psbt_open: method for adding a witness_stack to a psbt input

Set a stack of witnesses onto a PSBT input

common/psbt_open.c

@@ -471,3 +471,15 @@ bool psbt_has_required_fields(struct wally_psbt *psbt)
 
 	return true;
 }
+
+void psbt_input_set_final_witness_stack(struct wally_psbt_input *in,
+					const struct witness_element **elements)
+{
+	wally_tx_witness_stack_init_alloc(tal_count(elements),
+					  &in->final_witness);
+
+	for (size_t i = 0; i < tal_count(elements); i++)
+		wally_tx_witness_stack_add(in->final_witness,
+					   elements[i]->witness,
+					   tal_bytelen(elements[i]->witness));
+}

common/psbt_open.h

@@ -14,6 +14,7 @@ struct wally_psbt;
 struct wally_psbt_input;
 struct wally_psbt_output;
 struct wally_map;
+struct witness_element;
 
 struct input_set {
 	struct wally_tx_input tx_input;
@@ -140,4 +141,11 @@ int psbt_find_serial_output(struct wally_psbt *psbt, u16 serial_id);
  */
 bool psbt_has_required_fields(struct wally_psbt *psbt);
 
+/* psbt_input_set_final_witness_stack - Set the witness stack for PSBT input
+ *
+ * @in - input to set final_witness for
+ * @witness_element - elements to add to witness stack
+ */
+void psbt_input_set_final_witness_stack(struct wally_psbt_input *in,
+					const struct witness_element **elements);
 #endif /* LIGHTNING_COMMON_PSBT_OPEN_H */