features: Move feature-handling code to a common/features.c source.

common/features.c

@@ -0,0 +1,62 @@
+#include "features.h"
+#include <wire/peer_wire.h>
+
+static const u8 supported_local_features[]
+= {LOCALFEATURES_INITIAL_ROUTING_SYNC};
+static const u8 supported_global_features[]
+= {};
+
+u8 *get_supported_global_features(const tal_t *ctx)
+{
+	return tal_dup_arr(ctx, u8, supported_global_features,
+			   sizeof(supported_global_features), 0);
+}
+
+u8 *get_supported_local_features(const tal_t *ctx)
+{
+	return tal_dup_arr(ctx, u8, supported_local_features,
+			   sizeof(supported_local_features), 0);
+}
+
+/**
+ * requires_unsupported_features - Check if we support what's being asked
+ *
+ * Given the features vector that the remote connection is expecting
+ * from us, we check to see if we support all even bit features, i.e.,
+ * the required features. We do so by subtracting our own features in
+ * the provided positions and see if even bits remain.
+ *
+ * @bitmap: the features bitmap the peer is asking for
+ * @supportmap: what do we support
+ * @smlen: how long is our supportmap
+ */
+static bool requires_unsupported_features(const u8 *bitmap,
+					  const u8 *supportmap,
+					  size_t smlen)
+{
+	size_t len = tal_count(bitmap);
+	u8 support;
+	for (size_t i=0; i<len; i++) {
+		/* Find matching bitmap byte in supportmap, 0x00 if none */
+		if (len > smlen) {
+			support = 0x00;
+		} else {
+			support = supportmap[smlen-1];
+		}
+
+		/* Cancel out supported bits, check for even bits */
+		if ((~support & bitmap[i]) & 0x55)
+			return true;
+	}
+	return false;
+}
+
+bool unsupported_features(const u8 *gfeatures, const u8 *lfeatures)
+{
+	return requires_unsupported_features(gfeatures,
+					     supported_global_features,
+					     sizeof(supported_global_features))
+		|| requires_unsupported_features(lfeatures,
+						 supported_local_features,
+						 sizeof(supported_local_features));
+}