package goodjava.io;
import java.io.InputStream;
import java.io.FilterInputStream;
import java.io.IOException;


public final class LimitedInputStream extends FilterInputStream {
	private final long limit;
	private long pos = 0;

	public LimitedInputStream(InputStream in, long limit) {
		super(in);
		this.limit = limit;
	}

	public synchronized int read() throws IOException {
		if( pos >= limit )
			return -1;
		int n = super.read();
		if( n != -1 )
			pos++;
		return n;
	}

	public synchronized int read(byte[] b, int off, int len) throws IOException {
		long avail = limit - pos;
		if( avail <= 0 )
			return -1;
		if( len > avail )
			len = (int)avail;
		int n = super.read(b,off,len);
		if( n > 0 )
			pos += n;
		return n;
	}

	public synchronized long skip(long n) throws IOException {
		long avail = limit - pos;
		if( avail <= 0 )
			return 0;
		if( n > avail )
			n = (int)avail;
		n = super.skip(n);
		pos += n;
		return n;
	}

	public synchronized int available() throws IOException {
		long avail = limit - pos;
		if( avail <= 0 )
			return 0;
		int n = super.available();
		if( n > avail )
			n = (int)avail;
		return n;
	}

}