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A Java Bitcoin library
There is a newer version: 0.15-cm06
/*
 * Copyright 2011 Google Inc.
 * Copyright 2014 Andreas Schildbach
 *
 * Licensed 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.bitcoinj.core;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Represents an "addr" message on the P2P network, which contains broadcast IP addresses of other peers. This is
 * one of the ways peers can find each other without using the DNS or IRC discovery mechanisms. However storing and
 * using addr messages is not presently implemented.
 * 
 * Instances of this class are not safe for use by multiple threads.
 */
public class AddressMessage extends Message {

    private static final long MAX_ADDRESSES = 1024;
    private List addresses;

    /**
     * Contruct a new 'addr' message.
     * @param params NetworkParameters object.
     * @param offset The location of the first payload byte within the array.
     * @param serializer the serializer to use for this message.
     * @param length The length of message if known.  Usually this is provided when deserializing of the wire
     * as the length will be provided as part of the header.  If unknown then set to Message.UNKNOWN_LENGTH
     * @throws ProtocolException
     */
    AddressMessage(NetworkParameters params, byte[] payload, int offset, MessageSerializer serializer, int length) throws ProtocolException {
        super(params, payload, offset, serializer, length);
    }

    /**
     * Contruct a new 'addr' message.
     * @param params NetworkParameters object.
     * @param serializer the serializer to use for this block.
     * @param length The length of message if known.  Usually this is provided when deserializing of the wire
     * as the length will be provided as part of the header.  If unknown then set to Message.UNKNOWN_LENGTH
     * @throws ProtocolException
     */
    AddressMessage(NetworkParameters params, byte[] payload, MessageSerializer serializer, int length) throws ProtocolException {
        super(params, payload, 0, serializer, length);
    }

    AddressMessage(NetworkParameters params, byte[] payload, int offset) throws ProtocolException {
        super(params, payload, offset, params.getDefaultSerializer(), UNKNOWN_LENGTH);
    }

    AddressMessage(NetworkParameters params, byte[] payload) throws ProtocolException {
        super(params, payload, 0, params.getDefaultSerializer(), UNKNOWN_LENGTH);
    }

    @Override
    protected void parse() throws ProtocolException {
        long numAddresses = readVarInt();
        // Guard against ultra large messages that will crash us.
        if (numAddresses > MAX_ADDRESSES)
            throw new ProtocolException("Address message too large.");
        addresses = new ArrayList<>((int) numAddresses);
        for (int i = 0; i < numAddresses; i++) {
            PeerAddress addr = new PeerAddress(params, payload, cursor, protocolVersion, this, serializer);
            addresses.add(addr);
            cursor += addr.getMessageSize();
        }
        length = new VarInt(addresses.size()).getSizeInBytes();
        // The 4 byte difference is the uint32 timestamp that was introduced in version 31402
        length += addresses.size() * (protocolVersion > 31402 ? PeerAddress.MESSAGE_SIZE : PeerAddress.MESSAGE_SIZE - 4);
    }

    @Override
    protected void bitcoinSerializeToStream(OutputStream stream) throws IOException {
        if (addresses == null)
            return;
        stream.write(new VarInt(addresses.size()).encode());
        for (PeerAddress addr : addresses) {
            addr.bitcoinSerialize(stream);
        }
    }

    /**
     * @return An unmodifiableList view of the backing List of addresses.  Addresses contained within the list may be safely modified.
     */
    public List getAddresses() {
        return Collections.unmodifiableList(addresses);
    }

    public void addAddress(PeerAddress address) {
        unCache();
        address.setParent(this);
        addresses.add(address);
        if (length == UNKNOWN_LENGTH)
            getMessageSize();
        else
            length += address.getMessageSize();
    }

    public void removeAddress(int index) {
        unCache();
        PeerAddress address = addresses.remove(index);
        address.setParent(null);
        if (length == UNKNOWN_LENGTH)
            getMessageSize();
        else
            length -= address.getMessageSize();
    }

    @Override
    public String toString() {
        return "addr: " + Utils.SPACE_JOINER.join(addresses);
    }
}