CrockfordBase32

An Elixir Implementation of Douglas Crockford's Base32 encoding.

Please see https://www.crockford.com/base32.html.

This library can encode an integer or a binary in Crockford's Base32, and also provide the way to decode the corresponding encoded.

Installation

def deps do
  [
    {:crockford_base32, "~> 0.3"}
  ]
end

Usage

Encode

Encode an integer:

iex> CrockfordBase32.encode(1234)
"16J"

Encode an integer with checksum: true:

iex> CrockfordBase32.encode(1234, checksum: true)
"16JD"

Encode an inetger, and insert hyphens (-) per the step size(via split_size) in encoded result:

iex> CrockfordBase32.encode(1234, split_size: 2)
"16-J"
iex> CrockfordBase32.encode(1234, split_size: 1)
"1-6-J"
iex> CrockfordBase32.encode(1234, split_size: 1, checksum: true)
"1-6-J-D"

Encode a binary, and optional split_size and checksum options are both working:

iex> CrockfordBase32.encode(<<12345678::size(48)>>)
"00001F319R"
iex> CrockfordBase32.encode("abc")
"C5H66"
iex> CrockfordBase32.encode("abc", checksum: true)
"C5H66C"
iex> CrockfordBase32.encode("abc", checksum: true, split_size: 3)
"C5H-66C"

Decode

There will internally remove all hyphen(s) before decoding.

Decode the encoded to an integer:

iex> CrockfordBase32.decode_to_integer("16J")
{:ok, 1234}
iex> CrockfordBase32.decode_to_integer("16-J")
{:ok, 1234}
iex> CrockfordBase32.decode_to_integer("16-j")
{:ok, 1234}

With a check symbol, and decode the encoded to an integer:

iex> CrockfordBase32.decode_to_integer("16JD", checksum: true)
{:ok, 1234}
iex> CrockfordBase32.decode_to_integer("16J1", checksum: true)
{:error, "invalid_checksum"}

Decode the encoded to a binary:

iex> CrockfordBase32.decode_to_binary("00001F319R")
{:ok, <<0, 0, 0, 188, 97, 78>>}
iex> CrockfordBase32.decode_to_binary("C5H66")
{:ok, "abc"}
iex> CrockfordBase32.decode_to_binary("C5H-66")
{:ok, "abc"}
iex> CrockfordBase32.decode_to_binary("c5H-66")
{:ok, "abc"}
iex> CrockfordBase32.decode_to_binary("c5h-66")
{:ok, "abc"}
iex> CrockfordBase32.decode_to_binary("c5h66")
{:ok, "abc"}

With a check symbol, and decode the encoded to a binary:

iex> CrockfordBase32.decode_to_binary("C5H66C", checksum: true)
{:ok, "abc"}
iex> CrockfordBase32.decode_to_binary("C5H66D", checksum: true)
{:error, "invalid_checksum"}

Some invalid cases:

iex> CrockfordBase32.decode_to_binary("F1")
{:error, "invalid"}
iex> CrockfordBase32.decode_to_binary(<<1, 2, 3>>)
{:error, "invalid"}
iex> CrockfordBase32.decode_to_binary(<<>>)
{:error, "invalid"}
iex> CrockfordBase32.decode_to_integer(<<1, 2, 3>>)
{:error, "invalid"}
iex> CrockfordBase32.decode_to_integer(<<>>)
{:error, "invalid"}

Fixed Size Encoding

In some cases, you may want to encode the fixed size bytes, we can do this be with a better performance leverages the benefit of the pattern match of Elixir/Erlang. I use this feature to implement a ULID in Elixir.

Refer ULID specification, a ULID concatenates a UNIX timestamp in milliseconds(a 48 bit integer) and a randomness in 80 bits, since an integer in bits are padded with some <<0::1>> leading when needed, and a ULID in 128 bits after encoded its length is 26 (can be divisible by 5), apply the fixed size encoding with type: :integer can efficiently encode/decode a ULID, for example:

defmoule ULID do

  defmoule Base32.Bits128 do
    use CrockfordBase32,
      bits_size: 128,
      type: :integer # Optional, defaults to `:bitstring`
  end

end

Then we can use ULID.Base32.Bits128 to encode/decode a 128 bit binary which concatenates an integer (as UNIX timestamp in millisecond) in 48 bits and a random generated in 80 bits.

Credits

These libraries or tools are very helpful in understanding and reference, thanks!

cabello / crockford_base32