Data.Store.Core

Core Types

newtype Poke a

Poke actions are useful for building sequential serializers.

They are actions which write values to bytes into memory specified by a Ptr base. The Applicative and Monad instances make it easy to write serializations, by keeping track of the Offset of the current byte. They allow you to chain Poke action such that subsequent Pokes write into subsequent portions of the output.

Constructors

Poke

Fields

• runPoke :: PokeState -> Offset -> IO (Offset, a)

  Run the Poke action, with the Ptr to the buffer where data is poked, and the current Offset. The result is the new offset, along with a return value.

  May throw a PokeException, though this should be avoided when possible. They usually indicate a programming error.

Instances

Monad Poke

Methods

(>>=) :: Poke a -> (a -> Poke b) -> Poke b

(>>) :: Poke a -> Poke b -> Poke b

return :: a -> Poke a

fail :: String -> Poke a

Functor Poke

Methods

fmap :: (a -> b) -> Poke a -> Poke b

(<$) :: a -> Poke b -> Poke a

MonadFail Poke

Methods

fail :: String -> Poke a

Applicative Poke

Methods

pure :: a -> Poke a

(<*>) :: Poke (a -> b) -> Poke a -> Poke b

(*>) :: Poke a -> Poke b -> Poke b

(<*) :: Poke a -> Poke b -> Poke a

MonadIO Poke

Methods

liftIO :: IO a -> Poke a

data PokeException

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

PokeExceptions are not expected to occur in ordinary circumstances, and usually indicate a programming error.

Constructors

PokeException

Fields

• pokeExByteIndex :: Offset
• pokeExMessage :: Text

Instances

Eq PokeException

Methods

(==) :: PokeException -> PokeException -> Bool

(/=) :: PokeException -> PokeException -> Bool

Show PokeException

Methods

showsPrec :: Int -> PokeException -> ShowS

show :: PokeException -> String

showList :: [PokeException] -> ShowS

Exception PokeException

Methods

toException :: PokeException -> SomeException

fromException :: SomeException -> Maybe PokeException

displayException :: PokeException -> String

pokeException :: Text -> Poke a

Throws a PokeException. These should be avoided when possible, they usually indicate a programming error.

newtype Peek a

Peek actions are useful for building sequential deserializers.

They are actions which read from memory and construct values from it. The Applicative and Monad instances make it easy to chain these together to get more complicated deserializers. This machinery keeps track of the current Ptr and end-of-buffer Ptr.

Constructors

Peek

Fields

• runPeek :: PeekState -> Ptr Word8 -> IO (PeekResult a)

  Run the Peek action, with a Ptr to the end of the buffer where data is poked, and a Ptr to the current position. The result is the Ptr, along with a return value.

  May throw a PeekException if the memory contains invalid values.

Instances

Monad Peek

Methods

(>>=) :: Peek a -> (a -> Peek b) -> Peek b

(>>) :: Peek a -> Peek b -> Peek b

return :: a -> Peek a

fail :: String -> Peek a

Functor Peek

Methods

fmap :: (a -> b) -> Peek a -> Peek b

(<$) :: a -> Peek b -> Peek a

MonadFail Peek

Methods

fail :: String -> Peek a

Applicative Peek

Methods

pure :: a -> Peek a

(<*>) :: Peek (a -> b) -> Peek a -> Peek b

(*>) :: Peek a -> Peek b -> Peek b

(<*) :: Peek a -> Peek b -> Peek a

MonadIO Peek

Methods

liftIO :: IO a -> Peek a

PrimMonad Peek

Associated Types

type PrimState (Peek :: * -> *) :: *

Methods

primitive :: (State# (PrimState Peek) -> (#VoidRep, PtrRepLifted, State# (PrimState Peek), a#)) -> Peek a

type PrimState Peek

type PrimState Peek = RealWorld

data PeekResult a

A result of a Peek action containing the current Ptr and a return value.

Constructors

PeekResult !(Ptr Word8) !a

Instances

Functor PeekResult

Methods

fmap :: (a -> b) -> PeekResult a -> PeekResult b

(<$) :: a -> PeekResult b -> PeekResult a

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

Methods

(==) :: PeekException -> PeekException -> Bool

(/=) :: PeekException -> PeekException -> Bool

Show PeekException

Methods

showsPrec :: Int -> PeekException -> ShowS

show :: PeekException -> String

showList :: [PeekException] -> ShowS

Exception PeekException

Methods

toException :: PeekException -> SomeException

fromException :: SomeException -> Maybe PeekException

displayException :: PeekException -> String

peekException :: Text -> Peek a

Throws a PeekException.

tooManyBytes :: Int -> Int -> String -> IO void

Throws a PeekException about an attempt to read too many bytes.

data PokeState

Holds a pokeStatePtr, which is passed in to each Poke action. If the package is built with the 'force-alignment' flag, this also has a hidden Ptr field, which is used as scratch space during unaligned writes.

pokeStatePtr :: PokeState -> Ptr Word8

data PeekState

Holds a peekStatePtr, which is passed in to each Peek action. If the package is built with the 'force-alignment' flag, this also has a hidden Ptr field, which is used as scratch space during unaligned reads.

peekStateEndPtr :: PeekState -> Ptr Word8

type Offset = Int

How far into the given Ptr to look

Encode ByteString

unsafeEncodeWith :: Poke () -> Int -> ByteString

Given a Poke and its length, uses it to fill a ByteString

This function is unsafe because the provided length must exactly match the number of bytes used by the Poke. It will throw PokeException errors when the buffer is under or overshot. However, in the case of overshooting the buffer, memory corruption and segfaults may occur.

Decode ByteString

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.

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.

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.

decodeIOWithFromPtr :: Peek a -> Ptr Word8 -> Int -> IO a

Like decodeIOWith, but using Ptr and length instead of a ByteString.

decodeIOPortionWithFromPtr :: Peek a -> Ptr Word8 -> Int -> IO (Offset, a)

Like decodeIOPortionWith, but using Ptr and length instead of a ByteString.

Storable

pokeStorable :: Storable a => a -> Poke ()

A poke implementation based on an instance of Storable.

peekStorable :: forall a. (Storable a, Typeable a) => Peek a

A peek implementation based on an instance of Storable and Typeable.

peekStorableTy :: forall a. Storable a => String -> Peek a

A peek implementation based on an instance of Storable. Use this if the type is not Typeable.

ForeignPtr

pokeFromForeignPtr :: ForeignPtr a -> Int -> Int -> Poke ()

Copy a section of memory, based on a ForeignPtr, to the output. Note that this operation is unsafe, the offset and length parameters are not checked.

peekToPlainForeignPtr :: String -> Int -> Peek (ForeignPtr a)

Allocate a plain ForeignPtr (no finalizers), of the specified length and fill it with bytes from the input.

pokeFromPtr :: Ptr a -> Int -> Int -> Poke ()

Copy a section of memory, based on a Ptr, to the output. Note that this operation is unsafe, because the offset and length parameters are not checked.

ByteArray

pokeFromByteArray :: ByteArray# -> Int -> Int -> Poke ()

Copy a section of memory, based on a ByteArray#, to the output. Note that this operation is unsafe, because the offset and length parameters are not checked.

peekToByteArray :: String -> Int -> Peek ByteArray

Allocate a ByteArray of the specified length and fill it with bytes from the input.