Use temporary files to process zips

Fix #96

app/src/main/java/com/topjohnwu/magisk/asyncs/ProcessRepoZip.java

@@ -12,6 +12,10 @@ import com.topjohnwu.magisk.utils.Shell;
 import com.topjohnwu.magisk.utils.Utils;
 import com.topjohnwu.magisk.utils.ZipUtils;
 
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
 import java.io.OutputStream;
 
 public class ProcessRepoZip extends ParallelTask<Void, Void, Boolean> {
@@ -33,26 +37,59 @@ public class ProcessRepoZip extends ParallelTask<Void, Void, Boolean> {
 
     @Override
     protected Boolean doInBackground(Void... params) {
-        // Create a buffer in memory for input/output
-        ByteArrayInOutStream buffer = new ByteArrayInOutStream();
+
+        FileInputStream in;
+        FileOutputStream out;
 
         try {
-            // First remove top folder (the folder with the repo name) in Github source zip
-            ZipUtils.removeTopFolder(activity.getContentResolver().openInputStream(mUri), buffer);
 
-            // Then sign the zip for the first time
-            ZipUtils.signZip(activity, buffer.getInputStream(), buffer, false);
-
-            // Adjust the zip to prevent unzip issues
-            ZipUtils.adjustZip(buffer);
-
-            // Finally, sign the whole zip file again
-            ZipUtils.signZip(activity, buffer.getInputStream(), buffer, true);
-
-            // Write it back to the downloaded zip
-            try (OutputStream out = activity.getContentResolver().openOutputStream(mUri)) {
-                buffer.writeTo(out);
+            // Create temp file
+            File temp1 = new File(magiskManager.getCacheDir(), "1.zip");
+            File temp2 = new File(magiskManager.getCacheDir(), "2.zip");
+            if (magiskManager.getCacheDir().mkdirs()) {
+                temp1.createNewFile();
+                temp2.createNewFile();
             }
+
+            out = new FileOutputStream(temp1);
+
+            // First remove top folder in Github source zip, Uri -> temp1
+            ZipUtils.removeTopFolder(activity.getContentResolver().openInputStream(mUri), out);
+            out.flush();
+            out.close();
+
+            out = new FileOutputStream(temp2);
+
+            // Then sign the zip for the first time, temp1 -> temp2
+            ZipUtils.signZip(activity, temp1, out, false);
+            out.flush();
+            out.close();
+
+            // Adjust the zip to prevent unzip issues, temp2 -> temp2
+            ZipUtils.adjustZip(temp2);
+
+            out = new FileOutputStream(temp1);
+
+            // Finally, sign the whole zip file again, temp2 -> temp1
+            ZipUtils.signZip(activity, temp2, out, true);
+            out.flush();
+            out.close();
+
+            in = new FileInputStream(temp1);
+
+            // Write it back to the downloaded zip, temp1 -> Uri
+            try (OutputStream target = activity.getContentResolver().openOutputStream(mUri)) {
+                byte[] buffer = new byte[4096];
+                int length;
+                if (target == null) throw  new FileNotFoundException();
+                while ((length = in.read(buffer)) > 0)
+                    target.write(buffer, 0, length);
+            }
+
+            // Delete the temp file
+            temp1.delete();
+            temp2.delete();
+
             return true;
         } catch (Exception e) {
             Logger.error("ProcessRepoZip: Error!");