util.id: New util for producing random identifiers of varying sizes

util/id.lua

@@ -0,0 +1,26 @@
+-- Prosody IM
+-- Copyright (C) 2008-2017 Matthew Wild
+-- Copyright (C) 2008-2017 Waqas Hussain
+-- Copyright (C) 2008-2017 Kim Alvefur
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+local s_gsub = string.gsub;
+local random_bytes = require "util.random".bytes;
+local base64_encode = require "util.encodings".base64.encode;
+
+local b64url = { ["+"] = "-", ["/"] = "_", ["="] = "" };
+local function b64url_random(len)
+	return (s_gsub(base64_encode(random_bytes(len)), "[+/=]", b64url));
+end
+
+return {
+	short =  function () return b64url_random(6); end;
+	medium = function () return b64url_random(12); end;
+	long =   function () return b64url_random(24); end;
+	custom = function (size)
+		return function () return b64url_random(size); end;
+	end;
+}