GHC.IO.BufferedIO

Class of buffered IO devices

Documentation

class BufferedIO dev where

The purpose of BufferedIO is to provide a common interface for I/O devices that can read and write data through a buffer. Devices that implement BufferedIO include ordinary files, memory-mapped files, and bytestrings. The underlying device implementing a Handle must provide BufferedIO.

Minimal complete definition

newBuffer, fillReadBuffer, fillReadBuffer0, flushWriteBuffer, flushWriteBuffer0

Methods

newBuffer ∷ dev → BufferState → IO (Buffer Word8)

allocate a new buffer. The size of the buffer is at the discretion of the device; e.g. for a memory-mapped file the buffer will probably cover the entire file.

fillReadBuffer ∷ dev → Buffer Word8 → IO (Int, Buffer Word8)

reads bytes into the buffer, blocking if there are no bytes available. Returns the number of bytes read (zero indicates end-of-file), and the new buffer.

fillReadBuffer0 ∷ dev → Buffer Word8 → IO (Maybe Int, Buffer Word8)

reads bytes into the buffer without blocking. Returns the number of bytes read (Nothing indicates end-of-file), and the new buffer.

emptyWriteBuffer ∷ dev → Buffer Word8 → IO (Buffer Word8)

Prepares an empty write buffer. This lets the device decide how to set up a write buffer: the buffer may need to point to a specific location in memory, for example. This is typically used by the client when switching from reading to writing on a buffered read/write device.

There is no corresponding operation for read buffers, because before reading the client will always call fillReadBuffer.

flushWriteBuffer ∷ dev → Buffer Word8 → IO (Buffer Word8)

Flush all the data from the supplied write buffer out to the device. The returned buffer should be empty, and ready for writing.

flushWriteBuffer0 ∷ dev → Buffer Word8 → IO (Int, Buffer Word8)

Flush data from the supplied write buffer out to the device without blocking. Returns the number of bytes written and the remaining buffer.

readBuf ∷ RawIO dev ⇒ dev → Buffer Word8 → IO (Int, Buffer Word8)

readBufNonBlocking ∷ RawIO dev ⇒ dev → Buffer Word8 → IO (Maybe Int, Buffer Word8)

writeBuf ∷ RawIO dev ⇒ dev → Buffer Word8 → IO (Buffer Word8)

writeBufNonBlocking ∷ RawIO dev ⇒ dev → Buffer Word8 → IO (Int, Buffer Word8)