Counting bits

Here’s a simple input stream which will tell you the current position. You should insert this after any buffered input streams if you want an accurate position after a read.

public class CountingInputStream extends PushbackInputStream {

    private long bytesRead;

    public CountingInputStream(InputStream is) {
        super(is);
    }
    public CountingInputStream(InputStream is,int len) {
        super(is,len);
    }

    public long getPosition() {
        return bytesRead;
    }

    @Override
    public void unread(byte[] b, int off, int len) throws IOException {
        bytesRead -= len;
        super.unread(b, off, len);
    }

    @Override
    public void unread(int b) throws IOException {
        bytesRead--;
        super.unread(b);
    }

    @Override
    public void unread(byte[] b) throws IOException {
        bytesRead -= b.length;
        super.unread(b);
    }

    @Override
    public boolean markSupported() {
        return false;
    }

    @Override
    public synchronized void reset() throws IOException {
        throw new IOException("Mark not supported");
    }

    @Override
    public int read() throws IOException {
        int rd = super.read();
        if (rd != -1) {
            bytesRead++;
        }
        return rd;
    }

    @Override
    public int read(byte[] b) throws IOException {
        int read = super.read(b);
        if (read != -1) {
            bytesRead += read;
        }
        return read;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int read = super.read(b, off, len);
        if (read != -1) {
            bytesRead += read;
        }
        return read;
    }

    @Override
    public long skip(long n) throws IOException {
        long skipped = super.skip(n);
        bytesRead += skipped;
        return skipped;
    }
}