add benchmarks for encoding tree data structures

common/Word16Tree.hs

@@ -0,0 +1,83 @@
+{-# language BangPatterns #-}
+
+module Word16Tree
+  ( Word16Tree
+  , encode
+  , exampleSmall
+  , example2000
+  , example9000
+  , expectedSmall
+  ) where
+
+import Data.ByteArray.Builder as B
+import Data.Word (Word16)
+import Data.Primitive (ByteArray)
+import qualified Data.Bytes as Bytes
+
+data Word16Tree
+  = Branch !Word16Tree !Word16Tree
+  | Leaf {-# UNPACK #-} !Word16
+
+encode :: Word16Tree -> Builder
+encode (Leaf w) = B.word16PaddedUpperHex w
+encode (Branch a b) =
+  B.ascii '('
+  <>
+  encode a
+  <>
+  B.ascii ','
+  <>
+  encode b
+  <>
+  B.ascii ')'
+
+expectedSmall :: ByteArray
+expectedSmall = Bytes.toByteArray $ Bytes.fromAsciiString
+  "((AB59,(1F33,2E71)),((((FA9A,247B),890C),(0F13,((55BF,7CF1),389B))),1205))"
+
+exampleSmall :: Word16Tree
+exampleSmall = Branch
+  (Branch
+    (Leaf 0xAB59)
+    (Branch
+      (Leaf 0x1F33)
+      (Leaf 0x2E71)
+    )
+  )
+  (Branch
+    (Branch 
+      (Branch
+        (Branch
+          (Leaf 0xFA9A)
+          (Leaf 0x247B)
+        )
+        (Leaf 0x890C)
+      )
+      (Branch
+        (Leaf 0x0F13)
+        (Branch
+          (Branch
+            (Leaf 0x55BF)
+            (Leaf 0x7CF1)
+          )
+          (Leaf 0x389B)
+        )
+      )
+    )
+    (Leaf 0x1205)
+  )
+
+example2000 :: Word16Tree
+{-# noinline example2000 #-}
+example2000 = balanced 0 2000
+
+example9000 :: Word16Tree
+{-# noinline example9000 #-}
+example9000 = balanced 0 9000
+
+balanced :: Word16 -> Word16 -> Word16Tree
+balanced !off !n
+  | n == 0 = Leaf off
+  | n == 1 = Leaf (off + 1)
+  | otherwise = let x = div n 2 in
+      Branch (balanced off x) (balanced (off + x) (n - x))