Add a Copy method to options, and tests for options.

dhcp/options.go

@@ -72,6 +72,15 @@ func (o Options) MarshalTo(w io.Writer) error {
 	return nil
 }
 
+// Copy returns a shallow copy of o.
+func (o Options) Copy() Options {
+	ret := make(Options, len(o))
+	for k, v := range o {
+		ret[k] = v
+	}
+	return ret
+}
+
 // marshalLimited serializes o into w. If nBytes > 0, as many options
 // as possible are packed into that many bytes, inserting padding as
 // needed, and the remaining unwritten options are returned.

dhcp/options_test.go

@@ -0,0 +1,46 @@
+package dhcp
+
+import "testing"
+
+func TestOptionReading(t *testing.T) {
+	o := Options{
+		1: []byte{1, 2, 3},
+		2: []byte{3},
+		3: []byte{0, 1},
+	}
+
+	b, ok := o.Byte(2)
+	if !ok {
+		t.Fatalf("Option 2 should be a valid byte")
+	}
+	if b != 3 {
+		t.Fatalf("Wanted value 3 for option 2, got %d", b)
+	}
+
+	b, ok = o.Byte(3)
+	if ok {
+		t.Fatalf("Option 3 shouldn't be a valid byte")
+	}
+
+	u, ok := o.Uint16(3)
+	if !ok {
+		t.Fatalf("Option 3 should be a valid byte")
+	}
+	if u != 1 {
+		t.Fatalf("Wanted value 1 for option 3, got %d", u)
+	}
+}
+
+func TestCopy(t *testing.T) {
+	o := Options{
+		1: []byte{2},
+		2: []byte{3, 4},
+	}
+
+	o2 := o.Copy()
+	delete(o2, 2)
+
+	if len(o) != 2 {
+		t.Fatalf("Mutating Option copy mutated the original")
+	}
+}