Copyright	(C) Koz Ross 2019
License	GPL version 3.0 or later
Maintainer	koz.ross@retro-freedom.nz
Stability	Experimental
Portability	GHC only
Safe Haskell	Trustworthy
Language	Haskell2010

Data.Finitary.PackBytes

Description

If a type a is Finitary, each inhabitant of a has an index, which can be represented as a byte string of a fixed length (as the number of indexes is finite). Essentially, we can represent any value of a as a fixed-length string over an alphabet of cardinality \(256\). Based on this, we can derive a Unbox instance, representing a Vector as a large byte string. This also allows us to provide a Storable instance for a.

This encoding is fairly tight in terms of space use, especially for types whose cardinalities are large. Additionally, byte-access is considerably faster than bit-access on most architectures. If your types have large cardinalities, and minimal space use isn't a concern, this encoding is good.

Some architectures prefer whole-word access - on these, there can be some overheads using this encoding. Additionally, the encoding and decoding step for this encoding is longer than the one for Data.Finitary.PackWords. If Cardinality a < Cardinality Word, you should consider a different encoding - in particular, check Data.Finitary.PackInto, which is more flexible and faster, with greater control over space usage.

Synopsis

data PackBytes (a :: Type)
pattern Packed :: forall (a :: Type). (Finitary a, 1 <= Cardinality a) => a -> PackBytes a

Documentation

data PackBytes (a :: Type) Source #

An opaque wrapper around a, representing each value as a byte string.

Instances

Instances details

(Finitary a, 1 <= Cardinality a) => Vector Vector (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods basicUnsafeFreeze :: PrimMonad m => Mutable Vector (PrimState m) (PackBytes a) -> m (Vector (PackBytes a)) # basicUnsafeThaw :: PrimMonad m => Vector (PackBytes a) -> m (Mutable Vector (PrimState m) (PackBytes a)) # basicLength :: Vector (PackBytes a) -> Int # basicUnsafeSlice :: Int -> Int -> Vector (PackBytes a) -> Vector (PackBytes a) # basicUnsafeIndexM :: Monad m => Vector (PackBytes a) -> Int -> m (PackBytes a) # basicUnsafeCopy :: PrimMonad m => Mutable Vector (PrimState m) (PackBytes a) -> Vector (PackBytes a) -> m () # elemseq :: Vector (PackBytes a) -> PackBytes a -> b -> b #
(Finitary a, 1 <= Cardinality a) => MVector MVector (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods basicLength :: MVector s (PackBytes a) -> Int # basicUnsafeSlice :: Int -> Int -> MVector s (PackBytes a) -> MVector s (PackBytes a) # basicOverlaps :: MVector s (PackBytes a) -> MVector s (PackBytes a) -> Bool # basicUnsafeNew :: PrimMonad m => Int -> m (MVector (PrimState m) (PackBytes a)) # basicInitialize :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> m () # basicUnsafeReplicate :: PrimMonad m => Int -> PackBytes a -> m (MVector (PrimState m) (PackBytes a)) # basicUnsafeRead :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> Int -> m (PackBytes a) # basicUnsafeWrite :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> Int -> PackBytes a -> m () # basicClear :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> m () # basicSet :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> PackBytes a -> m () # basicUnsafeCopy :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> MVector (PrimState m) (PackBytes a) -> m () # basicUnsafeMove :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> MVector (PrimState m) (PackBytes a) -> m () # basicUnsafeGrow :: PrimMonad m => MVector (PrimState m) (PackBytes a) -> Int -> m (MVector (PrimState m) (PackBytes a)) #
(Finitary a, 1 <= Cardinality a) => Bounded (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods minBound :: PackBytes a # maxBound :: PackBytes a #
Eq (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods (==) :: PackBytes a -> PackBytes a -> Bool # (/=) :: PackBytes a -> PackBytes a -> Bool #
Ord (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods compare :: PackBytes a -> PackBytes a -> Ordering # (<) :: PackBytes a -> PackBytes a -> Bool # (<=) :: PackBytes a -> PackBytes a -> Bool # (>) :: PackBytes a -> PackBytes a -> Bool # (>=) :: PackBytes a -> PackBytes a -> Bool # max :: PackBytes a -> PackBytes a -> PackBytes a # min :: PackBytes a -> PackBytes a -> PackBytes a #
Show (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods showsPrec :: Int -> PackBytes a -> ShowS # show :: PackBytes a -> String # showList :: [PackBytes a] -> ShowS #
(Finitary a, 1 <= Cardinality a) => Storable (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods sizeOf :: PackBytes a -> Int # alignment :: PackBytes a -> Int # peekElemOff :: Ptr (PackBytes a) -> Int -> IO (PackBytes a) # pokeElemOff :: Ptr (PackBytes a) -> Int -> PackBytes a -> IO () # peekByteOff :: Ptr b -> Int -> IO (PackBytes a) # pokeByteOff :: Ptr b -> Int -> PackBytes a -> IO () # peek :: Ptr (PackBytes a) -> IO (PackBytes a) # poke :: Ptr (PackBytes a) -> PackBytes a -> IO () #
Binary (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods put :: PackBytes a -> Put # get :: Get (PackBytes a) # putList :: [PackBytes a] -> Put #
NFData (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods rnf :: PackBytes a -> () #
(Finitary a, 1 <= Cardinality a) => Finitary (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Associated Types type Cardinality (PackBytes a) :: Nat # Methods fromFinite :: Finite (Cardinality (PackBytes a)) -> PackBytes a # toFinite :: PackBytes a -> Finite (Cardinality (PackBytes a)) # start :: PackBytes a # end :: PackBytes a # previous :: Alternative f => PackBytes a -> f (PackBytes a) # next :: Alternative f => PackBytes a -> f (PackBytes a) #
Hashable (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes Methods hashWithSalt :: Int -> PackBytes a -> Int # hash :: PackBytes a -> Int #
(Finitary a, 1 <= Cardinality a) => Unbox (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes
newtype MVector s (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes newtype MVector s (PackBytes a) = MV_PackBytes (MVector s Word8)
newtype Vector (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes newtype Vector (PackBytes a) = V_PackBytes (Vector Word8)
type Cardinality (PackBytes a) Source #
Instance details Defined in Data.Finitary.PackBytes type Cardinality (PackBytes a) = Cardinality a

pattern Packed :: forall (a :: Type). (Finitary a, 1 <= Cardinality a) => a -> PackBytes a Source #

To provide (something that resembles a) data constructor for PackBytes, we provide the following pattern. It can be used like any other data constructor:

import Data.Finitary.PackBytes

anInt :: PackBytes Int
anInt = Packed 10

isPackedEven :: PackBytes Int -> Bool
isPackedEven (Packed x) = even x

Every pattern match, and data constructor call, performs a \(\Theta(\log_{256}(\texttt{Cardinality a}))\) encoding or decoding of a. Use with this in mind.