common: add programatic initialization of msat

common/amount.c

@@ -370,6 +370,16 @@ bool amount_msat_to_u32(struct amount_msat msat, u32 *millisatoshis)
 	return true;
 }
 
+void amount_msat_from_u64(struct amount_msat *msat, u64 millisatoshis)
+{
+	msat->millisatoshis = millisatoshis;
+}
+
+void amount_msat_from_sat_u64(struct amount_msat *msat, u64 satoshis)
+{
+	msat->millisatoshis = satoshis * 1000;
+}
+
 bool amount_msat_fee(struct amount_msat *fee,
 		     struct amount_msat amt,
 		     u32 fee_base_msat,

common/amount.h

@@ -102,6 +102,10 @@ bool amount_msat_less_eq_sat(struct amount_msat msat, struct amount_sat sat);
 WARN_UNUSED_RESULT bool amount_msat_to_u32(struct amount_msat msat,
 					   u32 *millisatoshis);
 
+/* Programatically initialize from various types */
+void amount_msat_from_u64(struct amount_msat *msat, u64 millisatoshis);
+void amount_msat_from_sat_u64(struct amount_msat *msat, u64 satoshis);
+
 /* Common operation: what is the HTLC fee for given feerate?  Can overflow! */
 WARN_UNUSED_RESULT bool amount_msat_fee(struct amount_msat *fee,
 					struct amount_msat amt,