blaze-builder-0.2.1.4: Efficient buffered output.ContentsIndex
Blaze.ByteString.Builder.Internal.Buffer
Portabilitytested on GHC only
Stabilityexperimental
MaintainerSimon Meier <iridcode@gmail.com>
Contents
Buffers
Status information
Creation and modification
Conversion to bytestings
Buffer allocation strategies
Executing puts respect to some monad
Description
Execution of the Put monad and hence also Builders with respect to buffers.
Synopsis
data Buffer
freeSize :: Buffer -> Int
sliceSize :: Buffer -> Int
bufferSize :: Buffer -> Int
allocBuffer :: Int -> IO Buffer
reuseBuffer :: Buffer -> Buffer
nextSlice :: Int -> Buffer -> Maybe Buffer
updateEndOfSlice :: Buffer -> Ptr Word8 -> Buffer
execBuildStep :: BuildStep a -> Buffer -> IO (BuildSignal a)
unsafeFreezeBuffer :: Buffer -> ByteString
unsafeFreezeNonEmptyBuffer :: Buffer -> Maybe ByteString
type BufferAllocStrategy = (IO Buffer, Int -> Buffer -> IO (IO Buffer))
allNewBuffersStrategy :: Int -> BufferAllocStrategy
reuseBufferStrategy :: IO Buffer -> BufferAllocStrategy
runPut :: Monad m => (IO (BuildSignal a) -> m (BuildSignal a)) -> (Int -> Buffer -> m Buffer) -> (ByteString -> m ()) -> Put a -> Buffer -> m (a, Buffer)
Buffers
data Buffer
A buffer Buffer fpbuf p0 op ope describes a buffer with the underlying byte array fpbuf..ope, the currently written slice p0..op and the free space op..ope.
Status information
freeSize :: Buffer -> Int
The size of the free space of the buffer.
sliceSize :: Buffer -> Int
The size of the written slice in the buffer.
bufferSize :: Buffer -> Int
The size of the whole byte array underlying the buffer.
Creation and modification
allocBuffer :: Int -> IO Buffer
allocBuffer size allocates a new buffer of size size.
reuseBuffer :: Buffer -> Buffer
Resets the beginning of the next slice and the next free byte such that the whole buffer can be filled again.
nextSlice :: Int -> Buffer -> Maybe Buffer
Move the beginning of the slice to the next free byte such that the remaining free space of the buffer can be filled further. This operation is safe and can be used to fill the remaining part of the buffer after a direct insertion of a bytestring or a flush.
updateEndOfSlice :: Buffer -> Ptr Word8 -> Buffer
Update the end of slice pointer.
execBuildStep :: BuildStep a -> Buffer -> IO (BuildSignal a)
Execute a build step on the given buffer.
Conversion to bytestings
unsafeFreezeBuffer :: Buffer -> ByteString
Convert the buffer to a bytestring. This operation is unsafe in the sense that created bytestring shares the underlying byte array with the buffer. Hence, depending on the later use of this buffer (e.g., if it gets reset and filled again) referential transparency may be lost.
unsafeFreezeNonEmptyBuffer :: Buffer -> Maybe ByteString
Convert a buffer to a non-empty bytestring. See unsafeFreezeBuffer for the explanation of why this operation may be unsafe.
Buffer allocation strategies
type BufferAllocStrategy = (IO Buffer, Int -> Buffer -> IO (IO Buffer))
A buffer allocation strategy (buf0, nextBuf) specifies the initial buffer to use and how to compute a new buffer nextBuf minSize buf with at least size minSize from a filled buffer buf. The double nesting of the IO monad helps to ensure that the reference to the filled buffer buf is lost as soon as possible, but the new buffer doesn't have to be allocated too early.
allNewBuffersStrategy :: Int -> BufferAllocStrategy

The simplest buffer allocation strategy: whenever a buffer is requested, allocate a new one that is big enough for the next build step to execute.

NOTE that this allocation strategy may spill quite some memory upon direct insertion of a bytestring by the builder. Thats no problem for garbage collection, but it may lead to unreasonably high memory consumption in special circumstances.

reuseBufferStrategy :: IO Buffer -> BufferAllocStrategy
An unsafe, but possibly more efficient buffer allocation strategy: reuse the buffer, if it is big enough for the next build step to execute.
Executing puts respect to some monad
runPut :: Monad m => (IO (BuildSignal a) -> m (BuildSignal a)) -> (Int -> Buffer -> m Buffer) -> (ByteString -> m ()) -> Put a -> Buffer -> m (a, Buffer)

Execute a put on a buffer.

TODO: Generalize over buffer allocation strategy.

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