package goodjava.rpc;

import java.io.InputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.EOFException;


public class FixedLengthInputStream extends FilterInputStream {
	private long left;

	public FixedLengthInputStream(InputStream in,long len) {
		super(in);
		if( len < 0 )
			throw new IllegalArgumentException("len can't be negative");
		this.left = len;
	}

	public int read() throws IOException {
		if( left == 0 )
			return -1;
		int n = in.read();
		if( n == -1 )
			throw new EOFException();
		left--;
		return n;
	}

	public int read(byte b[], int off, int len) throws IOException {
		if( len == 0 )
			return 0;
		if( left == 0 )
			return -1;
		if( len > left )
			len = (int)left;
		int n = in.read(b, off, len);
		if( n == -1 )
			throw new EOFException();
		left -= n;
		return n;
	}

	public long skip(long n) throws IOException {
		if( n > left )
			n = left;
		n = in.skip(n);
		left -= n;
		return n;
	}

	public int available() throws IOException {
		int n = in.available();
		if( n > left )
			n = (int)left;
		return n;
	}

    public void close() throws IOException {
        while( left > 0 ) {
			if( skip(left) == 0 )
				throw new EOFException();
		}
    }

	public void mark(int readlimit) {}

	public void reset() throws IOException {
		throw new IOException("not supported");
	}

	public boolean markSupported() {
		return false;
	}

}