diff --git a/README.md b/README.md index 3765eed2..8711ca07 100644 --- a/README.md +++ b/README.md @@ -45,6 +45,8 @@ an existing package to this repository. - [Clock](/clock) provides an interface for time-based operations. It allows mocking time for testing. + +- [Pointers](/pointers) provides some functions for pointer-based operations. [Build Status]: https://travis-ci.org/kubernetes/utils.svg?branch=master [Go standard libs]: https://golang.org/pkg/#stdlib diff --git a/pointer/pointer.go b/pointer/pointer.go new file mode 100644 index 00000000..5fbfc6e0 --- /dev/null +++ b/pointer/pointer.go @@ -0,0 +1,76 @@ +/* +Copyright 2018 The Kubernetes Authors. + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. +*/ + +package pointer + +import ( + "fmt" + "reflect" +) + +// AllPtrFieldsNil tests whether all pointer fields in a struct are nil. This is useful when, +// for example, an API struct is handled by plugins which need to distinguish +// "no plugin accepted this spec" from "this spec is empty". +// +// This function is only valid for structs and pointers to structs. Any other +// type will cause a panic. Passing a typed nil pointer will return true. +func AllPtrFieldsNil(obj interface{}) bool { + v := reflect.ValueOf(obj) + if !v.IsValid() { + panic(fmt.Sprintf("reflect.ValueOf() produced a non-valid Value for %#v", obj)) + } + if v.Kind() == reflect.Ptr { + if v.IsNil() { + return true + } + v = v.Elem() + } + for i := 0; i < v.NumField(); i++ { + if v.Field(i).Kind() == reflect.Ptr && !v.Field(i).IsNil() { + return false + } + } + return true +} + +// Int32Ptr returns a pointer to an int32 +func Int32Ptr(i int32) *int32 { + return &i +} + +// Int64Ptr returns a pointer to an int64 +func Int64Ptr(i int64) *int64 { + return &i +} + +// Int32PtrDerefOr dereference the int32 ptr and returns it i not nil, +// else returns def. +func Int32PtrDerefOr(ptr *int32, def int32) int32 { + if ptr != nil { + return *ptr + } + return def +} + +// BoolPtr returns a pointer to a bool +func BoolPtr(b bool) *bool { + return &b +} + +// StringPtr returns a pointer to the passed string. +func StringPtr(s string) *string { + return &s +} diff --git a/pointer/pointer_test.go b/pointer/pointer_test.go new file mode 100644 index 00000000..751db633 --- /dev/null +++ b/pointer/pointer_test.go @@ -0,0 +1,66 @@ +/* +Copyright 2018 The Kubernetes Authors. + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. +*/ + +package pointer + +import ( + "testing" +) + +func TestAllPtrFieldsNil(t *testing.T) { + testCases := []struct { + obj interface{} + expected bool + }{ + {struct{}{}, true}, + {struct{ Foo int }{12345}, true}, + {&struct{ Foo int }{12345}, true}, + {struct{ Foo *int }{nil}, true}, + {&struct{ Foo *int }{nil}, true}, + {struct { + Foo int + Bar *int + }{12345, nil}, true}, + {&struct { + Foo int + Bar *int + }{12345, nil}, true}, + {struct { + Foo *int + Bar *int + }{nil, nil}, true}, + {&struct { + Foo *int + Bar *int + }{nil, nil}, true}, + {struct{ Foo *int }{new(int)}, false}, + {&struct{ Foo *int }{new(int)}, false}, + {struct { + Foo *int + Bar *int + }{nil, new(int)}, false}, + {&struct { + Foo *int + Bar *int + }{nil, new(int)}, false}, + {(*struct{})(nil), true}, + } + for i, tc := range testCases { + if AllPtrFieldsNil(tc.obj) != tc.expected { + t.Errorf("case[%d]: expected %t, got %t", i, tc.expected, !tc.expected) + } + } +}