Branch.hs

module StmHamt.Constructors.Branch where

import qualified PrimitiveExtras.By6Bits as By6Bits
import qualified StmHamt.IntOps as IntOps
import StmHamt.Prelude
import StmHamt.Types

singleton :: Int -> a -> Branch a
singleton hash a = LeavesBranch hash (pure a)

pair :: Int -> Int -> Branch a -> Int -> Branch a -> STM (Branch a)
pair depth hash1 branch1 hash2 branch2 =
  {-# SCC "pair" #-}
  let index1 = IntOps.indexAtDepth depth hash1
      index2 = IntOps.indexAtDepth depth hash2
   in if index1 == index2
        then do
          deeperBranch <- pair (IntOps.nextDepth depth) hash1 branch1 hash2 branch2
          var <- newTVar (By6Bits.singleton index1 deeperBranch)
          return (BranchesBranch (Hamt var))
        else BranchesBranch . Hamt <$> newTVar (By6Bits.pair index1 branch1 index2 branch2)