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

Modulebase64-1.0Haskell2010

Data.Text.Short.Encoding.Base64.URL

This module contains ShortText-valued combinators implementing the RFC 4648 specification for the Base64url encoding format. This includes strictly padded/unpadded and lenient decoding variants, and external + internal validations for canonicity.

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

Encoding

2 declarations

Decoding

10 declarations

Decode an untyped padded Base64url-encoded ShortText 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 T.decodeUtf8. 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:
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. :: (ShortByteString -> Either err ShortText)

    convert a bytestring to text (e.g. T.decodeUtf8')

  2. -> ShortByteString

    Input text to decode

  3. -> Either (Base64Error err) ShortText
#

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

See: RFC-4648 section 4

Examples:
decodeBase64With T.decodeUtf8'
  :: ShortByteString -> Either (Base64Error UnicodeException) ShortText
valuedecodeBase64UnpaddedUntypedWith
  1. :: (ShortByteString -> Either err ShortText)

    convert a bytestring to text (e.g. T.decodeUtf8')

  2. -> ShortByteString

    Input text to decode

  3. -> Either (Base64Error err) ShortText
#

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

See: RFC-4648 section 4

Examples:
decodeBase64UnpaddedWith T.decodeUtf8'
  :: ShortByteString -> Either (Base64Error UnicodeException) ShortText
valuedecodeBase64PaddedUntypedWith
  1. :: (ShortByteString -> Either err ShortText)

    convert a bytestring to text (e.g. T.decodeUtf8')

  2. -> ShortByteString

    Input text to decode

  3. -> Either (Base64Error err) ShortText
#

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

See: RFC-4648 section 4

Examples:
decodeBase64With T.decodeUtf8'
  :: ShortByteString -> Either (Base64Error UnicodeException) ShortText

Leniently decode an untyped, unpadded Base64url-encoded ShortText. 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 :: ShortText -> Bool
#

Tell whether an untyped ShortText value is Base64url-encoded.

Examples:
Example1 expression
isBase64Url "PDw_Pj4="True
Example1 expression
isBase64Url "PDw_Pj4"True
Example1 expression
isBase64Url "PDw_Pj"False

Tell whether an untyped ShortText 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 ShortText value, use isBase64Url.

Examples:
Example1 expression
isValidBase64Url "PDw_Pj4="True
Example1 expression
isValidBase64Url "PDw_Pj"True
Example1 expression
isValidBase64Url "%"False