Index: trunk/src/attrib.c
===================================================================
--- trunk/src/attrib.c	(revision 10797)
+++ trunk/src/attrib.c	(revision 10798)
@@ -76,6 +76,7 @@
 	i = list->Number;
 	list->List[i].name = pcb_strdup_null(name);
 	list->List[i].value = pcb_strdup_null(value);
+	list->List[i].cpb_written = 1;
 	NOTIFY(list, list->List[i].name, list->List[i].value);
 	list->Number++;
 	return 0;
@@ -128,3 +129,36 @@
 		pcb_attribute_put(dest, src->List[i].name, src->List[i].value, replace);
 }
 
+
+void pcb_attribute_copyback_begin(pcb_attribute_list_t *dst)
+{
+	int i;
+
+	for (i = 0; i < dst->Number; i++)
+		dst->List[i].cpb_written = 0;
+}
+
+void pcb_attribute_copyback(pcb_attribute_list_t *dst, const char *name, const char *value)
+{
+	int i;
+	for (i = 0; i < dst->Number; i++) {
+		if (strcmp(name, dst->List[i].name) == 0) {
+			dst->List[i].cpb_written = 1;
+			if (strcmp(value, dst->List[i].value) != 0) {
+				free(dst->List[i].value);
+				dst->List[i].value = pcb_strdup(value);
+				NOTIFY(dst, dst->List[i].name, dst->List[i].value);
+			}
+			return;
+		}
+	}
+}
+
+void pcb_attribute_copyback_end(pcb_attribute_list_t *dst)
+{
+	int i;
+	for (i = 0; i < dst->Number; i++)
+		if (!dst->List[i].cpb_written)
+			pcb_attribute_remove_idx(dst, i);
+}
+
Index: trunk/src/attrib.h
===================================================================
--- trunk/src/attrib.h	(revision 10797)
+++ trunk/src/attrib.h	(revision 10798)
@@ -34,6 +34,7 @@
 typedef struct pcb_attribute_s {
 	char *name;
 	char *value;
+	unsigned cpb_written:1; /* copyback: written */
 } pcb_attribute_t;
 
 struct pcb_attribute_list_s {
@@ -45,6 +46,8 @@
 /* Returns NULL if the name isn't found, else the value for that named
    attribute.  */
 char *pcb_attribute_get(pcb_attribute_list_t * list, const char *name);
+pcb_attribute_t *pcb_attribute_get_attr(pcb_attribute_list_t * list, const char *name);
+
 /* Adds an attribute to the list.  If the attribute already exists,
    whether it's replaced or a second copy added depends on
    REPLACE.  Returns non-zero if an existing attribute was replaced.  */
@@ -67,4 +70,9 @@
 /* Copy eacg attribute from src to dest */
 void pcb_attribute_copy_all(pcb_attribute_list_t *dest, const pcb_attribute_list_t *src, int replace);
 
+/* Copy back a mirrored attribute list, minimizing the changes */
+void pcb_attribute_copyback_begin(pcb_attribute_list_t *dst);
+void pcb_attribute_copyback(pcb_attribute_list_t *dst, const char *name, const char *value);
+void pcb_attribute_copyback_end(pcb_attribute_list_t *dst);
+
 #endif