type_to_string: add secp256k1_pubkey

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

bitcoin/pubkey.c

@@ -62,6 +62,18 @@ char *pubkey_to_hexstr(const tal_t *ctx, const struct pubkey *key)
 	return tal_hexstr(ctx, der, sizeof(der));
 }
 
+char *secp256k1_pubkey_to_hexstr(const tal_t *ctx, const secp256k1_pubkey *key)
+{
+	unsigned char der[PUBKEY_DER_LEN];
+	size_t outlen = sizeof(der);
+	if (!secp256k1_ec_pubkey_serialize(secp256k1_ctx, der, &outlen, key,
+					   SECP256K1_EC_COMPRESSED))
+		abort();
+	assert(outlen == sizeof(der));
+	return tal_hexstr(ctx, der, sizeof(der));
+}
+REGISTER_TYPE_TO_STRING(secp256k1_pubkey, secp256k1_pubkey_to_hexstr);
+
 bool pubkey_eq(const struct pubkey *a, const struct pubkey *b)
 {
 	return structeq(&a->pubkey, &b->pubkey);

bitcoin/pubkey.h

@@ -20,6 +20,9 @@ bool pubkey_from_hexstr(const char *derstr, size_t derlen, struct pubkey *key);
 /* Convert from hex string of DER (scriptPubKey from validateaddress) */
 char *pubkey_to_hexstr(const tal_t *ctx, const struct pubkey *key);
 
+/* Convenience wrapper for a raw secp256k1_pubkey */
+char *secp256k1_pubkey_to_hexstr(const tal_t *ctx, const secp256k1_pubkey *key);
+
 /* Pubkey from privkey */
 bool pubkey_from_privkey(const struct privkey *privkey,
 			 struct pubkey *key);

type_to_string.h

@@ -3,6 +3,7 @@
 #include "config.h"
 #include "utils.h"
 #include <ccan/autodata/autodata.h>
+#include <secp256k1.h>
 
 /* This must match the type_to_string_ cases. */
 union printable_types {
@@ -17,6 +18,7 @@ union printable_types {
 	const struct channel_state *channel_state;
 	const struct channel_oneside *channel_oneside;
 	const struct netaddr *netaddr;
+	const secp256k1_pubkey *secp256k1_pubkey;
 	const char *charp_;
 };