73 lines
2.1 KiB
Haskell
73 lines
2.1 KiB
Haskell
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-- | This module defines a connection interface. It could be a regular
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-- network connection, TLS connection, a mock or anything else.
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module Database.MongoDB.Internal.Connection (
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Connection(..),
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readExactly,
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fromHandle,
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) where
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import Prelude hiding (read)
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import Data.Monoid
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import Data.IORef
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import Data.ByteString (ByteString)
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import qualified Data.ByteString as ByteString
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import qualified Data.ByteString.Lazy as Lazy (ByteString)
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import qualified Data.ByteString.Lazy as Lazy.ByteString
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import Control.Monad
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import System.IO
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import System.IO.Error (mkIOError, eofErrorType)
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-- | Abstract connection interface
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--
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-- `read` should return `ByteString.null` on EOF
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data Connection = Connection {
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read :: IO ByteString,
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unread :: ByteString -> IO (),
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write :: ByteString -> IO (),
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flush :: IO (),
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close :: IO ()}
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readExactly :: Connection -> Int -> IO Lazy.ByteString
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-- ^ Read specified number of bytes
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--
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-- If EOF is reached before N bytes then raise EOF exception.
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readExactly conn count = go mempty count
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where
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go acc n = do
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-- read until get enough bytes
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chunk <- read conn
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when (ByteString.null chunk) $
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ioError eof
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let len = ByteString.length chunk
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if len >= n
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then do
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let (res, rest) = ByteString.splitAt n chunk
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unless (ByteString.null rest) $
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unread conn rest
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return (acc <> Lazy.ByteString.fromStrict res)
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else go (acc <> Lazy.ByteString.fromStrict chunk) (n - len)
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eof = mkIOError eofErrorType "Database.MongoDB.Internal.Connection"
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Nothing Nothing
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fromHandle :: Handle -> IO Connection
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-- ^ Make connection form handle
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fromHandle handle = do
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restRef <- newIORef mempty
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return Connection
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{ read = do
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rest <- readIORef restRef
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writeIORef restRef mempty
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if ByteString.null rest
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-- 32k corresponds to the default chunk size
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-- used in bytestring package
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then ByteString.hGetSome handle (32 * 1024)
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else return rest
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, unread = \rest ->
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modifyIORef restRef (rest <>)
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, write = ByteString.hPut handle
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, flush = hFlush handle
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, close = hClose handle
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}
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