/**
* Copyright 2011 Google Inc.
*
* 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 com.google.bitcoin.core;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
/**
* Represents the "getblocks" P2P network message, which requests the hashes of the parts of the block chain we're
* missing. Those blocks can then be downloaded with a {@link GetDataMessage}.
*/
public class GetBlocksMessage extends Message {
private static final long serialVersionUID = 3479412877853645644L;
protected long version;
protected List<Sha256Hash> locator;
protected Sha256Hash stopHash;
public GetBlocksMessage(NetworkParameters params, List<Sha256Hash> locator, Sha256Hash stopHash) {
super(params);
this.version = protocolVersion;
this.locator = locator;
this.stopHash = stopHash;
}
public GetBlocksMessage(NetworkParameters params, byte[] msg) throws ProtocolException {
super(params, msg, 0);
}
protected void parseLite() throws ProtocolException {
cursor = offset;
version = readUint32();
int startCount = (int) readVarInt();
if (startCount > 500)
throw new ProtocolException("Number of locators cannot be > 500, received: " + startCount);
length = (int) (cursor - offset + ((startCount + 1) * 32));
}
public void parse() throws ProtocolException {
cursor = offset;
version = readUint32();
int startCount = (int) readVarInt();
if (startCount > 500)
throw new ProtocolException("Number of locators cannot be > 500, received: " + startCount);
locator = new ArrayList<Sha256Hash>(startCount);
for (int i = 0; i < startCount; i++) {
locator.add(readHash());
}
stopHash = readHash();
}
public List<Sha256Hash> getLocator() {
return locator;
}
public Sha256Hash getStopHash() {
return stopHash;
}
public String toString() {
StringBuffer b = new StringBuffer();
b.append("getblocks: ");
for (Sha256Hash hash : locator) {
b.append(hash.toString());
b.append(" ");
}
return b.toString();
}
protected void bitcoinSerializeToStream(OutputStream stream) throws IOException {
// Version, for some reason.
Utils.uint32ToByteStreamLE(NetworkParameters.PROTOCOL_VERSION, stream);
// Then a vector of block hashes. This is actually a "block locator", a set of block
// identifiers that spans the entire chain with exponentially increasing gaps between
// them, until we end up at the genesis block. See CBlockLocator::Set()
stream.write(new VarInt(locator.size()).encode());
for (Sha256Hash hash : locator) {
// Have to reverse as wire format is little endian.
stream.write(Utils.reverseBytes(hash.getBytes()));
}
// Next, a block ID to stop at.
stream.write(Utils.reverseBytes(stopHash.getBytes()));
}
@Override
public boolean equals(Object o) {
if (o == null || o.getClass() != getClass()) return false;
GetBlocksMessage other = (GetBlocksMessage) o;
return (other.version == version &&
locator.size() == other.locator.size() && locator.containsAll(other.locator) &&
stopHash.equals(other.stopHash));
}
@Override
public int hashCode() {
int hashCode = (int) version ^ "getblocks".hashCode();
for (Sha256Hash aLocator : locator) hashCode ^= aLocator.hashCode();
hashCode ^= stopHash.hashCode();
return hashCode;
}
}