base-4.20.0.1: Core data structures and operations
Copyright(c) The FFI task force 2001
Licensesee libraries/base/LICENSE
Maintainerffi@haskell.org
Stabilityprovisional
Portabilityportable
Safe HaskellSafe
LanguageHaskell2010

Foreign.Storable

Description

The module Foreign.Storable provides most elementary support for marshalling and is part of the language-independent portion of the Foreign Function Interface (FFI), and will normally be imported via the Foreign module.

Synopsis

Documentation

class Storable a where Source #

The member functions of this class facilitate writing values of primitive types to raw memory (which may have been allocated with the above mentioned routines) and reading values from blocks of raw memory. The class, furthermore, includes support for computing the storage requirements and alignment restrictions of storable types.

Memory addresses are represented as values of type Ptr a, for some a which is an instance of class Storable. The type argument to Ptr helps provide some valuable type safety in FFI code (you can't mix pointers of different types without an explicit cast), while helping the Haskell type system figure out which marshalling method is needed for a given pointer.

All marshalling between Haskell and a foreign language ultimately boils down to translating Haskell data structures into the binary representation of a corresponding data structure of the foreign language and vice versa. To code this marshalling in Haskell, it is necessary to manipulate primitive data types stored in unstructured memory blocks. The class Storable facilitates this manipulation on all types for which it is instantiated, which are the standard basic types of Haskell, the fixed size Int types (Int8, Int16, Int32, Int64), the fixed size Word types (Word8, Word16, Word32, Word64), StablePtr, all types from Foreign.C.Types, as well as Ptr.

Minimal complete definition

sizeOf, alignment, (peek | peekElemOff | peekByteOff), (poke | pokeElemOff | pokeByteOff)

Methods

sizeOf :: a -> Int Source #

Computes the storage requirements (in bytes) of the argument. The value of the argument is not used.

alignment :: a -> Int Source #

Computes the alignment constraint of the argument. An alignment constraint x is fulfilled by any address divisible by x. The alignment must be a power of two if this instance is to be used with alloca or allocaArray. The value of the argument is not used.

peekElemOff :: Ptr a -> Int -> IO a Source #

Read a value from a memory area regarded as an array of values of the same kind. The first argument specifies the start address of the array and the second the index into the array (the first element of the array has index 0). The following equality holds,

peekElemOff addr idx = IOExts.fixIO $ \result ->
  peek (addr `plusPtr` (idx * sizeOf result))

Note that this is only a specification, not necessarily the concrete implementation of the function.

pokeElemOff :: Ptr a -> Int -> a -> IO () Source #

Write a value to a memory area regarded as an array of values of the same kind. The following equality holds:

pokeElemOff addr idx x =
  poke (addr `plusPtr` (idx * sizeOf x)) x

peekByteOff :: Ptr b -> Int -> IO a Source #

Read a value from a memory location given by a base address and offset. The following equality holds:

peekByteOff addr off = peek (addr `plusPtr` off)

pokeByteOff :: Ptr b -> Int -> a -> IO () Source #

Write a value to a memory location given by a base address and offset. The following equality holds:

pokeByteOff addr off x = poke (addr `plusPtr` off) x

peek :: Ptr a -> IO a Source #

Read a value from the given memory location.

Note that the peek and poke functions might require properly aligned addresses to function correctly. This is architecture dependent; thus, portable code should ensure that when peeking or poking values of some type a, the alignment constraint for a, as given by the function alignment is fulfilled.

poke :: Ptr a -> a -> IO () Source #

Write the given value to the given memory location. Alignment restrictions might apply; see peek.

Instances

Instances details
Storable Fingerprint

Since: base-4.4.0.0

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable CBool 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CChar 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CClock 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CDouble 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CFloat 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CInt 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CIntMax 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CIntPtr 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CLLong 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CLong 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CPtrdiff 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CSChar 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CSUSeconds 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CShort 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CSigAtomic 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CSize 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CTime 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUChar 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUInt 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUIntMax 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUIntPtr 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CULLong 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CULong 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUSeconds 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CUShort 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable CWchar 
Instance details

Defined in GHC.Internal.Foreign.C.Types

Storable IntPtr 
Instance details

Defined in GHC.Internal.Foreign.Ptr

Storable WordPtr 
Instance details

Defined in GHC.Internal.Foreign.Ptr

Storable Int16

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Int32

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Int64

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Int8

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable IoSubSystem

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.RTS.Flags

Storable CBlkCnt 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CBlkSize 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CCc 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CClockId 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CDev 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CFsBlkCnt 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CFsFilCnt 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CGid 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CId 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CIno 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CKey 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CMode 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CNfds 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CNlink 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable COff 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CPid 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CRLim 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CSocklen 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CSpeed 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CSsize 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CTcflag 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CTimer 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable CUid 
Instance details

Defined in GHC.Internal.System.Posix.Types

Storable Fd 
Instance details

Defined in GHC.Internal.System.Posix.Types

Methods

sizeOf :: Fd -> Int Source #

alignment :: Fd -> Int Source #

peekElemOff :: Ptr Fd -> Int -> IO Fd Source #

pokeElemOff :: Ptr Fd -> Int -> Fd -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO Fd Source #

pokeByteOff :: Ptr b -> Int -> Fd -> IO () Source #

peek :: Ptr Fd -> IO Fd Source #

poke :: Ptr Fd -> Fd -> IO () Source #

Storable Word16

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Word32

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Word64

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Word8

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable ()

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Foreign.Storable

Methods

sizeOf :: () -> Int Source #

alignment :: () -> Int Source #

peekElemOff :: Ptr () -> Int -> IO () Source #

pokeElemOff :: Ptr () -> Int -> () -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO () Source #

pokeByteOff :: Ptr b -> Int -> () -> IO () Source #

peek :: Ptr () -> IO () Source #

poke :: Ptr () -> () -> IO () Source #

Storable Bool

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Char

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Double

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Float

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Int

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable Word

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable a => Storable (Complex a) Source #

Since: base-4.8.0.0

Instance details

Defined in Data.Complex

Methods

sizeOf :: Complex a -> Int Source #

alignment :: Complex a -> Int Source #

peekElemOff :: Ptr (Complex a) -> Int -> IO (Complex a) Source #

pokeElemOff :: Ptr (Complex a) -> Int -> Complex a -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO (Complex a) Source #

pokeByteOff :: Ptr b -> Int -> Complex a -> IO () Source #

peek :: Ptr (Complex a) -> IO (Complex a) Source #

poke :: Ptr (Complex a) -> Complex a -> IO () Source #

Storable a => Storable (Identity a)

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Storable a => Storable (Down a)

Since: base-4.14.0.0

Instance details

Defined in GHC.Internal.Data.Ord

Methods

sizeOf :: Down a -> Int Source #

alignment :: Down a -> Int Source #

peekElemOff :: Ptr (Down a) -> Int -> IO (Down a) Source #

pokeElemOff :: Ptr (Down a) -> Int -> Down a -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO (Down a) Source #

pokeByteOff :: Ptr b -> Int -> Down a -> IO () Source #

peek :: Ptr (Down a) -> IO (Down a) Source #

poke :: Ptr (Down a) -> Down a -> IO () Source #

Storable (ConstPtr a) 
Instance details

Defined in GHC.Internal.Foreign.Storable

Storable (FunPtr a)

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Methods

sizeOf :: FunPtr a -> Int Source #

alignment :: FunPtr a -> Int Source #

peekElemOff :: Ptr (FunPtr a) -> Int -> IO (FunPtr a) Source #

pokeElemOff :: Ptr (FunPtr a) -> Int -> FunPtr a -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO (FunPtr a) Source #

pokeByteOff :: Ptr b -> Int -> FunPtr a -> IO () Source #

peek :: Ptr (FunPtr a) -> IO (FunPtr a) Source #

poke :: Ptr (FunPtr a) -> FunPtr a -> IO () Source #

Storable (Ptr a)

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Methods

sizeOf :: Ptr a -> Int Source #

alignment :: Ptr a -> Int Source #

peekElemOff :: Ptr (Ptr a) -> Int -> IO (Ptr a) Source #

pokeElemOff :: Ptr (Ptr a) -> Int -> Ptr a -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO (Ptr a) Source #

pokeByteOff :: Ptr b -> Int -> Ptr a -> IO () Source #

peek :: Ptr (Ptr a) -> IO (Ptr a) Source #

poke :: Ptr (Ptr a) -> Ptr a -> IO () Source #

(Storable a, Integral a) => Storable (Ratio a)

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Foreign.Storable

Methods

sizeOf :: Ratio a -> Int Source #

alignment :: Ratio a -> Int Source #

peekElemOff :: Ptr (Ratio a) -> Int -> IO (Ratio a) Source #

pokeElemOff :: Ptr (Ratio a) -> Int -> Ratio a -> IO () Source #

peekByteOff :: Ptr b -> Int -> IO (Ratio a) Source #

pokeByteOff :: Ptr b -> Int -> Ratio a -> IO () Source #

peek :: Ptr (Ratio a) -> IO (Ratio a) Source #

poke :: Ptr (Ratio a) -> Ratio a -> IO () Source #

Storable (StablePtr a)

Since: base-2.1

Instance details

Defined in GHC.Internal.Foreign.Storable

Storable a => Storable (Const a b)

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Const

Methods

sizeOf :: Const a b -> Int Source #

alignment :: Const a b -> Int Source #

peekElemOff :: Ptr (Const a b) -> Int -> IO (Const a b) Source #

pokeElemOff :: Ptr (Const a b) -> Int -> Const a b -> IO () Source #

peekByteOff :: Ptr b0 -> Int -> IO (Const a b) Source #

pokeByteOff :: Ptr b0 -> Int -> Const a b -> IO () Source #

peek :: Ptr (Const a b) -> IO (Const a b) Source #

poke :: Ptr (Const a b) -> Const a b -> IO () Source #