mirror of
https://github.com/tailscale/tailscale.git
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0f18801716
In order to clone DERPMaps, it was necessary to extend the cloner so that it supports nested pointers inside of maps which are also cloneable. This also adds cloning for DERPRegions and DERPNodes because they are on DERPMap's maps. Signed-off-by: julianknodt <julianknodt@gmail.com>
312 lines
8.6 KiB
Go
312 lines
8.6 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Cloner is a tool to automate the creation of a Clone method.
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//
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// The result of the Clone method aliases no memory that can be edited
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// with the original.
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//
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// This tool makes lots of implicit assumptions about the types you feed it.
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// In particular, it can only write relatively "shallow" Clone methods.
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// That is, if a type contains another named struct type, cloner assumes that
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// named type will also have a Clone method.
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package main
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import (
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"bytes"
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"flag"
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"fmt"
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"go/ast"
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"go/format"
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"go/token"
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"go/types"
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"io/ioutil"
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"log"
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"os"
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"strings"
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"golang.org/x/tools/go/packages"
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)
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var (
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flagTypes = flag.String("type", "", "comma-separated list of types; required")
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flagOutput = flag.String("output", "", "output file; required")
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flagBuildTags = flag.String("tags", "", "compiler build tags to apply")
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flagCloneFunc = flag.Bool("clonefunc", false, "add a top-level Clone func")
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)
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func main() {
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log.SetFlags(0)
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log.SetPrefix("cloner: ")
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flag.Parse()
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if len(*flagTypes) == 0 {
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flag.Usage()
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os.Exit(2)
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}
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typeNames := strings.Split(*flagTypes, ",")
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cfg := &packages.Config{
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Mode: packages.NeedTypes | packages.NeedTypesInfo | packages.NeedSyntax | packages.NeedName,
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Tests: false,
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}
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if *flagBuildTags != "" {
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cfg.BuildFlags = []string{"-tags=" + *flagBuildTags}
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}
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pkgs, err := packages.Load(cfg, ".")
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if err != nil {
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log.Fatal(err)
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}
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if len(pkgs) != 1 {
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log.Fatalf("wrong number of packages: %d", len(pkgs))
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}
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pkg := pkgs[0]
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buf := new(bytes.Buffer)
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imports := make(map[string]struct{})
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for _, typeName := range typeNames {
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found := false
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for _, file := range pkg.Syntax {
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//var fbuf bytes.Buffer
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//ast.Fprint(&fbuf, pkg.Fset, file, nil)
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//fmt.Println(fbuf.String())
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for _, d := range file.Decls {
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decl, ok := d.(*ast.GenDecl)
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if !ok || decl.Tok != token.TYPE {
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continue
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}
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for _, s := range decl.Specs {
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spec, ok := s.(*ast.TypeSpec)
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if !ok || spec.Name.Name != typeName {
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continue
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}
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typeNameObj := pkg.TypesInfo.Defs[spec.Name]
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typ, ok := typeNameObj.Type().(*types.Named)
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if !ok {
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continue
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}
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pkg := typeNameObj.Pkg()
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gen(buf, imports, typeName, typ, pkg)
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found = true
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}
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}
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}
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if !found {
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log.Fatalf("could not find type %s", typeName)
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}
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}
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w := func(format string, args ...interface{}) {
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fmt.Fprintf(buf, format+"\n", args...)
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}
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if *flagCloneFunc {
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w("// Clone duplicates src into dst and reports whether it succeeded.")
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w("// To succeed, <src, dst> must be of types <*T, *T> or <*T, **T>,")
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w("// where T is one of %s.", *flagTypes)
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w("func Clone(dst, src interface{}) bool {")
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w(" switch src := src.(type) {")
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for _, typeName := range typeNames {
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w(" case *%s:", typeName)
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w(" switch dst := dst.(type) {")
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w(" case *%s:", typeName)
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w(" *dst = *src.Clone()")
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w(" return true")
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w(" case **%s:", typeName)
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w(" *dst = src.Clone()")
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w(" return true")
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w(" }")
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}
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w(" }")
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w(" return false")
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w("}")
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}
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contents := new(bytes.Buffer)
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fmt.Fprintf(contents, header, *flagTypes, pkg.Name)
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fmt.Fprintf(contents, "import (\n")
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for s := range imports {
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fmt.Fprintf(contents, "\t%q\n", s)
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}
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fmt.Fprintf(contents, ")\n\n")
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contents.Write(buf.Bytes())
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out, err := format.Source(contents.Bytes())
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if err != nil {
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log.Fatalf("%s, in source:\n%s", err, contents.Bytes())
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}
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output := *flagOutput
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if output == "" {
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flag.Usage()
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os.Exit(2)
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}
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if err := ioutil.WriteFile(output, out, 0644); err != nil {
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log.Fatal(err)
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}
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}
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const header = `// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Code generated by tailscale.com/cmd/cloner -type %s; DO NOT EDIT.
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package %s
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`
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func gen(buf *bytes.Buffer, imports map[string]struct{}, name string, typ *types.Named, thisPkg *types.Package) {
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pkgQual := func(pkg *types.Package) string {
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if thisPkg == pkg {
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return ""
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}
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imports[pkg.Path()] = struct{}{}
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return pkg.Name()
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}
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importedName := func(t types.Type) string {
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return types.TypeString(t, pkgQual)
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}
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switch t := typ.Underlying().(type) {
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case *types.Struct:
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// We generate two bits of code simultaneously while we walk the struct.
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// One is the Clone method itself, which we write directly to buf.
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// The other is a variable assignment that will fail if the struct
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// changes without the Clone method getting regenerated.
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// We write that to regenBuf, and then append it to buf at the end.
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regenBuf := new(bytes.Buffer)
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writeRegen := func(format string, args ...interface{}) {
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fmt.Fprintf(regenBuf, format+"\n", args...)
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}
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writeRegen("// A compilation failure here means this code must be regenerated, with command:")
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writeRegen("// tailscale.com/cmd/cloner -type %s", *flagTypes)
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writeRegen("var _%sNeedsRegeneration = %s(struct {", name, name)
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name := typ.Obj().Name()
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fmt.Fprintf(buf, "// Clone makes a deep copy of %s.\n", name)
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fmt.Fprintf(buf, "// The result aliases no memory with the original.\n")
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fmt.Fprintf(buf, "func (src *%s) Clone() *%s {\n", name, name)
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writef := func(format string, args ...interface{}) {
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fmt.Fprintf(buf, "\t"+format+"\n", args...)
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}
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writef("if src == nil {")
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writef("\treturn nil")
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writef("}")
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writef("dst := new(%s)", name)
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writef("*dst = *src")
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for i := 0; i < t.NumFields(); i++ {
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fname := t.Field(i).Name()
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ft := t.Field(i).Type()
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writeRegen("\t%s %s", fname, importedName(ft))
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if !containsPointers(ft) {
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continue
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}
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if named, _ := ft.(*types.Named); named != nil && !hasBasicUnderlying(ft) {
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writef("dst.%s = *src.%s.Clone()", fname, fname)
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continue
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}
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switch ft := ft.Underlying().(type) {
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case *types.Slice:
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if containsPointers(ft.Elem()) {
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n := importedName(ft.Elem())
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writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
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writef("for i := range dst.%s {", fname)
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if _, isPtr := ft.Elem().(*types.Pointer); isPtr {
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writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
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} else {
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writef("\tdst.%s[i] = *src.%s[i].Clone()", fname, fname)
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}
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writef("}")
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} else {
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writef("dst.%s = append(src.%s[:0:0], src.%s...)", fname, fname, fname)
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}
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case *types.Pointer:
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if named, _ := ft.Elem().(*types.Named); named != nil && containsPointers(ft.Elem()) {
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writef("dst.%s = src.%s.Clone()", fname, fname)
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continue
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}
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n := importedName(ft.Elem())
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writef("if dst.%s != nil {", fname)
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writef("\tdst.%s = new(%s)", fname, n)
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writef("\t*dst.%s = *src.%s", fname, fname)
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if containsPointers(ft.Elem()) {
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writef("\t" + `panic("TODO pointers in pointers")`)
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}
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writef("}")
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case *types.Map:
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writef("if dst.%s != nil {", fname)
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writef("\tdst.%s = map[%s]%s{}", fname, importedName(ft.Key()), importedName(ft.Elem()))
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if sliceType, isSlice := ft.Elem().(*types.Slice); isSlice {
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n := importedName(sliceType.Elem())
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writef("\tfor k := range src.%s {", fname)
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// use zero-length slice instead of nil to ensure
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// the key is always copied.
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writef("\t\tdst.%s[k] = append([]%s{}, src.%s[k]...)", fname, n, fname)
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writef("\t}")
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} else if containsPointers(ft.Elem()) {
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writef("\tfor k, v := range src.%s {", fname)
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writef("\t\tdst.%s[k] = v.Clone()", fname)
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writef("\t}")
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} else {
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writef("\tfor k, v := range src.%s {", fname)
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writef("\t\tdst.%s[k] = v", fname)
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writef("\t}")
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}
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writef("}")
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case *types.Struct:
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writef(`panic("TODO struct %s")`, fname)
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default:
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writef(`panic(fmt.Sprintf("TODO: %T", ft))`)
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}
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}
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writef("return dst")
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fmt.Fprintf(buf, "}\n\n")
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writeRegen("}{})\n")
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buf.Write(regenBuf.Bytes())
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}
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}
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func hasBasicUnderlying(typ types.Type) bool {
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switch typ.Underlying().(type) {
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case *types.Slice, *types.Map:
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return true
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default:
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return false
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}
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}
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func containsPointers(typ types.Type) bool {
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switch typ.String() {
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case "time.Time":
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// time.Time contains a pointer that does not need copying
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return false
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case "inet.af/netaddr.IP":
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return false
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}
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switch ft := typ.Underlying().(type) {
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case *types.Array:
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return containsPointers(ft.Elem())
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case *types.Chan:
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return true
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case *types.Interface:
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return true // a little too broad
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case *types.Map:
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return true
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case *types.Pointer:
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return true
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case *types.Slice:
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return true
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case *types.Struct:
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for i := 0; i < ft.NumFields(); i++ {
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if containsPointers(ft.Field(i).Type()) {
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return true
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}
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}
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}
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return false
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}
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