+function hexstring(val)
+ if val then
+ return (val:match("^[a-fA-F0-9]+$") ~= nil)
+ end
+ return false
+end
+
+function hex(val, maxbytes)
+ maxbytes = tonumber(maxbytes)
+ if val and maxbytes ~= nil then
+ return ((val:match("^0x[a-fA-F0-9]+$") ~= nil) and (#val <= 2 + maxbytes * 2))
+ end
+ return false
+end
+
+function base64(val)
+ if val then
+ return (val:match("^[a-zA-Z0-9/+]+=?=?$") ~= nil) and (math.fmod(#val, 4) == 0)
+ end
+ return false
+end
+