Base64

The Base64 module provides for the encoding (#encode64, strict_encode64, urlsafe_encode64) and decoding (#decode64, strict_decode64, urlsafe_decode64) of binary data using a Base64 representation.

Example¶ ↑

A simple encoding and decoding.

require "base64"

enc   = Base64.encode64('Send reinforcements')
                    # -> "U2VuZCByZWluZm9yY2VtZW50cw==\n"
plain = Base64.decode64(enc)
                    # -> "Send reinforcements"

The purpose of using base64 to encode data is that it translates any binary data into purely printable characters.

Public Instance Methods

decode64(str)

Returns the Base64-decoded version of str. This method complies with RFC 2045. Characters outside the base alphabet are ignored.

require 'base64'
str = 'VGhpcyBpcyBsaW5lIG9uZQpUaGlzIG' +
      'lzIGxpbmUgdHdvClRoaXMgaXMgbGlu' +
      'ZSB0aHJlZQpBbmQgc28gb24uLi4K'
puts Base64.decode64(str)

Generates:

This is line one
This is line two
This is line three
And so on...

 
               # File base64.rb, line 58
def decode64(str)
  str.unpack("m").first
end

encode64(bin)

Returns the Base64-encoded version of bin. This method complies with RFC 2045. Line feeds are added to every 60 encoded characters.

require 'base64'
Base64.encode64("Now is the time for all good coders\nto learn Ruby")

Generates:

Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwgZ29vZCBjb2RlcnMKdG8gbGVhcm4g
UnVieQ==

 
               # File base64.rb, line 38
def encode64(bin)
  [bin].pack("m")
end

strict_decode64(str)

Returns the Base64-decoded version of str. This method complies with RFC 4648. ArgumentError is raised if str is incorrectly padded or contains non-alphabet characters. Note that CR or LF are also rejected.

 
               # File base64.rb, line 73
def strict_decode64(str)
  str.unpack("m0").first
end

strict_encode64(bin)

Returns the Base64-encoded version of bin. This method complies with RFC 4648. No line feeds are added.

 
               # File base64.rb, line 65
def strict_encode64(bin)
  [bin].pack("m0")
end

urlsafe_decode64(str)

Returns the Base64-decoded version of str. This method complies with “Base 64 Encoding with URL and Filename Safe Alphabet” in RFC 4648. The alphabet uses ‘-’ instead of ‘+’ and ‘_’ instead of ‘/’.

The padding character is optional. This method accepts both correctly-padded and unpadded input. Note that it still rejects incorrectly-padded input.

 
               # File base64.rb, line 97
def urlsafe_decode64(str)
  # NOTE: RFC 4648 does say nothing about unpadded input, but says that
  # "the excess pad characters MAY also be ignored", so it is inferred that
  # unpadded input is also acceptable.
  str = str.tr("-_", "+/")
  if !str.end_with?("=") && str.length % 4 != 0
    str = str.ljust((str.length + 3) & ~3, "=")
  end
  strict_decode64(str)
end

urlsafe_encode64(bin, padding: true)

Returns the Base64-encoded version of bin. This method complies with “Base 64 Encoding with URL and Filename Safe Alphabet” in RFC 4648. The alphabet uses ‘-’ instead of ‘+’ and ‘_’ instead of ‘/’. Note that the result can still contain ‘=’. You can remove the padding by setting padding as false.

 
               # File base64.rb, line 83
def urlsafe_encode64(bin, padding: true)
  str = strict_encode64(bin).tr("+/", "-_")
  str = str.delete("=") unless padding
  str
end