Add nil checks to prevent panics

Author: tonyghita

reader.go

@@ -107,6 +107,9 @@ func (r *Reader) startNode() (uint, error) {
 // Lookup takes an IP address as a net.IP structure and a pointer to the
 // result value to Decode into.
 func (r *Reader) Lookup(ipAddress net.IP, result interface{}) error {
+if r == nil {
+return errors.New("not initialized")
+}
 pointer, err := r.lookupPointer(ipAddress)
 if pointer == 0 || err != nil {
 return err
@@ -120,6 +123,9 @@ func (r *Reader) Lookup(ipAddress net.IP, result interface{}) error {
 // is an advanced API, which exists to provide clients with a means to cache
 // previously-decoded records.
 func (r *Reader) LookupOffset(ipAddress net.IP) (uintptr, error) {
+if r == nil {
+return 0, errors.New("not initialized")
+}
 pointer, err := r.lookupPointer(ipAddress)
 if pointer == 0 || err != nil {
 return NotFound, err
@@ -144,6 +150,9 @@ func (r *Reader) LookupOffset(ipAddress net.IP) (uintptr, error) {
 // single representative record for that country. This uintptr behavior allows
 // clients to leverage this normalization in their own sub-record caching.
 func (r *Reader) Decode(offset uintptr, result interface{}) error {
+if r == nil {
+return errors.New("not initialized")
+}
 rv := reflect.ValueOf(result)
 if rv.Kind() != reflect.Ptr || rv.IsNil() {
 return errors.New("result param must be a pointer")

reader_test.go

@@ -29,6 +29,20 @@ func TestReader(t *testing.T) {
 }
 }
 }
+
+var reader *Reader
+defer func() {
+assert.Nil(t, recover(), "unexpected panic")
+}()
+
+decodeErr := reader.Decode(0, interface{}(nil))
+assert.Error(t, decodeErr)
+
+lookupErr := reader.Lookup(net.IPv4(127, 0, 0, 1), interface{}(nil))
+assert.Error(t, lookupErr)
+
+_, offsetErr := reader.LookupOffset(net.IPv4(127, 0, 0, 1))
+assert.Error(t, offsetErr)
 }
 
 func TestReaderBytes(t *testing.T) {