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{-# LANGUAGE CPP, BangPatterns #-}
-- |
-- Module : BuilderBufferRange
-- Copyright : (c) 2010 Simon Meier
-- License : BSD3-style (see LICENSE)
--
-- Maintainer : Simon Meier <iridcode@gmail.com>
-- Stability : experimental
-- Portability : tested on GHC only
--
-- Benchmark the benefit of using a packed representation for the buffer range.
--
module BuilderBufferRange where
import Foreign
import Data.Monoid
import Control.Monad (unless)
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
#ifdef BYTESTRING_IN_BASE
import Data.ByteString.Base (inlinePerformIO)
import qualified Data.ByteString.Base as S
import qualified Data.ByteString.Lazy.Base as L -- FIXME: is this the right module for access to 'Chunks'?
#else
import Data.ByteString.Internal (inlinePerformIO)
import qualified Data.ByteString.Internal as S
import qualified Data.ByteString.Lazy.Internal as L
#endif
import qualified Blaze.ByteString.Builder.Internal as B
import Blaze.ByteString.Builder.Write
import Blaze.ByteString.Builder.Word
import Criterion.Main
------------------------------------------------------------------------------
-- Benchmarks
------------------------------------------------------------------------------
main :: IO ()
main = defaultMain $ concat
[ benchmark "putBuilder"
(putBuilder . mconcat . map fromWord8)
(mconcat . map fromWord8)
word8s
, benchmark "fromWriteSingleton"
(mconcat . map putWord8)
(mconcat . map fromWord8)
word8s
, benchmark "fromWrite"
(mconcat . map (putWrite . writeWord8))
(mconcat . map (fromWrite . writeWord8))
word8s
]
where
benchmark name putF builderF x =
[ bench (name ++ " Put") $
whnf (L.length . toLazyByteString . putF) x
, bench (name ++ " Builder") $
whnf (L.length . B.toLazyByteString . builderF) x
]
word8s :: [Word8]
word8s = take 100000 $ cycle [0..]
{-# NOINLINE word8s #-}
------------------------------------------------------------------------------
-- The Builder type
------------------------------------------------------------------------------
data BufferRange = BR {-# UNPACK #-} !(Ptr Word8)
{-# UNPACK #-} !(Ptr Word8)
newtype Put = Put (PutStep -> PutStep)
data PutSignal =
Done {-# UNPACK #-} !(Ptr Word8)
| BufferFull
{-# UNPACK #-} !Int
{-# UNPACK #-} !(Ptr Word8)
!PutStep
| ModifyChunks
{-# UNPACK #-} !(Ptr Word8)
!(L.ByteString -> L.ByteString)
!PutStep
type PutStep = BufferRange -> IO PutSignal
instance Monoid Put where
mempty = Put id
{-# INLINE mempty #-}
(Put p1) `mappend` (Put p2) = Put $ p1 . p2
{-# INLINE mappend #-}
mconcat = foldr mappend mempty
{-# INLINE mconcat #-}
putWrite :: Write -> Put
putWrite (Write size io) =
Put step
where
step k (BR pf pe)
| pf `plusPtr` size <= pe = do
io pf
let !br' = BR (pf `plusPtr` size) pe
k br'
| otherwise = return $ BufferFull size pf (step k)
{-# INLINE putWrite #-}
putWriteSingleton :: (a -> Write) -> a -> Put
putWriteSingleton write =
mkPut
where
mkPut x = Put step
where
step k (BR pf pe)
| pf `plusPtr` size <= pe = do
io pf
let !br' = BR (pf `plusPtr` size) pe
k br'
| otherwise = return $ BufferFull size pf (step k)
where
Write size io = write x
{-# INLINE putWriteSingleton #-}
putBuilder :: B.Builder -> Put
putBuilder (B.Builder b) =
Put step
where
finalStep _ pf = return $ B.Done pf
step k = go (b finalStep)
where
go buildStep (BR pf pe) = do
signal <- buildStep pf pe
case signal of
B.Done pf' -> do
let !br' = BR pf' pe
k br'
B.BufferFull minSize pf' nextBuildStep ->
return $ BufferFull minSize pf' (go nextBuildStep)
B.ModifyChunks _ _ _ ->
error "putBuilder: ModifyChunks not implemented"
putWord8 :: Word8 -> Put
putWord8 = putWriteSingleton writeWord8
{-
m >>= f = GetC $ \done empty pe ->
runGetC m (\pr' x -> runGetC (f x) done empty pe pr')
(\m' -> empty (m' >>= f))
pe
newtype GetC r a = GetC {
runGetC ::
(Ptr Word8 -> a -> IO r) -> -- done
(GetC r a -> IO r ) -> -- empty buffer
Ptr Word8 -> -- end of buffer
Ptr Word8 -> -- next byte to read
IO r
}
instance Functor (GetC r) where
fmap f g = GetC $ \done empty ->
runGetC g (\pr' x -> done pr' (f x))
(\g' -> empty (fmap f g'))
instance Monad (GetC r) where
return x = GetC $ \done _ _ pr -> done pr x
m >>= f = GetC $ \done empty pe ->
runGetC m (\pr' x -> runGetC (f x) done empty pe pr')
(\m' -> empty (m' >>= f))
pe
-}
------------------------------------------------------------------------------
-- Internal global constants.
------------------------------------------------------------------------------
-- | Default size (~32kb) for the buffer that becomes a chunk of the output
-- stream once it is filled.
--
defaultBufferSize :: Int
defaultBufferSize = 32 * 1024 - overhead -- Copied from Data.ByteString.Lazy.
where overhead = 2 * sizeOf (undefined :: Int)
-- | The minimal length (~4kb) a buffer must have before filling it and
-- outputting it as a chunk of the output stream.
--
-- This size determines when a buffer is spilled after a 'flush' or a direct
-- bytestring insertion. It is also the size of the first chunk generated by
-- 'toLazyByteString'.
defaultMinimalBufferSize :: Int
defaultMinimalBufferSize = 4 * 1024 - overhead
where overhead = 2 * sizeOf (undefined :: Int)
-- | The default length (64) for the first buffer to be allocated when
-- converting a 'Builder' to a lazy bytestring.
--
-- See 'toLazyByteStringWith' for further explanation.
defaultFirstBufferSize :: Int
defaultFirstBufferSize = 64
-- | The maximal number of bytes for that copying is cheaper than direct
-- insertion into the output stream. This takes into account the fragmentation
-- that may occur in the output buffer due to the early 'flush' implied by the
-- direct bytestring insertion.
--
-- @'defaultMaximalCopySize' = 2 * 'defaultMinimalBufferSize'@
--
defaultMaximalCopySize :: Int
defaultMaximalCopySize = 2 * defaultMinimalBufferSize
------------------------------------------------------------------------------
-- Flushing and running a Builder
------------------------------------------------------------------------------
-- | Output all data written in the current buffer and start a new chunk.
--
-- The use uf this function depends on how the resulting bytestrings are
-- consumed. 'flush' is possibly not very useful in non-interactive scenarios.
-- However, it is kept for compatibility with the builder provided by
-- Data.Binary.Builder.
--
-- When using 'toLazyByteString' to extract a lazy 'L.ByteString' from a
-- 'Builder', this means that a new chunk will be started in the resulting lazy
-- 'L.ByteString'. The remaining part of the buffer is spilled, if the
-- reamining free space is smaller than the minimal desired buffer size.
--
{-
flush :: Builder
flush = Builder $ \k pf _ -> return $ ModifyChunks pf id k
-}
-- | Run a 'Builder' with the given buffer sizes.
--
-- Use this function for integrating the 'Builder' type with other libraries
-- that generate lazy bytestrings.
--
-- Note that the builders should guarantee that on average the desired chunk
-- size is attained. Builders may decide to start a new buffer and not
-- completely fill the existing buffer, if this is faster. However, they should
-- not spill too much of the buffer, if they cannot compensate for it.
--
-- A call @toLazyByteStringWith bufSize minBufSize firstBufSize@ will generate
-- a lazy bytestring according to the following strategy. First, we allocate
-- a buffer of size @firstBufSize@ and start filling it. If it overflows, we
-- allocate a buffer of size @minBufSize@ and copy the first buffer to it in
-- order to avoid generating a too small chunk. Finally, every next buffer will
-- be of size @bufSize@. This, slow startup strategy is required to achieve
-- good speed for short (<200 bytes) resulting bytestrings, as for them the
-- allocation cost is of a large buffer cannot be compensated. Moreover, this
-- strategy also allows us to avoid spilling too much memory for short
-- resulting bytestrings.
--
-- Note that setting @firstBufSize >= minBufSize@ implies that the first buffer
-- is no longer copied but allocated and filled directly. Hence, setting
-- @firstBufSize = bufSize@ means that all chunks will use an underlying buffer
-- of size @bufSize@. This is recommended, if you know that you always output
-- more than @minBufSize@ bytes.
toLazyByteStringWith
:: Int -- ^ Buffer size (upper-bounds the resulting chunk size).
-> Int -- ^ Minimal free buffer space for continuing filling
-- the same buffer after a 'flush' or a direct bytestring
-- insertion. This corresponds to the minimal desired
-- chunk size.
-> Int -- ^ Size of the first buffer to be used and copied for
-- larger resulting sequences
-> Put -- ^ Builder to run.
-> L.ByteString -- ^ Lazy bytestring to output after the builder is
-- finished.
-> L.ByteString -- ^ Resulting lazy bytestring
toLazyByteStringWith bufSize minBufSize firstBufSize (Put b) k =
inlinePerformIO $ fillFirstBuffer (b finalStep)
where
finalStep (BR pf _) = return $ Done pf
-- fill a first very small buffer, if we need more space then copy it
-- to the new buffer of size 'minBufSize'. This way we don't pay the
-- allocation cost of the big 'bufSize' buffer, when outputting only
-- small sequences.
fillFirstBuffer !step0
| minBufSize <= firstBufSize = fillNewBuffer firstBufSize step0
| otherwise = do
fpbuf <- S.mallocByteString firstBufSize
withForeignPtr fpbuf $ \pf -> do
let !br = BR pf (pf `plusPtr` firstBufSize)
mkbs pf' = S.PS fpbuf 0 (pf' `minusPtr` pf)
{-# INLINE mkbs #-}
next <- step0 br
case next of
Done pf'
| pf' == pf -> return k
| otherwise -> return $ L.Chunk (mkbs pf') k
BufferFull newSize pf' nextStep -> do
let !l = pf' `minusPtr` pf
fillNewBuffer (max (l + newSize) minBufSize) $
\(BR pfNew peNew) -> do
copyBytes pfNew pf l
let !brNew = BR (pfNew `plusPtr` l) peNew
nextStep brNew
ModifyChunks pf' bsk nextStep
| pf' == pf ->
return $ bsk (inlinePerformIO $ fillNewBuffer bufSize nextStep)
| otherwise ->
return $ L.Chunk (mkbs pf')
(bsk (inlinePerformIO $ fillNewBuffer bufSize nextStep))
-- allocate and fill a new buffer
fillNewBuffer !size !step0 = do
fpbuf <- S.mallocByteString size
withForeignPtr fpbuf $ fillBuffer fpbuf
where
fillBuffer fpbuf !pbuf = fill pbuf step0
where
!pe = pbuf `plusPtr` size
fill !pf !step = do
let !br = BR pf pe
next <- step br
let mkbs pf' = S.PS fpbuf (pf `minusPtr` pbuf) (pf' `minusPtr` pf)
{-# INLINE mkbs #-}
case next of
Done pf'
| pf' == pf -> return k
| otherwise -> return $ L.Chunk (mkbs pf') k
BufferFull newSize pf' nextStep ->
return $ L.Chunk (mkbs pf')
(inlinePerformIO $
fillNewBuffer (max newSize bufSize) nextStep)
ModifyChunks pf' bsk nextStep
| pf' == pf ->
return $ bsk (inlinePerformIO $ fill pf' nextStep)
| minBufSize < pe `minusPtr` pf' ->
return $ L.Chunk (mkbs pf')
(bsk (inlinePerformIO $ fill pf' nextStep))
| otherwise ->
return $ L.Chunk (mkbs pf')
(bsk (inlinePerformIO $ fillNewBuffer bufSize nextStep))
-- | Extract the lazy 'L.ByteString' from the builder by running it with default
-- buffer sizes. Use this function, if you do not have any special
-- considerations with respect to buffer sizes.
--
-- @ 'toLazyByteString' b = 'toLazyByteStringWith' 'defaultBufferSize' 'defaultMinimalBufferSize' 'defaultFirstBufferSize' b L.empty@
--
-- Note that @'toLazyByteString'@ is a 'Monoid' homomorphism.
--
-- > toLazyByteString mempty == mempty
-- > toLazyByteString (x `mappend` y) == toLazyByteString x `mappend` toLazyByteString y
--
-- However, in the second equation, the left-hand-side is generally faster to
-- execute.
--
toLazyByteString :: Put -> L.ByteString
toLazyByteString b = toLazyByteStringWith
defaultBufferSize defaultMinimalBufferSize defaultFirstBufferSize b L.empty
{-# INLINE toLazyByteString #-}
{-
-- | Pack the chunks of a lazy bytestring into a single strict bytestring.
packChunks :: L.ByteString -> S.ByteString
packChunks lbs = do
S.unsafeCreate (fromIntegral $ L.length lbs) (copyChunks lbs)
where
copyChunks !L.Empty !_pf = return ()
copyChunks !(L.Chunk (S.PS fpbuf o l) lbs') !pf = do
withForeignPtr fpbuf $ \pbuf ->
copyBytes pf (pbuf `plusPtr` o) l
copyChunks lbs' (pf `plusPtr` l)
-- | Run the builder to construct a strict bytestring containing the sequence
-- of bytes denoted by the builder. This is done by first serializing to a lazy bytestring and then packing its
-- chunks to a appropriately sized strict bytestring.
--
-- > toByteString = packChunks . toLazyByteString
--
-- Note that @'toByteString'@ is a 'Monoid' homomorphism.
--
-- > toByteString mempty == mempty
-- > toByteString (x `mappend` y) == toByteString x `mappend` toByteString y
--
-- However, in the second equation, the left-hand-side is generally faster to
-- execute.
--
toByteString :: Builder -> S.ByteString
toByteString = packChunks . toLazyByteString
-- | @toByteStringIOWith bufSize io b@ runs the builder @b@ with a buffer of
-- at least the size @bufSize@ and executes the 'IO' action @io@ whenever the
-- buffer is full.
--
-- Compared to 'toLazyByteStringWith' this function requires less allocation,
-- as the output buffer is only allocated once at the start of the
-- serialization and whenever something bigger than the current buffer size has
-- to be copied into the buffer, which should happen very seldomly for the
-- default buffer size of 32kb. Hence, the pressure on the garbage collector is
-- reduced, which can be an advantage when building long sequences of bytes.
--
toByteStringIOWith :: Int -- ^ Buffer size (upper bounds
-- the number of bytes forced
-- per call to the 'IO' action).
-> (S.ByteString -> IO ()) -- ^ 'IO' action to execute per
-- full buffer, which is
-- referenced by a strict
-- 'S.ByteString'.
-> Builder -- ^ 'Builder' to run.
-> IO () -- ^ Resulting 'IO' action.
toByteStringIOWith bufSize io (Builder b) =
fillNewBuffer bufSize (b finalStep)
where
finalStep pf _ = return $ Done pf
fillNewBuffer !size !step0 = do
S.mallocByteString size >>= fillBuffer
where
fillBuffer fpbuf = fill step0
where
-- safe because the constructed ByteString references the foreign
-- pointer AFTER its buffer was filled.
pf = unsafeForeignPtrToPtr fpbuf
fill !step = do
next <- step pf (pf `plusPtr` size)
case next of
Done pf' ->
unless (pf' == pf) (io $ S.PS fpbuf 0 (pf' `minusPtr` pf))
BufferFull newSize pf' nextStep -> do
io $ S.PS fpbuf 0 (pf' `minusPtr` pf)
if bufSize < newSize
then fillNewBuffer newSize nextStep
else fill nextStep
ModifyChunks pf' bsk nextStep -> do
unless (pf' == pf) (io $ S.PS fpbuf 0 (pf' `minusPtr` pf))
-- was: mapM_ io $ L.toChunks (bsk L.empty)
L.foldrChunks (\bs -> (io bs >>)) (return ()) (bsk L.empty)
fill nextStep
-- | Run the builder with a 'defaultBufferSize'd buffer and execute the given
-- 'IO' action whenever the buffer is full or gets flushed.
--
-- @ 'toByteStringIO' = 'toByteStringIOWith' 'defaultBufferSize'@
--
-- This is a 'Monoid' homomorphism in the following sense.
--
-- > toByteStringIO io mempty == return ()
-- > toByteStringIO io (x `mappend` y) == toByteStringIO io x >> toByteStringIO io y
--
toByteStringIO :: (S.ByteString -> IO ()) -> Builder -> IO ()
toByteStringIO = toByteStringIOWith defaultBufferSize
{-# INLINE toByteStringIO #-}
-}