+	witnessVersion byte
+	witnessProgram []byte
+}
+
+// EncodeAddress returns the bech32 (or bech32m for SegWit v1) string encoding
+// of an AddressSegWit.
+//
+// NOTE: This method is part of the Address interface.
+func (a *AddressSegWit) EncodeAddress() string {
+	str, err := encodeSegWitAddress(
+		a.hrp, a.witnessVersion, a.witnessProgram[:],
+	)
+	if err != nil {
+		return ""
+	}
+	return str
+}
+
+// ScriptAddress returns the witness program for this address.
+//
+// NOTE: This method is part of the Address interface.
+func (a *AddressSegWit) ScriptAddress() []byte {
+	return a.witnessProgram[:]
+}
+
+// IsForNet returns whether the AddressSegWit is associated with the passed
+// bitcoin network.
+//
+// NOTE: This method is part of the Address interface.
+func (a *AddressSegWit) IsForNet(net *chaincfg.Params) bool {
+	return a.hrp == net.Bech32HRPSegwit
+}
+
+// String returns a human-readable string for the AddressWitnessPubKeyHash.
+// This is equivalent to calling EncodeAddress, but is provided so the type
+// can be used as a fmt.Stringer.
+//
+// NOTE: This method is part of the Address interface.
+func (a *AddressSegWit) String() string {
+	return a.EncodeAddress()
+}
+
+// Hrp returns the human-readable part of the bech32 (or bech32m for SegWit v1)
+// encoded AddressSegWit.
+func (a *AddressSegWit) Hrp() string {
+	return a.hrp
+}
+
+// WitnessVersion returns the witness version of the AddressSegWit.
+func (a *AddressSegWit) WitnessVersion() byte {
+	return a.witnessVersion
+}
+
+// WitnessProgram returns the witness program of the AddressSegWit.
+func (a *AddressSegWit) WitnessProgram() []byte {
+	return a.witnessProgram[:]
+}
+
 // AddressWitnessPubKeyHash is an Address for a pay-to-witness-pubkey-hash
 // (P2WPKH) output. See BIP 173 for further details regarding native segregated
 // witness address encoding:
 // https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
 type AddressWitnessPubKeyHash struct {
-	hrp            string
+	AddressSegWit
-	witnessVersion byte
-	witnessProgram [20]byte
 }
 
 // NewAddressWitnessPubKeyHash returns a new AddressWitnessPubKeyHash.
-func NewAddressWitnessPubKeyHash(witnessProg []byte, net *chaincfg.Params) (*AddressWitnessPubKeyHash, error) {
+func NewAddressWitnessPubKeyHash(witnessProg []byte,
+	net *chaincfg.Params) (*AddressWitnessPubKeyHash, error) {
+
 	return newAddressWitnessPubKeyHash(net.Bech32HRPSegwit, witnessProg)
 }
 
 // newAddressWitnessPubKeyHash is an internal helper function to create an
 // AddressWitnessPubKeyHash with a known human-readable part, rather than
 // looking it up through its parameters.
-func newAddressWitnessPubKeyHash(hrp string, witnessProg []byte) (*AddressWitnessPubKeyHash, error) {
+func newAddressWitnessPubKeyHash(hrp string,
+	witnessProg []byte) (*AddressWitnessPubKeyHash, error) {
+
 	// Check for valid program length for witness version 0, which is 20
 	// for P2WPKH.
 	if len(witnessProg) != 20 {
@@ -533,68 +596,22 @@ func newAddressWitnessPubKeyHash(hrp string, witnessProg []byte) (*AddressWitnes
 	}
 
 	addr := &AddressWitnessPubKeyHash{
+		AddressSegWit{
 			hrp:            strings.ToLower(hrp),
 			witnessVersion: 0x00,
+			witnessProgram: witnessProg,
+		},
 	}
 
-	copy(addr.witnessProgram[:], witnessProg)
-
 	return addr, nil
 }
 
-// EncodeAddress returns the bech32 string encoding of an
-// AddressWitnessPubKeyHash.
-// Part of the Address interface.
-func (a *AddressWitnessPubKeyHash) EncodeAddress() string {
-	str, err := encodeSegWitAddress(a.hrp, a.witnessVersion,
-		a.witnessProgram[:])
-	if err != nil {
-		return ""
-	}
-	return str
-}
-
-// ScriptAddress returns the witness program for this address.
-// Part of the Address interface.
-func (a *AddressWitnessPubKeyHash) ScriptAddress() []byte {
-	return a.witnessProgram[:]
-}
-
-// IsForNet returns whether or not the AddressWitnessPubKeyHash is associated
-// with the passed bitcoin network.
-// Part of the Address interface.
-func (a *AddressWitnessPubKeyHash) IsForNet(net *chaincfg.Params) bool {
-	return a.hrp == net.Bech32HRPSegwit
-}
-
-// String returns a human-readable string for the AddressWitnessPubKeyHash.
-// This is equivalent to calling EncodeAddress, but is provided so the type
-// can be used as a fmt.Stringer.
-// Part of the Address interface.
-func (a *AddressWitnessPubKeyHash) String() string {
-	return a.EncodeAddress()
-}
-
-// Hrp returns the human-readable part of the bech32 encoded
-// AddressWitnessPubKeyHash.
-func (a *AddressWitnessPubKeyHash) Hrp() string {
-	return a.hrp
-}
-
-// WitnessVersion returns the witness version of the AddressWitnessPubKeyHash.
-func (a *AddressWitnessPubKeyHash) WitnessVersion() byte {
-	return a.witnessVersion
-}
-
-// WitnessProgram returns the witness program of the AddressWitnessPubKeyHash.
-func (a *AddressWitnessPubKeyHash) WitnessProgram() []byte {
-	return a.witnessProgram[:]
-}
-
 // Hash160 returns the witness program of the AddressWitnessPubKeyHash as a
 // byte array.
 func (a *AddressWitnessPubKeyHash) Hash160() *[20]byte {
-	return &a.witnessProgram
+	var pubKeyHashWitnessProgram [20]byte
+	copy(pubKeyHashWitnessProgram[:], a.witnessProgram)
+	return &pubKeyHashWitnessProgram
 }
 
 // AddressWitnessScriptHash is an Address for a pay-to-witness-script-hash
@@ -602,20 +619,22 @@ func (a *AddressWitnessPubKeyHash) Hash160() *[20]byte {
 // witness address encoding:
 // https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
 type AddressWitnessScriptHash struct {
-	hrp            string
+	AddressSegWit
-	witnessVersion byte
-	witnessProgram [32]byte
 }
 
 // NewAddressWitnessScriptHash returns a new AddressWitnessPubKeyHash.
-func NewAddressWitnessScriptHash(witnessProg []byte, net *chaincfg.Params) (*AddressWitnessScriptHash, error) {
+func NewAddressWitnessScriptHash(witnessProg []byte,
+	net *chaincfg.Params) (*AddressWitnessScriptHash, error) {
+
 	return newAddressWitnessScriptHash(net.Bech32HRPSegwit, witnessProg)
 }
 
 // newAddressWitnessScriptHash is an internal helper function to create an
 // AddressWitnessScriptHash with a known human-readable part, rather than
 // looking it up through its parameters.
-func newAddressWitnessScriptHash(hrp string, witnessProg []byte) (*AddressWitnessScriptHash, error) {
+func newAddressWitnessScriptHash(hrp string,
+	witnessProg []byte) (*AddressWitnessScriptHash, error) {
+
 	// Check for valid program length for witness version 0, which is 32
 	// for P2WSH.
 	if len(witnessProg) != 32 {
@@ -624,60 +643,12 @@ func newAddressWitnessScriptHash(hrp string, witnessProg []byte) (*AddressWitnes
 	}
 
 	addr := &AddressWitnessScriptHash{
+		AddressSegWit{
 			hrp:            strings.ToLower(hrp),
 			witnessVersion: 0x00,
+			witnessProgram: witnessProg,
+		},
 	}
 
-	copy(addr.witnessProgram[:], witnessProg)
-
 	return addr, nil
 }
-
-// EncodeAddress returns the bech32 string encoding of an
-// AddressWitnessScriptHash.
-// Part of the Address interface.
-func (a *AddressWitnessScriptHash) EncodeAddress() string {
-	str, err := encodeSegWitAddress(a.hrp, a.witnessVersion,
-		a.witnessProgram[:])
-	if err != nil {
-		return ""
-	}
-	return str
-}
-
-// ScriptAddress returns the witness program for this address.
-// Part of the Address interface.
-func (a *AddressWitnessScriptHash) ScriptAddress() []byte {
-	return a.witnessProgram[:]
-}
-
-// IsForNet returns whether or not the AddressWitnessScriptHash is associated
-// with the passed bitcoin network.
-// Part of the Address interface.
-func (a *AddressWitnessScriptHash) IsForNet(net *chaincfg.Params) bool {
-	return a.hrp == net.Bech32HRPSegwit
-}
-
-// String returns a human-readable string for the AddressWitnessScriptHash.
-// This is equivalent to calling EncodeAddress, but is provided so the type
-// can be used as a fmt.Stringer.
-// Part of the Address interface.
-func (a *AddressWitnessScriptHash) String() string {
-	return a.EncodeAddress()
-}
-
-// Hrp returns the human-readable part of the bech32 encoded
-// AddressWitnessScriptHash.
-func (a *AddressWitnessScriptHash) Hrp() string {
-	return a.hrp
-}
-
-// WitnessVersion returns the witness version of the AddressWitnessScriptHash.
-func (a *AddressWitnessScriptHash) WitnessVersion() byte {
-	return a.witnessVersion
-}
-
-// WitnessProgram returns the witness program of the AddressWitnessScriptHash.
-func (a *AddressWitnessScriptHash) WitnessProgram() []byte {
-	return a.witnessProgram[:]
-}

internal_test.go

@@ -59,9 +59,11 @@ func TstAddressWitnessPubKeyHash(version byte, program [20]byte,
 	hrp string) *AddressWitnessPubKeyHash {
 
 	return &AddressWitnessPubKeyHash{
+		AddressSegWit{
 			hrp:            hrp,
 			witnessVersion: version,
-		witnessProgram: program,
+			witnessProgram: program[:],
+		},
 	}
 }
 
@@ -71,9 +73,11 @@ func TstAddressWitnessScriptHash(version byte, program [32]byte,
 	hrp string) *AddressWitnessScriptHash {
 
 	return &AddressWitnessScriptHash{
+		AddressSegWit{
 			hrp:            hrp,
 			witnessVersion: version,
-		witnessProgram: program,
+			witnessProgram: program[:],
+		},
 	}
 }