expose a pubkey from sig method

Author: rohenaz

verify.go

@@ -18,37 +18,35 @@ const (
 	hBSV string = "Bitcoin Signed Message:\n"
 )
 
-// VerifyMessage verifies a string and address against the provided
-// signature and assumes Bitcoin Signed Message encoding
-//
-// Error will occur if verify fails or verification is not successful (no bool)
-// Spec: https://docs.moneybutton.com/docs/bsv-message.html
-func VerifyMessage(address, sig, data string) error {
-
+// PublicKeyFromSignature gets a publickey for a signature and tells you whether is was compressed
+func PublicKeyFromSignature(sig, data string) (pubKey *bsvec.PublicKey, wasCompressed bool, err error) {
 	decodedSig, err := base64.StdEncoding.DecodeString(sig)
 	if err != nil {
-		return err
+		return nil, false, err
 	}
 
 	// Validate the signature - this just shows that it was valid at all.
 	// we will compare it with the key next.
 	var buf bytes.Buffer
-	if err = wire.WriteVarString(&buf, 0, hBSV); err != nil {
-		return err
-	}
-	if err = wire.WriteVarString(&buf, 0, data); err != nil {
-		return err
-	}
+	wire.WriteVarString(&buf, 0, hBSV)
+	wire.WriteVarString(&buf, 0, data)
 
 	// Create the hash
 	expectedMessageHash := chainhash.DoubleHashB(buf.Bytes())
+	return bsvec.RecoverCompact(bsvec.S256(), decodedSig, expectedMessageHash)
+}
 
-	var publicKey *bsvec.PublicKey
-	var wasCompressed bool
-	if publicKey, wasCompressed, err = bsvec.RecoverCompact(bsvec.S256(), decodedSig, expectedMessageHash); err != nil {
+// VerifyMessage verifies a string and address against the provided
+// signature and assumes Bitcoin Signed Message encoding
+//
+// Error will occur if verify fails or verification is not successful (no bool)
+// Spec: https://docs.moneybutton.com/docs/bsv-message.html
+func VerifyMessage(address, sig, data string) error {
+
+	publicKey, wasCompressed, err := PublicKeyFromSignature(sig, data)
+	if err != nil {
 		return err
 	}
-
 	// Reconstruct the pubkey hash.
 	var serializedPK []byte
 	if wasCompressed {