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GHC.IO.BufferedIO

Portability | non-portable (GHC Extensions)
Stability | internal
Maintainer | cvs-ghc@haskell.org

Description
Class of buffered IO devices
Synopsis

class BufferedIO dev where

newBuffer :: dev -> BufferState -> IO (Buffer Word8)
fillReadBuffer :: dev -> Buffer Word8 -> IO (Int, Buffer Word8)
fillReadBuffer0 :: dev -> Buffer Word8 -> IO (Maybe Int, Buffer Word8)
emptyWriteBuffer :: dev -> Buffer Word8 -> IO (Buffer Word8)
flushWriteBuffer :: dev -> Buffer Word8 -> IO (Buffer Word8)
flushWriteBuffer0 :: dev -> Buffer Word8 -> IO (Int, Buffer Word8)

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)

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`.
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.

Instances

BufferedIO FD

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)
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