Binrep.BLen

Documentation

class BLen a where

The length in bytes of a value of the given type can be known on the cheap e.g. by reading a length field, or using compile time information.

Concepts such as null padding require the notion of length in bytes in order to handle. In a hand-rolled parser, you may keep count of the current length as you go. Here, the individual types keep track, and expose it via this typeclass.

Obtaining the length of a value is usually an O(1) operation like reading a field or returning a constant. When it's not, it's often an indicator of a problematic type e.g. plain Haskell lists.

We derive a default instance for constant-size types by throwing away the value and reifying the type level natural.

Note that one can derive a free BLen instance for any type with a Put instance via serializing it and checking the length. _Do not do this._ If you find you can't write a decent BLen instance for a type, it may be that you need to rethink the representation.

Minimal complete definition

Nothing

Methods

blen :: a -> BLenT

default blen :: KnownNat (CBLen a) => a -> BLenT

Instances

BLen Int16

Defined in Binrep.BLen

Methods

blen :: Int16 -> BLenT

BLen Int32

Defined in Binrep.BLen

Methods

blen :: Int32 -> BLenT

BLen Int64

Defined in Binrep.BLen

Methods

blen :: Int64 -> BLenT

BLen Int8

Defined in Binrep.BLen

Methods

blen :: Int8 -> BLenT

BLen Word16

Defined in Binrep.BLen

Methods

blen :: Word16 -> BLenT

BLen Word32

Defined in Binrep.BLen

Methods

blen :: Word32 -> BLenT

BLen Word64

Defined in Binrep.BLen

Methods

blen :: Word64 -> BLenT

BLen Word8

Defined in Binrep.BLen

Methods

blen :: Word8 -> BLenT

BLen DCS

Defined in Binrep.Example

Methods

blen :: DCS -> BLenT

BLen DSS

Defined in Binrep.Example

Methods

blen :: DSS -> BLenT

BLen DU

Defined in Binrep.Example

Methods

blen :: DU -> BLenT

BLen DX

Defined in Binrep.Example

Methods

blen :: DX -> BLenT

BLen Tar

Defined in Binrep.Example.Tar

Methods

blen :: Tar -> BLenT

BLen Tiff

Defined in Binrep.Example.Tiff

Methods

blen :: Tiff -> BLenT

BLen WavHeader

Defined in Binrep.Example.Wav

Methods

blen :: WavHeader -> BLenT

BLen ByteString

Defined in Binrep.BLen

Methods

blen :: ByteString -> BLenT

(bs ~ MagicVals (TiffMagic end), KnownNat (Length bs)) => BLen (TiffBody end)

Defined in Binrep.Example.Tiff

Methods

blen :: TiffBody end -> BLenT

KnownNat base => BLen (AsciiNat base)

The bytelength of an AsciiNat is the number of digits in the number in the given base. We can calculate this generically with great efficiency using GHC primitives.

Defined in Binrep.Type.AsciiNat

Methods

blen :: AsciiNat base -> BLenT

BLen (AsByteString 'C)

Defined in Binrep.Type.ByteString

Methods

blen :: AsByteString 'C -> BLenT

(itype ~ I 'U size end, irep ~ IRep 'U size, KnownNat (CBLen irep)) => BLen (AsByteString ('Pascal size end))

Defined in Binrep.Type.ByteString

Methods

blen :: AsByteString ('Pascal size end) -> BLenT

KnownSymbol str => BLen (MagicUTF8 str)

Defined in Binrep.Type.Magic.UTF8

Methods

blen :: MagicUTF8 str -> BLenT

BLen a => BLen [a]

O(n)

Defined in Binrep.BLen

Methods

blen :: [a] -> BLenT

KnownNat n => BLen (TarNat n)

Defined in Binrep.Example.Tar

Methods

blen :: TarNat n -> BLenT

KnownNat (Length (MagicVals a)) => BLen (Magic a)

Assumes magic values are individual bytes.

Defined in Binrep.Type.Magic

Methods

blen :: Magic a -> BLenT

KnownNat n => BLen (NullPadded n a)

Defined in Binrep.Type.NullPadded

Methods

blen :: NullPadded n a -> BLenT

KnownNat n => BLen (Sized n a)

Defined in Binrep.Type.Sized

Methods

blen :: Sized n a -> BLenT

BLen a => BLen (Vector n a)

Defined in Binrep.Type.Vector

Methods

blen :: Vector n a -> BLenT

(BLen a, BLen b) => BLen (a, b)

Defined in Binrep.BLen

Methods

blen :: (a, b) -> BLenT

KnownNat (CBLen (I sign size end)) => BLen (I sign size end)

Defined in Binrep.Type.Int

Methods

blen :: I sign size end -> BLenT

(BLen a, itype ~ I 'U size end, KnownNat (CBLen itype)) => BLen (LenPfx size end a)

Defined in Binrep.Type.LenPfx

Methods

blen :: LenPfx size end a -> BLenT

type BLenT = Int

typeNatToBLen :: forall n. KnownNat n => BLenT

cblen :: forall a n. (n ~ CBLen a, KnownNat n) => BLenT

Reify a type's constant byte length to the term level.

module Binrep.BLen.Internal.AsBLen