982a2dde23
It is currently possible to make non-atomic comparisons of atomic
values:
x := atomic.NewInt32(1)
y := atomic.NewInt32(1)
fmt.Println(*x == *y)
This is undesirable because it loads the value in a non-atomic way. The
correct method is,
x := atomic.NewInt32(1)
y := atomic.NewInt32(1)
fmt.Println(x.Load() == y.Load())
To prevent this, disallow comparison of atomic values by embedding an
uncomparable array into atomics. The empty array adds no runtime cost,
and does not increase the in-memory size of the structs. Inspired by
[go4.org/mem#RO][1].
[1]: 3dbcd07079/mem.go (L42)
Note that the Value struct, which embeds `"sync/atomic".Value` was also
changed. This will break usages in the following form, but that's
acceptable because unkeyed struct literals are among the exceptions
stated in the [Go 1 compatibility expectations][2].
import (
syncatomic "sync/atomic"
"go.uber.org/atomic"
)
atomic.Value{syncatomic.Value{..}}
[2]: https://golang.org/doc/go1compat#expectations
Resolves #72
96 lines
2.8 KiB
Go
96 lines
2.8 KiB
Go
// @generated Code generated by gen-atomicint.
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// Copyright (c) 2020 Uber Technologies, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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package atomic
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import (
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"encoding/json"
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"sync/atomic"
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)
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// Int64 is an atomic wrapper around int64.
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type Int64 struct {
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nocmp // disallow non-atomic comparison
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v int64
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}
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// NewInt64 creates a new Int64.
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func NewInt64(i int64) *Int64 {
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return &Int64{v: i}
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}
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// Load atomically loads the wrapped value.
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func (i *Int64) Load() int64 {
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return atomic.LoadInt64(&i.v)
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}
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// Add atomically adds to the wrapped int64 and returns the new value.
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func (i *Int64) Add(n int64) int64 {
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return atomic.AddInt64(&i.v, n)
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}
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// Sub atomically subtracts from the wrapped int64 and returns the new value.
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func (i *Int64) Sub(n int64) int64 {
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return atomic.AddInt64(&i.v, -n)
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}
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// Inc atomically increments the wrapped int64 and returns the new value.
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func (i *Int64) Inc() int64 {
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return i.Add(1)
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}
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// Dec atomically decrements the wrapped int64 and returns the new value.
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func (i *Int64) Dec() int64 {
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return i.Sub(1)
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}
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// CAS is an atomic compare-and-swap.
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func (i *Int64) CAS(old, new int64) bool {
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return atomic.CompareAndSwapInt64(&i.v, old, new)
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}
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// Store atomically stores the passed value.
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func (i *Int64) Store(n int64) {
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atomic.StoreInt64(&i.v, n)
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}
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// Swap atomically swaps the wrapped int64 and returns the old value.
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func (i *Int64) Swap(n int64) int64 {
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return atomic.SwapInt64(&i.v, n)
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}
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// MarshalJSON encodes the wrapped int64 into JSON.
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func (i *Int64) MarshalJSON() ([]byte, error) {
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return json.Marshal(i.Load())
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}
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// UnmarshalJSON decodes JSON into the wrapped int64.
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func (i *Int64) UnmarshalJSON(b []byte) error {
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var v int64
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if err := json.Unmarshal(b, &v); err != nil {
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return err
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}
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i.Store(v)
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return nil
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}
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