Added pgp_key_get_primary_userid, returning pointer to C string

dist/src/lib/keyring.c

@@ -522,6 +522,16 @@ const int32_t pgp_key_get_uid0(const pgp_key_t *key)
         res;
 }
 
+const uint8_t *pgp_key_get_primary_userid(const pgp_key_t *key)
+{
+    const int32_t uid0 = pgp_key_get_uid0(key);
+    if( uid0 >= 0 && key->uids && key->uidc > uid0)
+    {
+        return key->uids[uid0];
+    }
+    return NULL;
+}
+
 unsigned key_bit_len(const pgp_pubkey_t *key)
 {
 	switch (key->alg) {

dist/src/lib/keyring.h

@@ -202,6 +202,7 @@ pgp_subpacket_t * pgp_copy_packet(pgp_subpacket_t *, const pgp_subpacket_t *);
 uint8_t * pgp_copy_userid(uint8_t **dst, const uint8_t *src);
 
 const int32_t pgp_key_get_uid0(const pgp_key_t *keydata);
+const uint8_t *pgp_key_get_primary_userid(const pgp_key_t *key);
 
 const pgp_pubkey_t * pgp_key_get_sigkey(const pgp_key_t *key);
 const pgp_seckey_t * pgp_key_get_certkey(const pgp_key_t *key);