base64
Copyright(c) 2019-2026 Emily Pillmore
LicenseBSD-style
MaintainerEmily Pillmore <emilypi@cohomolo.gy>
Stabilitystable
Portabilitynon-portable
Safe HaskellNone
LanguageHaskell2010

Data.Text.Encoding.Base64

Description

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

Synopsis

Encoding

encodeBase64 :: Text -> Base64 'StdPadded Text Source #

Encode a Text value in Base64 with padding.

See: RFC-4648 section 4

Examples:

>>> encodeBase64 "Sun"
"U3Vu"

Decoding

decodeBase64 :: forall (k :: Alphabet). StdAlphabet k => Base64 k Text -> Text Source #

Decode a padded Base64-encoded Text value.

See: RFC-4648 section 4

Examples:

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

decodeBase64Untyped :: Text -> Either Text Text Source #

Decode a padded, untyped Base64-encoded Text value.

See: RFC-4648 section 4

Examples:

>>> decodeBase64Untyped "U3Vu"
Right "Sun"

decodeBase64UntypedWith Source #

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 untyped Text 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 Source #

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"

Parsing

parseBase64 :: Text -> Either Text (Base64 'StdPadded Text) Source #

Parse a canonical, padded Base64-encoded Text value.

Checks the alphabet, length, padding, and unused padding bits. On success, returns the original encoded value wrapped in Base64, ready for decodeBase64. On failure, returns the same error as decodeBase64Untyped. The input is neither decoded nor normalized in the returned value.

This validates the Base64 encoding, not the UTF-8 validity of the decoded bytes. Use decodeBase64UntypedWith to check the decoded text encoding.

Examples:

>>> parseBase64 "U3Vu"
Right "U3Vu"
>>> fmap decodeBase64 (parseBase64 "U3Vu")
Right "Sun"
>>> parseBase64 "U3V"
Left "Base64-encoded bytestring requires padding"
>>> parseBase64 "U3V="
Left "non-canonical encoding detected at offset: 2"

Since: 2.0