Lua - Base64 Fast Encode

b64fastenc.lua

local encodeByte = {
	'A','B','C','D','E','F','G','H',
	'I','J','K','L','M','N','O','P',
	'Q','R','S','T','U','V','W','X',
	'Y','Z','a','b','c','d','e','f',
	'g','h','i','j','k','l','m','n',
	'o','p','q','r','s','t','u','v',
	'w','x','y','z','0','1','2','3',
	'4','5','6','7','8','9','-','_',
}
local byte = string.byte
local concat = table.concat
local function b64fastenc(data)
	local out = {}
	local nout = 1
	local ndata = #data

	for i = 1, ndata-ndata%3, 3 do
		local b1,b2,b3 = byte(data, i, i+2)

		local b1r = b1/4
		local b2r = b2/16
		local b3r = b3/64

		local x = b1%4*16
		local v = b2%16*4
		local y = b2r%256 - b2r%1
		local w = b3r%256 - b3r%1

		local x0,x1,x2,x3,x4,x5,x6,x7,x8 = x%1,x%2,x%4,x%8,x%16,x%32,x%64,x%128,x%256
		local y0,y1,y2,y3,y4,y5,y6,y7,y8 = y%1,y%2,y%4,y%8,y%16,y%32,y%64,y%128,y%256
		local v0,v1,v2,v3,v4,v5,v6,v7,v8 = v%1,v%2,v%4,v%8,v%16,v%32,v%64,v%128,v%256
		local w0,w1,w2,w3,w4,w5,w6,w7,w8 = w%1,w%2,w%4,w%8,w%16,w%32,w%64,w%128,w%256

		out[nout] = encodeByte[1 + b1r%256 - b1r%1]
		out[nout+1] = encodeByte[1
		+ ((x1 - x0 ~= 0 or y1 - y0 ~= 0) and 1 or 0)
		+ ((x2 - x1 ~= 0 or y2 - y1 ~= 0) and 2 or 0)
		+ ((x3 - x2 ~= 0 or y3 - y2 ~= 0) and 4 or 0)
		+ ((x4 - x3 ~= 0 or y4 - y3 ~= 0) and 8 or 0)
		+ ((x5 - x4 ~= 0 or y5 - y4 ~= 0) and 16 or 0)
		+ ((x6 - x5 ~= 0 or y6 - y5 ~= 0) and 32 or 0)
		+ ((x7 - x6 ~= 0 or y7 - y6 ~= 0) and 64 or 0)
		+ ((x8 - x7 ~= 0 or y8 - y7 ~= 0) and 128 or 0)]
		out[nout+2] = encodeByte[1
		+ ((v1 - v0 ~= 0 or w1 - w0 ~= 0) and 1 or 0)
		+ ((v2 - v1 ~= 0 or w2 - w1 ~= 0) and 2 or 0)
		+ ((v3 - v2 ~= 0 or w3 - w2 ~= 0) and 4 or 0)
		+ ((v4 - v3 ~= 0 or w4 - w3 ~= 0) and 8 or 0)
		+ ((v5 - v4 ~= 0 or w5 - w4 ~= 0) and 16 or 0)
		+ ((v6 - v5 ~= 0 or w6 - w5 ~= 0) and 32 or 0)
		+ ((v7 - v6 ~= 0 or w7 - w6 ~= 0) and 64 or 0)
		+ ((v8 - v7 ~= 0 or w8 - w7 ~= 0) and 128 or 0)]
		out[nout+3] = encodeByte[1 + b3 % 64]
		nout = nout + 4
	end

	if -ndata%3 > 0 then
		local i = ndata-ndata%3
		local b1 = byte(data, i+1) or 0
		local b2 = byte(data, i+2) or 0
		local b3 = byte(data, i+3) or 0

		local b1r = b1/4
		local b2r = b2/16
		local b3r = b3/64

		local x = b1%4*16
		local v = b2%16*4
		local y = b2r%256 - b2r%1
		local w = b3r%256 - b3r%1

		local x0,x1,x2,x3,x4,x5,x6,x7,x8 = x%1,x%2,x%4,x%8,x%16,x%32,x%64,x%128,x%256
		local y0,y1,y2,y3,y4,y5,y6,y7,y8 = y%1,y%2,y%4,y%8,y%16,y%32,y%64,y%128,y%256
		local v0,v1,v2,v3,v4,v5,v6,v7,v8 = v%1,v%2,v%4,v%8,v%16,v%32,v%64,v%128,v%256
		local w0,w1,w2,w3,w4,w5,w6,w7,w8 = w%1,w%2,w%4,w%8,w%16,w%32,w%64,w%128,w%256

		out[nout] = encodeByte[1 + b1r%256 - b1r%1]
		out[nout+1] = encodeByte[1
		+ ((x1 - x0 ~= 0 or y1 - y0 ~= 0) and 1 or 0)
		+ ((x2 - x1 ~= 0 or y2 - y1 ~= 0) and 2 or 0)
		+ ((x3 - x2 ~= 0 or y3 - y2 ~= 0) and 4 or 0)
		+ ((x4 - x3 ~= 0 or y4 - y3 ~= 0) and 8 or 0)
		+ ((x5 - x4 ~= 0 or y5 - y4 ~= 0) and 16 or 0)
		+ ((x6 - x5 ~= 0 or y6 - y5 ~= 0) and 32 or 0)
		+ ((x7 - x6 ~= 0 or y7 - y6 ~= 0) and 64 or 0)
		+ ((x8 - x7 ~= 0 or y8 - y7 ~= 0) and 128 or 0)] or '='
		out[nout+2] = ndata-i > 1 and encodeByte[1
		+ ((v1 - v0 ~= 0 or w1 - w0 ~= 0) and 1 or 0)
		+ ((v2 - v1 ~= 0 or w2 - w1 ~= 0) and 2 or 0)
		+ ((v3 - v2 ~= 0 or w3 - w2 ~= 0) and 4 or 0)
		+ ((v4 - v3 ~= 0 or w4 - w3 ~= 0) and 8 or 0)
		+ ((v5 - v4 ~= 0 or w5 - w4 ~= 0) and 16 or 0)
		+ ((v6 - v5 ~= 0 or w6 - w5 ~= 0) and 32 or 0)
		+ ((v7 - v6 ~= 0 or w7 - w6 ~= 0) and 64 or 0)
		+ ((v8 - v7 ~= 0 or w8 - w7 ~= 0) and 128 or 0)] or '='
		out[nout+3] = ndata-i > 2 and encodeByte[1 + b3 % 64] or '='
		nout = nout + 4
	end

	return concat(out)
end