lib: add HammingDistance

* lib/hamming.go (HammingDistance, setBits): New functions.

1 files changed, 27 insertions, 0 deletions

diff --git a/lib/hamming.go b/lib/hamming.go
new file mode 100644
index 0000000..c267c43
--- /dev/null
+++ b/lib/hamming.go
@@ -0,0 +1,27 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+func HammingDistance(a, b string) int {
+	if len(a) != len(b) {
+		return -1 // Fail.
+	}
+
+	d := 0
+	for i := 0; i < len(a); i++ {
+		c := a[i] ^ b[i]
+		d += setBits(c)
+	}
+	return d
+}
+
+// Returns number of set bits.
+func setBits(b byte) int {
+	var c byte = 0
+	for i := 0; i < 8; i++ {
+		c += b & 0x1
+		b = b >> 1
+	}
+	return int(c)
+}