Bytezap.Struct.TypeLits.Bytes

Efficient type-level bytestring serialization.

[Natural]s have a convenient syntax, and we can use them as a type-level bytestring by asserting that each Natural is <=255 when reifying. This module provides type classes which give you a serializer for a given [Natural].

We maximize efficiency by grouping bytes into machine words. We have to be pretty verbose to achieve this. Each type class attempts to group bytes into its machine word type, and if it can't (i.e. not enough bytes remain), it hands off to the next type class which handles the next smaller machine word.

I did a quick Core check and found that GHC seems to successfully generate minimal code for this e.g. for an 8-byte magic, GHC will do one writeWord64OffAddr# of a constant. Great!

The only way I can think of to make this faster is to somehow obtain an Addr# with a known length. With that, we could memcpy. But that would be slower for small magics, and maybe others. And I doubt we can conjure up an Addr# at compile time. So I'm fairly confident that this is the best you're gonna get.

Documentation

class ReifyBytesW64 (ns :: [Natural]) where

Serialize a type-level bytestring, largest grouping Word64.

Methods

reifyBytesW64 :: Poke s

Instances

ReifyBytesW32 ns => ReifyBytesW64 ns

Try to group Word32s next.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW64 :: Poke s

(ReifyW8 n1, ReifyW8 n2, ReifyW8 n3, ReifyW8 n4, ReifyW8 n5, ReifyW8 n6, ReifyW8 n7, ReifyW8 n8, ReifyBytesW64 ns) => ReifyBytesW64 (n1 ': (n2 ': (n3 ': (n4 ': (n5 ': (n6 ': (n7 ': (n8 ': ns))))))))

Enough bytes to make a Word64.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW64 :: Poke s

class ReifyBytesW32 (ns :: [Natural]) where

Serialize a type-level bytestring, largest grouping Word32.

Methods

reifyBytesW32 :: Poke s

Instances

ReifyBytesW16 ns => ReifyBytesW32 ns

Try to group Word16s next.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW32 :: Poke s

(ReifyW8 n1, ReifyW8 n2, ReifyW8 n3, ReifyW8 n4, ReifyBytesW32 ns) => ReifyBytesW32 (n1 ': (n2 ': (n3 ': (n4 ': ns))))

Enough bytes to make a Word32.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW32 :: Poke s

class ReifyBytesW16 (ns :: [Natural]) where

Serialize a type-level bytestring, largest grouping Word16.

Methods

reifyBytesW16 :: Poke s

Instances

ReifyBytesW8 ns => ReifyBytesW16 ns

Reify byte-by-byte next.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW16 :: Poke s

(ReifyW8 n1, ReifyW8 n2, ReifyBytesW16 ns) => ReifyBytesW16 (n1 ': (n2 ': ns))

Enough bytes to make a Word16.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW16 :: Poke s

class ReifyBytesW8 (ns :: [Natural]) where

Serialize a type-level bytestring, byte-by-byte.

Methods

reifyBytesW8 :: Poke s

Instances

ReifyBytesW8 ('[] :: [Natural])

End of the line.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW8 :: Poke s

(ReifyW8 n1, ReifyBytesW8 ns) => ReifyBytesW8 (n1 ': ns)

Reify the next byte.

Defined in Bytezap.Struct.TypeLits.Bytes

Methods

reifyBytesW8 :: Poke s