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Diffstat (limited to 'haddock-library/vendor/attoparsec-0.13.1.0/Data/Attoparsec/ByteString/Buffer.hs')
| -rw-r--r-- | haddock-library/vendor/attoparsec-0.13.1.0/Data/Attoparsec/ByteString/Buffer.hs | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/haddock-library/vendor/attoparsec-0.13.1.0/Data/Attoparsec/ByteString/Buffer.hs b/haddock-library/vendor/attoparsec-0.13.1.0/Data/Attoparsec/ByteString/Buffer.hs new file mode 100644 index 00000000..ac94dfcc --- /dev/null +++ b/haddock-library/vendor/attoparsec-0.13.1.0/Data/Attoparsec/ByteString/Buffer.hs @@ -0,0 +1,156 @@ +{-# LANGUAGE BangPatterns #-} +-- | +-- Module : Data.Attoparsec.ByteString.Buffer +-- Copyright : Bryan O'Sullivan 2007-2015 +-- License : BSD3 +-- +-- Maintainer : bos@serpentine.com +-- Stability : experimental +-- Portability : GHC +-- +-- An "immutable" buffer that supports cheap appends. +-- +-- A Buffer is divided into an immutable read-only zone, followed by a +-- mutable area that we've preallocated, but not yet written to. +-- +-- We overallocate at the end of a Buffer so that we can cheaply +-- append. Since a user of an existing Buffer cannot see past the end +-- of its immutable zone into the data that will change during an +-- append, this is safe. +-- +-- Once we run out of space at the end of a Buffer, we do the usual +-- doubling of the buffer size. +-- +-- The fact of having a mutable buffer really helps with performance, +-- but it does have a consequence: if someone misuses the Partial API +-- that attoparsec uses by calling the same continuation repeatedly +-- (which never makes sense in practice), they could overwrite data. +-- +-- Since the API *looks* pure, it should *act* pure, too, so we use +-- two generation counters (one mutable, one immutable) to track the +-- number of appends to a mutable buffer. If the counters ever get out +-- of sync, someone is appending twice to a mutable buffer, so we +-- duplicate the entire buffer in order to preserve the immutability +-- of its older self. +-- +-- While we could go a step further and gain protection against API +-- abuse on a multicore system, by use of an atomic increment +-- instruction to bump the mutable generation counter, that would be +-- very expensive, and feels like it would also be in the realm of the +-- ridiculous. Clients should never call a continuation more than +-- once; we lack a linear type system that could enforce this; and +-- there's only so far we should go to accommodate broken uses. + +module Data.Attoparsec.ByteString.Buffer + ( + Buffer + , buffer + , unbuffer + , pappend + , length + , unsafeIndex + , substring + , unsafeDrop + ) where + +import Control.Exception (assert) +import Data.ByteString.Internal (ByteString(..), memcpy, nullForeignPtr) +import Data.Attoparsec.Internal.Fhthagn (inlinePerformIO) +import Data.List (foldl1') +import Data.Monoid as Mon (Monoid(..)) +import Data.Semigroup (Semigroup(..)) +import Data.Word (Word8) +import Foreign.ForeignPtr (ForeignPtr, withForeignPtr) +import Foreign.Ptr (castPtr, plusPtr) +import Foreign.Storable (peek, peekByteOff, poke, sizeOf) +import GHC.ForeignPtr (mallocPlainForeignPtrBytes) +import Prelude hiding (length) + +-- If _cap is zero, this buffer is empty. +data Buffer = Buf { + _fp :: {-# UNPACK #-} !(ForeignPtr Word8) + , _off :: {-# UNPACK #-} !Int + , _len :: {-# UNPACK #-} !Int + , _cap :: {-# UNPACK #-} !Int + , _gen :: {-# UNPACK #-} !Int + } + +instance Show Buffer where + showsPrec p = showsPrec p . unbuffer + +-- | The initial 'Buffer' has no mutable zone, so we can avoid all +-- copies in the (hopefully) common case of no further input being fed +-- to us. +buffer :: ByteString -> Buffer +buffer (PS fp off len) = Buf fp off len len 0 + +unbuffer :: Buffer -> ByteString +unbuffer (Buf fp off len _ _) = PS fp off len + +instance Semigroup Buffer where + (Buf _ _ _ 0 _) <> b = b + a <> (Buf _ _ _ 0 _) = a + buf <> (Buf fp off len _ _) = append buf fp off len + +instance Monoid Buffer where + mempty = Buf nullForeignPtr 0 0 0 0 + + mappend = (<>) + + mconcat [] = Mon.mempty + mconcat xs = foldl1' mappend xs + +pappend :: Buffer -> ByteString -> Buffer +pappend (Buf _ _ _ 0 _) bs = buffer bs +pappend buf (PS fp off len) = append buf fp off len + +append :: Buffer -> ForeignPtr a -> Int -> Int -> Buffer +append (Buf fp0 off0 len0 cap0 gen0) !fp1 !off1 !len1 = + inlinePerformIO . withForeignPtr fp0 $ \ptr0 -> + withForeignPtr fp1 $ \ptr1 -> do + let genSize = sizeOf (0::Int) + newlen = len0 + len1 + gen <- if gen0 == 0 + then return 0 + else peek (castPtr ptr0) + if gen == gen0 && newlen <= cap0 + then do + let newgen = gen + 1 + poke (castPtr ptr0) newgen + memcpy (ptr0 `plusPtr` (off0+len0)) + (ptr1 `plusPtr` off1) + (fromIntegral len1) + return (Buf fp0 off0 newlen cap0 newgen) + else do + let newcap = newlen * 2 + fp <- mallocPlainForeignPtrBytes (newcap + genSize) + withForeignPtr fp $ \ptr_ -> do + let ptr = ptr_ `plusPtr` genSize + newgen = 1 + poke (castPtr ptr_) newgen + memcpy ptr (ptr0 `plusPtr` off0) (fromIntegral len0) + memcpy (ptr `plusPtr` len0) (ptr1 `plusPtr` off1) + (fromIntegral len1) + return (Buf fp genSize newlen newcap newgen) + +length :: Buffer -> Int +length (Buf _ _ len _ _) = len +{-# INLINE length #-} + +unsafeIndex :: Buffer -> Int -> Word8 +unsafeIndex (Buf fp off len _ _) i = assert (i >= 0 && i < len) . + inlinePerformIO . withForeignPtr fp $ flip peekByteOff (off+i) +{-# INLINE unsafeIndex #-} + +substring :: Int -> Int -> Buffer -> ByteString +substring s l (Buf fp off len _ _) = + assert (s >= 0 && s <= len) . + assert (l >= 0 && l <= len-s) $ + PS fp (off+s) l +{-# INLINE substring #-} + +unsafeDrop :: Int -> Buffer -> ByteString +unsafeDrop s (Buf fp off len _ _) = + assert (s >= 0 && s <= len) $ + PS fp (off+s) (len-s) +{-# INLINE unsafeDrop #-} |