Initial commit

README.md

@@ -0,0 +1,8 @@
+## Checking for `nil` in Go
+
+Benchmarks:
+```
+BenchmarkIsNilBasic-8           200000000            9.47 ns/op
+BenchmarkIsNilInterface-8       200000000            9.18 ns/op
+BenchmarkIsNilNil-8             1000000000           2.03 ns/op
+```

isnil.go

@@ -0,0 +1,15 @@
+package isnil
+
+import (
+	"reflect"
+)
+
+// IsNil returns true if a given value is nil.
+func IsNil(i interface{}) bool {
+	if i == nil {
+		return true
+	}
+
+	v := reflect.ValueOf(i)
+	return v.Kind() == reflect.Ptr && v.IsNil()
+}

isnil_test.go

@@ -0,0 +1,53 @@
+package isnil
+
+import (
+	"testing"
+)
+
+type foo struct{}
+
+func TestIsNil(t *testing.T) {
+	cases := []struct {
+		in  interface{}
+		exp bool
+	}{
+		{1, false},
+		{"nope", false},
+		{foo{}, false},
+		{&foo{}, false},
+		{nil, true},
+		{(*foo)(nil), true},
+		{(interface{})(nil), true},
+	}
+
+	for _, tcase := range cases {
+		if out := IsNil(tcase.in); out != tcase.exp {
+			if tcase.exp {
+				t.Errorf("Expected %++v to be nil", tcase.in)
+			} else {
+				t.Errorf("Expected %++v to not be nil", tcase.in)
+			}
+		}
+	}
+}
+
+func BenchmarkIsNilBasic(b *testing.B) {
+	var v *int
+	for i := 0; i < b.N; i++ {
+		IsNil(v)
+	}
+}
+
+func BenchmarkIsNilInterface(b *testing.B) {
+	var v interface{}
+	v = (*foo)(nil)
+	for i := 0; i < b.N; i++ {
+		IsNil(v)
+	}
+}
+
+func BenchmarkIsNilNil(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		IsNil(nil)
+	}
+}