SuperBlock data modification functions

Author: devyn

System/TPFS/SuperBlock.hs

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+module System.TPFS.SuperBlock (
+    module System.TPFS.SolidArray,
+    SuperBlockState(..),
+    bitsToSBStates,
+    sbStatesToBits
+  ) where
+
+import           Control.Applicative
+import qualified Data.ByteString.Lazy as B
+import           System.TPFS.Address
+import           System.TPFS.Bitmap
+import           System.TPFS.SolidArray
+
+data SuperBlockState = SBEmpty
+                     | SBSpaceAvailable
+                     | SBFull
+                     deriving (Show, Read, Eq)
+
+instance SolidArray SuperBlockState where
+  arrRead  h a (s,e) = bitsToSBStates <$> arrRead h a (s*2,e*2+1)
+  arrWrite h a o     = arrWrite h a (o*2) . sbStatesToBits
+
+-- | Converts a list of bits into the equivalent @['SuperBlockState']@. The
+-- input list length must be even, and the output list length will
+-- always be half that of the input list.
+bitsToSBStates (False : False : xs) = SBEmpty          : bitsToSBStates xs
+bitsToSBStates (True  : False : xs) = SBSpaceAvailable : bitsToSBStates xs
+bitsToSBStates (True  : True  : xs) = SBFull           : bitsToSBStates xs
+bitsToSBStates []                   = []
+
+-- | Converts @['SuperBlockState']@ into a list of bits. Dual of 'bitsToSBState'.
+sbStatesToBits (SBEmpty          : xs) = False : False : sbStatesToBits xs
+sbStatesToBits (SBSpaceAvailable : xs) = True  : False : sbStatesToBits xs
+sbStatesToBits (SBFull           : xs) = True  : True  : sbStatesToBits xs
+sbStatesToBits []                      = []