cmd/gogio: fix icon/resources for Android

Previously that patch, gogio unzip the `link.apk` (generated by AAPT2) to an temporary folder and then compress it again to a new `app.ap_` file.

For some unknown reason, that unzip-then-zip doesn't work. The resources are included but is corrupted in somehow. That PR aims to fix that by avoid the extraction to an temporary folder.

Signed-off-by: Inkeliz <inkeliz@inkeliz.com>

cmd/gogio/androidbuild.go

@@ -7,6 +7,8 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"golang.org/x/sync/errgroup"
+	"golang.org/x/tools/go/packages"
 	"io"
 	"io/ioutil"
 	"os"
@@ -16,9 +18,6 @@ import (
 	"strconv"
 	"strings"
 	"text/template"
-
-	"golang.org/x/sync/errgroup"
-	"golang.org/x/tools/go/packages"
 )
 
 type androidTools struct {
@@ -329,15 +328,15 @@ func exeAndroid(tmpDir string, tools *androidTools, bi *buildInfo, extraJars, pe
 		return nil
 	})
 	classFiles = append(classFiles, extraJars...)
-	apkDir := filepath.Join(tmpDir, "apk")
-	if err := os.MkdirAll(apkDir, 0755); err != nil {
+	dexDir := filepath.Join(tmpDir, "apk")
+	if err := os.MkdirAll(dexDir, 0755); err != nil {
 		return err
 	}
 	if len(classFiles) > 0 {
 		d8 := exec.Command(
 			filepath.Join(tools.buildtools, "d8"),
 			"--classpath", tools.androidjar,
-			"--output", apkDir,
+			"--output", dexDir,
 		)
 		d8.Args = append(d8.Args, classFiles...)
 		if _, err := runCmd(d8); err != nil {
@@ -440,60 +439,95 @@ func exeAndroid(tmpDir string, tools *androidTools, bi *buildInfo, extraJars, pe
 		return err
 	}
 
-	tmpapk := filepath.Join(tmpDir, "link.apk")
+	linkAPK := filepath.Join(tmpDir, "link.apk")
 	link := exec.Command(
 		aapt2,
 		"link",
 		"--manifest", manifest,
 		"-I", tools.androidjar,
-		"-o", tmpapk,
+		"-o", linkAPK,
 		resZip,
 	)
 	if _, err := runCmd(link); err != nil {
 		return err
 	}
 	// The Go standard library archive/zip doesn't support appending to zip
-	// files. Unpack the apk from aapt2 and re-zip its contents along with
-	// classes.dex and the Go libraries.
-	if err := unzip(apkDir, tmpapk); err != nil {
+	// files. Copy files from `link.apk` (generated by aapt2) along with classes.dex and
+	// the Go libraries to a new `app.ap_` file.
+
+	// Load link.apk as zip.
+	linkAPKZip, err := zip.OpenReader(linkAPK)
+	if err != nil {
 		return err
 	}
-	tmpApk := filepath.Join(tmpDir, "app.ap_")
-	ap_, err := os.Create(tmpApk)
+	defer linkAPKZip.Close()
+
+	// Create new "APK".
+	unsignedAPK := filepath.Join(tmpDir, "app.ap_")
+	unsignedAPKFile, err := os.Create(unsignedAPK)
 	if err != nil {
 		return err
 	}
 	defer func() {
-		if cerr := ap_.Close(); err == nil {
+		if cerr := unsignedAPKFile.Close(); err == nil {
 			err = cerr
 		}
 	}()
-	apkw := newZipWriter(ap_)
-	defer apkw.Close()
-	err = filepath.Walk(apkDir, func(path string, f os.FileInfo, err error) error {
+	unsignedAPKZip := zip.NewWriter(unsignedAPKFile)
+	defer unsignedAPKZip.Close()
+
+	// Copy files from linkAPK to unsignedAPK.
+	for _, f := range linkAPKZip.File {
+		header := zip.FileHeader{
+			Name:   f.FileHeader.Name,
+			Method: f.FileHeader.Method,
+		}
+
+		w, err := unsignedAPKZip.CreateHeader(&header)
 		if err != nil {
 			return err
 		}
-		if f.IsDir() {
-			return nil
+		r, err := f.Open()
+		if err != nil {
+			return err
 		}
-		zpath := path[len(apkDir)+1:]
-		if filepath.Base(path) == "resources.arsc" {
-			apkw.Store(zpath, path)
-		} else {
-			apkw.Add(zpath, path)
+		if _, err := io.Copy(w, r); err != nil {
+			return err
 		}
-		return nil
-	})
-	if err != nil {
+	}
+
+	// Append new files (that doesn't exists inside the link.apk).
+	appendToZip := func(path string, file string) error {
+		f, err := os.Open(file)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		w, err := unsignedAPKZip.CreateHeader(&zip.FileHeader{
+			Name:   filepath.ToSlash(path),
+			Method: zip.Deflate,
+		})
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(w, f)
 		return err
 	}
+
+	// Append Go binaries (libgio.so).
 	for _, a := range bi.archs {
 		arch := allArchs[a]
 		libFile := filepath.Join(arch.jniArch, "libgio.so")
-		apkw.Add(filepath.ToSlash(filepath.Join("lib", libFile)), filepath.Join(tmpDir, "jni", libFile))
+		if err := appendToZip(filepath.Join("lib", libFile), filepath.Join(tmpDir, "jni", libFile)); err != nil {
+			return err
+		}
 	}
-	return apkw.Close()
+
+	// Append classes.dex.
+	if err := appendToZip("classes.dex", filepath.Join(dexDir, "classes.dex")); err != nil {
+		return err
+	}
+	return unsignedAPKZip.Close()
 }
 
 func signAPK(tmpDir string, tools *androidTools, bi *buildInfo) error {
@@ -553,38 +587,6 @@ func signAPK(tmpDir string, tools *androidTools, bi *buildInfo) error {
 	return nil
 }
 
-func unzip(dir, zipfile string) (err error) {
-	zipr, err := zip.OpenReader(zipfile)
-	if err != nil {
-		return err
-	}
-	defer zipr.Close()
-	for _, f := range zipr.File {
-		path := filepath.Join(dir, f.Name)
-		if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
-			return err
-		}
-		out, err := os.Create(path)
-		if err != nil {
-			return err
-		}
-		defer func() {
-			if cerr := out.Close(); err == nil {
-				err = cerr
-			}
-		}()
-		in, err := f.Open()
-		if err != nil {
-			return err
-		}
-		defer in.Close()
-		if _, err := io.Copy(out, in); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 func findNDK(androidHome string) (string, error) {
 	ndks, err := filepath.Glob(filepath.Join(androidHome, "ndk", "*"))
 	if err != nil {