@@ -1,4 +1,15 @@
+local sanitable = {
+	['\xfe'] = '\xf0';
+	['\1'] = '\xf1';
+	['\2'] = '\xf2';
+	['\3'] = '\xf3';
+
+	['\xf0'] = '\xfe';
+	['\xf1'] = '\1';
+	['\xf2'] = '\2';
+	['\xf3'] = '\3';
+}
 return {
 	capitalize = function(str)
 		return string.upper(string.sub(str, 1,1)) .. string.sub(str, 2)
 	end;
@@ -35,5 +46,31 @@
 			str = string.sub(str, 1, #str - 1)
 		end
 		return str
 	end;
+
+	meta_armor = function(str,mark_struct)
+		-- binary values stored in metadata need to be sanitized so
+		-- they don't contain values that will disrupt parsing of the
+		-- KV store, as minetest (stupidly) uses in-band signalling
+		local sanitized = string.gsub(str, '[\xfe\1\2\3]', function(char)
+			return '\xfe' .. sanitable[char]
+		end)
+		if sanitized ~= str and mark_struct then
+			-- use different type code to mark struct headers for
+			-- back-compat
+			return string.gsub(sanitized,'^\xfe\xf0\x99','\xfe\x98')
+		else return sanitized end
+	end;
+	meta_dearmor = function(str,cond)
+		local dearmor = function(s)
+			return string.gsub(s, '\xfe([\xf0\xf1\xf2\xf3])', function(char)
+				return sanitable[char]
+			end)
+		end
+		if cond then
+			if string.sub(str,1,2) == '\xfe\x98' then
+				return dearmor(string.gsub(str,'^\xfe\x98','\xfe\xf0\x99'))
+			else return str end
+		else return dearmor(str) end
+	end;
 }