lib: add byte.go

- Add `ByteInBytes` function
- Add `BytesInCommon` function

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/byte.go b/lib/byte.go
new file mode 100644
index 0000000..744c0d7
--- /dev/null
+++ b/lib/byte.go
@@ -0,0 +1,31 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+// Returns true if byte `b` is in `bs`
+func ByteInBytes(b byte, bs []byte) bool {
+	for _, bi := range bs {
+		if b == bi {
+			return true
+		}
+	}
+	return false
+}
+
+// Returns bytes that are common in the given array of array of bytes `bbytes`.
+func BytesInCommon(bbytes [][]byte) []byte {
+	common := make([]byte, 0)
+	switch l := len(bbytes); {
+	case l == 1:
+		common = bbytes[0]
+	case l > 1:
+		commonRest := BytesInCommon(bbytes[1:])
+		for _, b := range bbytes[0] {
+			if ByteInBytes(b, commonRest) {
+				common = append(common, b)
+			}
+		}
+	}
+	return common
+}