[libaums]: FileSystemService class

@Override
public synchronized InputStream getInputStream(UsbMassStorageDevice device, FileItem fileItem)
        throws USBException, IOException {

    Timber.tag(TAG).d("getInputStream: open stream %s ...", fileItem.getPath());
    FileSystem fs = getFs(device);
    UsbFile rootDir = fs.getRootDirectory();

    // getRelativePath return /folder/file.txt for path /Usb_prefix/folder/file.txt
    UsbFile srcFile = rootDir.search(getRelativePath(fs, fileItem.getPath()));
    if (srcFile == null)
        throw new USBException(USBErrorCode.FILE_NOT_FOUND);

    return UsbFileStreamFactory.createBufferedInputStream(srcFile, fs);
}

@Override
public synchronized OutputStream getOutputStream(UsbMassStorageDevice device, FileItem fileItem)
        throws IOException, USBException {

    Timber.tag(TAG).d("getOutputStream: open stream %s ...", fileItem.getPath());
    FileSystem fs = getFs(device);
    UsbFile rootDir = fs.getRootDirectory();

    UsbFile srcFile = rootDir.search(getRelativePath(fs, fileItem.getPath()));
    if (srcFile != null)
        throw new USBException(USBErrorCode.FILE_EXISTS);

    //create parent folder for srcFile
    UsbFile srcFileParentFolder = mkDirs(device, constructParentFileItem(fileItem));
    srcFile = srcFileParentFolder.createFile(fileItem.getName());

    return UsbFileStreamFactory.createBufferedOutputStream(srcFile, fs);
}