mirror of
https://github.com/tailscale/tailscale.git
synced 2024-11-27 03:55:36 +00:00
310 lines
8.6 KiB
Go
310 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("\t\t" + `panic("TODO map value pointers")`)
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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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