Decode fails

[singpolyma]

base64.decode("BCVxsr7N_eNgVRqvHtD0zTZsEc6-VV-JvLexhqUzORcxaOzi6-AYWXvTBHm4bjyPjs7Vd8pZGH6SRpkNtoIAiw4", base64.makedecoder('-', '_')) gives an error. adding one or two = padding fixes it, but then it is missing the last three bytes

[oktoberfest6]

I encouter today the same problem.

local base64 = require('base64')
local s = "a"
local b = base64.encode(s)
print(b)
--> YQ==
local s2 = base64.decode(b)
print(s == s2)
--> true

The problem is that the padding is optional. An other base64 encoder can produce "YQ" which is a legal base64 value and then ...

local base64 = require('base64')
local s = "a"
local b = "YQ"
print(b)
--> YQ
local s2 = base64.decode(b)
--> base64.lua:141: attempt to perform arithmetic on a nil value (field '?')

As a workaround I add enough '=' characters so that the final length is a multiple of 4 :

local base64 = require('base64')
local s = "a"
local b = "YQ"
local rest = #b % 4
if rest ~= 0 then b = b .. string.rep('=', 4 - rest) end
print(b)
--> YQ==
local s2 = base64.decode(b)
print(s == s2)