diff --git a/core/definitions.mk b/core/definitions.mk
index e6f4a04..89ffcf7 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -1928,6 +1928,42 @@
 	$(hide) rm $@.tmpjill.jack
 endef
 
+# Moves $1.tmp to $1 if necessary. This is designed to be used with
+# .KATI_RESTAT. For kati, this function doesn't update the timestamp
+# of $1 when $1.tmp is identical to $1 so that ninja won't rebuild
+# targets which depend on $1. For GNU make, this function simply
+# copies $1.tmp to $1.
+ifeq ($(BUILDING_WITH_NINJA),true)
+define commit-change-for-toc
+$(hide) if cmp -s $1.tmp $1 ; then \
+ rm $1.tmp ; \
+else \
+ mv $1.tmp $1 ; \
+fi
+endef
+else
+define commit-change-for-toc
+@# make doesn't support restat. We always update .toc files so the dependents will always be updated too.
+$(hide) mv $1.tmp $1
+endef
+endif
+
+## Rule to creates a table of contents from a .jar file.
+## Must be called with $(eval).
+# $1: A .jar file
+define _transform-jar-to-toc
+$1.toc: $1 | $(IJAR)
+	@echo Generating TOC: $$@
+	$(hide) $(IJAR) $$< $$@.tmp
+	$$(call commit-change-for-toc,$$@)
+endef
+
+## Define a rule which generates .jar.toc and mark it as .KATI_RESTAT.
+define define-jar-to-toc-rule
+$(eval $(call _transform-jar-to-toc,$1))
+$(eval .KATI_RESTAT: $1.toc)
+endef
+
 
 # Invoke Jack to compile java from source to jack files without shrink or obfuscation.
 #