Reset BufferedInputStream Holding a FileInputStream

Question

I'm decoding a jpeg in two steps.

1. Check bounds, determine scale if necessary.
2. Decode within screen limits.

---

public static Bitmap decodeSampledBitmapFromInputStream(InputStream data, int reqWidth, int reqHeight)
{
    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(data, null, options);

    // Calculate inSampleSize
    options.inSampleSize = Util.getExactSampleSize(options, reqWidth, reqHeight);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;

    try {
        // TODO: This works, but is there a better way?
        if (data instanceof FileInputStream)
            ((FileInputStream)data).getChannel().position(0);
        else
            data.reset();
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }

    return BitmapFactory.decodeStream(data, null, options);
}

When the underlying stream is a FileInputStream it crashes on reset() with:

java.io.IOException: Mark has been invalidated.

So I added the instanceof section to manually reset the position of FileInputStreams, but this seems like a rather awkward solution. Is there no way to properly reset a BufferedInputStream encapsulating a FileInputStream?

Answer 1

Before using InputStream.reset you have to call InputStream.mark first to mark the position you want to return to later.