Data.Text.Lazy.Encoding.Base64.URL

This module contains Text-valued combinators for implementing the RFC 4648 specification of the Base64url encoding format. This includes strictly padded/unpadded and lenient decoding variants, as well as internal and external validation for canonicity.

Encoding

encodeBase64 :: Text -> Text

Encode a Text value in Base64url with padding.

See: RFC-4648 section 5

Examples:

>>> encodeBase64 "<<?>>"
"PDw_Pj4="

encodeBase64Unpadded :: Text -> Text

Encode a Text value in Base64url without padding. Note that for Base64url, padding is optional. If you call this function, you will simply be encoding as Base64url and stripping padding chars from the output.

See: RFC-4648 section 3.2

Examples:

>>> encodeBase64Unpadded "<<?>>"
"PDw_Pj4"

Decoding

decodeBase64 :: Text -> Either Text Text

Decode a padded Base64url-encoded Text value. If its length is not a multiple of 4, then padding chars will be added to fill out the input to a multiple of 4 for safe decoding as base64url encodings are optionally padded.

For a decoder that fails on unpadded input, use decodeBase64Unpadded.

Note: This function makes sure that decoding is total by deferring to decodeLatin1. This will always round trip for any valid Base64-encoded text value, but it may not round trip for bad inputs. The onus is on the caller to make sure inputs are valid. If unsure, defer to decodeBase64With and pass in a custom decode function.

See: RFC-4648 section 4

Examples:

>>> decodeBase64 "PDw_Pj4="
Right "<<?>>"

>>> decodeBase64 "PDw_Pj4"
Right "<<?>>"

>>> decodeBase64 "PDw-Pg="
Left "Base64-encoded bytestring has invalid padding"

>>> decodeBase64 "PDw-Pg"
Right "<<>>"

decodeBase64With

Arguments

:: (ByteString -> Either err Text)

convert a bytestring to text (e.g. decodeUtf8')

-> ByteString

Input text to decode

-> Either (Base64Error err) Text

Attempt to decode a lazy ByteString value as Base64url, converting from ByteString to Text according to some encoding function. In practice, This is something like decodeUtf8', which may produce an error.

See: RFC-4648 section 4

Examples:

decodeBase64With decodeUtf8'
  :: ByteString -> Either (Base64Error UnicodeException) Text

decodeBase64Unpadded :: Text -> Either Text Text

Decode an unpadded Base64url encoded Text value.

Note: This function makes sure that decoding is total by deferring to decodeLatin1. This will always round trip for any valid Base64-encoded text value, but it may not round trip for bad inputs. The onus is on the caller to make sure inputs are valid. If unsure, defer to decodeBase64WUnpaddedWith and pass in a custom decode function.

See: RFC-4648 section 4

Examples:

>>> decodeBase64Unpadded "PDw_Pj4"
Right "<<?>>"

>>> decodeBase64Unpadded "PDw_Pj4="
Left "Base64-encoded bytestring has invalid padding"

decodeBase64UnpaddedWith

Arguments

:: (ByteString -> Either err Text)

convert a bytestring to text (e.g. decodeUtf8')

-> ByteString

Input text to decode

-> Either (Base64Error err) Text

Attempt to decode an unpadded lazy ByteString value as Base64url, converting from ByteString to Text according to some encoding function. In practice, This is something like decodeUtf8', which may produce an error.

See: RFC-4648 section 4

Examples:

decodeBase64UnpaddedWith decodeUtf8'
  :: ByteString -> Either (Base64Error UnicodeException) Text

decodeBase64Padded :: Text -> Either Text Text

Decode an padded Base64url encoded Text value

Note: This function makes sure that decoding is total by deferring to decodeLatin1. This will always round trip for any valid Base64-encoded text value, but it may not round trip for bad inputs. The onus is on the caller to make sure inputs are valid. If unsure, defer to decodeBase64PaddedWith and pass in a custom decode function.

See: RFC-4648 section 4

Examples:

>>> decodeBase64Padded "PDw_Pj4="
Right "<<?>>"

>>> decodeBase64Padded "PDw_Pj4"
Left "Base64-encoded bytestring requires padding"

decodeBase64PaddedWith

Arguments

:: (ByteString -> Either err Text)

convert a bytestring to text (e.g. decodeUtf8')

-> ByteString

Input text to decode

-> Either (Base64Error err) Text

Attempt to decode a padded lazy ByteString value as Base64url, converting from ByteString to Text according to some encoding function. In practice, This is something like decodeUtf8', which may produce an error.

See: RFC-4648 section 4

Example:

decodeBase64PaddedWith decodeUtf8'
  :: ByteString -> Either (Base64Error UnicodeException) Text

decodeBase64Lenient :: Text -> Text

Leniently decode an unpadded Base64url-encoded Text. This function will not generate parse errors. If input data contains padding chars, then the input will be parsed up until the first pad character.

Note: This is not RFC 4648-compliant.

Examples:

>>> decodeBase64Lenient "PDw_Pj4="
"<<?>>"

>>> decodeBase64Lenient "PDw_%%%$}Pj4"
"<<?>>"

Validation

isBase64Url :: Text -> Bool

Tell whether a Text value is Base64url-encoded

Examples:

>>> isBase64Url "PDw_Pj4="
True

>>> isBase64Url "PDw_Pj4"
True

>>> isBase64Url "PDw_Pj"
False

isValidBase64Url :: Text -> Bool

Tell whether a Text value is a valid Base64url format.

This will not tell you whether or not this is a correct Base64url representation, only that it conforms to the correct shape. To check whether it is a true Base64 encoded Text value, use isBase64Url.

Examples:

>>> isValidBase64Url "PDw_Pj4="
True

>>> isValidBase64Url "PDw_Pj"
True

>>> isValidBase64Url "%"
False