66 lines
2.1 KiB
Haskell
66 lines
2.1 KiB
Haskell
-- | Miscellaneous general functions
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{-# LANGUAGE StandaloneDeriving #-}
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module Database.MongoDB.Util where
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import Prelude hiding (length)
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import Network (PortID(..))
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import Control.Applicative (Applicative(..), (<$>))
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import Control.Exception (assert)
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import Control.Monad.Reader
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import Control.Monad.Error
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import Data.UString as U (UString, cons, append)
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import Data.Bits (Bits, (.|.))
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import Data.Bson
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import System.IO (Handle)
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import Data.ByteString.Lazy as B (ByteString, length, append, hGet)
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deriving instance Show PortID
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deriving instance Eq PortID
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deriving instance Ord PortID
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instance (Monad m) => Applicative (ReaderT r m) where
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pure = return
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(<*>) = ap
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instance (Monad m, Error e) => Applicative (ErrorT e m) where
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pure = return
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(<*>) = ap
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ignore :: (Monad m) => a -> m ()
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ignore _ = return ()
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type Secs = Float
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bitOr :: (Bits a) => [a] -> a
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-- ^ bit-or all numbers together
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bitOr = foldl (.|.) 0
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(<.>) :: UString -> UString -> UString
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-- ^ Concat first and second together with period in between. Eg. @\"hello\" \<.\> \"world\" = \"hello.world\"@
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a <.> b = U.append a (cons '.' b)
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loop :: (Functor m, Monad m) => m (Maybe a) -> m [a]
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-- ^ Repeatedy execute action, collecting results, until it returns Nothing
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loop act = act >>= maybe (return []) (\a -> (a :) <$> loop act)
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true1 :: Label -> Document -> Bool
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-- ^ Is field's value a 1 or True (MongoDB use both Int and Bools for truth values). Error if field not in document or field not a Num or Bool.
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true1 k doc = case valueAt k doc of
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Bool b -> b
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Float n -> n == 1
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Int32 n -> n == 1
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Int64 n -> n == 1
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_ -> error $ "expected " ++ show k ++ " to be Num or Bool in " ++ show doc
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hGetN :: Handle -> Int -> IO ByteString
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-- ^ Read N bytes from hande, blocking until all N bytes are read.
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-- Unlike hGet which only blocks if no bytes are available, otherwise it returns the X bytes immediately available where X <= N.
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hGetN h n = assert (n >= 0) $ do
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bytes <- hGet h n
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let x = fromIntegral (length bytes)
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if x >= n then return bytes else do
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remainingBytes <- hGetN h (n - x)
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return (B.append bytes remainingBytes)
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