/**
* 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.devcoin.core;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Map;
import static com.google.devcoin.core.Utils.*;
/**
* <p>Methods to serialize and de-serialize messages to the Bitcoin network format as defined in
* <a href="https://en.bitcoin.it/wiki/Protocol_specification">the protocol specification</a>.</p>
*
* <p>To be able to serialize and deserialize new Message subclasses the following criteria needs to be met.</p>
*
* <ul>
* <li>The proper Class instance needs to be mapped to it's message name in the names variable below</li>
* <li>There needs to be a constructor matching: NetworkParameters params, byte[] payload</li>
* <li>Message.bitcoinSerializeToStream() needs to be properly subclassed</li>
* </ul>
*/
public class BitcoinSerializer {
private static final Logger log = LoggerFactory.getLogger(BitcoinSerializer.class);
private static final int COMMAND_LEN = 12;
private NetworkParameters params;
private boolean parseLazy = false;
private boolean parseRetain = false;
private static Map<Class<? extends Message>, String> names = new HashMap<Class<? extends Message>, String>();
static {
names.put(VersionMessage.class, "version");
names.put(InventoryMessage.class, "inv");
names.put(Block.class, "block");
names.put(GetDataMessage.class, "getdata");
names.put(Transaction.class, "tx");
names.put(AddressMessage.class, "addr");
names.put(Ping.class, "ping");
names.put(Pong.class, "pong");
names.put(VersionAck.class, "verack");
names.put(GetBlocksMessage.class, "getblocks");
names.put(GetHeadersMessage.class, "getheaders");
names.put(GetAddrMessage.class, "getaddr");
names.put(HeadersMessage.class, "headers");
names.put(BloomFilter.class, "filterload");
names.put(FilteredBlock.class, "merkleblock");
names.put(NotFoundMessage.class, "notfound");
names.put(MemoryPoolMessage.class, "mempool");
}
/**
* Constructs a BitcoinSerializer with the given behavior.
*
* @param params networkParams used to create Messages instances and termining packetMagic
*/
public BitcoinSerializer(NetworkParameters params) {
this(params, false, false);
}
/**
* Constructs a BitcoinSerializer with the given behavior.
*
* @param params networkParams used to create Messages instances and termining packetMagic
* @param parseLazy deserialize messages in lazy mode.
* @param parseRetain retain the backing byte array of a message for fast reserialization.
*/
public BitcoinSerializer(NetworkParameters params, boolean parseLazy, boolean parseRetain) {
this.params = params;
this.parseLazy = parseLazy;
this.parseRetain = parseRetain;
}
/**
* Writes message to to the output stream.
*/
public void serialize(String name, byte[] message, OutputStream out) throws IOException {
byte[] header = new byte[4 + COMMAND_LEN + 4 + 4 /* checksum */];
uint32ToByteArrayBE(params.getPacketMagic(), header, 0);
// The header array is initialized to zero by Java so we don't have to worry about
// NULL terminating the string here.
for (int i = 0; i < name.length() && i < COMMAND_LEN; i++) {
header[4 + i] = (byte) (name.codePointAt(i) & 0xFF);
}
Utils.uint32ToByteArrayLE(message.length, header, 4 + COMMAND_LEN);
byte[] hash = doubleDigest(message);
System.arraycopy(hash, 0, header, 4 + COMMAND_LEN + 4, 4);
out.write(header);
out.write(message);
if (log.isDebugEnabled())
log.debug("Sending {} message: {}", name, bytesToHexString(header) + bytesToHexString(message));
}
/**
* Writes message to to the output stream.
*/
public void serialize(Message message, OutputStream out) throws IOException {
String name = names.get(message.getClass());
if (name == null) {
throw new Error("BitcoinSerializer doesn't currently know how to serialize " + message.getClass());
}
serialize(name, message.bitcoinSerialize(), out);
}
/**
* Reads a message from the given InputStream and returns it.
*/
public Message deserialize(InputStream in) throws ProtocolException, IOException {
// A Bitcoin protocol message has the following format.
//
// - 4 byte magic number: 0xfabfb5da for the testnet or
// 0xf9beb4d9 for production
// - 12 byte command in ASCII
// - 4 byte payload size
// - 4 byte checksum
// - Payload data
//
// The checksum is the first 4 bytes of a SHA256 hash of the message payload. It isn't
// present for all messages, notably, the first one on a connection.
//
// Satoshi's implementation ignores garbage before the magic header bytes. We have to do the same because
// sometimes it sends us stuff that isn't part of any message.
seekPastMagicBytes(in);
BitcoinPacketHeader header = new BitcoinPacketHeader(in);
// Now try to read the whole message.
return deserializePayload(header, in);
}
/**
* Deserializes only the header in case packet meta data is needed before decoding
* the payload. This method assumes you have already called seekPastMagicBytes()
*/
public BitcoinPacketHeader deserializeHeader(InputStream in) throws ProtocolException, IOException {
return new BitcoinPacketHeader(in);
}
/**
* Deserialize payload only. You must provide a header, typically obtained by calling
* {@link BitcoinSerializer#deserializeHeader}.
*/
public Message deserializePayload(BitcoinPacketHeader header, InputStream in) throws ProtocolException, IOException {
int readCursor = 0;
byte[] payloadBytes = new byte[header.size];
while (readCursor < payloadBytes.length - 1) {
int bytesRead = in.read(payloadBytes, readCursor, header.size - readCursor);
if (bytesRead == -1) {
throw new IOException("Socket is disconnected");
}
readCursor += bytesRead;
}
// Verify the checksum.
byte[] hash;
hash = doubleDigest(payloadBytes);
if (header.checksum[0] != hash[0] || header.checksum[1] != hash[1] ||
header.checksum[2] != hash[2] || header.checksum[3] != hash[3]) {
throw new ProtocolException("Checksum failed to verify, actual " +
bytesToHexString(hash) +
" vs " + bytesToHexString(header.checksum));
}
if (log.isDebugEnabled()) {
log.info("Received {} byte '{}' message: {}", new Object[]{
header.size,
header.command,
Utils.bytesToHexString(payloadBytes)
});
}
try {
return makeMessage(header.command, header.size, payloadBytes, hash, header.checksum);
} catch (Exception e) {
throw new ProtocolException("Error deserializing message " + Utils.bytesToHexString(payloadBytes) + "\n", e);
}
}
private Message makeMessage(String command, int length, byte[] payloadBytes, byte[] hash, byte[] checksum) throws ProtocolException {
// We use an if ladder rather than reflection because reflection is very slow on Android.
Message message;
if (command.equals("version")) {
return new VersionMessage(params, payloadBytes);
} else if (command.equals("inv")) {
message = new InventoryMessage(params, payloadBytes, parseLazy, parseRetain, length);
} else if (command.equals("block")) {
message = new Block(params, payloadBytes, parseLazy, parseRetain, length);
} else if (command.equals("merkleblock")) {
message = new FilteredBlock(params, payloadBytes);
} else if (command.equals("getdata")) {
message = new GetDataMessage(params, payloadBytes, parseLazy, parseRetain, length);
} else if (command.equals("tx")) {
Transaction tx = new Transaction(params, payloadBytes, null, parseLazy, parseRetain, length);
if (hash != null)
tx.setHash(new Sha256Hash(Utils.reverseBytes(hash)));
message = tx;
} else if (command.equals("addr")) {
message = new AddressMessage(params, payloadBytes, parseLazy, parseRetain, length);
} else if (command.equals("ping")) {
message = new Ping(params, payloadBytes);
} else if (command.equals("pong")) {
message = new Pong(params, payloadBytes);
} else if (command.equals("verack")) {
return new VersionAck(params, payloadBytes);
} else if (command.equals("headers")) {
return new HeadersMessage(params, payloadBytes);
} else if (command.equals("alert")) {
return new AlertMessage(params, payloadBytes);
} else if (command.equals("filterload")) {
return new BloomFilter(params, payloadBytes);
} else if (command.equals("notfound")) {
return new NotFoundMessage(params, payloadBytes);
} else if (command.equals("mempool")) {
return new MemoryPoolMessage();
} else {
log.warn("No support for deserializing message with name {}", command);
return new UnknownMessage(params, command, payloadBytes);
}
if (checksum != null)
message.setChecksum(checksum);
return message;
}
public void seekPastMagicBytes(InputStream in) throws IOException {
int magicCursor = 3; // Which byte of the magic we're looking for currently.
while (true) {
int b = in.read(); // Read a byte.
if (b == -1) {
// There's no more data to read.
throw new IOException("Socket is disconnected");
}
// We're looking for a run of bytes that is the same as the packet magic but we want to ignore partial
// magics that aren't complete. So we keep track of where we're up to with magicCursor.
int expectedByte = 0xFF & (int) (params.getPacketMagic() >>> (magicCursor * 8));
if (b == expectedByte) {
magicCursor--;
if (magicCursor < 0) {
// We found the magic sequence.
return;
} else {
// We still have further to go to find the next message.
}
} else {
magicCursor = 3;
}
}
}
/**
* Whether the serializer will produce lazy parse mode Messages
*/
public boolean isParseLazyMode() {
return parseLazy;
}
/**
* Whether the serializer will produce cached mode Messages
*/
public boolean isParseRetainMode() {
return parseRetain;
}
public static class BitcoinPacketHeader {
public final byte[] header;
public final String command;
public final int size;
public final byte[] checksum;
public BitcoinPacketHeader(InputStream in) throws ProtocolException, IOException {
header = new byte[COMMAND_LEN + 4 + 4];
int readCursor = 0;
while (readCursor < header.length) {
int bytesRead = in.read(header, readCursor, header.length - readCursor);
if (bytesRead == -1) {
// There's no more data to read.
throw new IOException("Incomplete packet in underlying stream");
}
readCursor += bytesRead;
}
int cursor = 0;
// The command is a NULL terminated string, unless the command fills all twelve bytes
// in which case the termination is implicit.
int mark = cursor;
for (; header[cursor] != 0 && cursor - mark < COMMAND_LEN; cursor++) ;
byte[] commandBytes = new byte[cursor - mark];
System.arraycopy(header, mark, commandBytes, 0, cursor - mark);
try {
command = new String(commandBytes, "US-ASCII");
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e); // Cannot happen.
}
cursor = mark + COMMAND_LEN;
size = (int) readUint32(header, cursor);
cursor += 4;
if (size > Message.MAX_SIZE)
throw new ProtocolException("Message size too large: " + size);
// Old clients don't send the checksum.
checksum = new byte[4];
// Note that the size read above includes the checksum bytes.
System.arraycopy(header, cursor, checksum, 0, 4);
cursor += 4;
}
}
}