some data types

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

diff --git a/Codec/Audio/WavPack/Words.hs b/Codec/Audio/WavPack/Words.hs
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+{-# LANGUAGE
+    BangPatterns
+  , UnboxedTuples
+  , UnicodeSyntax
+  #-}
+-- | FIXME
+module Codec.Audio.WavPack.Words
+    ( WordsData(..)
+    )
+    where
+import Codec.Audio.WavPack.Entropy
+import Codec.Audio.WavPack.Internal
+import Data.Bits
+import Data.Bitstream.Generic (Bitstream)
+import qualified Data.Bitstream.Generic as B
+import Data.Word
+import Prelude.Unicode
+
+-- | FIXME
+data WordsData
+    = WordsData {
+        wdBitrateDelta ∷ !(Word32, Word32)
+      , wdBitrateAcc   ∷ !(Word32, Word32)
+      , wdPendingData  ∷ !Word32
+      , wdHoldingOne   ∷ !Word32
+      , wdZeroesAcc    ∷ !Word32
+      , wdHoldingZero  ∷ !Bool
+      , wdPendingCount ∷ !Int
+      , wdEntropyData  ∷ !(EntropyData, EntropyData)
+      }
+    deriving (Eq, Show)
+
+-- This is an optimized version of 'getWord' that is used for lossless
+-- only (error_limit ≡ 0). Also, rather than obtaining a single
+-- sample, it can be used to obtain an entire buffer of either mono or
+-- stereo samples.
+--getWordsLossless ∷ 
+
+-- Read a single unsigned value from the specified bitstream with a
+-- value from 0 to maxCode. If there are exactly a power of two number
+-- of possible codes then this will read a fixed number of bits;
+-- otherwise it reads the minimum number of bits and then determines
+-- whether another bit is needed to define the code.
+readCode ∷ Bitstream bs ⇒ bs → Word32 → (# Word32, bs #)
+{-# INLINEABLE readCode #-}
+readCode bs 0       = (# 0, bs #)
+readCode bs 1       = (# b2n (B.head bs), B.tail bs #)
+readCode bs maxCode
+    = let !bitCount = countBits maxCode
+          !extras   = bit bitCount - maxCode - 1
+          !code     = B.toBits (B.take (bitCount - 1) bs)
+          (# code', bitCount' #)
+                    = if code ≥ extras then
+                          (# (code `shiftL` 1)
+                             - extras
+                             + b2n (bs B.!! bitCount)
+                           , bitCount #)
+                      else
+                          (# code, bitCount - 1 #)
+          !bs'      = B.drop bitCount' bs
+      in
+        (# code', bs' #)