private boolean unpackFile(ZipFile zip, byte[] buf, ZipEntry fileEntry, String name)
      throws IOException, FileNotFoundException {
    if (fileEntry == null) fileEntry = zip.getEntry(name);
    if (fileEntry == null)
      throw new FileNotFoundException("Can't find " + name + " in " + zip.getName());

    File outFile = new File(sGREDir, name);
    if (outFile.lastModified() == fileEntry.getTime() && outFile.length() == fileEntry.getSize())
      return false;

    File dir = outFile.getParentFile();
    if (!dir.exists()) dir.mkdirs();

    InputStream fileStream;
    fileStream = zip.getInputStream(fileEntry);

    OutputStream outStream = new FileOutputStream(outFile);

    while (fileStream.available() > 0) {
      int read = fileStream.read(buf, 0, buf.length);
      outStream.write(buf, 0, read);
    }

    fileStream.close();
    outStream.close();
    outFile.setLastModified(fileEntry.getTime());
    return true;
  }
  protected void unpackComponents() throws IOException, FileNotFoundException {
    File applicationPackage = new File(getApplication().getPackageResourcePath());
    File componentsDir = new File(sGREDir, "components");
    if (componentsDir.lastModified() == applicationPackage.lastModified()) return;

    componentsDir.mkdir();
    componentsDir.setLastModified(applicationPackage.lastModified());

    GeckoAppShell.killAnyZombies();

    ZipFile zip = new ZipFile(applicationPackage);

    byte[] buf = new byte[32768];
    try {
      if (unpackFile(zip, buf, null, "removed-files")) removeFiles();
    } catch (Exception ex) {
      // This file may not be there, so just log any errors and move on
      Log.w(LOG_FILE_NAME, "error removing files", ex);
    }

    // copy any .xpi file into an extensions/ directory
    Enumeration<? extends ZipEntry> zipEntries = zip.entries();
    while (zipEntries.hasMoreElements()) {
      ZipEntry entry = zipEntries.nextElement();
      if (entry.getName().startsWith("extensions/") && entry.getName().endsWith(".xpi")) {
        Log.i("GeckoAppJava", "installing extension : " + entry.getName());
        unpackFile(zip, buf, entry, entry.getName());
      }
    }
  }