47 lines
1.7 KiB
Lua
47 lines
1.7 KiB
Lua
if not B64 then
|
|
B64 = {}
|
|
end
|
|
local encode, decode = {}, {
|
|
[strbyte("=")] = false
|
|
}
|
|
for value = 0, 63 do
|
|
local char = strsub('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', value + 1, value + 1)
|
|
encode[value] = char
|
|
decode[strbyte(char)] = value
|
|
end
|
|
|
|
local t = {}
|
|
function B64.Encode(str)
|
|
local j = 1
|
|
for i = 1, strlen(str), 3 do
|
|
local a, b, c = strbyte(str, i, i + 2)
|
|
t[j] = encode[bit.rshift(a, 2)]
|
|
t[j + 1] = encode[bit.band(bit.lshift(a, 4) + bit.rshift(b or 0, 4), 0x3F)]
|
|
t[j + 2] = b and encode[bit.band(bit.lshift(b, 2) + bit.rshift(c or 0, 6), 0x3F)] or "="
|
|
t[j + 3] = c and encode[bit.band(c, 0x3F)] or "="
|
|
j = j + 4
|
|
end
|
|
return table.concat(t, "", 1, j - 1)
|
|
end
|
|
|
|
function B64.Decode(str)
|
|
local j = 1
|
|
if strlen(str) % 4 ~= 0 then
|
|
str = str .. string.rep("=", 4 - strlen(str) % 4)
|
|
end
|
|
assert(strlen(str) % 4 == 0, format("invalid data length: %d", strlen(str)))
|
|
for i = 1, strlen(str), 4 do
|
|
local ba, bb, bc, bd = strbyte(str, i, i + 3)
|
|
local a, b, c, d = decode[ba], decode[bb], decode[bc], decode[bd]
|
|
assert(a ~= nil, format("invalid data at position %d: '%s'", i, ba))
|
|
assert(b ~= nil, format("invalid data at position %d: '%s'", i + 1, bb))
|
|
assert(c ~= nil, format("invalid data at position %d: '%s'", i + 2, bc))
|
|
assert(d ~= nil, format("invalid data at position %d: '%s'", i + 3, bd))
|
|
t[j] = strchar(bit.lshift(a, 2) + bit.rshift(b, 4))
|
|
t[j + 1] = c and strchar(bit.band(bit.lshift(b, 4) + bit.rshift(c, 2), 0xFF)) or ""
|
|
t[j + 2] = d and strchar(bit.band(bit.lshift(c, 6) + d, 0xFF)) or ""
|
|
j = j + 3
|
|
end
|
|
return table.concat(t, "", 1, j - 1)
|
|
end
|