local byte, char, concat = string.byte, string.char, table.concat
local band, bxor, rshift, lshift = bit32.band, bit32.bxor, bit32.rshift, bit32.lshift
local wait = function() end
local B64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
local B64R = {}
for i = 1, #B64 do B64R[byte(B64, i)] = i - 1 end
local function b64(s)
    local out, cur = {}, {}
    local acc, bits = 0, 0
    for i = 1, #s do
        local c = byte(s, i)
        if c == 61 then break end
        local v = B64R[c]
        if v then
            acc = acc * 64 + v
            bits = bits + 6
            if bits >= 8 then
                bits = bits - 8
                cur[#cur + 1] = char(band(rshift(acc, bits), 255))
                acc = band(acc, lshift(1, bits) - 1)
                if #cur >= 4096 then out[#out + 1] = concat(cur); cur = {} end
            end
        end
    end
    out[#out + 1] = concat(cur)
    return concat(out)
end
local function decrypt(s, key)
    local n = #key
    if n == 0 then return nil end
    local out, cur = {}, {}
    for i = 1, #s do
        local x = bxor(byte(s, i), byte(key, ((i - 1) % n) + 1))
        x = bxor(x, band(i, 255))
        x = bxor(x, band(rshift(i, 8), 255))
        cur[#cur + 1] = char(x)
        if #cur >= 4096 then out[#out + 1] = concat(cur); cur = {} end
    end
    out[#out + 1] = concat(cur)
    return concat(out)
end

local B64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
local function b64enc(s)
    local out, cur, cn = {}, {}, 0
    local i, len = 1, #s
    while i + 2 <= len do
        local a, b, c = byte(s, i, i + 2)
        local x = a * 65536 + b * 256 + c
        cn = cn + 1
        cur[cn] = string.sub(B64, band(rshift(x, 18), 63) + 1, band(rshift(x, 18), 63) + 1)
            .. string.sub(B64, band(rshift(x, 12), 63) + 1, band(rshift(x, 12), 63) + 1)
            .. string.sub(B64, band(rshift(x, 6), 63) + 1, band(rshift(x, 6), 63) + 1)
            .. string.sub(B64, band(x, 63) + 1, band(x, 63) + 1)
        if cn >= 4096 then out[#out + 1] = concat(cur); cur = {}; cn = 0 end
        i = i + 3
    end
    local rem = len - i + 1
    if rem > 0 then
        local a, b = byte(s, i, i + 1)
        local x = a * 65536 + (b or 0) * 256
        cn = cn + 1
        cur[cn] = string.sub(B64, band(rshift(x, 18), 63) + 1, band(rshift(x, 18), 63) + 1)
            .. string.sub(B64, band(rshift(x, 12), 63) + 1, band(rshift(x, 12), 63) + 1)
            .. (rem == 2 and string.sub(B64, band(rshift(x, 6), 63) + 1, band(rshift(x, 6), 63) + 1) or "=")
            .. "="
    end
    out[#out + 1] = concat(cur)
    return concat(out)
end
local n = 619155
local t = {}
for i = 1, n do t[i] = char((i * 37) % 256) end
local data = concat(t)
local key = "0123456789abcdef0123456789abcdef"
local enc = b64enc(data)
print("sizes", #data, #enc)
local t0 = os.clock(); local d = b64(enc)
print("b64", string.format("%.4f", os.clock() - t0), #d, d == data)
local t1 = os.clock(); local o = decrypt(data, key)
print("dec", string.format("%.4f", os.clock() - t1), #o)