From 122926f9f6bc413d02ed6a8765b81c0e3ef6dcfe Mon Sep 17 00:00:00 2001
From: Marcos Kirsch <bitbucket@kirsch.com.mx>
Date: Sun, 19 Jul 2015 13:32:59 -0500
Subject: [PATCH] Remove tabs, minor rework and comment updates

---
 httpserver-b64decode.lua | 65 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100755 httpserver-b64decode.lua

diff --git a/httpserver-b64decode.lua b/httpserver-b64decode.lua
new file mode 100755
index 0000000..e18bea6
--- /dev/null
+++ b/httpserver-b64decode.lua
@@ -0,0 +1,65 @@
+#!/usr/local/bin/lua
+-- httpserver-b64decode.lua
+-- Part of nodemcu-httpserver, contains b64 decoding used for HTTP Basic Authentication.
+-- Based on http://lua-users.org/wiki/BaseSixtyFour by Alex Kloss
+-- compatible with lua 5.1
+-- http://www.it-rfc.de
+-- Author: Marcos Kirsch
+
+-- bitshift functions (<<, >> equivalent)
+-- shift left
+local function lsh(value,shift)
+   return (value*(2^shift)) % 256
+end
+
+-- shift right
+local function rsh(value,shift)
+   -- Lua builds with no floating point don't define math.
+   if math then return math.floor(value/2^shift) % 256 end
+   return (value/2^shift) % 256
+end
+
+-- return single bit (for OR)
+local function bit(x,b)
+   return (x % 2^b - x % 2^(b-1) > 0)
+end
+
+-- logic OR for number values
+local function lor(x,y)
+   result = 0
+   for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end
+   return result
+end
+
+-- Character decoding table
+local function toBase64Byte(char)
+   ascii = string.byte(char, 1)
+   if ascii >= string.byte('A', 1) and ascii <= string.byte('Z', 1) then return ascii - string.byte('A', 1)
+   elseif ascii >= string.byte('a', 1) and ascii <= string.byte('z', 1) then return ascii - string.byte('a', 1) + 26
+   elseif ascii >= string.byte('0', 1) and ascii <= string.byte('9', 1) then return ascii + 4
+   elseif ascii == string.byte('-', 1) then return 62
+   elseif ascii == string.byte('_', 1) then return 63
+   elseif ascii == string.byte('=', 1) then return nil
+   else return nil, "ERROR! Char is invalid for Base64 encoding: "..char end
+end
+
+
+-- decode base64 input to string
+return function(data)
+   local chars = {}
+   local result=""
+   for dpos=0,string.len(data)-1,4 do
+      for char=1,4 do chars[char] = toBase64Byte((string.sub(data,(dpos+char),(dpos+char)) or "=")) end
+         result = string.format(
+         '%s%s%s%s',
+         result,
+         string.char(lor(lsh(chars[1],2), rsh(chars[2],4))),
+         (chars[3] ~= nil) and string.char(lor(lsh(chars[2],4),
+         rsh(chars[3],2))) or "",
+         (chars[4] ~= nil) and string.char(lor(lsh(chars[3],6) % 192,
+         (chars[4]))) or ""
+      )
+   end
+   return result
+end
+