wire: add HasFlag method

wire/protocol.go

@@ -126,6 +126,11 @@ var orderedSFStrings = []ServiceFlag{
 	SFNodeNetworkLimited,
 }
 
+// HasFlag returns a bool indicating if the service has the given flag.
+func (f ServiceFlag) HasFlag(s ServiceFlag) bool {
+	return f&s == s
+}
+
 // String returns the ServiceFlag in human-readable form.
 func (f ServiceFlag) String() string {
 	// No flags are set.

wire/protocol_test.go

@@ -4,7 +4,11 @@
 
 package wire
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
 
 // TestServiceFlagStringer tests the stringized output for service flag types.
 func TestServiceFlagStringer(t *testing.T) {
@@ -59,3 +63,19 @@ func TestBitcoinNetStringer(t *testing.T) {
 		}
 	}
 }
+
+func TestHasFlag(t *testing.T) {
+	tests := []struct {
+		in    ServiceFlag
+		check ServiceFlag
+		want  bool
+	}{
+		{0, SFNodeNetwork, false},
+		{SFNodeNetwork | SFNodeNetworkLimited | SFNodeWitness, SFNodeBloom, false},
+		{SFNodeNetwork | SFNodeNetworkLimited | SFNodeWitness, SFNodeNetworkLimited, true},
+	}
+
+	for _, test := range tests {
+		require.Equal(t, test.want, test.in.HasFlag(test.check))
+	}
+}