Pool FullDataPointIdMap Entries and improve hash logic

core/src/main/java/com/seibel/distanthorizons/core/dataObjects/fullData/FullDataPointIdMap.java

@@ -27,12 +27,12 @@ import com.seibel.distanthorizons.core.wrapperInterfaces.block.IBlockStateWrappe
 import com.seibel.distanthorizons.core.wrapperInterfaces.world.IBiomeWrapper;
 import com.seibel.distanthorizons.core.wrapperInterfaces.IWrapperFactory;
 import com.seibel.distanthorizons.core.wrapperInterfaces.world.ILevelWrapper;
+import it.unimi.dsi.fastutil.ints.Int2ReferenceOpenHashMap;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import java.io.*;
-import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.*;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 /**
@@ -131,7 +131,7 @@ public class FullDataPointIdMap
 	 * If an entry with the given values already exists nothing will
 	 * be added but the existing item's ID will still be returned.
 	 */
-	public int addIfNotPresentAndGetId(IBiomeWrapper biome, IBlockStateWrapper blockState) { return this.addIfNotPresentAndGetId(new Entry(biome, blockState), true); }
+	public int addIfNotPresentAndGetId(IBiomeWrapper biome, IBlockStateWrapper blockState) { return this.addIfNotPresentAndGetId(Entry.getEntry(biome, blockState), true); }
 	/** @param useWriteLocks should only be false if this method is already in a write lock to prevent unlocking at the wrong time */
 	private int addIfNotPresentAndGetId(Entry biomeBlockStateEntry, boolean useWriteLocks)
 	{
@@ -322,15 +322,81 @@ public class FullDataPointIdMap
 	{
 		private static final IWrapperFactory WRAPPER_FACTORY = SingletonInjector.INSTANCE.get(IWrapperFactory.class);
 		
+		private static final Int2ReferenceOpenHashMap<ArrayList<Entry>> ENTRY_POOL = new Int2ReferenceOpenHashMap<>();
+		/** lock is necessary since {@link Int2ReferenceOpenHashMap} isn't concurrent and concurrent threads can cause infinite loops */
+		private static final ReentrantReadWriteLock ENTRY_POOL_LOCK = new ReentrantReadWriteLock();
+		
 		public final IBiomeWrapper biome;
 		public final IBlockStateWrapper blockState;
 		
 		private Integer hashCode = null;
 		
 		
-		// constructor //
 		
-		public Entry(IBiomeWrapper biome, IBlockStateWrapper blockState)
+		//=============//
+		// constructor //
+		//=============//
+		
+		public static Entry getEntry(IBiomeWrapper biome, IBlockStateWrapper blockState)
+		{
+			int entryHash = getHashCode(biome, blockState);
+			
+			// try getting the existing entry
+			try
+			{
+				ENTRY_POOL_LOCK.readLock().lock();
+				
+				// check if an entry already exists
+				ArrayList<Entry> entryList = ENTRY_POOL.get(entryHash);
+				if (entryList != null)
+				{
+					// at least one entry exists with this hash code
+					for (int i = 0; i < entryList.size(); i++)
+					{
+						Entry entry = entryList.get(i);
+						if (entry.biome.equals(biome) && entry.blockState.equals(blockState))
+						{
+							return entry;
+						}
+					}
+					
+					// if we got here, then there was a hash collision and this entry wasn't present in the array
+				}
+			}
+			finally
+			{
+				ENTRY_POOL_LOCK.readLock().unlock();
+			}
+			
+			
+			// no entry exists,
+			// create a new one
+			try
+			{
+				ENTRY_POOL_LOCK.writeLock().lock();
+				
+				ArrayList<Entry> entryList = ENTRY_POOL.get(entryHash);
+				if (entryList == null)
+				{
+					// no entries exist for this hash code
+					
+					// we assume that hash collisions should basically never happen, 
+					// so the array starts with an initial capacity of 1.
+					// However, since collisions will eventually happen, using an arrayList prevents unexpected bugs caused by collisions.
+					entryList = new ArrayList<>(1);
+					ENTRY_POOL.put(entryHash, entryList);
+				}
+				
+				Entry newEntry = new Entry(biome, blockState);
+				entryList.add(newEntry);
+				return newEntry;
+			}
+			finally
+			{
+				ENTRY_POOL_LOCK.writeLock().unlock();
+			}
+		}
+		private Entry(IBiomeWrapper biome, IBlockStateWrapper blockState)
 		{
 			this.biome = biome;
 			this.blockState = blockState;
@@ -338,15 +404,29 @@ public class FullDataPointIdMap
 		
 		
 		
-		// methods //
+		//===========//
+		// overrides //
+		//===========//
 		
+		public static int getHashCode(Entry entry) { return getHashCode(entry.biome, entry.blockState); }
+		public static int getHashCode(IBiomeWrapper biome, IBlockStateWrapper blockState)
+		{
+			final int prime = 31;
+			
+			int result = 1;
+			// the biome and blockstate hashcode should be already calculated by the time
+			// we get here, so this operation should be very fast
+			result = prime * result + (biome == null ? 0 : biome.hashCode());
+			result = prime * result + (blockState == null ? 0 : blockState.hashCode());
+			return result;
+		}
 		@Override
 		public int hashCode()
 		{
 			// cache the hash code to improve speed
 			if (this.hashCode == null)
 			{
-				this.hashCode = this.serialize().hashCode();
+				this.hashCode = getHashCode(this);
 			}
 			
 			return this.hashCode;
@@ -371,6 +451,10 @@ public class FullDataPointIdMap
 		
 		
 		
+		//=================//
+		// (de)serializing //
+		//=================//
+		
 		public String serialize() { return this.biome.getSerialString() + BLOCK_STATE_SEPARATOR_STRING + this.blockState.getSerialString(); }
 		
 		public static Entry deserialize(String str, ILevelWrapper levelWrapper) throws IOException, InterruptedException
@@ -389,7 +473,7 @@ public class FullDataPointIdMap
 			
 			IBiomeWrapper biome = WRAPPER_FACTORY.deserializeBiomeWrapper(stringArray[0], levelWrapper);
 			IBlockStateWrapper blockState = WRAPPER_FACTORY.deserializeBlockStateWrapper(stringArray[1], levelWrapper);
-			return new Entry(biome, blockState);
+			return Entry.getEntry(biome, blockState);
 		}
 		
 	}

core/src/main/java/com/seibel/distanthorizons/core/sql/repo/FullDataSourceV2Repo.java

@@ -40,6 +40,11 @@ public class FullDataSourceV2Repo extends AbstractDhRepo<DhSectionPos, FullDataS
 	private static final Logger LOGGER = DhLoggerBuilder.getLogger();
 	
 	
+	
+	//=============//
+	// constructor //
+	//=============//
+	
 	public FullDataSourceV2Repo(String databaseType, String databaseLocation) throws SQLException
 	{
 		super(databaseType, databaseLocation, FullDataSourceV2DTO.class);
@@ -47,6 +52,10 @@ public class FullDataSourceV2Repo extends AbstractDhRepo<DhSectionPos, FullDataS
 	
 	
 	
+	//===========//
+	// overrides //
+	//===========//
+	
 	@Override 
 	public String getTableName() { return "FullData"; }