Documentation

Encoding function.

This function encodes as large a portion of the input as possible and returns the encoded part together with the remaining part. Enough space is allocated for the encoding to make sure that the remaining part is less than 3 bytes long, which means it can be passed to b64_encode_final as is.

>>> b64_encode_part $ Data.ByteString.Char8.pack "foo"
("Zm9v","")
>>> b64_encode_part $ Data.ByteString.Char8.pack "foob"
("Zm9v","b")

Encoding function for the final block.

The final block has to have a size less than 3.

>>> b64_encode_final $ Data.ByteString.Char8.pack "r"
Just "cg=="

Trying to pass in too large a block result in failure:

>>> b64_encode_final $ Data.ByteString.Char8.pack "foo"
Nothing

Decoding function.

Decode as large a portion of the input as possible. Enough data is allocated for the output to ensure that the remainder is less than 4 bytes in size. Success result in a Right value:

>>> b64_decode_part $ Data.ByteString.Char8.pack "Zm9v"
Right ("foo","")
>>> b64_decode_part $ Data.ByteString.Char8.pack "Zm9vYmE="
Right ("foo","YmE=")

Failures occur on bad input and result in a Left value:

>>> b64_decode_part $ Data.ByteString.Char8.pack "Z=9v"
Left ("","Z=9v")

Decoding function for the final block.

The final block has to have a size of 0 or 4:

>>> b64_decode_final $ Data.ByteString.Char8.pack "Zm8="
Just "fo"
>>> b64_decode_final $ Data.ByteString.Char8.pack ""
Just ""
>>> b64_decode_final $ Data.ByteString.Char8.pack "Zm="
Nothing

But it must be the encoding of a block that is less than 3 bytes:

>>> b64_decode_final $ encode $ Data.ByteString.Char8.pack "foo"
Nothing

Convenience function that combines b64_encode_part and b64_encode_final to encode a complete string.

>>> encode $ Data.ByteString.Char8.pack "foo"
"Zm9v"
>>> encode $ Data.ByteString.Char8.pack "foobar"
"Zm9vYmFy"

Convenience function that combines b64_decode_part and b64_decode_final to decode a complete string.

>>> decode $ Data.ByteString.Char8.pack "Zm9v"
Right "foo"
>>> decode $ Data.ByteString.Char8.pack "Zm9vYmFy"
Right "foobar"

Failures when decoding returns the decoded part and the remainder:

>>> decode $ Data.ByteString.Char8.pack "Zm9vYm=y"
Left ("foo","Ym=y")