Data.ByteString.Base64

This module contains ByteString-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.

Encoding

encodeBase64 :: ByteString -> Text

Encode a ByteString value as Base64 Text with padding.

See: RFC-4648 section 4

Examples:

>>> encodeBase64 "Sun"
"U3Vu"

encodeBase64' :: ByteString -> ByteString

Encode a ByteString value as a Base64 ByteString value with padding.

See: RFC-4648 section 4

Examples:

>>> encodeBase64' "Sun"
"U3Vu"

Decoding

decodeBase64 :: ByteString -> Either Text ByteString

Decode a padded Base64-encoded ByteString value.

See: RFC-4648 section 4

Examples:

>>> decodeBase64 "U3Vu"
Right "Sun"

>>> decodeBase64 "U3V"
Left "Base64-encoded bytestring requires padding"

>>> decodebase64 "U3V="
Left "non-canonical encoding detected at offset: 2"

decodeBase64Lenient :: ByteString -> ByteString

Leniently decode an unpadded Base64-encoded ByteString 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 :: ByteString -> Bool

Tell whether a ByteString value is base64 encoded.

This function will also detect non-canonical encodings such as ZE==, which are externally valid Base64url-encoded values, but are internally inconsistent "impossible" values.

Examples:

>>> isBase64 "U3Vu"
True

>>> isBase64 "U3V"
False

>>> isBase64 "U3V="
False

isValidBase64 :: ByteString -> Bool

Tell whether a ByteString value is a valid Base64 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 ByteString value, use isBase64.

Examples:

>>> isValidBase64 "U3Vu"
True

>>> isValidBase64 "U3V"
True

>>> isValidBase64 "U3V="
True

>>> isValidBase64 "%"
False