GHC.IO.Buffer

Buffers used in the IO system

Buffers of any element

data Buffer e

A mutable array of bytes that can be passed to foreign functions.

The buffer is represented by a record, where the record contains the raw buffer and the start/end points of the filled portion. The buffer contents itself is mutable, but the rest of the record is immutable. This is a slightly odd mix, but it turns out to be quite practical: by making all the buffer metadata immutable, we can have operations on buffer metadata outside of the IO monad.

The live elements of the buffer are those between the bufL and bufR offsets. In an empty buffer, bufL is equal to bufR, but they might not be zero: for exmaple, the buffer might correspond to a memory-mapped file and in which case bufL will point to the next location to be written, which is not necessarily the beginning of the file.

Constructors

Buffer

Fields

bufRaw :: !(RawBuffer e)

bufState :: BufferState

bufSize :: !Int

bufL :: !Int

bufR :: !Int

data BufferState

Constructors

ReadBuffer

WriteBuffer

Instances

Eq BufferState

type CharBuffer = Buffer Char

type CharBufElem = Char

Creation

newByteBuffer :: Int -> BufferState -> IO (Buffer Word8)

newCharBuffer :: Int -> BufferState -> IO CharBuffer

newBuffer :: Int -> Int -> BufferState -> IO (Buffer e)

emptyBuffer :: RawBuffer e -> Int -> BufferState -> Buffer e

Insertion/removal

bufferRemove :: Int -> Buffer e -> Buffer e

bufferAdd :: Int -> Buffer e -> Buffer e

slideContents :: Buffer Word8 -> IO (Buffer Word8)

slides the contents of the buffer to the beginning

bufferAdjustL :: Int -> Buffer e -> Buffer e

Inspecting

isEmptyBuffer :: Buffer e -> Bool

isFullBuffer :: Buffer e -> Bool

isFullCharBuffer :: Buffer e -> Bool

isWriteBuffer :: Buffer e -> Bool

bufferElems :: Buffer e -> Int

bufferAvailable :: Buffer e -> Int

summaryBuffer :: Buffer a -> String

Operating on the raw buffer as a Ptr

withBuffer :: Buffer e -> (Ptr e -> IO a) -> IO a

withRawBuffer :: RawBuffer e -> (Ptr e -> IO a) -> IO a

Assertions

checkBuffer :: Buffer a -> IO ()

Raw buffers

type RawBuffer e = ForeignPtr e

readWord8Buf :: RawBuffer Word8 -> Int -> IO Word8

writeWord8Buf :: RawBuffer Word8 -> Int -> Word8 -> IO ()

type RawCharBuffer = RawBuffer CharBufElem

peekCharBuf :: RawCharBuffer -> Int -> IO Char

readCharBuf :: RawCharBuffer -> Int -> IO (Char, Int)

writeCharBuf :: RawCharBuffer -> Int -> Char -> IO Int

readCharBufPtr :: Ptr CharBufElem -> Int -> IO (Char, Int)

writeCharBufPtr :: Ptr CharBufElem -> Int -> Char -> IO Int

charSize :: Int