Misc optimizations, the profiles look much better now.

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

@@ -379,7 +379,7 @@ public abstract class AbstractBlockChain {
             TransactionOutputChanges txOutChanges = null;
             if (shouldVerifyTransactions())
                 txOutChanges = connectTransactions(storedPrev.getHeight() + 1, block);
-            StoredBlock newStoredBlock = addToBlockStore(storedPrev, block.cloneAsHeader(), txOutChanges);
+            StoredBlock newStoredBlock = addToBlockStore(storedPrev, block, txOutChanges);
             setChainHead(newStoredBlock);
             log.debug("Chain is now {} blocks high", newStoredBlock.getHeight());
             // Notify the listeners of the new block, so the depth and workDone of stored transactions can be updated

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

@@ -72,7 +72,7 @@ public class HeadersMessage extends Message {
             byte[] blockHeader = readBytes(81);
             if (blockHeader[80] != 00)
                 throw new ProtocolException("Block header does not end with a null byte");
-            Block newBlockHeader = new Block(this.params, blockHeader);
+            Block newBlockHeader = new Block(this.params, blockHeader, true, true, 81);
             blockHeaders.add(newBlockHeader);
         }
 

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

@@ -95,7 +95,7 @@ public class StoredBlock implements Serializable {
         // the largest amount of work done not the tallest.
         BigInteger chainWork = this.chainWork.add(block.getWork());
         int height = this.height + 1;
-        return new StoredBlock(block.cloneAsHeader(), chainWork, height);
+        return new StoredBlock(block, chainWork, height);
     }
 
     /**

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

@@ -28,9 +28,7 @@ import java.nio.charset.Charset;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Date;
-import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantLock;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
@@ -40,6 +38,17 @@ import static com.google.common.base.Preconditions.checkArgument;
  */
 public class Utils {
     private static CycleDetectingLockFactory lockFactory = CycleDetectingLockFactory.newInstance(CycleDetectingLockFactory.Policies.THROW);
+    private static MessageDigest digest;
+
+    static {
+        try {
+            digest = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);  // Can't happen.
+        }
+    }
+
+
     /** Returns a cycle detecting re-entrant named lock. */
     public static ReentrantLock lock(String name) {
         return lockFactory.newReentrantLock(name);
@@ -167,23 +176,19 @@ public class Utils {
      * standard procedure in Bitcoin. The resulting hash is in big endian form.
      */
     public static byte[] doubleDigest(byte[] input, int offset, int length) {
-        try {
-            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        synchronized (digest) {
+            digest.reset();
             digest.update(input, offset, length);
             byte[] first = digest.digest();
             return digest.digest(first);
-        } catch (NoSuchAlgorithmException e) {
-            throw new RuntimeException(e);  // Cannot happen.
         }
     }
 
     public static byte[] singleDigest(byte[] input, int offset, int length) {
-        try {
-            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        synchronized (digest) {
+            digest.reset();
             digest.update(input, offset, length);
             return digest.digest();
-        } catch (NoSuchAlgorithmException e) {
-            throw new RuntimeException(e);  // Cannot happen.
         }
     }
 
@@ -192,14 +197,12 @@ public class Utils {
      */
     public static byte[] doubleDigestTwoBuffers(byte[] input1, int offset1, int length1,
                                                 byte[] input2, int offset2, int length2) {
-        try {
-            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        synchronized (digest) {
+            digest.reset();
             digest.update(input1, offset1, length1);
             digest.update(input2, offset2, length2);
             byte[] first = digest.digest();
             return digest.digest(first);
-        } catch (NoSuchAlgorithmException e) {
-            throw new RuntimeException(e);  // Cannot happen.
         }
     }
 

core/src/main/java/com/google/bitcoin/store/SPVBlockStore.java

@@ -181,8 +181,10 @@ public class SPVBlockStore implements BlockStore {
             }
             buffer.put(chainWorkBytes);
             buffer.putInt(block.getHeight());
-            byte[] header = block.getHeader().bitcoinSerialize();
-            buffer.put(header, 0, Block.HEADER_SIZE);  // Trim the trailing 00 byte (zero transactions).
+            // Using unsafeBitcoinSerialize here can give us direct access to the same bytes we read off the wire,
+            // avoiding serialization round-trips.
+            byte[] bytes = block.getHeader().unsafeBitcoinSerialize();
+            buffer.put(bytes, 0, Block.HEADER_SIZE);  // Trim the trailing 00 byte (zero transactions).
             setRingCursor(buffer, buffer.position());
             blockCache.put(hash, block);
         } finally { lock.unlock(); }