305 lines
8.0 KiB
Go
305 lines
8.0 KiB
Go
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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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// gen-atomicwrapper generates wrapper types around other atomic types.
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//
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// It supports plugging in functions which convert the value inside the atomic
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// type to the user-facing value. For example,
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//
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// Given, atomic.Value and the functions,
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//
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// func packString(string) interface{}
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// func unpackString(interface{}) string
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//
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// We can run the following command:
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//
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// gen-atomicwrapper -name String -wrapped Value \
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// -type string -pack fromString -unpack tostring
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//
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// This wil generate approximately,
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//
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// type String struct{ v Value }
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//
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// func (s *String) Load() string {
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// return unpackString(v.Load())
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// }
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//
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// func (s *String) Store(s string) {
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// return s.v.Store(packString(s))
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// }
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//
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// The packing/unpacking logic allows the stored value to be different from
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// the user-facing value.
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//
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// Without -pack and -unpack, the output will be cast to the target type,
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// defaulting to the zero value.
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package main
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import (
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"bytes"
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"errors"
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"flag"
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"fmt"
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"go/format"
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"io"
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"log"
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"os"
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"sort"
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"strings"
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"text/template"
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"time"
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)
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func main() {
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log.SetFlags(0)
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if err := run(os.Args[1:]); err != nil {
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log.Fatalf("%+v", err)
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}
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}
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type stringList []string
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func (sl *stringList) String() string {
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return strings.Join(*sl, ",")
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}
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func (sl *stringList) Set(s string) error {
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for _, i := range strings.Split(s, ",") {
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*sl = append(*sl, strings.TrimSpace(i))
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}
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return nil
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}
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func run(args []string) error {
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var opts struct {
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Name string
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Wrapped string
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Type string
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Imports stringList
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Pack, Unpack string
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CAS bool
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Swap bool
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JSON bool
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File string
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ToYear int
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}
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opts.ToYear = time.Now().Year()
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flag := flag.NewFlagSet("gen-atomicwrapper", flag.ContinueOnError)
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// Required flags
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flag.StringVar(&opts.Name, "name", "",
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"name of the generated type (e.g. Duration)")
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flag.StringVar(&opts.Wrapped, "wrapped", "",
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"name of the wrapped atomic (e.g. Int64)")
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flag.StringVar(&opts.Type, "type", "",
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"name of the type exposed by the atomic (e.g. time.Duration)")
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// Optional flags
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flag.Var(&opts.Imports, "imports",
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"comma separated list of imports to add")
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flag.StringVar(&opts.Pack, "pack", "",
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"function to transform values with before storage")
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flag.StringVar(&opts.Unpack, "unpack", "",
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"function to reverse packing on loading")
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flag.StringVar(&opts.File, "file", "",
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"output file path (default: stdout)")
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// Switches for individual methods. Underlying atomics must support
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// these.
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flag.BoolVar(&opts.CAS, "cas", false,
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"generate a `CAS(old, new) bool` method; requires -pack")
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flag.BoolVar(&opts.Swap, "swap", false,
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"generate a `Swap(new) old` method; requires -pack and -unpack")
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flag.BoolVar(&opts.JSON, "json", false,
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"generate `MarshalJSON/UnmarshJSON` methods")
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if err := flag.Parse(args); err != nil {
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return err
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}
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if len(opts.Name) == 0 || len(opts.Wrapped) == 0 || len(opts.Type) == 0 {
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return errors.New("flags -name, -wrapped, and -type are required")
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}
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if (len(opts.Pack) == 0) != (len(opts.Unpack) == 0) {
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return errors.New("either both, or neither of -pack and -unpack must be specified")
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}
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if opts.CAS && len(opts.Pack) == 0 {
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return errors.New("flag -cas requires -pack")
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}
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if opts.Swap && len(opts.Pack) == 0 {
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return errors.New("flag -swap requires -pack and -unpack")
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}
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var w io.Writer = os.Stdout
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if file := opts.File; len(file) > 0 {
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f, err := os.Create(file)
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if err != nil {
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return fmt.Errorf("create %q: %v", file, err)
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}
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defer f.Close()
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w = f
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}
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// Import encoding/json if needed.
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if opts.JSON {
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found := false
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for _, imp := range opts.Imports {
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if imp == "encoding/json" {
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found = true
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break
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}
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}
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if !found {
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opts.Imports = append(opts.Imports, "encoding/json")
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}
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}
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sort.Strings([]string(opts.Imports))
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var buff bytes.Buffer
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if err := _tmpl.Execute(&buff, opts); err != nil {
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return fmt.Errorf("render template: %v", err)
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}
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bs, err := format.Source(buff.Bytes())
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if err != nil {
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return fmt.Errorf("reformat source: %v", err)
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}
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_, err = w.Write(bs)
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return err
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}
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var _tmpl = template.Must(template.New("int.go").Parse(`// @generated Code generated by gen-atomicwrapper.
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// Copyright (c) 2020-{{.ToYear}} 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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{{ with .Imports }}
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import (
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{{ range . -}}
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{{ printf "%q" . }}
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{{ end }}
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)
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{{ end }}
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// {{ .Name }} is an atomic type-safe wrapper for {{ .Type }} values.
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type {{ .Name }} struct{
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_ nocmp // disallow non-atomic comparison
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v {{ .Wrapped }}
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}
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var _zero{{ .Name }} {{ .Type }}
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// New{{ .Name }} creates a new {{ .Name }}.
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func New{{ .Name}}(val {{ .Type }}) *{{ .Name }} {
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x := &{{ .Name }}{}
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if val != _zero{{ .Name }} {
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x.Store(val)
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}
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return x
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}
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// Load atomically loads the wrapped {{ .Type }}.
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func (x *{{ .Name }}) Load() {{ .Type }} {
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{{ if .Unpack -}}
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return {{ .Unpack }}(x.v.Load())
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{{- else -}}
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if v := x.v.Load(); v != nil {
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return v.({{ .Type }})
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}
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return _zero{{ .Name }}
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{{- end }}
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}
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// Store atomically stores the passed {{ .Type }}.
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func (x *{{ .Name }}) Store(val {{ .Type }}) {
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{{ if .Pack -}}
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x.v.Store({{ .Pack }}(val))
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{{- else -}}
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x.v.Store(val)
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{{- end }}
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}
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{{ if .CAS -}}
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// CAS is an atomic compare-and-swap for {{ .Type }} values.
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func (x *{{ .Name }}) CAS(old, new {{ .Type }}) (swapped bool) {
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return x.v.CAS({{ .Pack }}(old), {{ .Pack }}(new))
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}
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{{- end }}
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{{ if .Swap -}}
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// Swap atomically stores the given {{ .Type }} and returns the old
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// value.
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func (x *{{ .Name }}) Swap(val {{ .Type }}) (old {{ .Type }}) {
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return {{ .Unpack }}(x.v.Swap({{ .Pack }}(val)))
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}
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{{- end }}
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{{ if .JSON -}}
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// MarshalJSON encodes the wrapped {{ .Type }} into JSON.
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func (x *{{ .Name }}) MarshalJSON() ([]byte, error) {
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return json.Marshal(x.Load())
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}
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// UnmarshalJSON decodes a {{ .Type }} from JSON.
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func (x *{{ .Name }}) UnmarshalJSON(b []byte) error {
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var v {{ .Type }}
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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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x.Store(v)
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return nil
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}
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{{- end }}
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`))
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