{-# LANGUAGE CPP,MagicHash,ScopedTypeVariables,FlexibleInstances,RankNTypes,TypeSynonymInstances,MultiParamTypeClasses,BangPatterns #-}
-- | By Chris Kuklewicz, drawing heavily from binary and binary-strict,
-- but all the bugs are my own.
--
-- This file is under the usual BSD3 licence, copyright 2008.
--
-- Modified the monad to be strict for version 2.0.0
--
-- This started out as an improvement to
-- "Data.Binary.Strict.IncrementalGet" with slightly better internals.
-- The simplified 'Get', 'runGet', 'Result' trio with the
-- "Data.Binary.Strict.Class.BinaryParser" instance are an _untested_
-- upgrade from IncrementalGet. Especially untested are the
-- strictness properties.
--
-- 'Get' usefully implements Applicative and Monad, MonadError,
-- Alternative and MonadPlus. Unhandled errors are reported along
-- with the number of bytes successfully consumed. Effects of
-- 'suspend' and 'putAvailable' are visible after
-- fail/throwError/mzero.
--
-- Each time the parser reaches the end of the input it will return a
-- Partial wrapped continuation which requests a (Maybe
-- Lazy.ByteString). Passing (Just bs) will append bs to the input so
-- far and continue processing. If you pass Nothing to the
-- continuation then you are declaring that there will never be more
-- input and that the parser should never again return a partial
-- contination; it should return failure or finished.
--
-- 'suspendUntilComplete' repeatedly uses a partial continuation to
-- ask for more input until 'Nothing' is passed and then it proceeds
-- with parsing.
--
-- The 'getAvailable' command returns the lazy byte string the parser
-- has remaining before calling 'suspend'. The 'putAvailable'
-- replaces this input and is a bit fancy: it also replaces the input
-- at the current offset for all the potential catchError/mplus
-- handlers. This change is _not_ reverted by fail/throwError/mzero.
--
-- The three 'lookAhead' and 'lookAheadM' and 'lookAheadE' functions are
-- very similar to the ones in binary's Data.Binary.Get.
--
--
-- Add specialized high-bit-run
module Text.ProtocolBuffers.Get
(Get,runGet,runGetAll,Result(..)
-- main primitives
,ensureBytes,getStorable,getLazyByteString,suspendUntilComplete
-- parser state manipulation
,getAvailable,putAvailable
-- lookAhead capabilities
,lookAhead,lookAheadM,lookAheadE
-- below is for implementation of BinaryParser (for Int64 and Lazy bytestrings)
,skip,bytesRead,isEmpty,isReallyEmpty,remaining,spanOf,highBitRun
,getWord8,getByteString
,getWord16be,getWord32be,getWord64be
,getWord16le,getWord32le,getWord64le
,getWordhost,getWord16host,getWord32host,getWord64host
--
-- ,scan
,decode7,decode7size,decode7unrolled
) where
-- The Get monad is an instance of binary-strict's BinaryParser:
-- import qualified Data.Binary.Strict.Class as P(BinaryParser(..))
-- The Get monad is an instance of all of these library classes:
import Control.Applicative(Applicative(pure,(<*>)),Alternative(empty,(<|>)))
import Control.Monad(MonadPlus(mzero,mplus),when)
import Control.Monad.Error.Class(MonadError(throwError,catchError),Error(strMsg))
-- It can be a MonadCont, but the semantics are too broken without a ton of work.
-- implementation imports
--import Control.Monad(replicateM,(>=>)) -- XXX testing
--import qualified Data.ByteString as S(unpack) -- XXX testing
--import qualified Data.ByteString.Lazy as L(pack) -- XXX testing
import Control.Monad(ap) -- instead of Functor.fmap; ap for Applicative
import Data.Bits(Bits((.|.),(.&.)),shiftL)
import qualified Data.ByteString as S(concat,length,null,splitAt,findIndex)
import qualified Data.ByteString.Internal as S(ByteString(..),toForeignPtr,inlinePerformIO)
import qualified Data.ByteString.Unsafe as S(unsafeIndex,unsafeDrop {-,unsafeTake-})
import qualified Data.ByteString.Lazy as L(take,drop,length,span,toChunks,fromChunks,null,findIndex)
import qualified Data.ByteString.Lazy.Internal as L(ByteString(..),chunk)
import qualified Data.Foldable as F(foldr,foldr1) -- used with Seq
import Data.Int(Int32,Int64) -- index type for L.ByteString
import Data.Monoid(Monoid(mempty,mappend)) -- Writer has a Monoid contraint
import Data.Sequence(Seq,null,(|>)) -- used for future queue in handler state
import Data.Word(Word,Word8,Word16,Word32,Word64)
import Foreign.ForeignPtr(withForeignPtr)
import Foreign.Ptr(Ptr,castPtr,plusPtr,minusPtr,nullPtr)
import Foreign.Storable(Storable(peek,sizeOf))
import System.IO.Unsafe(unsafePerformIO)
#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
import GHC.Base(Int(..),uncheckedShiftL#)
import GHC.Word(Word16(..),Word32(..),Word64(..),uncheckedShiftL64#)
#endif
--import Debug.Trace(trace)
trace :: a -> b -> b
trace _ = id
-- Simple external return type
data Result a = Failed {-# UNPACK #-} !Int64 String
| Finished !L.ByteString {-# UNPACK #-} !Int64 a
| Partial (Maybe L.ByteString -> Result a)
-- Internal state type, not exposed to the user.
-- Invariant: (S.null _top) implies (L.null _current)
data S = S { _top :: {-# UNPACK #-} !S.ByteString
, _current :: !L.ByteString
, consumed :: {-# UNPACK #-} !Int64
} deriving Show
data T3 s = T3 !Int !s !Int
--data TU s = TU'OK !s !Int | TU'DO (Get s)
data TU s = TU'OK !s !Int
{-# SPECIALIZE decode7unrolled :: Get Int64 #-}
{-# SPECIALIZE decode7unrolled :: Get Int32 #-}
{-# SPECIALIZE decode7unrolled :: Get Word64 #-}
{-# SPECIALIZE decode7unrolled :: Get Word32 #-}
{-# SPECIALIZE decode7unrolled :: Get Int #-}
{-# SPECIALIZE decode7unrolled :: Get Integer #-}
decode7unrolled :: forall s. (Num s,Integral s, Bits s) => Get s
{-# NOINLINE decode7unrolled #-}
decode7unrolled = Get $ \ sc sIn@(S ss@(S.PS fp off len) bs n) pc -> trace ("decode7unrolled: "++show (len,n)) $
if S.null ss
then trace ("decode7unrolled: S.null ss") $ unGet decode7 sc sIn pc -- decode7 will try suspend then will fail if still bad
else
let (TU'OK x i) =
unsafePerformIO $ withForeignPtr fp $ \ptr0 -> do
if ptr0 == nullPtr || len < 1 then error "Get.decode7unrolled: ByteString invariant failed" else do
let ok :: s -> Int -> IO (TU s)
ok x0 i0 = return (TU'OK x0 i0)
more,err :: IO (TU s)
more = return (TU'OK 0 0) -- decode7
err = return (TU'OK 0 (-1)) -- throwError
{-# INLINE ok #-}
{-# INLINE more #-}
{-# INLINE err #-}
-- -- Next line is segfault fix for null bytestrings from Nathan Howell <nhowell@alphaheavy.com>
-- if ptr0 == nullPtr then more else do
let start = ptr0 `plusPtr` off :: Ptr Word8
b'1 <- peek start
if b'1 < 128 then ok (fromIntegral b'1) 1 else do
let !val'1 = fromIntegral (b'1 .&. 0x7F)
!end = start `plusPtr` len
!ptr2 = start `plusPtr` 1 :: Ptr Word8
if ptr2 >= end then more else do
b'2 <- peek ptr2
if b'2 < 128 then ok (val'1 .|. (fromIntegral b'2 `shiftL` 7)) 2 else do
let !val'2 = (val'1 .|. (fromIntegral (b'2 .&. 0x7F) `shiftL` 7))
!ptr3 = ptr2 `plusPtr` 1
if ptr3 >= end then more else do
b'3 <- peek ptr3
if b'3 < 128 then ok (val'2 .|. (fromIntegral b'3 `shiftL` 14)) 3 else do
let !val'3 = (val'2 .|. (fromIntegral (b'3 .&. 0x7F) `shiftL` 14))
!ptr4 = ptr3 `plusPtr` 1
if ptr4 >= end then more else do
b'4 <- peek ptr4
if b'4 < 128 then ok (val'3 .|. (fromIntegral b'4 `shiftL` 21)) 4 else do
let !val'4 = (val'3 .|. (fromIntegral (b'4 .&. 0x7F) `shiftL` 21))
!ptr5 = ptr4 `plusPtr` 1
if ptr5 >= end then more else do
b'5 <- peek ptr5
if b'5 < 128 then ok (val'4 .|. (fromIntegral b'5 `shiftL` 28)) 5 else do
let !val'5 = (val'4 .|. (fromIntegral (b'5 .&. 0x7F) `shiftL` 28))
!ptr6 = ptr5 `plusPtr` 1
if ptr6 >= end then more else do
b'6 <- peek ptr6
if b'6 < 128 then ok (val'5 .|. (fromIntegral b'6 `shiftL` 35)) 6 else do
let !val'6 = (val'5 .|. (fromIntegral (b'6 .&. 0x7F) `shiftL` 35))
!ptr7 = ptr6 `plusPtr` 1
if ptr7 >= end then more else do
b'7 <- peek ptr7
if b'7 < 128 then ok (val'6 .|. (fromIntegral b'7 `shiftL` 42)) 7 else do
let !val'7 = (val'6 .|. (fromIntegral (b'7 .&. 0x7F) `shiftL` 42))
!ptr8 = ptr7 `plusPtr` 1
if ptr8 >= end then more else do
b'8 <- peek ptr8
if b'8 < 128 then ok (val'7 .|. (fromIntegral b'8 `shiftL` 49)) 8 else do
let !val'8 = (val'7 .|. (fromIntegral (b'8 .&. 0x7F) `shiftL` 49))
!ptr9 = ptr8 `plusPtr` 1
if ptr9 >= end then more else do
b'9 <- peek ptr9
if b'9 < 128 then ok (val'8 .|. (fromIntegral b'9 `shiftL` 56)) 9 else do
let !val'9 = (val'8 .|. (fromIntegral (b'9 .&. 0x7F) `shiftL` 56))
!ptrA = ptr9 `plusPtr` 1
if ptrA >= end then more else do
b'A <- peek ptrA
if b'A < 128 then ok (val'9 .|. (fromIntegral b'A `shiftL` 63)) 10 else do
err
in if i > 0
then let ss' = (S.unsafeDrop i ss)
n' = n+fromIntegral i
s'safe = make_safe (S ss' bs n')
in sc x s'safe pc
else if i==0 then unGet decode7 sc sIn pc
else unGet (throwError $ "Text.ProtocolBuffers.Get.decode7unrolled: more than 10 bytes needed at bytes read of "++show n) sc sIn pc
{-# SPECIALIZE decode7 :: Get Int64 #-}
{-# SPECIALIZE decode7 :: Get Int32 #-}
{-# SPECIALIZE decode7 :: Get Word64 #-}
{-# SPECIALIZE decode7 :: Get Word32 #-}
{-# SPECIALIZE decode7 :: Get Int #-}
{-# SPECIALIZE decode7 :: Get Integer #-}
decode7 :: forall s. (Integral s, Bits s) => Get s
{-# NOINLINE decode7 #-}
decode7 = go 0 0
where
go !s1 !shift1 = trace ("decode7.go: "++show (toInteger s1, shift1)) $ do
let -- scanner's inner loop decodes only in current top strict bytestring, does not advance input state
scanner (S.PS fp off len) =
withForeignPtr fp $ \ptr0 -> do
if ptr0 == nullPtr || len < 1 then error "Get.decode7: ByteString invariant failed" else do
let start = ptr0 `plusPtr` off -- start is a pointer to the next valid byte
end = start `plusPtr` len -- end is a pointer one byte past the last valid byte
inner :: (Ptr Word8) -> s -> Int -> IO (T3 s)
inner !ptr !s !shift
| ptr < end = do
w <- peek ptr
trace ("w: " ++ show w) $ do
if (128>) w
then return $ T3 (succ (ptr `minusPtr` start) ) -- length of capture
(s .|. ((fromIntegral w) `shiftL` shift)) -- put the last bits into high position
(-1) -- negative shift indicates satisfied
else inner (ptr `plusPtr` 1) -- loop on next byte
(s .|. ((fromIntegral (w .&. 0x7F)) `shiftL` shift)) -- put the new bits into high position
(shift+7) -- increase high position for next loop
| otherwise = return $ T3 (ptr `minusPtr` start) -- length so far (ptr past end-of-string so no succ)
s -- value so far
shift -- next shift to use
inner start s1 shift1
(S ss bs n) <- getFull
trace ("getFull says: "++ show ((S.length ss,ss),(L.length bs),n)) $ do
if S.null ss
then do
continue <- suspend
if continue
then go s1 shift1
else fail "Get.decode7: Zero length input" -- XXX can be triggered!
else do
let (T3 i sOut shiftOut) = unsafePerformIO $ scanner ss
t = S.unsafeDrop i ss -- Warning: 't' may be mempty
n' = n + fromIntegral i
trace ("scanner says "++show ((i,toInteger sOut,shiftOut),(S.length t,n'))) $ do
if 0 <= shiftOut
then do
putFull_unsafe (make_state bs n')
if L.null bs
then do
continue <- suspend
if continue
then go sOut shiftOut
else return sOut
else do
go sOut shiftOut
else do
putFull_safe (S t bs n') -- bs from getFull is still valid
return sOut
data T2 = T2 !Int64 !Bool
decode7size :: Get Int64
decode7size = go 0
where
go !len1 = do
let scanner (S.PS fp off len) =
withForeignPtr fp $ \ptr0 -> do
if ptr0 == nullPtr || len < 1 then error "Get.decode7size: ByteString invariant failed" else do
let start = ptr0 `plusPtr` off
end = start `plusPtr` len
inner :: (Ptr Word8) -> IO T2
inner !ptr
| ptr < end = do
w <- peek ptr
if (128>) w
then return $ T2 (fromIntegral (ptr `minusPtr` start)) True
else inner (ptr `plusPtr` 1)
| otherwise = return $ T2 (fromIntegral (ptr `minusPtr` start)) False
inner start
(S ss bs n) <- getFull
if S.null ss
then do
continue <- suspend
if continue
then go len1
else fail "Get.decode7size: zero length input"
else do
let (T2 i ok) = unsafePerformIO $ scanner ss
t = S.unsafeDrop (fromIntegral i) ss
n' = n + i
len2 = len1 + i
if ok
then do
putFull_unsafe (S t bs n')
return len2
else do
putFull_unsafe (make_state bs n')
if L.null bs
then do
continue <- suspend
if continue
then go len2
else return len2
else
go len2
-- Private Internal error handling stack type
-- This must NOT be exposed by this module
--
-- The ErrorFrame is the top-level error handler setup when execution begins.
-- It starts with the Bool set to True: meaning suspend can ask for more input.
-- Once suspend get 'Nothing' in reply the Bool is set to False, which means
-- that 'suspend' should no longer ask for input -- the input is finished.
-- Why store the Bool there? It was handy when I needed to add it.
data FrameStack b = ErrorFrame (String -> S -> Result b) -- top level handler
Bool -- True at start, False if Nothing passed to suspend continuation
| HandlerFrame (Maybe ( S -> FrameStack b -> String -> Result b )) -- encapsulated handler
S -- stored state to pass to handler
(Seq L.ByteString) -- additional input to hass to handler
(FrameStack b) -- earlier/shallower/outer handlers
type Success b a = (a -> S -> FrameStack b -> Result b)
-- Internal monad type
newtype Get a = Get {
unGet :: forall b. -- the forall hides the CPS style (and prevents use of MonadCont)
Success b a -- main continuation
-> S -- parser state
-> FrameStack b -- error handler stack
-> Result b -- operation
}
-- These implement the checkponting needed to store and revive the
-- state for lookAhead. They are fragile because the setCheckpoint
-- must preceed either useCheckpoint or clearCheckpoint but not both.
-- The FutureFrame must be the most recent handler, so the commands
-- must be in the same scope depth. Because of these constraints, the reader
-- value 'r' does not need to be stored and can be taken from the Get
-- parameter.
--
-- IMPORTANT: Any FutureFrame at the top level(s) is discarded by throwError.
setCheckpoint,useCheckpoint,clearCheckpoint :: Get ()
setCheckpoint = Get $ \ sc s pc -> sc () s (HandlerFrame Nothing s mempty pc)
useCheckpoint = Get $ \ sc (S _ _ _) frame ->
case frame of
(HandlerFrame Nothing s future pc) -> sc () (collect s future) pc
_ -> error "Text.ProtocolBuffers.Get: Impossible useCheckpoint frame!"
clearCheckpoint = Get $ \ sc s frame ->
case frame of
(HandlerFrame Nothing _s _future pc) -> sc () s pc
_ -> error "Text.ProtocolBuffers.Get: Impossible clearCheckpoint frame!"
-- | 'lookAhead' runs the @todo@ action and then rewinds only the
-- BinaryParser state. Any new input from 'suspend' or changes from
-- 'putAvailable' are kept. Changes to the user state (MonadState)
-- are kept. The MonadWriter output is retained.
--
-- If an error is thrown then the entire monad state is reset to last
-- catchError as usual.
lookAhead :: Get a -> Get a
lookAhead todo = do
setCheckpoint
a <- todo
useCheckpoint
return a
-- | 'lookAheadM' runs the @todo@ action. If the action returns 'Nothing' then the
-- BinaryParser state is rewound (as in 'lookAhead'). If the action return 'Just' then
-- the BinaryParser is not rewound, and lookAheadM acts as an identity.
--
-- If an error is thrown then the entire monad state is reset to last
-- catchError as usual.
lookAheadM :: Get (Maybe a) -> Get (Maybe a)
lookAheadM todo = do
setCheckpoint
a <- todo
maybe useCheckpoint (const clearCheckpoint) a
return a
-- | 'lookAheadE' runs the @todo@ action. If the action returns 'Left' then the
-- BinaryParser state is rewound (as in 'lookAhead'). If the action return 'Right' then
-- the BinaryParser is not rewound, and lookAheadE acts as an identity.
--
-- If an error is thrown then the entire monad state is reset to last
-- catchError as usual.
lookAheadE :: Get (Either a b) -> Get (Either a b)
lookAheadE todo = do
setCheckpoint
a <- todo
either (const useCheckpoint) (const clearCheckpoint) a
return a
-- 'collect' is used by 'putCheckpoint' and 'throwError'
collect :: S -> Seq L.ByteString -> S
collect s@(S ss bs n) future | Data.Sequence.null future = make_safe $ s
| otherwise = make_safe $ S ss (mappend bs (F.foldr1 mappend future)) n
-- Put the Show instances here
instance (Show a) => Show (Result a) where
showsPrec _ (Failed n msg) = ("(Failed "++) . shows n . (' ':) . shows msg . (")"++)
showsPrec _ (Finished bs n a) =
("(CFinished ("++)
. shows bs . (") ("++)
. shows n . (") ("++)
. shows a . ("))"++)
showsPrec _ (Partial {}) = ("(Partial <Maybe Data.ByteString.Lazy.ByteString-> Result a)"++)
instance Show (FrameStack b) where
showsPrec _ (ErrorFrame _ p) =(++) "(ErrorFrame <e->s->m b> " . shows p . (")"++)
showsPrec _ (HandlerFrame _ s future pc) = ("(HandlerFrame <> ("++)
. shows s . (") ("++) . shows future . (") ("++)
. shows pc . (")"++)
-- | 'runGet' is the simple executor
runGet :: Get a -> L.ByteString -> Result a
runGet (Get f) bsIn = f scIn sIn (ErrorFrame ec True)
where scIn a (S ss bs n) _pc = Finished (L.chunk ss bs) n a
sIn = make_state bsIn 0
ec msg sOut = Failed (consumed sOut) msg
-- | 'runGetAll' is the simple executor, and will not ask for any continuation because this lazy bytestring is all the input
runGetAll :: Get a -> L.ByteString -> Result a
runGetAll (Get f) bsIn = f scIn sIn (ErrorFrame ec False)
where scIn a (S ss bs n) _pc = Finished (L.chunk ss bs) n a
sIn = make_state bsIn 0
ec msg sOut = Failed (consumed sOut) msg
-- | Get the input currently available to the parser.
getAvailable :: Get L.ByteString
getAvailable = Get $ \ sc s@(S ss bs _) pc -> sc (L.chunk ss bs) s pc
-- | 'putAvailable' replaces the bytestream past the current # of read
-- bytes. This will also affect pending MonadError handler and
-- MonadPlus branches. I think all pending branches have to have
-- fewer bytesRead than the current one. If this is wrong then an
-- error will be thrown.
--
-- WARNING : 'putAvailable' is still untested.
putAvailable :: L.ByteString -> Get ()
putAvailable !bsNew = Get $ \ sc (S _ss _bs n) pc ->
let !s' = make_state bsNew n
rebuild (HandlerFrame catcher (S ss1 bs1 n1) future pc') =
HandlerFrame catcher sNew mempty (rebuild pc')
where balance = n - n1
whole | balance < 0 = error "Impossible? Cannot rebuild HandlerFrame in MyGet.putAvailable: balance is negative!"
| otherwise = L.take balance $ L.chunk ss1 bs1 `mappend` F.foldr mappend mempty future
sNew | balance /= L.length whole = error "Impossible? MyGet.putAvailable.rebuild.sNew HandlerFrame assertion failed."
| otherwise = make_state (mappend whole bsNew) n1
rebuild x@(ErrorFrame {}) = x
in sc () s' (rebuild pc)
-- Internal access to full internal state, as helper functions
getFull :: Get S
getFull = Get $ \ sc s pc -> sc s s pc
{-# INLINE putFull_unsafe #-}
putFull_unsafe :: S -> Get ()
putFull_unsafe !s = Get $ \ sc _s pc -> sc () s pc
{-# INLINE make_safe #-}
make_safe :: S -> S
make_safe s@(S ss bs n) =
if S.null ss
then make_state bs n
else s
{-# INLINE make_state #-}
make_state :: L.ByteString -> Int64 -> S
make_state L.Empty n = S mempty mempty n
make_state (L.Chunk ss bs) n = S ss bs n
putFull_safe :: S -> Get ()
putFull_safe= putFull_unsafe . make_safe
-- | Keep calling 'suspend' until Nothing is passed to the 'Partial'
-- continuation. This ensures all the data has been loaded into the
-- state of the parser.
suspendUntilComplete :: Get ()
suspendUntilComplete = do
continue <- suspend
when continue suspendUntilComplete
-- | Call suspend and throw and error with the provided @msg@ if
-- Nothing has been passed to the 'Partial' continuation. Otherwise
-- return ().
suspendMsg :: String -> Get ()
suspendMsg msg = do continue <- suspend
if continue then return ()
else throwError msg
-- | check that there are at least @n@ bytes available in the input.
-- This will suspend if there is to little data.
ensureBytes :: Int64 -> Get ()
ensureBytes n = do
(S ss bs _read) <- getFull
if S.null ss
then suspendMsg "ensureBytes failed" >> ensureBytes n
else do
if n < fromIntegral (S.length ss)
then return ()
else do if n == L.length (L.take n (L.chunk ss bs))
then return ()
else suspendMsg "ensureBytes failed" >> ensureBytes n
{-# INLINE ensureBytes #-}
-- | Pull @n@ bytes from the input, as a lazy ByteString. This will
-- suspend if there is too little data.
getLazyByteString :: Int64 -> Get L.ByteString
getLazyByteString n | n<=0 = return mempty
| otherwise = do
(S ss bs offset) <- getFull
if S.null ss
then do
suspendMsg ("getLazyByteString S.null ss failed with "++show (n,(S.length ss,L.length bs,offset)))
getLazyByteString n
else do
case splitAtOrDie n (L.chunk ss bs) of -- safe use of L.chunk because of S.null ss check above
Just (consume,rest) -> do
putFull_unsafe (make_state rest (offset+n))
return $! consume
Nothing -> do
suspendMsg ("getLazyByteString (Nothing from splitAtOrDie) failed with "++show (n,(S.length ss,L.length bs,offset)))
getLazyByteString n
{-# INLINE getLazyByteString #-} -- important
-- | 'suspend' is supposed to allow the execution of the monad to be
-- halted, awaiting more input. The computation is supposed to
-- continue normally if this returns True, and is supposed to halt
-- without calling suspend again if this returns False. All future
-- calls to suspend will return False automatically and no nothing
-- else.
--
-- These semantics are too specialized to let this escape this module.
class MonadSuspend m where
suspend :: m Bool
-- The instance here is fairly specific to the stack manipluation done
-- by 'addFuture' to ('S' user) and to the packaging of the resumption
-- function in 'IResult'('IPartial').
instance MonadSuspend Get where
suspend = Get (
let checkBool (ErrorFrame _ b) = b
checkBool (HandlerFrame _ _ _ pc) = checkBool pc
-- addFuture puts the new data in 'future' where throwError's collect can find and use it
addFuture bs (HandlerFrame catcher s future pc) =
HandlerFrame catcher s (future |> bs) (addFuture bs pc)
addFuture _bs x@(ErrorFrame {}) = x
-- Once suspend is given Nothing, it remembers this and always returns False
rememberFalse (ErrorFrame ec _) = ErrorFrame ec False
rememberFalse (HandlerFrame catcher s future pc) =
HandlerFrame catcher s future (rememberFalse pc)
in \ sc sIn pcIn ->
if checkBool pcIn -- Has Nothing ever been given to a partial continuation?
then let f Nothing = let pcOut = rememberFalse pcIn
in sc False sIn pcOut
f (Just bs') = let sOut = appendBS sIn bs'
pcOut = addFuture bs' pcIn
in sc True sOut pcOut
in Partial f
else sc False sIn pcIn -- once Nothing has been given suspend is a no-op
)
where appendBS (S ss bs n) bs' = make_safe (S ss (mappend bs bs') n)
-- A unique sort of command...
-- | 'discardInnerHandler' causes the most recent catchError to be
-- discarded, i.e. this reduces the stack of error handlers by removing
-- the top one. These are the same handlers which Alternative((<|>)) and
-- MonadPlus(mplus) use. This is useful to commit to the current branch and let
-- the garbage collector release the suspended handler and its hold on
-- the earlier input.
discardInnerHandler :: Get ()
discardInnerHandler = Get $ \ sc s pcIn ->
let pcOut = case pcIn of ErrorFrame {} -> pcIn
HandlerFrame _ _ _ pc' -> pc'
in sc () s pcOut
{-# INLINE discardInnerHandler #-}
{- Currently unused, commented out to satisfy -Wall
-- | 'discardAllHandlers' causes all catchError handler to be
-- discarded, i.e. this reduces the stack of error handlers to the top
-- level handler. These are the same handlers which Alternative((<|>))
-- and MonadPlus(mplus) use. This is useful to commit to the current
-- branch and let the garbage collector release the suspended handlers
-- and their hold on the earlier input.
discardAllHandlers :: Get ()
discardAllHandlers = Get $ \ sc s pcIn ->
let base pc@(ErrorFrame {}) = pc
base (HandlerFrame _ _ _ pc) = base pc
in sc () s (base pcIn)
{-# INLINE discardAllHandlers #-}
-}
-- The BinaryParser instance:
-- | Discard the next @m@ bytes
skip :: Int64 -> Get ()
skip m | m <=0 = return ()
| otherwise = do
ensureBytes m
(S ss bs n) <- getFull
-- Could ignore impossible S.null ss due to (ensureBytes m) and (0 < m) but be paranoid
let lbs = L.chunk ss bs -- L.chunk is safe
putFull_unsafe (make_state (L.drop m lbs) (n+m)) -- drop will not perform less than 'm' bytes due to ensureBytes above
-- | Return the number of 'bytesRead' so far. Initially 0, never negative.
bytesRead :: Get Int64
bytesRead = fmap consumed getFull
-- | Return the number of bytes 'remaining' before the current input
-- runs out and 'suspend' might be called.
remaining :: Get Int64
remaining = do (S ss bs _) <- getFull
return $ fromIntegral (S.length ss) + (L.length bs)
-- | Return True if the number of bytes 'remaining' is 0. Any futher
-- attempts to read an empty parser will call 'suspend' which might
-- result in more input to consume.
--
-- Compare with 'isReallyEmpty'
isEmpty :: Get Bool
isEmpty = do (S ss _bs _n) <- getFull
return (S.null ss) -- && (L.null bs)
-- | Return True if the input is exhausted and will never be added to.
-- Returns False if there is input left to consume.
--
-- Compare with 'isEmpty'
isReallyEmpty :: Get Bool
isReallyEmpty = isEmpty >>= loop
where loop False = return False
loop True = do
continue <- suspend
if continue
then isReallyEmpty
else return True
-- | get the longest prefix of the input where the high bit is set as well as following byte.
-- This made getVarInt slower.
highBitRun :: Get Int64
{-# INLINE highBitRun #-}
highBitRun = loop where
loop :: Get Int64
{-# INLINE loop #-}
loop = do
(S ss bs _n) <- getFull
-- S.null ss is okay, will lead to Nothing, Nothing, suspend below
let mi = S.findIndex (128>) ss
case mi of
Just i -> return (succ $ fromIntegral i)
Nothing -> do
let mj = L.findIndex (128>) bs
case mj of
Just j -> return (fromIntegral (S.length ss) + succ j)
Nothing -> do
continue <- suspend
if continue then loop
else fail "highBitRun has failed"
-- | get the longest prefix of the input where all the bytes satisfy the predicate.
spanOf :: (Word8 -> Bool) -> Get (L.ByteString)
spanOf f = do let loop = do (S ss bs n) <- getFull
let (pre,post) = L.span f (L.chunk ss bs) -- L.chunk is safe
putFull_unsafe (make_state post (n + L.length pre))
if L.null post
then do continue <- suspend
if continue then fmap ((L.toChunks pre)++) loop
else return (L.toChunks pre)
else return (L.toChunks pre)
fmap L.fromChunks loop
{-# INLINE spanOf #-}
-- | Pull @n@ bytes from the input, as a strict ByteString. This will
-- suspend if there is too little data. If the result spans multiple
-- lazy chunks then the result occupies a freshly allocated strict
-- bytestring, otherwise it fits in a single chunk and refers to the
-- same immutable memory block as the whole chunk.
getByteString :: Int -> Get S.ByteString
getByteString nIn | nIn <= 0 = return mempty
| otherwise = do
(S ss bs n) <- getFull
if nIn < S.length ss -- Leave at least one character of 'ss' in 'post' allowing putFull_unsafe below
then do let (pre,post) = S.splitAt nIn ss
putFull_unsafe (S post bs (n+fromIntegral nIn))
return $! pre
-- Expect nIn to be less than S.length ss the vast majority of times
-- so do not worry about doing anything fancy here.
else do now <- fmap (S.concat . L.toChunks) (getLazyByteString (fromIntegral nIn))
return $! now
{-# INLINE getByteString #-} -- important
getWordhost :: Get Word
getWordhost = getStorable
{-# INLINE getWordhost #-}
getWord8 :: Get Word8
getWord8 = getPtr 1
{-# INLINE getWord8 #-}
getWord16be,getWord16le,getWord16host :: Get Word16
getWord16be = do
s <- getByteString 2
return $! (fromIntegral (s `S.unsafeIndex` 0) `shiftl_w16` 8) .|.
(fromIntegral (s `S.unsafeIndex` 1))
{-# INLINE getWord16be #-}
getWord16le = do
s <- getByteString 2
return $! (fromIntegral (s `S.unsafeIndex` 1) `shiftl_w16` 8) .|.
(fromIntegral (s `S.unsafeIndex` 0) )
{-# INLINE getWord16le #-}
getWord16host = getStorable
{-# INLINE getWord16host #-}
getWord32be,getWord32le,getWord32host :: Get Word32
getWord32be = do
s <- getByteString 4
return $! (fromIntegral (s `S.unsafeIndex` 0) `shiftl_w32` 24) .|.
(fromIntegral (s `S.unsafeIndex` 1) `shiftl_w32` 16) .|.
(fromIntegral (s `S.unsafeIndex` 2) `shiftl_w32` 8) .|.
(fromIntegral (s `S.unsafeIndex` 3) )
{-# INLINE getWord32be #-}
getWord32le = do
s <- getByteString 4
return $! (fromIntegral (s `S.unsafeIndex` 3) `shiftl_w32` 24) .|.
(fromIntegral (s `S.unsafeIndex` 2) `shiftl_w32` 16) .|.
(fromIntegral (s `S.unsafeIndex` 1) `shiftl_w32` 8) .|.
(fromIntegral (s `S.unsafeIndex` 0) )
{-# INLINE getWord32le #-}
getWord32host = getStorable
{-# INLINE getWord32host #-}
getWord64be,getWord64le,getWord64host :: Get Word64
getWord64be = do
s <- getByteString 8
return $! (fromIntegral (s `S.unsafeIndex` 0) `shiftl_w64` 56) .|.
(fromIntegral (s `S.unsafeIndex` 1) `shiftl_w64` 48) .|.
(fromIntegral (s `S.unsafeIndex` 2) `shiftl_w64` 40) .|.
(fromIntegral (s `S.unsafeIndex` 3) `shiftl_w64` 32) .|.
(fromIntegral (s `S.unsafeIndex` 4) `shiftl_w64` 24) .|.
(fromIntegral (s `S.unsafeIndex` 5) `shiftl_w64` 16) .|.
(fromIntegral (s `S.unsafeIndex` 6) `shiftl_w64` 8) .|.
(fromIntegral (s `S.unsafeIndex` 7) )
{-# INLINE getWord64be #-}
getWord64le = do
s <- getByteString 8
return $! (fromIntegral (s `S.unsafeIndex` 7) `shiftl_w64` 56) .|.
(fromIntegral (s `S.unsafeIndex` 6) `shiftl_w64` 48) .|.
(fromIntegral (s `S.unsafeIndex` 5) `shiftl_w64` 40) .|.
(fromIntegral (s `S.unsafeIndex` 4) `shiftl_w64` 32) .|.
(fromIntegral (s `S.unsafeIndex` 3) `shiftl_w64` 24) .|.
(fromIntegral (s `S.unsafeIndex` 2) `shiftl_w64` 16) .|.
(fromIntegral (s `S.unsafeIndex` 1) `shiftl_w64` 8) .|.
(fromIntegral (s `S.unsafeIndex` 0) )
{-# INLINE getWord64le #-}
getWord64host = getStorable
{-# INLINE getWord64host #-}
-- Below here are the class instances
instance Functor Get where
fmap f m = Get (\sc -> unGet m (sc . f))
{-# INLINE fmap #-}
instance Monad Get where
return a = seq a $ Get (\sc -> sc a)
{-# INLINE return #-}
m >>= k = Get (\sc -> unGet m (\ a -> seq a $ unGet (k a) sc))
{-# INLINE (>>=) #-}
fail = throwError . strMsg
instance MonadError String Get where
throwError msg = Get $ \_sc s pcIn ->
let go (ErrorFrame ec _) = ec msg s
go (HandlerFrame (Just catcher) s1 future pc1) = catcher (collect s1 future) pc1 msg
go (HandlerFrame Nothing _s1 _future pc1) = go pc1
in go pcIn
catchError mayFail handler = Get $ \sc s pc ->
let pcWithHandler = let catcher s1 pc1 e1 = unGet (handler e1) sc s1 pc1
in HandlerFrame (Just catcher) s mempty pc
actionWithCleanup = mayFail >>= \a -> discardInnerHandler >> return a
in unGet actionWithCleanup sc s pcWithHandler
instance MonadPlus Get where
mzero = throwError (strMsg "[mzero:no message]")
mplus m1 m2 = catchError m1 (const m2)
instance Applicative Get where
pure = return
(<*>) = ap
instance Alternative Get where
empty = mzero
(<|>) = mplus
-- | I use "splitAt" without tolerating too few bytes, so write a Maybe version.
-- This is the only place I invoke L.Chunk as constructor instead of pattern matching.
-- I claim that the first argument cannot be empty.
splitAtOrDie :: Int64 -> L.ByteString -> Maybe (L.ByteString, L.ByteString)
splitAtOrDie i ps | i <= 0 = Just (mempty, ps)
splitAtOrDie _i L.Empty = Nothing
splitAtOrDie i (L.Chunk x xs) | i < len = let (pre,post) = S.splitAt (fromIntegral i) x
in Just (L.chunk pre mempty, L.chunk post xs)
| otherwise = case splitAtOrDie (i-len) xs of
Nothing -> Nothing
Just (y1,y2) -> Just (L.chunk x y1,y2)
where len = fromIntegral (S.length x)
{-# INLINE splitAtOrDie #-}
------------------------------------------------------------------------
-- getPtr copied from binary's Get.hs
-- helper, get a raw Ptr onto a strict ByteString copied out of the
-- underlying lazy byteString. So many indirections from the raw parser
-- state that my head hurts...
-- Assume n>0
getPtr :: (Storable a) => Int -> Get a
getPtr n = do
(fp,o,_) <- fmap S.toForeignPtr (getByteString n)
return . S.inlinePerformIO $ withForeignPtr fp $ \p -> peek (castPtr $ p `plusPtr` o)
{-# INLINE getPtr #-}
-- I pushed the sizeOf into here (uses ScopedTypeVariables)
-- Assume sizeOf (undefined :: a)) > 0
getStorable :: forall a. (Storable a) => Get a
getStorable = do
(fp,o,_) <- fmap S.toForeignPtr (getByteString (sizeOf (undefined :: a)))
return . S.inlinePerformIO $ withForeignPtr fp $ \p -> peek (castPtr $ p `plusPtr` o)
{-# INLINE getStorable #-}
------------------------------------------------------------------------
------------------------------------------------------------------------
-- Unchecked shifts copied from binary's Get.hs
shiftl_w16 :: Word16 -> Int -> Word16
shiftl_w32 :: Word32 -> Int -> Word32
shiftl_w64 :: Word64 -> Int -> Word64
#if defined(__GLASGOW_HASKELL__) && !defined(__HADDOCK__)
shiftl_w16 (W16# w) (I# i) = W16# (w `uncheckedShiftL#` i)
shiftl_w32 (W32# w) (I# i) = W32# (w `uncheckedShiftL#` i)
#if WORD_SIZE_IN_BITS < 64
shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL64#` i)
#if __GLASGOW_HASKELL__ <= 606
-- Exported by GHC.Word in GHC 6.8 and higher
foreign import ccall unsafe "stg_uncheckedShiftL64"
uncheckedShiftL64# :: Word64# -> Int# -> Word64#
#endif
#else
shiftl_w64 (W64# w) (I# i) = W64# (w `uncheckedShiftL#` i)
#endif
#else
shiftl_w16 = shiftL
shiftl_w32 = shiftL
shiftl_w64 = shiftL
#endif