working on unpackSamples

[wavpack.git] / Codec / Audio / WavPack / Unpack.hs

diff --git a/Codec/Audio/WavPack/Unpack.hs b/Codec/Audio/WavPack/Unpack.hs
index 264072c71f7e3ce6f25dbbf32db5eccd48b49ed2..33c51522df4ea463bf641c2de927795961af1a64 100644 (file)
--- a/Codec/Audio/WavPack/Unpack.hs
+++ b/Codec/Audio/WavPack/Unpack.hs
@@ -1,4 +1,60 @@
+{-# LANGUAGE
+    DoAndIfThenElse
+  , FlexibleContexts
+  , ScopedTypeVariables
+  , UnicodeSyntax
+  #-}
 module Codec.Audio.WavPack.Unpack
-    (
+    ( WavpackStream(..)
+    , unpackSamples
     )
     where
+import Codec.Audio.WavPack.Block
+import Control.Monad.ST
+import Data.Int
+import Data.STRef
+import qualified Data.Vector.Generic.Mutable as MV
+import Data.Word
+import Prelude.Unicode
+
+-- | FIXME
+data WavpackStream s
+    = WavpackStream {
+        wpsHeader      ∷ !BlockHeader
+      , wpsMuteError   ∷ !(STRef s Bool)
+      , wpsSampleIndex ∷ !(STRef s Word32)
+      }
+
+-- |This monster actually unpacks the WavPack bitstream(s) into the
+-- specified buffer as 32-bit integers or floats (depending on orignal
+-- data). Lossy samples will be clipped to their original limits
+-- (i.e. 8-bit samples are clipped to -128/+127) but are still
+-- returned in longs. It is up to the caller to potentially reformat
+-- this for the final output including any multichannel distribution,
+-- block alignment or endian compensation.
+unpackSamples ∷ ∀v s. (MV.MVector v Int32)
+              ⇒ WavpackStream s
+              → Int    -- ^ Number of channels.
+              → Int    -- ^ Reduced number of channels (1 or 2).
+              → Word32 -- ^ Number of samples to get.
+              → ST s (v s Int32)
+{-# INLINEABLE unpackSamples #-}
+unpackSamples wps numChannels reducedChannels nSamples0
+    = do let hdr   = wpsHeader wps
+             flags = bhFlags hdr
+         nSamples ← do idx ← readSTRef (wpsSampleIndex wps)
+                       if idx + nSamples0 > bhBlockIndex hdr + bhBlockSamples hdr then
+                           return $ bhBlockIndex hdr + bhBlockSamples hdr - idx
+                       else
+                           return nSamples0
+
+         muteError ← readSTRef (wpsMuteError wps)
+         if muteError then
+             do v ← if reducedChannels ≡ 1 ∨ numChannels ≡ 1 ∨ bfMono flags then
+                        MV.replicate (fromIntegral nSamples) 0
+                    else
+                        MV.replicate (fromIntegral nSamples ⋅ 2) 0
+                modifySTRef (wpsSampleIndex wps) (+ nSamples)
+                return v
+         else
+             error "FIXME"