cmd/gomobile/bind.go - mobile - Git at Google

 // Copyright 2015 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package main

 import (
 	"archive/zip"
 	"bytes"
 	"errors"
 	"fmt"
 	"go/ast"
 	"go/build"
 	"go/parser"
 	"go/scanner"
 	"go/token"
 	"io"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"text/template"
 	"unicode"
 	"unicode/utf8"

 	"golang.org/x/mobile/bind"
 	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/types"
 )

 // ctx, pkg, ndkccpath, tmpdir in build.go

 var cmdBind = &command{
 	run:   runBind,
 	Name:  "bind",
 	Usage: "[-target android|ios] [-o output] [build flags] [package]",
 	Short: "build a shared library for android APK and iOS app",
 	Long: `
 Bind generates language bindings for the package named by the import
 path, and compiles a library for the named target system.

 The -target flag takes a target system name, either android (the
 default) or ios.

 For -target android, the bind command produces an AAR (Android ARchive)
 file that archives the precompiled Java API stub classes, the compiled
 shared libraries, and all asset files in the /assets subdirectory under
 the package directory. The output is named '<package_name>.aar' by
 default. This AAR file is commonly used for binary distribution of an
 Android library project and most Android IDEs support AAR import. For
 example, in Android Studio (1.2+), an AAR file can be imported using
 the module import wizard (File > New > New Module > Import .JAR or
 .AAR package), and setting it as a new dependency
 (File > Project Structure > Dependencies).  This requires 'javac'
 (version 1.7+) and Android SDK (API level 9 or newer) to build the
 library for Android. The environment variable ANDROID_HOME must be set
 to the path to Android SDK.

 For -target ios, gomobile must be run on an OS X machine with Xcode
 installed. Support is not complete.

 The -v flag provides verbose output, including the list of packages built.

 The build flags -a, -i, -n, -x, and -tags are shared with the build command.
 For documentation, see 'go help build'.
 `,
 }

 func runBind(cmd *command) error {
 	cwd, err := os.Getwd()
 	if err != nil {
 		panic(err)
 	}
 	args := cmd.flag.Args()

 	var bindPkg *build.Package
 	switch len(args) {
 	case 0:
 		bindPkg, err = ctx.ImportDir(cwd, build.ImportComment)
 	case 1:
 		bindPkg, err = ctx.Import(args[0], cwd, build.ImportComment)
 	default:
 		cmd.usage()
 		os.Exit(1)
 	}
 	if err != nil {
 		return err
 	}

 	switch *buildTarget {
 	case "android":
 		// implementation is below
 	case "ios":
 		return fmt.Errorf(`-target=ios not yet supported`)
 	default:
 		return fmt.Errorf(`unknown -target, %q.`, *buildTarget)
 	}

 	if sdkDir := os.Getenv("ANDROID_HOME"); sdkDir == "" {
 		return fmt.Errorf("this command requires ANDROID_HOME environment variable (path to the Android SDK)")
 	}

 	if buildN {
 		tmpdir = "$WORK"
 	} else {
 		tmpdir, err = ioutil.TempDir("", "gomobile-bind-work-")
 		if err != nil {
 			return err
 		}
 	}
 	defer removeAll(tmpdir)
 	if buildX {
 		fmt.Fprintln(os.Stderr, "WORK="+tmpdir)
 	}

 	binder, err := newBinder(bindPkg)
 	if err != nil {
 		return err
 	}

 	if err := binder.GenGo(tmpdir); err != nil {
 		return err
 	}

 	mainFile := filepath.Join(tmpdir, "androidlib/main.go")
 	err = writeFile(mainFile, func(w io.Writer) error {
 		return androidMainTmpl.Execute(w, "../go_"+binder.pkg.Name())
 	})
 	if err != nil {
 		return fmt.Errorf("failed to create the main package for android: %v", err)
 	}

 	androidDir := filepath.Join(tmpdir, "android")

 	err = goAndroidBuild(mainFile, filepath.Join(androidDir, "src/main/jniLibs/armeabi-v7a/libgojni.so"))
 	if err != nil {
 		return err
 	}

 	p, err := ctx.Import("golang.org/x/mobile/app", cwd, build.ImportComment)
 	if err != nil {
 		return fmt.Errorf(`"golang.org/x/mobile/app" is not found; run go get golang.org/x/mobile/app`)
 	}
 	repo := filepath.Clean(filepath.Join(p.Dir, "..")) // golang.org/x/mobile directory.

 	// TODO(crawshaw): use a better package path derived from the go package.
 	if err := binder.GenJava(filepath.Join(androidDir, "src/main/java/go/"+binder.pkg.Name())); err != nil {
 		return err
 	}

 	src := filepath.Join(repo, "app/Go.java")
 	dst := filepath.Join(androidDir, "src/main/java/go/Go.java")
 	rm(dst)
 	if err := symlink(src, dst); err != nil {
 		return err
 	}

 	src = filepath.Join(repo, "bind/java/Seq.java")
 	dst = filepath.Join(androidDir, "src/main/java/go/Seq.java")
 	rm(dst)
 	if err := symlink(src, dst); err != nil {
 		return err
 	}

 	return buildAAR(androidDir, bindPkg)
 }

 type binder struct {
 	files []*ast.File
 	fset  *token.FileSet
 	pkg   *types.Package
 }

 func (b *binder) GenJava(outdir string) error {
 	firstRune, size := utf8.DecodeRuneInString(b.pkg.Name())
 	className := string(unicode.ToUpper(firstRune)) + b.pkg.Name()[size:]
 	javaFile := filepath.Join(outdir, className+".java")

 	if buildX {
 		printcmd("gobind -lang=java %s > %s", b.pkg.Path(), javaFile)
 	}

 	generate := func(w io.Writer) error {
 		return bind.GenJava(w, b.fset, b.pkg)
 	}
 	if err := writeFile(javaFile, generate); err != nil {
 		return err
 	}
 	return nil
 }

 func (b *binder) GenGo(outdir string) error {
 	pkgName := "go_" + b.pkg.Name()
 	goFile := filepath.Join(outdir, pkgName, pkgName+".go")

 	if buildX {
 		printcmd("gobind -lang=go %s > %s", b.pkg.Path(), goFile)
 	}

 	generate := func(w io.Writer) error {
 		return bind.GenGo(w, b.fset, b.pkg)
 	}
 	if err := writeFile(goFile, generate); err != nil {
 		return err
 	}
 	return nil
 }

 func writeFile(filename string, generate func(io.Writer) error) error {
 	if buildV {
 		fmt.Fprintf(os.Stderr, "write %s\n", filename)
 	}

 	err := mkdir(filepath.Dir(filename))
 	if err != nil {
 		return err
 	}

 	if buildN {
 		return generate(ioutil.Discard)
 	}

 	f, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
 	defer func() {
 		if cerr := f.Close(); err == nil {
 			err = cerr
 		}
 	}()

 	return generate(f)
 }

 func newBinder(bindPkg *build.Package) (*binder, error) {
 	if bindPkg.Name == "main" {
 		return nil, fmt.Errorf("package %q: can only bind a library package", bindPkg.Name)
 	}

 	if len(bindPkg.CgoFiles) > 0 {
 		return nil, fmt.Errorf("cannot use cgo-dependent package as service definition: %s", bindPkg.CgoFiles[0])
 	}

 	fset := token.NewFileSet()

 	hasErr := false
 	var files []*ast.File
 	for _, filename := range bindPkg.GoFiles {
 		p := filepath.Join(bindPkg.Dir, filename)
 		file, err := parser.ParseFile(fset, p, nil, parser.AllErrors)
 		if err != nil {
 			hasErr = true
 			if list, _ := err.(scanner.ErrorList); len(list) > 0 {
 				for _, err := range list {
 					fmt.Fprintln(os.Stderr, err)
 				}
 			} else {
 				fmt.Fprintln(os.Stderr, err)
 			}
 		}
 		files = append(files, file)
 	}

 	if hasErr {
 		return nil, errors.New("package parsing failed.")
 	}

 	conf := loader.Config{
 		Fset: fset,
 	}
 	conf.TypeChecker.Error = func(err error) {
 		fmt.Fprintln(os.Stderr, err)
 	}

 	conf.CreateFromFiles(bindPkg.ImportPath, files...)
 	program, err := conf.Load()
 	if err != nil {
 		return nil, err
 	}
 	b := &binder{
 		files: files,
 		fset:  fset,
 		pkg:   program.Created[0].Pkg,
 	}
 	return b, nil
 }

 var androidMainTmpl = template.Must(template.New("android.go").Parse(`
 package main

 import (
 	"golang.org/x/mobile/app"
 	"golang.org/x/mobile/bind/java"

 	_ "{{.}}"
 )

 func main() {
 	app.Run(app.Callbacks{Start: java.Init})
 }
 `))

 // AAR is the format for the binary distribution of an Android Library Project
 // and it is a ZIP archive with extension .aar.
 // http://tools.android.com/tech-docs/new-build-system/aar-format
 //
 // These entries are directly at the root of the archive.
 //
 //	AndroidManifest.xml (mandatory)
 // 	classes.jar (mandatory)
 //	assets/ (optional)
 //	jni/<abi>/libgojni.so
 //	R.txt (mandatory)
 //	res/ (mandatory)
 //	libs/*.jar (optional, not relevant)
 //	proguard.txt (optional)
 //	lint.jar (optional, not relevant)
 //	aidl (optional, not relevant)
 //
 // javac and jar commands are needed to build classes.jar.
 func buildAAR(androidDir string, pkg *build.Package) (err error) {
 	var out io.Writer = ioutil.Discard
 	if *buildO == "" {
 		*buildO = pkg.Name + ".aar"
 	}
 	if !strings.HasSuffix(*buildO, ".apk") {
 		return fmt.Errorf("output file name %q does not end in '.aar'", *buildO)
 	}
 	if !buildN {
 		f, err := os.Create(*buildO)
 		if err != nil {
 			return err
 		}
 		defer func() {
 			if cerr := f.Close(); err == nil {
 				err = cerr
 			}
 		}()
 		out = f
 	}

 	aarw := zip.NewWriter(out)
 	aarwcreate := func(name string) (io.Writer, error) {
 		if buildV {
 			fmt.Fprintf(os.Stderr, "aar: %s\n", name)
 		}
 		return aarw.Create(name)
 	}
 	w, err := aarwcreate("AndroidManifest.xml")
 	if err != nil {
 		return err
 	}
 	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q />`
 	fmt.Fprintf(w, manifestFmt, "go."+pkg.Name+".gojni")

 	w, err = aarwcreate("proguard.txt")
 	if err != nil {
 		return err
 	}
 	fmt.Fprintln(w, `-keep class go.** { *; }`)

 	w, err = aarwcreate("classes.jar")
 	if err != nil {
 		return err
 	}
 	src := filepath.Join(androidDir, "src/main/java")
 	if err := buildJar(w, src); err != nil {
 		return err
 	}

 	assetsDir := filepath.Join(pkg.Dir, "assets")
 	assetsDirExists := false
 	if fi, err := os.Stat(assetsDir); err == nil {
 		assetsDirExists = fi.IsDir()
 	} else if !os.IsNotExist(err) {
 		return err
 	}

 	if assetsDirExists {
 		err := filepath.Walk(
 			assetsDir, func(path string, info os.FileInfo, err error) error {
 				if err != nil {
 					return err
 				}
 				if info.IsDir() {
 					return nil
 				}
 				f, err := os.Open(path)
 				if err != nil {
 					return err
 				}
 				defer f.Close()
 				name := "assets/" + path[len(assetsDir)+1:]
 				w, err := aarwcreate(name)
 				if err != nil {
 					return nil
 				}
 				_, err = io.Copy(w, f)
 				return err
 			})
 		if err != nil {
 			return err
 		}
 	}

 	lib := "armeabi-v7a/libgojni.so"
 	w, err = aarwcreate("jni/" + lib)
 	if err != nil {
 		return err
 	}
 	if !buildN {
 		r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
 		if err != nil {
 			return err
 		}
 		defer r.Close()
 		if _, err := io.Copy(w, r); err != nil {
 			return err
 		}
 	}

 	// TODO(hyangah): do we need to use aapt to create R.txt?
 	w, err = aarwcreate("R.txt")
 	if err != nil {
 		return err
 	}

 	w, err = aarwcreate("res/")
 	if err != nil {
 		return err
 	}

 	return aarw.Close()
 }

 const (
 	javacTargetVer = "1.7"
 	minAndroidAPI  = 9
 )

 func buildJar(w io.Writer, srcDir string) error {
 	var srcFiles []string
 	if buildN {
 		srcFiles = []string{"*.java"}
 	} else {
 		err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
 			if err != nil {
 				return err
 			}
 			if filepath.Ext(path) == ".java" {
 				srcFiles = append(srcFiles, filepath.Join(".", path[len(srcDir):]))
 			}
 			return nil
 		})
 		if err != nil {
 			return err
 		}
 	}

 	dst := filepath.Join(tmpdir, "javac-output")
 	if !buildN {
 		if err := os.MkdirAll(dst, 0700); err != nil {
 			return err
 		}
 	}
 	defer removeAll(dst)

 	apiPath, err := androidAPIPath()
 	if err != nil {
 		return err
 	}

 	args := []string{
 		"-d", dst,
 		"-source", javacTargetVer,
 		"-target", javacTargetVer,
 		"-bootclasspath", filepath.Join(apiPath, "android.jar"),
 	}
 	args = append(args, srcFiles...)

 	buf := new(bytes.Buffer)
 	javac := exec.Command("javac", args...)
 	javac.Dir = srcDir
 	if buildV {
 		javac.Stdout = os.Stdout
 		javac.Stderr = os.Stderr
 	} else {
 		javac.Stdout = buf
 		javac.Stderr = buf
 	}
 	if buildX {
 		printcmd("%s", strings.Join(javac.Args, " "))
 	}
 	if !buildN {
 		if err := javac.Run(); err != nil {
 			buf.WriteTo(xout)
 			return err
 		}
 	}

 	if buildX {
 		printcmd("jar c -C %s .", dst)
 	}
 	if buildN {
 		return nil
 	}

 	jarw := zip.NewWriter(w)
 	jarwcreate := func(name string) (io.Writer, error) {
 		if buildV {
 			fmt.Fprintf(os.Stderr, "jar: %s\n", name)
 		}
 		return jarw.Create(name)
 	}
 	f, err := jarwcreate("META-INF/MANIFEST.MF")
 	if err != nil {
 		return err
 	}
 	fmt.Fprintf(f, manifestHeader)

 	err = filepath.Walk(dst, func(path string, info os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
 		if info.IsDir() {
 			return nil
 		}
 		out, err := jarwcreate(filepath.ToSlash(path[len(dst)+1:]))
 		if err != nil {
 			return err
 		}
 		in, err := os.Open(path)
 		if err != nil {
 			return err
 		}
 		defer in.Close()
 		_, err = io.Copy(out, in)
 		return err
 	})
 	if err != nil {
 		return err
 	}
 	return jarw.Close()
 }

 // androidAPIPath returns an android SDK platform directory under ANDROID_HOME.
 // If there are multiple platforms that satisfy the minimum version requirement
 // androidAPIPath returns the latest one among them.
 func androidAPIPath() (string, error) {
 	sdk := os.Getenv("ANDROID_HOME")
 	if sdk == "" {
 		return "", fmt.Errorf("ANDROID_HOME environment var is not set")
 	}
 	sdkDir, err := os.Open(filepath.Join(sdk, "platforms"))
 	if err != nil {
 		return "", fmt.Errorf("failed to find android SDK platform: %v", err)
 	}
 	defer sdkDir.Close()
 	fis, err := sdkDir.Readdir(-1)
 	if err != nil {
 		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d): %v", minAndroidAPI, err)
 	}

 	var apiPath string
 	var apiVer int
 	for _, fi := range fis {
 		name := fi.Name()
 		if !fi.IsDir() || !strings.HasPrefix(name, "android-") {
 			continue
 		}
 		n, err := strconv.Atoi(name[len("android-"):])
 		if err != nil || n < minAndroidAPI {
 			continue
 		}
 		p := filepath.Join(sdkDir.Name(), name)
 		_, err = os.Stat(filepath.Join(p, "android.jar"))
 		if err == nil && apiVer < n {
 			apiPath = p
 			apiVer = n
 		}
 	}
 	if apiVer == 0 {
 		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d) in %s",
 			minAndroidAPI, sdkDir.Name())
 	}
 	return apiPath, nil
 }
	// Copyright 2015 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package main

	import (
	"archive/zip"
	"bytes"
	"errors"
	"fmt"
	"go/ast"
	"go/build"
	"go/parser"
	"go/scanner"
	"go/token"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"text/template"
	"unicode"
	"unicode/utf8"

	"golang.org/x/mobile/bind"
	"golang.org/x/tools/go/loader"
	"golang.org/x/tools/go/types"
	)

	// ctx, pkg, ndkccpath, tmpdir in build.go

	var cmdBind = &command{
	run: runBind,
	Name: "bind",
	Usage: "[-target android\|ios] [-o output] [build flags] [package]",
	Short: "build a shared library for android APK and iOS app",
	Long: `
	Bind generates language bindings for the package named by the import
	path, and compiles a library for the named target system.

	The -target flag takes a target system name, either android (the
	default) or ios.

	For -target android, the bind command produces an AAR (Android ARchive)
	file that archives the precompiled Java API stub classes, the compiled
	shared libraries, and all asset files in the /assets subdirectory under
	the package directory. The output is named '<package_name>.aar' by
	default. This AAR file is commonly used for binary distribution of an
	Android library project and most Android IDEs support AAR import. For
	example, in Android Studio (1.2+), an AAR file can be imported using
	the module import wizard (File > New > New Module > Import .JAR or
	.AAR package), and setting it as a new dependency
	(File > Project Structure > Dependencies). This requires 'javac'
	(version 1.7+) and Android SDK (API level 9 or newer) to build the
	library for Android. The environment variable ANDROID_HOME must be set
	to the path to Android SDK.

	For -target ios, gomobile must be run on an OS X machine with Xcode
	installed. Support is not complete.

	The -v flag provides verbose output, including the list of packages built.

	The build flags -a, -i, -n, -x, and -tags are shared with the build command.
	For documentation, see 'go help build'.
	`,
	}

	func runBind(cmd *command) error {
	cwd, err := os.Getwd()
	if err != nil {
	panic(err)
	}
	args := cmd.flag.Args()

	var bindPkg *build.Package
	switch len(args) {
	case 0:
	bindPkg, err = ctx.ImportDir(cwd, build.ImportComment)
	case 1:
	bindPkg, err = ctx.Import(args[0], cwd, build.ImportComment)
	default:
	cmd.usage()
	os.Exit(1)
	}
	if err != nil {
	return err
	}

	switch *buildTarget {
	case "android":
	// implementation is below
	case "ios":
	return fmt.Errorf(`-target=ios not yet supported`)
	default:
	return fmt.Errorf(`unknown -target, %q.`, *buildTarget)
	}

	if sdkDir := os.Getenv("ANDROID_HOME"); sdkDir == "" {
	return fmt.Errorf("this command requires ANDROID_HOME environment variable (path to the Android SDK)")
	}

	if buildN {
	tmpdir = "$WORK"
	} else {
	tmpdir, err = ioutil.TempDir("", "gomobile-bind-work-")
	if err != nil {
	return err
	}
	}
	defer removeAll(tmpdir)
	if buildX {
	fmt.Fprintln(os.Stderr, "WORK="+tmpdir)
	}

	binder, err := newBinder(bindPkg)
	if err != nil {
	return err
	}

	if err := binder.GenGo(tmpdir); err != nil {
	return err
	}

	mainFile := filepath.Join(tmpdir, "androidlib/main.go")
	err = writeFile(mainFile, func(w io.Writer) error {
	return androidMainTmpl.Execute(w, "../go_"+binder.pkg.Name())
	})
	if err != nil {
	return fmt.Errorf("failed to create the main package for android: %v", err)
	}

	androidDir := filepath.Join(tmpdir, "android")

	err = goAndroidBuild(mainFile, filepath.Join(androidDir, "src/main/jniLibs/armeabi-v7a/libgojni.so"))
	if err != nil {
	return err
	}

	p, err := ctx.Import("golang.org/x/mobile/app", cwd, build.ImportComment)
	if err != nil {
	return fmt.Errorf(`"golang.org/x/mobile/app" is not found; run go get golang.org/x/mobile/app`)
	}
	repo := filepath.Clean(filepath.Join(p.Dir, "..")) // golang.org/x/mobile directory.

	// TODO(crawshaw): use a better package path derived from the go package.
	if err := binder.GenJava(filepath.Join(androidDir, "src/main/java/go/"+binder.pkg.Name())); err != nil {
	return err
	}

	src := filepath.Join(repo, "app/Go.java")
	dst := filepath.Join(androidDir, "src/main/java/go/Go.java")
	rm(dst)
	if err := symlink(src, dst); err != nil {
	return err
	}

	src = filepath.Join(repo, "bind/java/Seq.java")
	dst = filepath.Join(androidDir, "src/main/java/go/Seq.java")
	rm(dst)
	if err := symlink(src, dst); err != nil {
	return err
	}

	return buildAAR(androidDir, bindPkg)
	}

	type binder struct {
	files []*ast.File
	fset *token.FileSet
	pkg *types.Package
	}

	func (b *binder) GenJava(outdir string) error {
	firstRune, size := utf8.DecodeRuneInString(b.pkg.Name())
	className := string(unicode.ToUpper(firstRune)) + b.pkg.Name()[size:]
	javaFile := filepath.Join(outdir, className+".java")

	if buildX {
	printcmd("gobind -lang=java %s > %s", b.pkg.Path(), javaFile)
	}

	generate := func(w io.Writer) error {
	return bind.GenJava(w, b.fset, b.pkg)
	}
	if err := writeFile(javaFile, generate); err != nil {
	return err
	}
	return nil
	}

	func (b *binder) GenGo(outdir string) error {
	pkgName := "go_" + b.pkg.Name()
	goFile := filepath.Join(outdir, pkgName, pkgName+".go")

	if buildX {
	printcmd("gobind -lang=go %s > %s", b.pkg.Path(), goFile)
	}

	generate := func(w io.Writer) error {
	return bind.GenGo(w, b.fset, b.pkg)
	}
	if err := writeFile(goFile, generate); err != nil {
	return err
	}
	return nil
	}

	func writeFile(filename string, generate func(io.Writer) error) error {
	if buildV {
	fmt.Fprintf(os.Stderr, "write %s\n", filename)
	}

	err := mkdir(filepath.Dir(filename))
	if err != nil {
	return err
	}

	if buildN {
	return generate(ioutil.Discard)
	}

	f, err := os.Create(filename)
	if err != nil {
	return err
	}
	defer func() {
	if cerr := f.Close(); err == nil {
	err = cerr
	}
	}()

	return generate(f)
	}

	func newBinder(bindPkg build.Package) (binder, error) {
	if bindPkg.Name == "main" {
	return nil, fmt.Errorf("package %q: can only bind a library package", bindPkg.Name)
	}

	if len(bindPkg.CgoFiles) > 0 {
	return nil, fmt.Errorf("cannot use cgo-dependent package as service definition: %s", bindPkg.CgoFiles[0])
	}

	fset := token.NewFileSet()

	hasErr := false
	var files []*ast.File
	for _, filename := range bindPkg.GoFiles {
	p := filepath.Join(bindPkg.Dir, filename)
	file, err := parser.ParseFile(fset, p, nil, parser.AllErrors)
	if err != nil {
	hasErr = true
	if list, _ := err.(scanner.ErrorList); len(list) > 0 {
	for _, err := range list {
	fmt.Fprintln(os.Stderr, err)
	}
	} else {
	fmt.Fprintln(os.Stderr, err)
	}
	}
	files = append(files, file)
	}

	if hasErr {
	return nil, errors.New("package parsing failed.")
	}

	conf := loader.Config{
	Fset: fset,
	}
	conf.TypeChecker.Error = func(err error) {
	fmt.Fprintln(os.Stderr, err)
	}

	conf.CreateFromFiles(bindPkg.ImportPath, files...)
	program, err := conf.Load()
	if err != nil {
	return nil, err
	}
	b := &binder{
	files: files,
	fset: fset,
	pkg: program.Created[0].Pkg,
	}
	return b, nil
	}

	var androidMainTmpl = template.Must(template.New("android.go").Parse(`
	package main

	import (
	"golang.org/x/mobile/app"
	"golang.org/x/mobile/bind/java"

	_ "{{.}}"
	)

	func main() {
	app.Run(app.Callbacks{Start: java.Init})
	}
	`))

	// AAR is the format for the binary distribution of an Android Library Project
	// and it is a ZIP archive with extension .aar.
	// http://tools.android.com/tech-docs/new-build-system/aar-format
	//
	// These entries are directly at the root of the archive.
	//
	// AndroidManifest.xml (mandatory)
	// classes.jar (mandatory)
	// assets/ (optional)
	// jni/<abi>/libgojni.so
	// R.txt (mandatory)
	// res/ (mandatory)
	// libs/*.jar (optional, not relevant)
	// proguard.txt (optional)
	// lint.jar (optional, not relevant)
	// aidl (optional, not relevant)
	//
	// javac and jar commands are needed to build classes.jar.
	func buildAAR(androidDir string, pkg *build.Package) (err error) {
	var out io.Writer = ioutil.Discard
	if *buildO == "" {
	*buildO = pkg.Name + ".aar"
	}
	if !strings.HasSuffix(*buildO, ".apk") {
	return fmt.Errorf("output file name %q does not end in '.aar'", *buildO)
	}
	if !buildN {
	f, err := os.Create(*buildO)
	if err != nil {
	return err
	}
	defer func() {
	if cerr := f.Close(); err == nil {
	err = cerr
	}
	}()
	out = f
	}

	aarw := zip.NewWriter(out)
	aarwcreate := func(name string) (io.Writer, error) {
	if buildV {
	fmt.Fprintf(os.Stderr, "aar: %s\n", name)
	}
	return aarw.Create(name)
	}
	w, err := aarwcreate("AndroidManifest.xml")
	if err != nil {
	return err
	}
	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q />`
	fmt.Fprintf(w, manifestFmt, "go."+pkg.Name+".gojni")

	w, err = aarwcreate("proguard.txt")
	if err != nil {
	return err
	}
	fmt.Fprintln(w, `-keep class go.** { *; }`)

	w, err = aarwcreate("classes.jar")
	if err != nil {
	return err
	}
	src := filepath.Join(androidDir, "src/main/java")
	if err := buildJar(w, src); err != nil {
	return err
	}

	assetsDir := filepath.Join(pkg.Dir, "assets")
	assetsDirExists := false
	if fi, err := os.Stat(assetsDir); err == nil {
	assetsDirExists = fi.IsDir()
	} else if !os.IsNotExist(err) {
	return err
	}

	if assetsDirExists {
	err := filepath.Walk(
	assetsDir, func(path string, info os.FileInfo, err error) error {
	if err != nil {
	return err
	}
	if info.IsDir() {
	return nil
	}
	f, err := os.Open(path)
	if err != nil {
	return err
	}
	defer f.Close()
	name := "assets/" + path[len(assetsDir)+1:]
	w, err := aarwcreate(name)
	if err != nil {
	return nil
	}
	_, err = io.Copy(w, f)
	return err
	})
	if err != nil {
	return err
	}
	}

	lib := "armeabi-v7a/libgojni.so"
	w, err = aarwcreate("jni/" + lib)
	if err != nil {
	return err
	}
	if !buildN {
	r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
	if err != nil {
	return err
	}
	defer r.Close()
	if _, err := io.Copy(w, r); err != nil {
	return err
	}
	}

	// TODO(hyangah): do we need to use aapt to create R.txt?
	w, err = aarwcreate("R.txt")
	if err != nil {
	return err
	}

	w, err = aarwcreate("res/")
	if err != nil {
	return err
	}

	return aarw.Close()
	}

	const (
	javacTargetVer = "1.7"
	minAndroidAPI = 9
	)

	func buildJar(w io.Writer, srcDir string) error {
	var srcFiles []string
	if buildN {
	srcFiles = []string{"*.java"}
	} else {
	err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
	if err != nil {
	return err
	}
	if filepath.Ext(path) == ".java" {
	srcFiles = append(srcFiles, filepath.Join(".", path[len(srcDir):]))
	}
	return nil
	})
	if err != nil {
	return err
	}
	}

	dst := filepath.Join(tmpdir, "javac-output")
	if !buildN {
	if err := os.MkdirAll(dst, 0700); err != nil {
	return err
	}
	}
	defer removeAll(dst)

	apiPath, err := androidAPIPath()
	if err != nil {
	return err
	}

	args := []string{
	"-d", dst,
	"-source", javacTargetVer,
	"-target", javacTargetVer,
	"-bootclasspath", filepath.Join(apiPath, "android.jar"),
	}
	args = append(args, srcFiles...)

	buf := new(bytes.Buffer)
	javac := exec.Command("javac", args...)
	javac.Dir = srcDir
	if buildV {
	javac.Stdout = os.Stdout
	javac.Stderr = os.Stderr
	} else {
	javac.Stdout = buf
	javac.Stderr = buf
	}
	if buildX {
	printcmd("%s", strings.Join(javac.Args, " "))
	}
	if !buildN {
	if err := javac.Run(); err != nil {
	buf.WriteTo(xout)
	return err
	}
	}

	if buildX {
	printcmd("jar c -C %s .", dst)
	}
	if buildN {
	return nil
	}

	jarw := zip.NewWriter(w)
	jarwcreate := func(name string) (io.Writer, error) {
	if buildV {
	fmt.Fprintf(os.Stderr, "jar: %s\n", name)
	}
	return jarw.Create(name)
	}
	f, err := jarwcreate("META-INF/MANIFEST.MF")
	if err != nil {
	return err
	}
	fmt.Fprintf(f, manifestHeader)

	err = filepath.Walk(dst, func(path string, info os.FileInfo, err error) error {
	if err != nil {
	return err
	}
	if info.IsDir() {
	return nil
	}
	out, err := jarwcreate(filepath.ToSlash(path[len(dst)+1:]))
	if err != nil {
	return err
	}
	in, err := os.Open(path)
	if err != nil {
	return err
	}
	defer in.Close()
	_, err = io.Copy(out, in)
	return err
	})
	if err != nil {
	return err
	}
	return jarw.Close()
	}

	// androidAPIPath returns an android SDK platform directory under ANDROID_HOME.
	// If there are multiple platforms that satisfy the minimum version requirement
	// androidAPIPath returns the latest one among them.
	func androidAPIPath() (string, error) {
	sdk := os.Getenv("ANDROID_HOME")
	if sdk == "" {
	return "", fmt.Errorf("ANDROID_HOME environment var is not set")
	}
	sdkDir, err := os.Open(filepath.Join(sdk, "platforms"))
	if err != nil {
	return "", fmt.Errorf("failed to find android SDK platform: %v", err)
	}
	defer sdkDir.Close()
	fis, err := sdkDir.Readdir(-1)
	if err != nil {
	return "", fmt.Errorf("failed to find android SDK platform (min API level: %d): %v", minAndroidAPI, err)
	}

	var apiPath string
	var apiVer int
	for _, fi := range fis {
	name := fi.Name()
	if !fi.IsDir() \|\| !strings.HasPrefix(name, "android-") {
	continue
	}
	n, err := strconv.Atoi(name[len("android-"):])
	if err != nil \|\| n < minAndroidAPI {
	continue
	}
	p := filepath.Join(sdkDir.Name(), name)
	_, err = os.Stat(filepath.Join(p, "android.jar"))
	if err == nil && apiVer < n {
	apiPath = p
	apiVer = n
	}
	}
	if apiVer == 0 {
	return "", fmt.Errorf("failed to find android SDK platform (min API level: %d) in %s",
	minAndroidAPI, sdkDir.Name())
	}
	return apiPath, nil
	}