lib/crypto: Introduce hamming distance on Bytes

New method to calculate the bitwise hamming distance on Bytes.

Signed-off-by: Philippe Pepos Petitclerc <ppeposp@gmail.com>

diff --git a/lib/crypto.nit b/lib/crypto.nit
index 2abe5d7..0b52c99 100644 (file)
--- a/lib/crypto.nit
+++ b/lib/crypto.nit
@@ -172,6 +172,24 @@ redef class Bytes
 
                return xored
        end
+
+       # Computes the edit/hamming distance of two sequences of bytes.
+       #
+       #     assert "this is a test".to_bytes.hamming_distance("wokka wokka!!!".bytes) == 37
+       #     assert "this is a test".to_bytes.hamming_distance("this is a test".bytes) == 0
+       #
+       fun hamming_distance(other: SequenceRead[Byte]): Int do
+               var diff = 0
+               for idx in self.length.times do
+                       var res_byte = self[idx] ^ other[idx]
+                       for bit in [0..8[ do
+                               if res_byte & 1u8 == 1u8 then diff += 1
+                               res_byte = res_byte >> 1
+                       end
+               end
+               return diff
+       end
+
 end
 
 redef class Int