Index: trunk/src/extobj.c
===================================================================
--- trunk/src/extobj.c	(revision 25603)
+++ trunk/src/extobj.c	(revision 25604)
@@ -28,22 +28,58 @@
 
 #include <genvector/vtp0.h>
 #include <genht/htsi.h>
+#include <genht/hash.h>
 
 #include "extobj.h"
 
 
-vtp0_t extobj_i2o;  /* extobj_idx -> (pcb_ext_obj_t *) */
-htsi_t extobj_n2i;  /* extobj name -> index */
+static htsi_t pcb_extobj_n2i;  /* extobj name -> index */
+vtp0_t pcb_extobj_i2o;         /* extobj_idx -> (pcb_ext_obj_t *) */
+int pcb_extobj_invalid;        /* this changes upon each new extobj reg, forcing the caches to be invalidated eventually */
 
+void pcb_extobj_unreg(pcb_extobj_t *o)
+{
+	if (!o->registered)
+		return;
+	htsi_pop(&pcb_extobj_n2i, o->name);
+	vtp0_set(&pcb_extobj_i2o, o->idx, NULL);
+	o->registered = 0;
+	o->idx = 0;
+}
 
+void pcb_extobj_reg(pcb_extobj_t *o)
+{
+	o->idx = pcb_extobj_i2o.used;
+	vtp0_append(&pcb_extobj_i2o, o);
+	o->registered = 0;
+	htsi_set(&pcb_extobj_n2i, (char *)o->name, o->idx);
+	pcb_extobj_invalid = -o->idx;
+}
+
+int pcb_extobj_lookup_idx(const char *name)
+{
+	return htsi_get(&pcb_extobj_n2i, (char *)name);
+}
+
 void pcb_extobj_init(void)
 {
+	vtp0_init(&pcb_extobj_i2o);
+	htsi_init(&pcb_extobj_n2i, strhash, strkeyeq);
 
+	vtp0_append(&pcb_extobj_i2o, NULL); /* idx=0 is reserved for no extended obj */
 }
 
 
 void pcb_extobj_uninit(void)
 {
+	size_t n;
 
+	for(n = 0; n < pcb_extobj_i2o.used; n++) {
+		pcb_extobj_t *o = pcb_extobj_i2o.array[n];
+		if (o != NULL)
+			pcb_extobj_unreg(o);
+	}
+	htsi_uninit(&pcb_extobj_n2i);
+	vtp0_uninit(&pcb_extobj_i2o);
 }
 
Index: trunk/src/extobj.h
===================================================================
--- trunk/src/extobj.h	(revision 25603)
+++ trunk/src/extobj.h	(revision 25604)
@@ -27,14 +27,55 @@
 #ifndef PCB_EXT_OBJ_H
 #define PCB_EXT_OBJ_H
 
+#include <genvector/vtp0.h>
+
 #include "obj_common.h"
 #include "draw.h"
 
-struct pcb_ext_obj_s {
+
+typedef struct pcb_extobj_s pcb_extobj_t;
+
+struct pcb_extobj_s {
+	/* static data - filled in by the extobj code */
+	const char *name;
 	void (*draw)(pcb_draw_info_t *info, pcb_any_obj_t *obj);
+
+	/* dynamic data - filled in by core */
+	int idx;
+	unsigned registered:1;
 };
 
 void pcb_extobj_init(void);
 void pcb_extobj_uninit(void);
 
+void pcb_extobj_unreg(pcb_extobj_t *o);
+void pcb_extobj_reg(pcb_extobj_t *o);
+
+int pcb_extobj_lookup_idx(const char *name);
+
+extern int pcb_extobj_invalid; /* this changes upon each new extobj reg, forcing the caches to be invalidated eventually */
+extern vtp0_t pcb_extobj_i2o;  /* extobj_idx -> (pcb_ext_obj_t *) */
+
+PCB_INLINE pcb_extobj_t *pcb_extobj_get(pcb_any_obj_t *obj)
+{
+	pcb_extobj_t **eo;
+
+	if ((obj->extobj == NULL) || (obj->extobj_idx == pcb_extobj_invalid))
+		return NULL; /* known negative */
+
+	if (obj->extobj_idx <= 0) { /* invalid idx cache - look up by name */
+		obj->extobj_idx = pcb_extobj_lookup_idx(obj->extobj);
+		if (obj->extobj_idx == 0) { /* no such name */
+			obj->extobj_idx = pcb_extobj_invalid; /* make the next lookup cheaper */
+			return NULL;
+		}
+	}
+
+	eo = (pcb_extobj_t **)vtp0_get(&pcb_extobj_i2o, obj->extobj_idx, 0);
+	if ((eo == NULL) || (*eo == NULL)) /* extobj backend got deregistered meanwhile */
+		obj->extobj_idx = pcb_extobj_invalid; /* make the next lookup cheaper */
+	return *eo;
+}
+
+
 #endif
Index: trunk/src/obj_common.h
===================================================================
--- trunk/src/obj_common.h	(revision 25603)
+++ trunk/src/obj_common.h	(revision 25604)
@@ -186,7 +186,7 @@
 	PCB_ANY_OBJ_FIELDS; \
 	const char           *term; \
 	const char           *extobj; \
-	unsigned int         extobj_idx; \
+	int                  extobj_idx; \
 	void                 *ratconn; \
 	unsigned char        thermal; \
 	unsigned char        intconn, intnoconn; \