/*
* 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 org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* A protocol message that contains a repeated series of block headers, sent in response to the "getheaders" command.
* This is useful when you want to traverse the chain but know you don't care about the block contents, for example,
* because you have a freshly created wallet with no keys.
*/
public class HeadersMessage extends Message {
private static final Logger log = LoggerFactory.getLogger(HeadersMessage.class);
// The main client will never send us more than this number of headers.
public static final int MAX_HEADERS = 2000;
private List<Block> blockHeaders;
public HeadersMessage(NetworkParameters params, byte[] payload) throws ProtocolException {
super(params, payload, 0);
}
public HeadersMessage(NetworkParameters params, Block... headers) throws ProtocolException {
super(params);
blockHeaders = Arrays.asList(headers);
}
@Override
public void bitcoinSerializeToStream(OutputStream stream) throws IOException {
stream.write(new VarInt(blockHeaders.size()).encode());
for (Block header : blockHeaders) {
if (header.transactions == null)
header.bitcoinSerializeToStream(stream);
else
header.cloneAsHeader().bitcoinSerializeToStream(stream);
stream.write(0);
}
}
@Override
protected void parseLite() throws ProtocolException {
if (length == UNKNOWN_LENGTH) {
int saveCursor = cursor;
long numHeaders = readVarInt();
cursor = saveCursor;
// Each header has 80 bytes and one more byte for transactions number which is 00.
length = 81 * (int)numHeaders;
}
}
@Override
void parse() throws ProtocolException {
long numHeaders = readVarInt();
if (numHeaders > MAX_HEADERS)
throw new ProtocolException("Too many headers: got " + numHeaders + " which is larger than " +
MAX_HEADERS);
blockHeaders = new ArrayList<Block>();
for (int i = 0; i < numHeaders; ++i) {
// Read 80 bytes of the header and one more byte for the transaction list, which is always a 00 because the
// transaction list is empty.
byte[] blockHeader = readBytes(81);
if (blockHeader[80] != 0)
throw new ProtocolException("Block header does not end with a null byte");
Block newBlockHeader = new Block(this.params, blockHeader, true, true, 81);
blockHeaders.add(newBlockHeader);
}
if (log.isDebugEnabled()) {
for (int i = 0; i < numHeaders; ++i) {
log.debug(this.blockHeaders.get(i).toString());
}
}
}
public List<Block> getBlockHeaders() {
return blockHeaders;
}
}