From a39133d370224023932fdd73119c3940db4149cc Mon Sep 17 00:00:00 2001
From: Aiden <12055114+aidenwallis@users.noreply.github.com>
Date: Fri, 11 Nov 2022 01:40:09 +0000
Subject: [PATCH] Add bitmask utils (#15)

* Add bitmask utils

* Create README.md
---
 bitmask/README.md       |  3 +++
 bitmask/bitmask.go      | 26 ++++++++++++++++++++++++++
 bitmask/bitmask_test.go | 23 +++++++++++++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 bitmask/README.md
 create mode 100644 bitmask/bitmask.go
 create mode 100644 bitmask/bitmask_test.go

diff --git a/bitmask/README.md b/bitmask/README.md
new file mode 100644
index 0000000..e1346ac
--- /dev/null
+++ b/bitmask/README.md
@@ -0,0 +1,3 @@
+# bitmask
+
+Simple utilities for working with bitmasks. Built with generics so any form of unsigned or signed integer is supported.
diff --git a/bitmask/bitmask.go b/bitmask/bitmask.go
new file mode 100644
index 0000000..4871909
--- /dev/null
+++ b/bitmask/bitmask.go
@@ -0,0 +1,26 @@
+package bitmask
+
+import "golang.org/x/exp/constraints"
+
+// Bit is a generic type that exports the supported values that can be used in the bitmask.
+// Any form of integer is currently supported.
+type Bit interface {
+	constraints.Integer
+}
+
+// Add adds a given bit to the sum.
+func Add[T Bit](sum, bit T) T {
+	sum |= bit
+	return sum
+}
+
+// Remove removes bit from the sum.
+func Remove[T Bit](sum, bit T) T {
+	sum &= ^bit
+	return sum
+}
+
+// Has checks whether a given bit exists in sum.
+func Has[T Bit](sum, bit T) bool {
+	return (sum & bit) == bit
+}
diff --git a/bitmask/bitmask_test.go b/bitmask/bitmask_test.go
new file mode 100644
index 0000000..03a2b1c
--- /dev/null
+++ b/bitmask/bitmask_test.go
@@ -0,0 +1,23 @@
+package bitmask_test
+
+import (
+	"testing"
+
+	"github.com/aidenwallis/go-utils/bitmask"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBits(t *testing.T) {
+	t.Parallel()
+
+	const (
+		a = 1 << 0
+		b = 1 << 1
+		c = 1 << 2
+	)
+
+	assert.Equal(t, a|b, bitmask.Add(a, b))
+	assert.Equal(t, a, bitmask.Remove(a|b, b))
+	assert.True(t, bitmask.Has(a|b, b))
+	assert.False(t, bitmask.Has(a|b, c))
+}