PrependableSocket.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server.quorum;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.net.Socket;
import java.net.SocketImpl;

public class PrependableSocket extends Socket {

    private PushbackInputStream pushbackInputStream;

    public PrependableSocket(SocketImpl base) throws IOException {
        super(base);
    }

    @Override
    public InputStream getInputStream() throws IOException {
        if (pushbackInputStream == null) {
            return super.getInputStream();
        }

        return pushbackInputStream;
    }

    /**
     * Prepend some bytes that have already been read back to the socket's input stream. Note that this method can be
     * called at most once with a non-0 length per socket instance.
     * @param bytes the bytes to prepend.
     * @param offset offset in the byte array to start at.
     * @param length number of bytes to prepend.
     * @throws IOException if this method was already called on the socket instance, or if super.getInputStream() throws.
     */
    public void prependToInputStream(byte[] bytes, int offset, int length) throws IOException {
        if (length == 0) {
            return; // nothing to prepend
        }
        if (pushbackInputStream != null) {
            throw new IOException("prependToInputStream() called more than once");
        }
        PushbackInputStream pushbackInputStream = new PushbackInputStream(getInputStream(), length);
        pushbackInputStream.unread(bytes, offset, length);
        this.pushbackInputStream = pushbackInputStream;
    }

}