9720ee9e56
This only performs some basic tests so far; no testing of chunking or resuming. Also, the existing encryption type of the remote is used; it would be good later to derive an encrypted and a non-encrypted version of the remote and test them both. This commit was sponsored by Joseph Liu.
135 lines
4.4 KiB
Haskell
135 lines
4.4 KiB
Haskell
{- Metered IO
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-
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- Copyright 2012, 2013 Joey Hess <joey@kitenet.net>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE TypeSynonymInstances #-}
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module Utility.Metered where
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import Common
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import qualified Data.ByteString.Lazy as L
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import qualified Data.ByteString as S
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import System.IO.Unsafe
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import Foreign.Storable (Storable(sizeOf))
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import System.Posix.Types
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import Data.Int
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{- An action that can be run repeatedly, updating it on the bytes processed.
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-
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- Note that each call receives the total number of bytes processed, so
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- far, *not* an incremental amount since the last call. -}
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type MeterUpdate = (BytesProcessed -> IO ())
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nullMeterUpdate :: MeterUpdate
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nullMeterUpdate _ = return ()
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{- Total number of bytes processed so far. -}
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newtype BytesProcessed = BytesProcessed Integer
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deriving (Eq, Ord, Show)
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class AsBytesProcessed a where
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toBytesProcessed :: a -> BytesProcessed
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fromBytesProcessed :: BytesProcessed -> a
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instance AsBytesProcessed BytesProcessed where
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toBytesProcessed = id
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fromBytesProcessed = id
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instance AsBytesProcessed Integer where
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toBytesProcessed i = BytesProcessed i
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fromBytesProcessed (BytesProcessed i) = i
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instance AsBytesProcessed Int where
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toBytesProcessed i = BytesProcessed $ toInteger i
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fromBytesProcessed (BytesProcessed i) = fromInteger i
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instance AsBytesProcessed Int64 where
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toBytesProcessed i = BytesProcessed $ toInteger i
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fromBytesProcessed (BytesProcessed i) = fromInteger i
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instance AsBytesProcessed FileOffset where
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toBytesProcessed sz = BytesProcessed $ toInteger sz
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fromBytesProcessed (BytesProcessed sz) = fromInteger sz
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addBytesProcessed :: AsBytesProcessed v => BytesProcessed -> v -> BytesProcessed
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addBytesProcessed (BytesProcessed i) v =
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let (BytesProcessed n) = toBytesProcessed v
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in BytesProcessed $! i + n
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zeroBytesProcessed :: BytesProcessed
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zeroBytesProcessed = BytesProcessed 0
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{- Sends the content of a file to an action, updating the meter as it's
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- consumed. -}
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withMeteredFile :: FilePath -> MeterUpdate -> (L.ByteString -> IO a) -> IO a
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withMeteredFile f meterupdate a = withBinaryFile f ReadMode $ \h ->
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hGetContentsMetered h meterupdate >>= a
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{- Sends the content of a file to a Handle, updating the meter as it's
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- written. -}
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streamMeteredFile :: FilePath -> MeterUpdate -> Handle -> IO ()
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streamMeteredFile f meterupdate h = withMeteredFile f meterupdate $ L.hPut h
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{- Writes a ByteString to a Handle, updating a meter as it's written. -}
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meteredWrite :: MeterUpdate -> Handle -> L.ByteString -> IO ()
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meteredWrite meterupdate h = go zeroBytesProcessed . L.toChunks
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where
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go _ [] = return ()
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go sofar (c:cs) = do
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S.hPut h c
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let sofar' = addBytesProcessed sofar $ S.length c
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meterupdate sofar'
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go sofar' cs
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meteredWriteFile :: MeterUpdate -> FilePath -> L.ByteString -> IO ()
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meteredWriteFile meterupdate f b = withBinaryFile f WriteMode $ \h ->
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meteredWrite meterupdate h b
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{- Applies an offset to a MeterUpdate. This can be useful when
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- performing a sequence of actions, such as multiple meteredWriteFiles,
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- that all update a common meter progressively. Or when resuming.
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-}
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offsetMeterUpdate :: MeterUpdate -> BytesProcessed -> MeterUpdate
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offsetMeterUpdate base offset = \n -> base (offset `addBytesProcessed` n)
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{- This is like L.hGetContents, but after each chunk is read, a meter
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- is updated based on the size of the chunk.
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-
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- Note that the meter update is run in unsafeInterleaveIO, which means that
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- it can be run at any time. It's even possible for updates to run out
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- of order, as different parts of the ByteString are consumed.
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-
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- All the usual caveats about using unsafeInterleaveIO apply to the
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- meter updates, so use caution.
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-}
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hGetContentsMetered :: Handle -> MeterUpdate -> IO L.ByteString
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hGetContentsMetered h meterupdate = lazyRead zeroBytesProcessed
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where
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lazyRead sofar = unsafeInterleaveIO $ loop sofar
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loop sofar = do
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c <- S.hGetSome h defaultChunkSize
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if S.null c
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then do
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hClose h
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return $ L.empty
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else do
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let sofar' = addBytesProcessed sofar $
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S.length c
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meterupdate sofar'
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{- unsafeInterleaveIO causes this to be
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- deferred until the data is read from the
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- ByteString. -}
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cs <- lazyRead sofar'
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return $ L.append (L.fromChunks [c]) cs
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{- Same default chunk size Lazy ByteStrings use. -}
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defaultChunkSize :: Int
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defaultChunkSize = 32 * k - chunkOverhead
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where
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k = 1024
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chunkOverhead = 2 * sizeOf (undefined :: Int) -- GHC specific
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