Added check for nettle < 3.0

configure.ac

@@ -50,6 +50,11 @@ AC_CHECK_LIB(gnutls, gnutls_pkcs11_reinit, [
 AC_DEFINE([HAVE_PKCS11], [], [PKCS11 detected in gnutls])
 ])
 
+if ! $PKG_CONFIG --atleast-version=3.0 nettle; then
+	AC_DEFINE([NETTLE_OLD_BASE64_API], [1],
+		  [nettle uses the pre-3.x base64 API])
+fi
+
 AC_ARG_WITH(protobuf,
   AS_HELP_STRING([--without-protobuf], [use the included protobuf library]),
   test_for_protobuf=$withval,

src/base64-helper.c

@@ -44,7 +44,17 @@ oc_base64_decode(const uint8_t *src, unsigned src_length,
 
 	base64_decode_init(&ctx);
 
+#ifdef NETTLE_OLD_BASE64_API
+	{
+		unsigned int len = *dst_length;
+		ret = base64_decode_update(&ctx, &len, dst, src_length, src);
+		if (ret != 0)
+			*dst_length = len;
+	}
+#else
 	ret = base64_decode_update(&ctx, dst_length, dst, src_length, src);
+#endif
+
 	if (ret == 0)
 		return 0;