bitcoin_tx: add helper for extracting output amount

bitcoin/tx.c

@@ -263,6 +263,16 @@ struct amount_asset bitcoin_tx_output_get_amount(const struct bitcoin_tx *tx,
 	return amount;
 }
 
+void bitcoin_tx_output_get_amount_sat(struct bitcoin_tx *tx, int outnum,
+				      struct amount_sat *amount)
+{
+	struct amount_asset asset_amt;
+	asset_amt = bitcoin_tx_output_get_amount(tx, outnum);
+	assert(amount_asset_is_main(&asset_amt));
+	*amount = amount_asset_to_sat(&asset_amt);
+}
+
+
 void bitcoin_tx_input_set_witness(struct bitcoin_tx *tx, int innum,
 				  u8 **witness)
 {

bitcoin/tx.h

@@ -115,6 +115,13 @@ void bitcoin_tx_output_set_amount(struct bitcoin_tx *tx, int outnum,
  */
 const u8 *bitcoin_tx_output_get_script(const tal_t *ctx, const struct bitcoin_tx *tx, int outnum);
 
+/** bitcoin_tx_output_get_amount_sat - Helper to get transaction output's amount
+ *
+ * Internally we use a `wally_tx` to represent the transaction. The
+ * satoshi amount isn't a struct amount_sat, so we need a conversion
+ */
+void bitcoin_tx_output_get_amount_sat(struct bitcoin_tx *tx, int outnum,
+				      struct amount_sat *amount);
 /**
  * Helper to just get an amount_sat for the output amount.
  */