Text.Hex

Encoding and decoding

encodeHex :: ByteString -> Text

Encodes a byte string as hexidecimal number represented in text. Each byte of the input is converted into two characters in the resulting text.

>>> (encodeHex . ByteString.singleton) 192
"c0"

>>> (encodeHex . ByteString.singleton) 168
"a8"

>>> (encodeHex . ByteString.pack) [192, 168, 1, 2]
"c0a80102"

Text produced by encodeHex can be converted back to a ByteString using decodeHex.

The lazy variant of encodeHex is lazilyEncodeHex.

decodeHex :: Text -> Maybe ByteString

Decodes hexidecimal text as a byte string. If the text contains an even number of characters and consists only of the digits 0 through 9 and letters a through f, then the result is a Just value.

Unpacking the ByteString in the following examples allows for prettier printing in the REPL.

>>> (fmap ByteString.unpack . decodeHex . Text.pack) "c0a80102"
Just [192,168,1,2]

If the text contains an odd number of characters, decoding fails and produces Nothing.

>>> (fmap ByteString.unpack . decodeHex . Text.pack) "c0a8010"
Nothing

If the text contains non-hexidecimal characters, decoding fails and produces Nothing.

>>> (fmap ByteString.unpack . decodeHex . Text.pack) "x0a80102"
Nothing

The letters may be in either upper or lower case. This next example therefore gives the same result as the first one above:

>>> (fmap ByteString.unpack . decodeHex . Text.pack) "C0A80102"
Just [192,168,1,2]

lazilyEncodeHex :: LazyByteString -> LazyText

lazilyEncodeHex is the lazy variant of encodeHex.

With laziness, it is possible to encode byte strings of infinite length:

>>> (LazyText.take 8 . lazilyEncodeHex . LazyByteString.pack . cycle) [1, 2, 3]
"01020301"

Types

type Text = Text

Strict text

type LazyText = Text

Lazy text

type ByteString = ByteString

Strict byte string

type LazyByteString = ByteString

Lazy byte string

Type conversions

lazyText :: Text -> LazyText

strictText :: LazyText -> Text

lazyByteString :: ByteString -> LazyByteString

strictByteString :: LazyByteString -> ByteString