Decoders for interval

src/Database/PostgreSQL/Protocol/Codecs/Decoders.hs

@@ -3,7 +3,7 @@ module Database.PostgreSQL.Protocol.Codecs.Decoders where
 import Data.Word
 import Data.Int
 import Data.Char
-import Data.Time (Day, UTCTime, LocalTime)
+import Data.Time (Day, UTCTime, LocalTime, DiffTime)
 import qualified Data.ByteString as B
 import qualified Data.Vector as V
 
@@ -112,8 +112,9 @@ int4 _ =  getInt32BE
 int8 :: FieldDecoder Int64
 int8 _ =  getInt64BE 
 
--- interval :: FieldDecoder ?
--- interval = undefined
+{-# INLINE interval #-}
+interval :: FieldDecoder DiffTime
+interval _ = intervalToDiffTime <$> getInt64BE <*> getInt32BE <*> getInt32BE
 
 -- | Decodes representation of JSON as @ByteString@.
 {-# INLINE bsJsonText #-}

src/Database/PostgreSQL/Protocol/Codecs/Time.hs

@@ -5,9 +5,11 @@ module Database.PostgreSQL.Protocol.Codecs.Time
     , pgjToDay
     , microsToUTC
     , microsToLocalTime
+    , intervalToDiffTime
+    , diffTimeToInterval
     ) where
 
-import Data.Int  (Int64)
+import Data.Int  (Int64, Int32)
 import Data.Time (Day(..), UTCTime(..), LocalTime(..), DiffTime, TimeOfDay,
                   picosecondsToDiffTime, timeToTimeOfDay,
                   diffTimeToPicoseconds, timeOfDayToTime)
@@ -43,6 +45,17 @@ microsToLocalTime mcs =
     let (d, r) = mcs `divMod` microsInDay
     in LocalTime (pgjToDay d) (mcsToTimeOfDay r)
 
+{-# INLINE intervalToDiffTime #-}
+intervalToDiffTime :: Int64 -> Int32 -> Int32 -> DiffTime
+intervalToDiffTime mcs days months = picosecondsToDiffTime . mcsToPcs $ 
+    microsInDay * (fromIntegral months * daysInMonth + fromIntegral days) 
+    + fromIntegral mcs
+
+-- TODO consider adjusted encoding
+{-# INLINE diffTimeToInterval #-}
+diffTimeToInterval :: DiffTime -> (Int64, Int32, Int32)
+diffTimeToInterval dt = (fromIntegral $ diffTimeToMcs dt, 0, 0)
+
 --
 -- Utils
 --
@@ -82,3 +95,6 @@ postgresEpoch = 2451545
 
 microsInDay :: Num a => a
 microsInDay = 24 * 60 * 60 * 10 ^ 6
+
+daysInMonth :: Num a => a
+daysInMonth = 30