libs/core: introduce luci.util.imatch()

libs/core/luasrc/util.lua

@@ -282,6 +282,22 @@ function cmatch(str, pat)
 	return count
 end
 
+--- Return a matching iterator for the given value. The iterator will return
+-- one token per invocation, the tokens are separated by whitespace. If the
+-- input value is a table, it is transformed into a string first. A nil value
+-- will result in a valid interator which aborts with the first invocation.
+-- @param val		The value to scan (table, string or nil)
+-- @return			Iterator which returns one token per call
+function imatch(v)
+	if v == nil then
+		v = ""
+	elseif type(v) == "table" then
+		v = table.concat(v, " ")
+	end
+
+	return v:gmatch("%S+")
+end
+
 --- Parse certain units from the given string and return the canonical integer
 -- value or 0 if the unit is unknown. Upper- or lower case is irrelevant.
 -- Recognized units are: