Foreign.Storable

Methods

• sizeOf :: a -> Int

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

• alignment :: a -> Int

  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

  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 ()

  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

  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 ()

  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

  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 ()

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