Change to how "best block" is determined.

src/main/java/org/qora/block/BlockGenerator.java

@@ -142,12 +142,11 @@ public class BlockGenerator extends Thread {
 
 				boolean newBlockGenerated = false;
 
-				generation: try {
+				try {
 					// Clear repository's "in transaction" state so we don't cause a repository deadlock
 					repository.discardChanges();
 
 					List<Block> goodBlocks = new ArrayList<>();
-
 					for (Block testBlock : newBlocks) {
 						// Is new block's timestamp valid yet?
 						// We do a separate check as some timestamp checks are skipped for testchains
@@ -162,7 +161,7 @@ public class BlockGenerator extends Thread {
 					}
 
 					if (goodBlocks.isEmpty())
-						break generation;
+						continue;
 
 					// Pick random generator
 					int winningIndex = new Random().nextInt(goodBlocks.size());
@@ -182,8 +181,10 @@ public class BlockGenerator extends Thread {
 					if (validationResult != ValidationResult.OK) {
 						// No longer valid? Report and discard
 						LOGGER.error("Valid, generated block now invalid '" + validationResult.name() + "' after adding unconfirmed transactions?");
+
+						// Rebuild block candidates, just to be sure
 						newBlocks.clear();
-						break generation;
+						continue;
 					}
 
 					// Add to blockchain - something else will notice and broadcast new block to network

src/main/java/org/qora/controller/Controller.java

@@ -29,7 +29,7 @@ import org.qora.block.BlockGenerator;
 import org.qora.controller.Synchronizer.SynchronizationResult;
 import org.qora.crypto.Crypto;
 import org.qora.data.block.BlockData;
-import org.qora.data.network.BlockSummaryData;
+import org.qora.data.block.BlockSummaryData;
 import org.qora.data.network.PeerData;
 import org.qora.data.transaction.ArbitraryTransactionData;
 import org.qora.data.transaction.ArbitraryTransactionData.DataType;

src/main/java/org/qora/controller/Synchronizer.java

@@ -10,7 +10,7 @@ import org.apache.logging.log4j.Logger;
 import org.qora.block.Block;
 import org.qora.block.Block.ValidationResult;
 import org.qora.data.block.BlockData;
-import org.qora.data.network.BlockSummaryData;
+import org.qora.data.block.BlockSummaryData;
 import org.qora.data.transaction.TransactionData;
 import org.qora.network.Peer;
 import org.qora.network.message.BlockMessage;

src/main/java/org/qora/data/block/BlockSummaryData.java

@@ -1,6 +1,4 @@
-package org.qora.data.network;
+package org.qora.data.block;
-
-import org.qora.data.block.BlockData;
 
 public class BlockSummaryData {
 

src/main/java/org/qora/network/message/BlockSummariesMessage.java

@@ -7,7 +7,7 @@ import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 
-import org.qora.data.network.BlockSummaryData;
+import org.qora.data.block.BlockSummaryData;
 import org.qora.transform.Transformer;
 import org.qora.transform.block.BlockTransformer;
 

src/main/java/org/qora/repository/BlockRepository.java

@@ -4,6 +4,7 @@ import java.util.List;
 
 import org.qora.api.model.BlockForgerSummary;
 import org.qora.data.block.BlockData;
+import org.qora.data.block.BlockSummaryData;
 import org.qora.data.block.BlockTransactionData;
 import org.qora.data.transaction.TransactionData;
 
@@ -117,6 +118,11 @@ public interface BlockRepository {
 	 */
 	public List<BlockData> getBlocks(int firstBlockHeight, int lastBlockHeight) throws DataException;
 
+	/**
+	 * Returns block summaries for the passed height range.
+	 */
+	public List<BlockSummaryData> getBlockSummaries(int firstBlockHeight, int lastBlockHeight) throws DataException;
+
 	/**
 	 * Saves block into repository.
 	 * 

src/main/java/org/qora/repository/hsqldb/HSQLDBBlockRepository.java

@@ -9,6 +9,7 @@ import java.util.List;
 
 import org.qora.api.model.BlockForgerSummary;
 import org.qora.data.block.BlockData;
+import org.qora.data.block.BlockSummaryData;
 import org.qora.data.block.BlockTransactionData;
 import org.qora.data.transaction.TransactionData;
 import org.qora.repository.BlockRepository;
@@ -265,6 +266,31 @@ public class HSQLDBBlockRepository implements BlockRepository {
 		}
 	}
 
+	@Override
+	public List<BlockSummaryData> getBlockSummaries(int firstBlockHeight, int lastBlockHeight) throws DataException {
+		String sql = "SELECT signature, height, generator FROM Blocks WHERE height BETWEEN ? AND ?";
+
+		List<BlockSummaryData> blockSummaries = new ArrayList<>();
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, firstBlockHeight, lastBlockHeight)) {
+			if (resultSet == null)
+				return blockSummaries;
+
+			do {
+				byte[] signature = resultSet.getBytes(1);
+				int height = resultSet.getInt(2);
+				byte[] generatorPublicKey = resultSet.getBytes(3);
+
+				BlockSummaryData blockSummary = new BlockSummaryData(height, signature, generatorPublicKey);
+				blockSummaries.add(blockSummary);
+			} while (resultSet.next());
+
+			return blockSummaries;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch height-ranged block summaries from repository", e);
+		}
+	}
+
 	@Override
 	public void save(BlockData blockData) throws DataException {
 		HSQLDBSaver saveHelper = new HSQLDBSaver("Blocks");

src/main/java/org/qora/utils/ByteArray.java

@@ -0,0 +1,46 @@
+package org.qora.utils;
+
+import java.util.Comparator;
+
+import com.google.common.hash.HashCode;
+
+public class ByteArray implements Comparable<ByteArray> {
+
+	private static final Comparator<ByteArray> COMPARATOR;
+	static {
+		COMPARATOR = Comparator.comparing(byteArray -> byteArray.comparable);
+	}
+
+	private final String comparable;
+
+	public final byte[] raw;
+
+	public ByteArray(byte[] content) {
+		this.comparable = HashCode.fromBytes(content).toString();
+		this.raw = content;
+	}
+
+	@Override
+	public boolean equals(Object other) {
+		if (this == other)
+			return true;
+
+		if (!(other instanceof ByteArray))
+			return false;
+
+		ByteArray otherByteArray = (ByteArray) other;
+
+		return this.comparable.equals(otherByteArray.comparable);
+	}
+
+	@Override
+	public int hashCode() {
+		return this.comparable.hashCode();
+	}
+
+	@Override
+	public int compareTo(ByteArray other) {
+		return COMPARATOR.compare(this, other);
+	}
+
+}

src/test/java/org/qora/test/ByteArrayTests.java

@@ -0,0 +1,66 @@
+package org.qora.test;
+
+import static org.junit.Assert.*;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.qora.utils.ByteArray;
+
+public class ByteArrayTests {
+
+	private static List<byte[]> testValues;
+
+	@Before
+	public void createTestValues() {
+		Random random = new Random();
+
+		testValues = new ArrayList<>();
+		for (int i = 0; i < 5; ++i) {
+			byte[] testValue = new byte[32];
+			random.nextBytes(testValue);
+			testValues.add(testValue);
+		}
+	}
+
+	public void fillMap(Map<ByteArray, String> map) {
+		for (byte[] testValue : testValues)
+			map.put(new ByteArray(testValue), String.valueOf(map.size()));
+	}
+
+	@Test
+	public void testByteArray() {
+		// Create two objects, which will have different references, but same content.
+		byte[] testValue = testValues.get(0);
+		ByteArray ba1 = new ByteArray(testValue);
+		ByteArray ba2 = new ByteArray(testValue);
+
+		// Confirm JVM-assigned references are different
+		assertNotSame(ba1, ba2);
+
+		// Confirm "equals" works as intended
+		assertTrue("equals did not return true", ba1.equals(ba2));
+		assertEquals("ba1 not equal to ba2", ba1, ba2);
+
+		// Confirm "hashCode" results match
+		assertEquals("hashCodes do not match", ba1.hashCode(), ba2.hashCode());
+	}
+
+	@Test
+	public void testByteArrayMap() {
+		Map<ByteArray, String> testMap = new HashMap<>();
+		fillMap(testMap);
+
+		// Create new ByteArray object with an existing value.
+		ByteArray ba = new ByteArray(testValues.get(3));
+
+		// Confirm object can be found in map
+		assertTrue("ByteArray not found in map", testMap.containsKey(ba));
+	}
+
+}