From 78a3b8ec6cb2e156b91140c7d53b16e12b7b3f91 Mon Sep 17 00:00:00 2001 From: josephinedotlee <84732210+josephinedotlee@users.noreply.github.com> Date: Tue, 20 Sep 2022 15:23:16 -0700 Subject: [PATCH] Implement String method for pointers (#122) * Implement String method for pointers By implementing this method ourselves using atomic loading and fmt.Sprint, we can avoid possible unguarded accesses to the embedded pointer if someone attempts to fmt.Print the atomic.Pointer . * Use Pointer.Load, not wrapped.Load Co-authored-by: Abhinav Gupta --- CHANGELOG.md | 5 ++++ pointer_go118.go | 41 +++++----------------------- pointer_go118_pre119.go | 60 +++++++++++++++++++++++++++++++++++++++++ pointer_test.go | 5 ++++ 4 files changed, 76 insertions(+), 35 deletions(-) create mode 100644 pointer_go118_pre119.go diff --git a/CHANGELOG.md b/CHANGELOG.md index 5fe03f2..729a316 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file. The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). +## Unreleased +### Added +- Add `String` method to `atomic.Pointer[T]` type allowing users to safely print +underlying values of pointers. + ## [1.10.0] - 2022-08-11 ### Added - Add `atomic.Float32` type for atomic operations on `float32`. diff --git a/pointer_go118.go b/pointer_go118.go index e0f47db..1fb6c03 100644 --- a/pointer_go118.go +++ b/pointer_go118.go @@ -18,43 +18,14 @@ // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN // THE SOFTWARE. -//go:build go1.18 && !go1.19 -// +build go1.18,!go1.19 +//go:build go1.18 +// +build go1.18 package atomic -import "unsafe" +import "fmt" -type Pointer[T any] struct { - _ nocmp // disallow non-atomic comparison - p UnsafePointer -} - -// NewPointer creates a new Pointer. -func NewPointer[T any](v *T) *Pointer[T] { - var p Pointer[T] - if v != nil { - p.p.Store(unsafe.Pointer(v)) - } - return &p -} - -// Load atomically loads the wrapped value. -func (p *Pointer[T]) Load() *T { - return (*T)(p.p.Load()) -} - -// Store atomically stores the passed value. -func (p *Pointer[T]) Store(val *T) { - p.p.Store(unsafe.Pointer(val)) -} - -// Swap atomically swaps the wrapped pointer and returns the old value. -func (p *Pointer[T]) Swap(val *T) (old *T) { - return (*T)(p.p.Swap(unsafe.Pointer(val))) -} - -// CompareAndSwap is an atomic compare-and-swap. -func (p *Pointer[T]) CompareAndSwap(old, new *T) (swapped bool) { - return p.p.CompareAndSwap(unsafe.Pointer(old), unsafe.Pointer(new)) +// String returns a human readable representation of a Pointer's underlying value. +func (p *Pointer[T]) String() string { + return fmt.Sprint(p.Load()) } diff --git a/pointer_go118_pre119.go b/pointer_go118_pre119.go new file mode 100644 index 0000000..e0f47db --- /dev/null +++ b/pointer_go118_pre119.go @@ -0,0 +1,60 @@ +// Copyright (c) 2022 Uber Technologies, Inc. +// +// Permission is hereby granted, free of charge, to any person obtaining a copy +// of this software and associated documentation files (the "Software"), to deal +// in the Software without restriction, including without limitation the rights +// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +// copies of the Software, and to permit persons to whom the Software is +// furnished to do so, subject to the following conditions: +// +// The above copyright notice and this permission notice shall be included in +// all copies or substantial portions of the Software. +// +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +// THE SOFTWARE. + +//go:build go1.18 && !go1.19 +// +build go1.18,!go1.19 + +package atomic + +import "unsafe" + +type Pointer[T any] struct { + _ nocmp // disallow non-atomic comparison + p UnsafePointer +} + +// NewPointer creates a new Pointer. +func NewPointer[T any](v *T) *Pointer[T] { + var p Pointer[T] + if v != nil { + p.p.Store(unsafe.Pointer(v)) + } + return &p +} + +// Load atomically loads the wrapped value. +func (p *Pointer[T]) Load() *T { + return (*T)(p.p.Load()) +} + +// Store atomically stores the passed value. +func (p *Pointer[T]) Store(val *T) { + p.p.Store(unsafe.Pointer(val)) +} + +// Swap atomically swaps the wrapped pointer and returns the old value. +func (p *Pointer[T]) Swap(val *T) (old *T) { + return (*T)(p.p.Swap(unsafe.Pointer(val))) +} + +// CompareAndSwap is an atomic compare-and-swap. +func (p *Pointer[T]) CompareAndSwap(old, new *T) (swapped bool) { + return p.p.CompareAndSwap(unsafe.Pointer(old), unsafe.Pointer(new)) +} diff --git a/pointer_test.go b/pointer_test.go index ecd3763..7d2d32b 100644 --- a/pointer_test.go +++ b/pointer_test.go @@ -24,6 +24,7 @@ package atomic import ( + "fmt" "testing" "github.com/stretchr/testify/require" @@ -89,6 +90,10 @@ func TestPointer(t *testing.T) { atom.Store(&i) require.Equal(t, &i, atom.Load(), "Store didn't set the correct value.") }) + t.Run("String", func(t *testing.T) { + atom := tt.newAtomic() + require.Equal(t, fmt.Sprint(tt.initial), atom.String(), "String did not return the correct value.") + }) }) } }