Data.Store

This is the main public API of the store package. The functions exported here are more likely to be stable between versions.

Usually you won't need to write your own Store instances, and instead can rely on either using the Generic deriving approach or Data.Store.TH for defining Store instances for your datatypes. There are some tradeoffs here - the generics instances do not require -XTemplateHaskell, but they do not optimize as well for sum types that only require a constant number of bytes.

Encoding and decoding strict ByteStrings.

encode :: Store a => a -> ByteString

Serializes a value to a ByteString. In order to do this, it first allocates a ByteString of the correct size (based on size), and then uses poke to fill it.

decode :: Store a => ByteString -> Either PeekException a

Decodes a value from a ByteString. Returns an exception if there's an error while decoding, or if decoding undershoots / overshoots the end of the buffer.

decodeWith :: Peek a -> ByteString -> Either PeekException a

Decodes a value from a ByteString, potentially throwing exceptions, and taking a Peek to run. It is an exception to not consume all input.

decodeEx :: Store a => ByteString -> a

Decodes a value from a ByteString, potentially throwing exceptions. It is an exception to not consume all input.

decodeExWith :: Peek a -> ByteString -> a

Decodes a value from a ByteString, potentially throwing exceptions, and taking a Peek to run. It is an exception to not consume all input.

decodeExPortionWith :: Peek a -> ByteString -> (Offset, a)

Similar to decodeExWith, but it allows there to be more of the buffer remaining. The Offset of the buffer contents immediately after the decoded value is returned.

decodeIO :: Store a => ByteString -> IO a

Decodes a value from a ByteString, potentially throwing exceptions. It is an exception to not consume all input.

decodeIOWith :: Peek a -> ByteString -> IO a

Decodes a value from a ByteString, potentially throwing exceptions, and taking a Peek to run. It is an exception to not consume all input.

decodeIOPortionWith :: Peek a -> ByteString -> IO (Offset, a)

Similar to decodeExPortionWith, but runs in the IO monad.

Store class and related types.

class Store a where

The Store typeclass provides efficient serialization and deserialization to raw pointer addresses.

The peek and poke methods should be defined such that decodeEx (encode x) == x .

Minimal complete definition

Nothing

Methods

size :: Size a

Yields the Size of the buffer, in bytes, required to store the encoded representation of the type.

Note that the correctness of this function is crucial for the safety of poke, as it does not do any bounds checking. It is the responsibility of the invoker of poke (encode and similar functions) to ensure that there's enough space in the output buffer. If poke writes beyond, then arbitrary memory can be overwritten, causing undefined behavior and segmentation faults.

poke :: a -> Poke ()

Serializes a value to bytes. It is the responsibility of the caller to ensure that at least the number of bytes required by size are available. These details are handled by encode and similar utilities.

peek :: Peek a

Serialized a value from bytes, throwing exceptions if it encounters invalid data or runs out of input bytes.

Instances

Store TypeHash

(Store a, HasTypeHash a) => Store (Tagged a)

KnownNat n => Store (StaticSize n ByteString)

data Size a

Info about a type's serialized length. Either the length is known independently of the value, or the length depends on the value.

Constructors

VarSize (a -> Int)

ConstSize !Int

data Poke a

Instances

Monad Poke

Functor Poke

Applicative Poke

MonadFail Poke

MonadIO Poke

data Peek a

Instances

Monad Peek

Functor Peek

Applicative Peek

MonadFail Peek

MonadIO Peek

PrimMonad Peek

type PrimState Peek = RealWorld

Exceptions thrown by Peek

data PeekException

Exception thrown while running peek. Note that other types of exceptions can also be thrown. Invocations of fail in the Poke monad causes this exception to be thrown.

PeekException is thrown when the data being decoded is invalid.

Constructors

PeekException

Fields

peekExBytesFromEnd :: Offset

peekExMessage :: Text

Instances

Eq PeekException

Show PeekException

Exception PeekException

peekException :: Text -> Peek a