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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Modulebase64-1.0Haskell2010

Data.Text.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.

  • 14 values
  • Packagebase64-1.0
  • Exports14
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceURL.hs

Encoding

2 declarations

Decoding

10 declarations
valuedecodeBase64 :: UrlAlphabet k => Base64 k Text -> Text
#

Decode a Base64url encoded Text value, either padded or unpadded. The correct decoding function is dispatched based on the existence of padding.

For typed values: - If a padded value is required, use decodeBase64Padded - If an unpadded value is required, use decodeBase64Unpadded

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64 $ assertBase64 @'UrlPadded "PDw_Pj4=""<<?>>"
Example1 expression
decodeBase64 $ assertBase64 @'UrlUnpadded "PDw_Pj4""<<?>>"

Decode an untyped 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-encoded values are optionally padded.

For a decoder that fails to decode untyped values of incorrect size: - If a padded value is required, use decodeBase64PaddedUntyped - If an unpadded value is required, use decodeBase64UnpaddedUntyped

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64Untyped "PDw_Pj4="Right "<<?>>"
Example1 expression
decodeBase64Untyped "PDw_Pj4"Right "<<?>>"
Example1 expression
decodeBase64Untyped "PDw-Pg="Left "Base64-encoded bytestring has invalid padding"
Example1 expression
decodeBase64Untyped "PDw-Pg"Right "<<>>"
valuedecodeBase64UntypedWith
  1. :: (ByteString -> Either err Text)

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

  2. -> ByteString

    Input text to decode

  3. -> Either (Base64Error err) Text
#

Attempt to decode an untyped 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:
decodeBase64UntypedWith decodeUtf8'
  :: Text -> Either (Base64Error UnicodeException) Text

Decode a unpadded, untyped 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 decodeBase64PaddedUntyped

See: RFC-4648 section 4

Examples:
Example1 expression
decodeBase64UnpaddedUntyped "PDw_Pj4"Right "<<?>>"
Example1 expression
decodeBase64UnpaddedUntyped "PDw-Pg="Left "Base64-encoded bytestring has invalid padding"
Example1 expression
decodeBase64UnpaddedUntyped "PDw-Pg"Right "<<>>"
valuedecodeBase64UnpaddedUntypedWith
  1. :: (ByteString -> Either err Text)

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

  2. -> ByteString

    Input text to decode

  3. -> Either (Base64Error err) Text
#

Attempt to decode an untyped, unpadded 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:
decodeBase64UnpaddedUntypedWith decodeUtf8'
  :: ByteString -> Either (Base64Error UnicodeException) Text
valuedecodeBase64PaddedUntypedWith
  1. :: (ByteString -> Either err Text)

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

  2. -> ByteString

    Input text to decode

  3. -> Either (Base64Error err) Text
#

Attempt to decode a padded, untyped 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

Leniently decode an untyped 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:
Example1 expression
decodeBase64Lenient "PDw_Pj4=""<<?>>"
Example1 expression
decodeBase64Lenient "PDw_%%%$}Pj4""<<?>>"

Validation

2 declarations
valueisBase64Url :: Text -> Bool
#

Tell whether an untyped Text value is Base64url-encoded.

Examples:
Example1 expression
isBase64Url "PDw_Pj4="True
Example1 expression
isBase64Url "PDw_Pj4"True
Example1 expression
isBase64Url "PDw_Pj"False
valueisValidBase64Url :: Text -> Bool
#

Tell whether an untyped 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:
Example1 expression
isValidBase64Url "PDw_Pj4="True
Example1 expression
isValidBase64Url "PDw_Pj"True
Example1 expression
isValidBase64Url "%"False