Data.Text.Lazy.Encoding.Base64

This module contains Text-valued combinators implementing the RFC 4648 specification for the Base64 encoding format. This includes lenient decoding variants, and external + internal validations for canonicity.

Encoding

encodeBase64 :: Text -> Base64 'StdPadded Text

Encode a Text value in Base64 with padding.

See: RFC-4648 section 4

Examples:

>>> encodeBase64 "Sun"
"U3Vu"

Decoding

decodeBase64 :: StdAlphabet k => Base64 k Text -> Text

Decode a padded Base64-encoded Text value

See: RFC-4648 section 4

Examples:

>>> decodeBase64 $ assertBase64 @'StdPadded "U3Vu"
"Sun"

decodeBase64Untyped :: Text -> Either Text Text

Decode a padded, untyped Base64-encoded Text value

See: RFC-4648 section 4

Examples:

>>> decodeBase64Untyped "U3Vu"
Right "Sun"

>>> decodeBase64Untyped "U3V"
Left "Base64-encoded bytestring requires padding"

>>> decodeBase64Untyped "U3V="
Left "non-canonical encoding detected at offset: 2"

decodeBase64UntypedWith

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 ByteString value as Base64, 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:

decodeBase64UntypedWith decodeUtf8'
  :: ByteString -> Either (Base64Error UnicodeException) Text

decodeBase64Lenient :: Text -> Text

Leniently decode an untyped Base64-encoded Text value. 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 "U3Vu"
"Sun"

>>> decodeBase64Lenient "U3V"
"Su"

>>> decodeBase64Lenient "U3V="
"Su"

Validation

isBase64 :: Text -> Bool

Tell whether an untyped Text value is Base64-encoded.

Examples:

>>> isBase64 "U3Vu"
True

>>> isBase64 "U3V"
False

>>> isBase64 "U3V="
False

isValidBase64 :: Text -> Bool

Tell whether an untyped Text value is a valid Base64 format.

This will not tell you whether or not this is a correct Base64 representation, only that it conforms to the correct shape. To check whether it is a true Base64 encoded Text value, use isBase64.

Examples:

>>> isValidBase64 "U3Vu"
True

>>> isValidBase64 "U3V"
True

>>> isValidBase64 "U3V="
True

>>> isValidBase64 "%"
False