Network.Socket.BufferPool

This module provides efficient receiving functions from the network. recv uses createAndTrim which behaves as follows:

• Allocates a buffer whose size is decided from the first argument.
• Receives data with the buffer.
• Allocates another buffer whose size fits the received data.
• Copies the data from the first buffer to the second buffer.

On 64bit machines, the global lock is taken for the allocation of a byte string whose length is larger than or equal to 3272 bytes. So, for instance, if 4,096 is specified to recv and the size of received data is 3,300, the global lock is taken twice with the copy overhead.

The efficient receiving functions provided here use a buffer pool. A large buffer is allocated at the beginning and it is divided into a used one and a leftover when receiving. The latter is kept in the buffer pooll and will be used next time. When the buffer gets small and usefless, a new large buffer is allocated.

Recv

type Recv = IO ByteString

Type for the receiving function with a buffer pool.

receive :: Socket -> BufferPool -> Recv

The receiving function with a buffer pool. The buffer pool is automatically managed.

data BufferPool

Type for read buffer pool.

newBufferPool :: Int -> Int -> IO BufferPool

Creating a buffer pool. The first argument is the lower limit. When the size of the buffer in the poll is lower than this limit, the buffer is thrown awany (and is eventually freed). Then a new buffer is allocated. The second argument is the size for the new allocation.

withBufferPool :: BufferPool -> (Buffer -> BufSize -> IO Int) -> IO ByteString

Using a buffer pool. The second argument is a function which returns how many bytes are filled in the buffer. The buffer in the buffer pool is automatically managed.

RecvBuf

type RecvBuf = Buffer -> BufSize -> IO Bool

Type for the receiving function with a buffer. The result boolean indicates whether or not the buffer is fully filled.

receiveBuf :: Socket -> RecvBuf

The receiving function with a buffer. This tries to fill the buffer. This returns when the buffer is filled or reaches EOF.

RecvN

type RecvN = Int -> IO ByteString

Type for the receiving function which receives N bytes.

makeReceiveN :: ByteString -> Recv -> RecvBuf -> IO RecvN

This function returns a receiving function based on two receiving functions. The returned function receives exactly N bytes. The first argument is an initial received data. After consuming the initial data, the two functions is used. When N is less than equal to 4096, the buffer pool is used. Otherwise, a new buffer is allocated. In this case, the global lock is taken.

makePlainReceiveN :: Socket -> Int -> Int -> ByteString -> IO RecvN

This function returns a receiving function with two receiving functions is created internally. The second argument is the lower limit of the buffer pool. The third argument is the size of the allocated buffer in the pool. The fourth argument is an initial received data. The returned function behaves as described in makeReceiveN.

Types

type Buffer = Ptr Word8

Type for buffer.

type BufSize = Int

Type for buffer size.

Utilities

mallocBS :: Int -> IO ByteString

Allocating a byte string.

copy :: Buffer -> ByteString -> IO Buffer

Copying the bytestring to the buffer. This function returns the point where the next copy should start.