|
local SEQ = { |
|
[0] = "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 STRING_FAST = {} |
|
local INDEX = {[61] = 0, [65] = 0} |
|
|
|
for key, val in ipairs(SEQ) do |
|
-- memoization |
|
INDEX[string.byte(val)] = key |
|
end |
|
|
|
-- string.char has a MASSIVE overhead, its faster to precompute |
|
-- the values for performance |
|
for i = 0, 255 do |
|
local c = string.char(i) |
|
STRING_FAST[i] = c |
|
end |
|
|
|
local b64 = {} |
|
|
|
function b64.encode(str) |
|
local len = string.len(str) |
|
local output = table.create(math.ceil(len/4)*4) |
|
local index = 1 |
|
|
|
for i = 1, len, 3 do |
|
local b0, b1, b2 = string.byte(str, i, i + 2) |
|
local b = bit32.lshift(b0, 16) + bit32.lshift(b1 or 0, 8) + (b2 or 0) |
|
|
|
output[index] = SEQ[bit32.extract(b, 18, 6)] |
|
output[index + 1] = SEQ[bit32.extract(b, 12, 6)] |
|
output[index + 2] = b1 and SEQ[bit32.extract(b, 6, 6)] or "=" |
|
output[index + 3] = b2 and SEQ[bit32.band(b, 63)] or "=" |
|
|
|
index += 4 |
|
end |
|
|
|
return table.concat(output) |
|
end |
|
|
|
function b64.decode(hash) |
|
-- given a 24 bit word (4 6-bit letters), decode 3 bytes from it |
|
local len = string.len(hash) |
|
local output = table.create(len * 0.75) |
|
|
|
local index = 1 |
|
for i = 1, len, 4 do |
|
local c0, c1, c2, c3 = string.byte(hash, i, i + 3) |
|
|
|
local b = |
|
bit32.lshift(INDEX[c0], 18) |
|
+ bit32.lshift(INDEX[c1], 12) |
|
+ bit32.lshift(INDEX[c2], 6) |
|
+ (INDEX[c3]) |
|
|
|
|
|
output[index] = STRING_FAST[bit32.extract(b, 16, 8)] |
|
output[index + 1] = c2 ~= "=" and STRING_FAST[bit32.extract(b, 8, 8)] or "=" |
|
output[index + 2] = c3 ~= "=" and STRING_FAST[bit32.band(b, 0xFF)] or "=" |
|
index += 3 |
|
end |
|
|
|
return table.concat(output) |
|
end |
|
|
|
return b64 |
