module Base64

Base64.decode64("MDEyMzQ1Njc==") # => "01234567"
Base64.decode64("MDEyMzQ1Njc=") # => "01234567"
Base64.decode64("MDEyMzQ1Njc") # => "01234567"

Padding in +encoded_string+ (even if incorrect) is ignored:

Base64.decode64("\x00\n-_") # => ""

these include newline characters and characters - and /:
see {Encoding Character Set}[Base64.html#module-Base64-label-Encoding+Character+Sets] above:
Non-\Base64 characters in +encoded_string+ are ignored;

Base64.decode64(s) # => "This is line 1\nThis is line 2\n"
s = "VGhpcyBpcyBsaW5lIDEKVGhpcyBpcyBsaW5lIDIK\n"

\Base64-encoded string +encoded_string+:
Returns a string containing the decoding of an RFC-2045-compliant

Base64.decode(encoded_string) -> decoded_string
:call-seq:

def decode64(str)
  str.unpack1("m")
end