-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Zigzag encoding of integers into unsigned integers.
--   
--   Zigzag encoding is usually a precursor to a varint encoding such as
--   LEB128. It has the advantage that numbers nearer zero are represented
--   with only the lower-order bits set.
@package zigzag
@version 0.1.0.0


-- | Zigzag encoding maps signed integers to unsigned integers so that
--   numbers with a small absolute value (for instance, -1) have a small
--   varint encoded value too. It does this in a way that "zig-zags" back
--   and forth through the positive and negative integers, so that -1 is
--   encoded as 1, 1 is encoded as 2, -2 is encoded as 3, and so on.
--   
--   <pre>
--   zigzag(n) = { 2 * n       if 0 &lt;= n
--               { -2 * n - 1  if n &lt; 0
--   </pre>
--   
--   This description was adapted from
--   https:/<i>developers.google.com</i>protocol-buffers<i>docs</i>encoding#signed-ints
--   which is released under
--   <a>https://creativecommons.org/licenses/by/4.0/</a>
module Data.Word.Zigzag

-- | Encode a big integer with zigzag.
--   
--   If you know the size of the data, it is likely more efficient to use
--   one of <a>toZigzagNative</a>, <a>toZigzag32</a>, or <a>toZigzag64</a>.
toZigzag :: Integer -> Natural

-- | Decode a zigzag-encoded big ingeter.
--   
--   If you know the size of the data, it is likely more efficient to use
--   one of <a>fromZigzagNative</a>, <a>fromZigzag32</a>, or
--   <a>fromZigzag64</a>.
fromZigzag :: Natural -> Integer

-- | Encode a native-size integer with zigzag.
--   
--   In C, this is:
--   
--   <pre>
--   (n &lt;&lt; 1) ^ (n &gt;&gt; (CHAR_BIT * sizeof(int) - 1))
--   </pre>
toZigzagNative :: Int -> Word

-- | Decode a native-size zigzag-encoded integer.
--   
--   In C, this is:
--   
--   <pre>
--   (n &gt;&gt; 1) ^ (~(n &amp; 1) + 1)
--   </pre>
fromZigzagNative :: Word -> Int

-- | Encode a 32-bit integer with zigzag.
--   
--   In C, this is:
--   
--   <pre>
--   (n &lt;&lt; 1) ^ (n &gt;&gt; 31)
--   </pre>
toZigzag32 :: Int32 -> Word32

-- | Decode a 32-bit zigzag-encoded integer.
--   
--   In C, this is:
--   
--   <pre>
--   (n &gt;&gt; 1) ^ (~(n &amp; 1) + 1)
--   </pre>
fromZigzag32 :: Word32 -> Int32

-- | Encode a 64-bit integer with zigzag.
--   
--   In C, this is:
--   
--   <pre>
--   (n &lt;&lt; 1) ^ (n &gt;&gt; 63)
--   </pre>
toZigzag64 :: Int64 -> Word64

-- | Decode a 64-bit zigzag-encoded integer.
--   
--   In C, this is:
--   
--   <pre>
--   (n &gt;&gt; 1) ^ (~(n &amp; 1) + 1)
--   </pre>
fromZigzag64 :: Word64 -> Int64