+
+# Case conversion macros. Taken from
+# http://git.buildroot.net/buildroot/tree/package/pkg-utils.mk. This
+# is inspired by the 'up' macro from gmsl (http://gmsl.sf.net). It is
+# optimised very heavily because these macros are used a lot. It is
+# about 5 times faster than forking a shell and tr.
+#
+# The caseconvert-helper creates a definition of the case conversion macro.
+# After expansion by the outer $(eval ), the UPPERCASE macro is defined as:
+# $(strip $(eval __tmp := $(1)) $(eval __tmp := $(subst a,A,$(__tmp))) ... )
+# In other words, every letter is substituted one by one.
+#
+# The caseconvert-helper allows us to create this definition out of the
+# [FROM] and [TO] lists, so we don't need to write down every substition
+# manually. The uses of $ and $$ quoting are chosen in order to do as
+# much expansion as possible up-front.
+#
+# Note that it would be possible to conceive a slightly more optimal
+# implementation that avoids the use of __tmp, but that would be even
+# more unreadable and is not worth the effort.
+
+[FROM] := a b c d e f g h i j k l m n o p q r s t u v w x y z - .
+[TO] := A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _ _
+
+define caseconvert-helper
+$(1) = $$(strip \
+ $$(eval __tmp := $$(1))\
+ $(foreach c, $(2),\
+ $$(eval __tmp := $$(subst $(word 1,$(subst :, ,$c)),$(word 2,$(subst :, ,$c)),$$(__tmp))))\
+ $$(__tmp))
+endef
+
+$(eval $(call caseconvert-helper,UPPERCASE,$(join $(addsuffix :,$([FROM])),$([TO]))))
+$(eval $(call caseconvert-helper,LOWERCASE,$(join $(addsuffix :,$([TO])),$([FROM]))))