{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE BangPatterns #-}
-- | Convert a stream of blaze-builder @Builder@s into a stream of @ByteString@s.
--
-- Adapted from blaze-builder-enumerator, written by myself and Simon Meier.
--
-- Note that the functions here can work in any monad built on top of @IO@ or
-- @ST@.
module Data.Conduit.Blaze
(
-- * Buffers
Buffer
-- ** Status information
, freeSize
, sliceSize
, bufferSize
-- ** Creation and modification
, allocBuffer
, reuseBuffer
, nextSlice
-- ** Conversion to bytestings
, unsafeFreezeBuffer
, unsafeFreezeNonEmptyBuffer
-- * Buffer allocation strategies
, BufferAllocStrategy
, allNewBuffersStrategy
, reuseBufferStrategy
-- * Enumeratees from builders to bytestrings
, builderToByteString
, unsafeBuilderToByteString
, builderToByteStringWith
) where
import Data.Conduit hiding (SinkResult (Done))
import Control.Monad.Trans.Resource
import Control.Monad.Trans.Class
import qualified Data.ByteString as S
import Blaze.ByteString.Builder.Internal
import Blaze.ByteString.Builder.Internal.Types
import Blaze.ByteString.Builder.Internal.Buffer
-- | Incrementally execute builders and pass on the filled chunks as
-- bytestrings.
builderToByteString :: ResourceUnsafeIO m => Conduit Builder m S.ByteString
builderToByteString =
builderToByteStringWith (allNewBuffersStrategy defaultBufferSize)
-- | Incrementally execute builders on the given buffer and pass on the filled
-- chunks as bytestrings. Note that, if the given buffer is too small for the
-- execution of a build step, a larger one will be allocated.
--
-- WARNING: This conduit yields bytestrings that are NOT
-- referentially transparent. Their content will be overwritten as soon
-- as control is returned from the inner sink!
unsafeBuilderToByteString :: ResourceUnsafeIO m
=> IO Buffer -- action yielding the inital buffer.
-> Conduit Builder m S.ByteString
unsafeBuilderToByteString = builderToByteStringWith . reuseBufferStrategy
-- | A conduit that incrementally executes builders and passes on the
-- filled chunks as bytestrings to an inner sink.
--
-- INV: All bytestrings passed to the inner sink are non-empty.
builderToByteStringWith :: ResourceUnsafeIO m
=> BufferAllocStrategy
-> Conduit Builder m S.ByteString
builderToByteStringWith (ioBuf0, nextBuf) = conduitState
ioBuf0
push
close
where
finalStep !(BufRange pf _) = return $ Done pf ()
close ioBuf = lift $ unsafeFromIO $ do
buf <- ioBuf
return $ maybe [] return $ unsafeFreezeNonEmptyBuffer buf
push ioBuf x = lift $ unsafeFromIO $ do
(ioBuf', front) <- go (unBuilder x (buildStep finalStep)) ioBuf id
return (ioBuf', Producing $ front [])
go bStep ioBuf front = do
!buf <- ioBuf
signal <- (execBuildStep bStep buf)
case signal of
Done op' _ -> return (return $ updateEndOfSlice buf op', front)
BufferFull minSize op' bStep' -> do
let buf' = updateEndOfSlice buf op'
{-# INLINE cont #-}
cont front' = do
-- sequencing the computation of the next buffer
-- construction here ensures that the reference to the
-- foreign pointer `fp` is lost as soon as possible.
ioBuf' <- nextBuf minSize buf'
go bStep' ioBuf' front'
case unsafeFreezeNonEmptyBuffer buf' of
Nothing -> cont front
Just bs -> cont (front . (bs:))
InsertByteString op' bs bStep' -> do
let buf' = updateEndOfSlice buf op'
bsk = maybe id (:) $ unsafeFreezeNonEmptyBuffer buf'
front' = front . bsk . (bs:)
ioBuf' <- nextBuf 1 buf'
go bStep' ioBuf' front'