Index: trunk/src/obj_pstk.c
===================================================================
--- trunk/src/obj_pstk.c	(revision 22087)
+++ trunk/src/obj_pstk.c	(revision 22088)
@@ -1435,3 +1435,15 @@
 		pcb_r_insert_entry(data->padstack_tree, (pcb_box_t *)pstk);
 	pcb_poly_clear_from_poly(data, PCB_OBJ_PSTK, NULL, pstk);
 }
+
+pcb_layer_id_t pcb_proto_board_layer_for(const pcb_data_t *data, pcb_layer_type_t mask, pcb_layer_combining_t comb)
+{
+	pcb_layer_id_t lid;
+	pcb_layer_t *ly;
+	for(lid = 0, ly = data->Layer; lid < data->LayerN; lid++,ly++) {
+		pcb_layer_type_t typ = pcb_layer_flags_(ly);
+		if ((typ == mask) && (ly->comb == comb))
+			return lid;
+	}
+	return -1;
+}
Index: trunk/src/obj_pstk.h
===================================================================
--- trunk/src/obj_pstk.h	(revision 22087)
+++ trunk/src/obj_pstk.h	(revision 22088)
@@ -281,6 +281,11 @@
 #define pcb_proto_num_layers 8
 const pcb_proto_layer_t pcb_proto_layers[pcb_proto_num_layers];
 
+
+/* Return the id of a board layer that matches a mask:comb pair or invalid if
+   nothing matched */
+pcb_layer_id_t pcb_proto_board_layer_for(const pcb_data_t *data, pcb_layer_type_t mask, pcb_layer_combining_t comb);
+
 /*** hash ***/
 unsigned int pcb_pstk_proto_hash(const pcb_pstk_proto_t *p);
 int pcb_pstk_proto_eq(const pcb_pstk_proto_t *p1, const pcb_pstk_proto_t *p2);