Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 386 insertions, 0 deletions

diff --git a/tools/go_stateify/main.go b/tools/go_stateify/main.go
new file mode 100644
index 000000000..5eb4fe51f
--- /dev/null
+++ b/tools/go_stateify/main.go
@@ -0,0 +1,386 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Stateify provides a simple way to generate Load/Save methods based on
+// existing types and struct tags.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"reflect"
+	"strings"
+)
+
+var (
+	pkg      = flag.String("pkg", "", "output package")
+	imports  = flag.String("imports", "", "extra imports for the output file")
+	output   = flag.String("output", "", "output file")
+	statePkg = flag.String("statepkg", "", "state import package; defaults to empty")
+)
+
+// resolveTypeName returns a qualified type name.
+func resolveTypeName(name string, typ ast.Expr) (field string, qualified string) {
+	for done := false; !done; {
+		// Resolve star expressions.
+		switch rs := typ.(type) {
+		case *ast.StarExpr:
+			qualified += "*"
+			typ = rs.X
+		case *ast.ArrayType:
+			if rs.Len == nil {
+				// Slice type declaration.
+				qualified += "[]"
+			} else {
+				// Array type declaration.
+				qualified += "[" + rs.Len.(*ast.BasicLit).Value + "]"
+			}
+			typ = rs.Elt
+		default:
+			// No more descent.
+			done = true
+		}
+	}
+
+	// Resolve a package selector.
+	sel, ok := typ.(*ast.SelectorExpr)
+	if ok {
+		qualified = qualified + sel.X.(*ast.Ident).Name + "."
+		typ = sel.Sel
+	}
+
+	// Figure out actual type name.
+	ident, ok := typ.(*ast.Ident)
+	if !ok {
+		panic(fmt.Sprintf("type not supported: %s (involves anonymous types?)", name))
+	}
+	field = ident.Name
+	qualified = qualified + field
+	return
+}
+
+// extractStateTag pulls the relevant state tag.
+func extractStateTag(tag *ast.BasicLit) string {
+	if tag == nil {
+		return ""
+	}
+	if len(tag.Value) < 2 {
+		return ""
+	}
+	return reflect.StructTag(tag.Value[1 : len(tag.Value)-1]).Get("state")
+}
+
+// scanFunctions is a set of functions passed to scanFields.
+type scanFunctions struct {
+	zerovalue func(name string)
+	normal    func(name string)
+	wait      func(name string)
+	value     func(name, typName string)
+}
+
+// scanFields scans the fields of a struct.
+//
+// Each provided function will be applied to appropriately tagged fields, or
+// skipped if nil.
+//
+// Fields tagged nosave are skipped.
+func scanFields(ss *ast.StructType, fn scanFunctions) {
+	if ss.Fields.List == nil {
+		// No fields.
+		return
+	}
+
+	// Scan all fields.
+	for _, field := range ss.Fields.List {
+		// Calculate the name.
+		name := ""
+		if field.Names != nil {
+			// It's a named field; override.
+			name = field.Names[0].Name
+		} else {
+			// Anonymous types can't be embedded, so we don't need
+			// to worry about providing a useful name here.
+			name, _ = resolveTypeName("", field.Type)
+		}
+
+		// Skip _ fields.
+		if name == "_" {
+			continue
+		}
+
+		switch tag := extractStateTag(field.Tag); tag {
+		case "zerovalue":
+			if fn.zerovalue != nil {
+				fn.zerovalue(name)
+			}
+
+		case "":
+			if fn.normal != nil {
+				fn.normal(name)
+			}
+
+		case "wait":
+			if fn.wait != nil {
+				fn.wait(name)
+			}
+
+		case "manual", "nosave", "ignore":
+			// Do nothing.
+
+		default:
+			if strings.HasPrefix(tag, ".(") && strings.HasSuffix(tag, ")") {
+				if fn.value != nil {
+					fn.value(name, tag[2:len(tag)-1])
+				}
+			}
+		}
+	}
+}
+
+func camelCased(name string) string {
+	return strings.ToUpper(name[:1]) + name[1:]
+}
+
+func main() {
+	// Parse flags.
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s [options]\n", os.Args[0])
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+	if len(flag.Args()) == 0 {
+		flag.Usage()
+		os.Exit(1)
+	}
+	if *pkg == "" {
+		fmt.Fprintf(os.Stderr, "Error: package required.")
+		os.Exit(1)
+	}
+
+	// Open the output file.
+	var (
+		outputFile *os.File
+		err        error
+	)
+	if *output == "" || *output == "-" {
+		outputFile = os.Stdout
+	} else {
+		outputFile, err = os.OpenFile(*output, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error opening output %q: %v", *output, err)
+		}
+		defer outputFile.Close()
+	}
+
+	// Set the statePrefix for below, depending on the import.
+	statePrefix := ""
+	if *statePkg != "" {
+		parts := strings.Split(*statePkg, "/")
+		statePrefix = parts[len(parts)-1] + "."
+	}
+
+	// initCalls is dumped at the end.
+	var initCalls []string
+
+	// Declare our emission closures.
+	emitRegister := func(name string) {
+		initCalls = append(initCalls, fmt.Sprintf("%sRegister(\"%s.%s\", (*%s)(nil), state.Fns{Save: (*%s).save, Load: (*%s).load})", statePrefix, *pkg, name, name, name, name))
+	}
+	emitZeroCheck := func(name string) {
+		fmt.Fprintf(outputFile, "	if !%sIsZeroValue(x.%s) { m.Failf(\"%s is %%v, expected zero\", x.%s) }\n", statePrefix, name, name, name)
+	}
+	emitLoadValue := func(name, typName string) {
+		fmt.Fprintf(outputFile, "	m.LoadValue(\"%s\", new(%s), func(y interface{}) { x.load%s(y.(%s)) })\n", name, typName, camelCased(name), typName)
+	}
+	emitLoad := func(name string) {
+		fmt.Fprintf(outputFile, "	m.Load(\"%s\", &x.%s)\n", name, name)
+	}
+	emitLoadWait := func(name string) {
+		fmt.Fprintf(outputFile, "	m.LoadWait(\"%s\", &x.%s)\n", name, name)
+	}
+	emitSaveValue := func(name, typName string) {
+		fmt.Fprintf(outputFile, "	var %s %s = x.save%s()\n", name, typName, camelCased(name))
+		fmt.Fprintf(outputFile, "	m.SaveValue(\"%s\", %s)\n", name, name)
+	}
+	emitSave := func(name string) {
+		fmt.Fprintf(outputFile, "	m.Save(\"%s\", &x.%s)\n", name, name)
+	}
+
+	// Emit the package name.
+	fmt.Fprintf(outputFile, "// automatically generated by stateify.\n\n")
+	fmt.Fprintf(outputFile, "package %s\n\n", *pkg)
+	fmt.Fprintln(outputFile, "import (")
+	if *statePkg != "" {
+		fmt.Fprintf(outputFile, "	\"%s\"\n", *statePkg)
+	}
+	if *imports != "" {
+		for _, i := range strings.Split(*imports, ",") {
+			fmt.Fprintf(outputFile, "	\"%s\"\n", i)
+		}
+	}
+	fmt.Fprintln(outputFile, ")\n")
+
+	files := make([]*ast.File, 0, len(flag.Args()))
+
+	// Parse the input files.
+	for _, filename := range flag.Args() {
+		// Parse the file.
+		fset := token.NewFileSet()
+		f, err := parser.ParseFile(fset, filename, nil, 0)
+		if err != nil {
+			// Not a valid input file?
+			fmt.Fprintf(os.Stderr, "Input %q can't be parsed: %v\n", filename, err)
+			os.Exit(1)
+		}
+		files = append(files, f)
+	}
+
+	type method struct {
+		receiver string
+		name     string
+	}
+
+	// Search for and add all methods with a pointer receiver and no other
+	// arguments to a set. We support auto-detecting the existence of
+	// several different methods with this signature.
+	simpleMethods := map[method]struct{}{}
+	for _, f := range files {
+
+		// Go over all functions.
+		for _, decl := range f.Decls {
+			d, ok := decl.(*ast.FuncDecl)
+			if !ok {
+				continue
+			}
+			if d.Name == nil || d.Recv == nil || d.Type == nil {
+				// Not a named method.
+				continue
+			}
+			if len(d.Recv.List) != 1 {
+				// Wrong number of receivers?
+				continue
+			}
+			if d.Type.Params != nil && len(d.Type.Params.List) != 0 {
+				// Has argument(s).
+				continue
+			}
+			if d.Type.Results != nil && len(d.Type.Results.List) != 0 {
+				// Has return(s).
+				continue
+			}
+
+			pt, ok := d.Recv.List[0].Type.(*ast.StarExpr)
+			if !ok {
+				// Not a pointer receiver.
+				continue
+			}
+
+			t, ok := pt.X.(*ast.Ident)
+			if !ok {
+				// This shouldn't happen with valid Go.
+				continue
+			}
+
+			simpleMethods[method{t.Name, d.Name.Name}] = struct{}{}
+		}
+	}
+
+	for _, f := range files {
+		// Go over all named types.
+		for _, decl := range f.Decls {
+			d, ok := decl.(*ast.GenDecl)
+			if !ok || d.Tok != token.TYPE {
+				continue
+			}
+
+			for _, gs := range d.Specs {
+				ts := gs.(*ast.TypeSpec)
+				switch ts.Type.(type) {
+				case *ast.InterfaceType, *ast.ChanType, *ast.FuncType, *ast.ParenExpr, *ast.StarExpr:
+					// Don't register.
+					break
+				case *ast.StructType:
+					ss := ts.Type.(*ast.StructType)
+
+					// Define beforeSave if a definition was not found. This
+					// prevents the code from compiling if a custom beforeSave
+					// was defined in a file not provided to this binary and
+					// prevents inherited methods from being called multiple times
+					// by overriding them.
+					if _, ok := simpleMethods[method{ts.Name.Name, "beforeSave"}]; !ok {
+						fmt.Fprintf(outputFile, "func (x *%s) beforeSave() {}\n", ts.Name.Name)
+					}
+
+					// Generate the save method.
+					fmt.Fprintf(outputFile, "func (x *%s) save(m %sMap) {\n", ts.Name.Name, statePrefix)
+					fmt.Fprintf(outputFile, "	x.beforeSave()\n")
+					scanFields(ss, scanFunctions{zerovalue: emitZeroCheck})
+					scanFields(ss, scanFunctions{value: emitSaveValue})
+					scanFields(ss, scanFunctions{normal: emitSave, wait: emitSave})
+					fmt.Fprintf(outputFile, "}\n\n")
+
+					// Define afterLoad if a definition was not found. We do this
+					// for the same reason that we do it for beforeSave.
+					_, hasAfterLoad := simpleMethods[method{ts.Name.Name, "afterLoad"}]
+					if !hasAfterLoad {
+						fmt.Fprintf(outputFile, "func (x *%s) afterLoad() {}\n", ts.Name.Name)
+					}
+
+					// Generate the load method.
+					//
+					// Note that the manual loads always follow the
+					// automated loads.
+					fmt.Fprintf(outputFile, "func (x *%s) load(m %sMap) {\n", ts.Name.Name, statePrefix)
+					scanFields(ss, scanFunctions{normal: emitLoad, wait: emitLoadWait})
+					scanFields(ss, scanFunctions{value: emitLoadValue})
+					if hasAfterLoad {
+						// The call to afterLoad is made conditionally, because when
+						// AfterLoad is called, the object encodes a dependency on
+						// referred objects (i.e. fields). This means that afterLoad
+						// will not be called until the other afterLoads are called.
+						fmt.Fprintf(outputFile, "	m.AfterLoad(x.afterLoad)\n")
+					}
+					fmt.Fprintf(outputFile, "}\n\n")
+
+					// Add to our registration.
+					emitRegister(ts.Name.Name)
+				case *ast.Ident, *ast.SelectorExpr, *ast.ArrayType:
+					_, val := resolveTypeName(ts.Name.Name, ts.Type)
+
+					// Dispatch directly.
+					fmt.Fprintf(outputFile, "func (x *%s) save(m %sMap) {\n", ts.Name.Name, statePrefix)
+					fmt.Fprintf(outputFile, "	m.SaveValue(\"\", (%s)(*x))\n", val)
+					fmt.Fprintf(outputFile, "}\n\n")
+					fmt.Fprintf(outputFile, "func (x *%s) load(m %sMap) {\n", ts.Name.Name, statePrefix)
+					fmt.Fprintf(outputFile, "	m.LoadValue(\"\", new(%s), func(y interface{}) { *x = (%s)(y.(%s)) })\n", val, ts.Name.Name, val)
+					fmt.Fprintf(outputFile, "}\n\n")
+
+					// See above.
+					emitRegister(ts.Name.Name)
+				}
+			}
+		}
+	}
+
+	// Emit the init() function.
+	fmt.Fprintf(outputFile, "func init() {\n")
+	for _, ic := range initCalls {
+		fmt.Fprintf(outputFile, "	%s\n", ic)
+	}
+	fmt.Fprintf(outputFile, "}\n")
+}