Flat.AsBin

Wrapper type to decode a value to its flat serialisation.

See ../test/Big.hs for an example of use.

See also listTDecoder and Flat.AsSize for other ways to handle large decoded values.

In 0.5.X this type was called Repr.

Since: 0.6

Documentation

data AsBin a

When the flat serialisation of a value takes a lot less memory than the value itself, it can be convenient to keep the value in its encoded representation and decode it on demand.

To do so, just decode a value a as a `AsBin a`.

Examples:

Encode a list of Ints and then decode it to a list of AsBin Int:

>>> unflat (flat [1::Int .. 3]) :: Decoded ([AsBin Int])
Right [AsBin {repr = "\129A", offsetBits = 1},AsBin {repr = "A ", offsetBits = 2},AsBin {repr = " \193", offsetBits = 3}]

To decode an `AsBin a` to an a, use unbin:

>>> unbin <$> (unflat (flat 'a') :: Decoded (AsBin Char))
Right 'a'

Keep the values of a list of Ints encoded and decode just one on demand:

>>> let Right l :: Decoded [AsBin Int] = unflat (flat [1..5]) in unbin (l  !! 2)
3

Show exactly how values are encoded:

>>> let Right t :: Decoded (AsBin Bool,AsBin Word8,AsBin Bool) = unflat (flat (False,3:: Word64,True)) in prettyShow t
"(0, _0000001 1, _1)"

Ten bits in total spread over two bytes:

0
_0000001 1
         _1
=
00000001 11

Tests:

>>> unflat (flat ()) :: Decoded (AsBin ())
Right (AsBin {repr = "", offsetBits = 0})

>>> unflat (flat (False,True)) :: Decoded (Bool,AsBin Bool)
Right (False,AsBin {repr = "A", offsetBits = 1})

>>> unflat (flat (False,False,255 :: Word8)) :: Decoded (Bool,Bool,AsBin Word8)
Right (False,False,AsBin {repr = "?\193", offsetBits = 2})

>>> let Right (b0,b1,rw,b3) :: Decoded (Bool,Bool,AsBin Word8,Bool) = unflat (flat (False,False,255 :: Word8,True)) in (b0,b1,unbin rw,b3)
(False,False,255,True)

Instances

Show (AsBin a)

Defined in Flat.AsBin

Methods

showsPrec :: Int -> AsBin a -> ShowS

show :: AsBin a -> String

showList :: [AsBin a] -> ShowS

Flat a => Flat (AsBin a)

Defined in Flat.AsBin

Methods

encode :: AsBin a -> Encoding

decode :: Get (AsBin a)

size :: AsBin a -> NumBits -> NumBits

Flat a => Pretty (AsBin a)

Defined in Flat.AsBin

Methods

pPrintPrec :: PrettyLevel -> Rational -> AsBin a -> Doc

pPrint :: AsBin a -> Doc

pPrintList :: PrettyLevel -> [AsBin a] -> Doc

unbin :: Flat a => AsBin a -> a

Decode a value