Implement some (de)serialization (so we can roundtrip msgs in test)

Implements deserialization for getblocks/getheaders and supports
FilteredBlock entries in ListMessage (for getdata).
Implements serialization for FilteredBlock, HeadersMessage, and
PartialMerkleTree.

core/src/main/java/com/google/bitcoin/core/BitcoinSerializer.java

@@ -213,6 +213,10 @@ public class BitcoinSerializer {
             message = new FilteredBlock(params, payloadBytes);
         } else if (command.equals("getdata")) {
             message = new GetDataMessage(params, payloadBytes, parseLazy, parseRetain, length);
+        } else if (command.equals("getblocks")) {
+            message = new GetBlocksMessage(params, payloadBytes);
+        } else if (command.equals("getheaders")) {
+            message = new GetHeadersMessage(params, payloadBytes);
         } else if (command.equals("tx")) {
             Transaction tx = new Transaction(params, payloadBytes, null, parseLazy, parseRetain, length);
             if (hash != null)

core/src/main/java/com/google/bitcoin/core/FilteredBlock.java

@@ -42,7 +42,11 @@ public class FilteredBlock extends Message {
     }
     
     public void bitcoinSerializeToStream(OutputStream stream) throws IOException {
-        throw new RuntimeException("Not implemented");
+        if (header.transactions == null)
+            header.bitcoinSerializeToStream(stream);
+        else
+            header.cloneAsHeader().bitcoinSerializeToStream(stream);
+        merkleTree.bitcoinSerializeToStream(stream);
     }
 
     @Override

core/src/main/java/com/google/bitcoin/core/GetBlocksMessage.java

@@ -38,8 +38,17 @@ public class GetBlocksMessage extends Message {
         this.stopHash = stopHash;
     }
 
+    public GetBlocksMessage(NetworkParameters params, byte[] msg) throws ProtocolException {
+        super(params, msg, 0);
+    }
+
     protected void parseLite() throws ProtocolException {
-        // NOP.  This is a root level message and should always be provided with a length.
+        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 {

core/src/main/java/com/google/bitcoin/core/GetHeadersMessage.java

@@ -29,6 +29,10 @@ public class GetHeadersMessage extends GetBlocksMessage {
         super(params, locator, stopHash);
     }
 
+    public GetHeadersMessage(NetworkParameters params, byte[] msg) throws ProtocolException {
+        super(params, msg);
+    }
+
     @Override
     public String toString() {
         StringBuffer b = new StringBuffer();

core/src/main/java/com/google/bitcoin/core/HeadersMessage.java

@@ -19,6 +19,8 @@ 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;
@@ -45,6 +47,18 @@ public class HeadersMessage extends Message {
         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) {

core/src/main/java/com/google/bitcoin/core/ListMessage.java

@@ -99,6 +99,9 @@ public abstract class ListMessage extends Message {
                 case 2:
                     type = InventoryItem.Type.Block;
                     break;
+                case 3:
+                    type = InventoryItem.Type.FilteredBlock;
+                    break;
                 default:
                     throw new ProtocolException("Unknown CInv type: " + typeCode);
             }

core/src/main/java/com/google/bitcoin/core/PartialMerkleTree.java

@@ -65,7 +65,14 @@ public class PartialMerkleTree extends Message {
     }
     
     public void bitcoinSerializeToStream(OutputStream stream) throws IOException {
-        throw new RuntimeException("Not implemented");
+        Utils.uint32ToByteStreamLE(transactionCount, stream);
+
+        stream.write(new VarInt(hashes.size()).encode());
+        for (Sha256Hash hash : hashes)
+            stream.write(Utils.reverseBytes(hash.getBytes()));
+
+        stream.write(new VarInt(matchedChildBits.length).encode());
+        stream.write(matchedChildBits);
     }
 
     @Override