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@actboy168
Created October 10, 2020 09:28
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local string_char = string.char
local string_byte = string.byte
local table_concat = table.concat
local pairs = pairs
local encoder = {}
local decoder = {}
for i, char in pairs {
'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','+','/'
} do
local b64code = i - 1
local charcode = string_byte(char)
encoder[b64code] = charcode
decoder[charcode] = b64code
end
local function encode(data)
local s = {}
local n = 1
local last = #data % 3
for i = 1, #data-last, 3 do
local a, b, c = string_byte(data, i, i+2)
local v = a*0x10000 + b*0x100 + c
s[n] = string_char(encoder[(v >> 18) & 0x3f], encoder[(v >> 12) & 0x3f], encoder[(v >> 6) & 0x3f], encoder[v & 0x3f])
n = n + 1
end
if last == 2 then
local a, b = string_byte(data, -2, -1)
local v = a*0x10000 + b*0x100
s[n] = string_char(encoder[(v >> 18) & 0x3f], encoder[(v >> 12) & 0x3f], encoder[(v >> 6) & 0x3f], 61--[[ "=" ]])
elseif last == 1 then
local v = string_byte(data, -1)*0x10000
s[n] = string_char(encoder[(v >> 18) & 0x3f], encoder[(v >> 12) & 0x3f], 61--[[ "=" ]], 61--[[ "=" ]])
end
return table_concat(s)
end
local function decode(data)
local s = {}
local n = 1
for i = 1, #data - 4, 4 do
local a, b, c, d = string_byte(data, i, i+3)
local v = decoder[a]*0x40000 + decoder[b]*0x1000 + decoder[c]*0x40 + decoder[d]
s[n] = string_char(v >> 16, (v >> 8) & 0xFF, v & 0xFF)
n = n + 1
end
local a, b, c, d = string_byte(data, -4, -1)
if c == 61 --[[ "=" ]] then
local v = (decoder[a] * 0x4) + (decoder[b] >> 4)
s[n] = string_char(v)
elseif d == 61 --[[ "=" ]] then
local v = decoder[a]*0x400 + decoder[b]*0x10 + (decoder[c] >> 2)
s[n] = string_char(v >> 8, v & 0xFF)
elseif a ~= nil then
local v = decoder[a]*0x40000 + decoder[b]*0x1000 + decoder[c]*0x40 + decoder[d]
s[n] = string_char(v >> 16, (v >> 8) & 0xFF, v & 0xFF)
end
return table_concat(s)
end
local base64 = {
encode = encode,
decode = decode,
}
for _, s in ipairs {
-- from RFC4648
{ "", "" },
{ "f", "Zg==" },
{ "fo", "Zm8=" },
{ "foo", "Zm9v" },
{ "foob", "Zm9vYg==" },
{ "fooba", "Zm9vYmE=" },
{ "foobar", "Zm9vYmFy" },
} do
assert(base64.encode(s[1]) == s[2])
assert(base64.decode(s[2]) == s[1])
end
print "ok"
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