type_to_string: add privkey.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

bitcoin/privkey.h

@@ -7,5 +7,4 @@
 struct privkey {
 	u8 secret[32];
 };
-
 #endif /* LIGHTNING_BITCOIN_PRIVKEY_H */

bitcoin/pubkey.c

@@ -88,3 +88,13 @@ int pubkey_cmp(const struct pubkey *a, const struct pubkey *b)
 	pubkey_to_der(keyb, b);
 	return memcmp(keya, keyb, sizeof(keya));
 }
+
+static char *privkey_to_hexstr(const tal_t *ctx, const struct privkey *secret)
+{
+	/* Bitcoin appends "01" to indicate the pubkey is compressed. */
+	char *str = tal_arr(ctx, char, hex_str_size(sizeof(*secret) + 1));
+	hex_encode(secret, sizeof(*secret), str, hex_str_size(sizeof(*secret)));
+	strcat(str, "01");
+	return str;
+}
+REGISTER_TYPE_TO_STRING(privkey, privkey_to_hexstr);

type_to_string.h

@@ -20,6 +20,7 @@ union printable_types {
 	const struct netaddr *netaddr;
 	const secp256k1_pubkey *secp256k1_pubkey;
 	const struct channel_id *channel_id;
+	const struct privkey *privkey;
 	const char *charp_;
 };