System.Posix.CircularBuffer

Create a circular buffer over shared memory that can be accessed from separate processes.

This module assumes that exactly one WriteBuffer and one ReadBuffer will be used to access the same shared memory object. The ReadBuffer and WriteBuffer may exist in separate processes.

to use this library, in one process

bracket (createBuffer "aBuffer" "aSemaphore" 256 0o600) (removeBuffer)
        (\buffer -> doSomethingWith buffer)

and in the other

bracket (openBuffer "aBuffer" "aSemaphore" 256 0o600) (closeBuffer)
        (\buffer -> doSomethingWith buffer)

The buffer may be opened from either the reader or writer end, but you should ensure that the buffer is created before it is opened.

As the underlying objects (shm and named posix semaphores) exist in the file system, failing to call removeBuffer will leave stale objects in the filesystem.

Opening multiple ReadBuffers or WriteBuffers with the same names (whether in one process or several) results in undefined behavior.

Documentation

data WriteBuffer a

Instances

Storable a => Shared (WriteBuffer a)

data ReadBuffer a

Instances

Storable a => Shared (ReadBuffer a)

class Shared b where

Functions for creatingopeningclosing/removing shared buffers.

Methods

createBuffer :: String -> String -> Int -> FileMode -> IO b

openBuffer :: String -> String -> Int -> FileMode -> IO b

closeBuffer :: b -> IO ()

removeBuffer :: b -> IO ()

unlinkBuffer :: b -> IO ()

Instances

Storable a => Shared (ReadBuffer a)

Storable a => Shared (WriteBuffer a)

Storable a => Shared (ReadBuffer a)

Storable a => Shared (WriteBuffer a)

data WaitStrategy

Constructors

KBlocking

Spin !Int !Int !Int

SpinContinuous !Int

normal interface

putBuffer :: Storable a => WriteBuffer a -> a -> IO ()

Write a value to the writer end.

This function is thread-safe.

getBuffer :: Storable a => WaitStrategy -> ReadBuffer a -> IO a

read the next value from the reader end.

This function is *NOT* thread-safe.

tryGetBuffer :: Storable a => ReadBuffer a -> IO (Maybe a)

Try to read the next value from the reader end.

This function is *NOT* thread-safe.

batch operations

putBufferList :: Storable a => WriteBuffer a -> [a] -> IO ()

Write a list of values to the writer end.

This function is thread-safe.

getAvailable :: Storable a => ReadBuffer a -> IO [a]

read all currently available values from the reader end.

This function is *NOT* thread-safe.

sizeOfInt :: Int