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Fix hash collisions in FullDataPointIdMap

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This commit is contained in:
James Seibel
2025-06-06 07:43:38 -05:00
parent a075e60e3e
commit d40d293f54
1 changed files with 27 additions and 24 deletions
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core/src/main/java/com/seibel/distanthorizons/core/dataObjects/fullData/FullDataPointIdMap.java
+27 -24
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@@ -29,14 +29,12 @@ 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.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* WARNING: This is not THREAD-SAFE! <br><br>
@@ -47,7 +45,7 @@ import java.util.concurrent.locks.ReentrantReadWriteLock;
* since it stringifies every block and biome name, which is quite bulky.
* It might be worth while to have a biome and block ID that then both get mapped
* to the data point ID to reduce file size.
* And/or it would be good to dynamically remove IDs that aren't currently in use.
* And/or it would be good to dynamically remove IDs that aren't currently in use.
*
* @author Leetom
*/
@@ -352,14 +350,14 @@ public class FullDataPointIdMap
{
private static final IWrapperFactory WRAPPER_FACTORY = SingletonInjector.INSTANCE.get(IWrapperFactory.class);
private static final ConcurrentHashMap<Integer, Entry> ENTRY_BY_HASH = new ConcurrentHashMap<>();
/** 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();
/** two levels are present so we don't need to use a key object */
private static final ConcurrentHashMap<IBiomeWrapper, ConcurrentHashMap<IBlockStateWrapper, Entry>> ENTRY_BY_BLOCKSTATE_BY_BIOMEWRAPPER = new ConcurrentHashMap<>();
public final IBiomeWrapper biome;
public final IBlockStateWrapper blockState;
private Integer hashCode = null;
private int hashCode = 0;
private boolean hashGenerated = false;
private String serialString = null;
@@ -370,25 +368,21 @@ public class FullDataPointIdMap
public static Entry getEntry(IBiomeWrapper biome, IBlockStateWrapper blockState)
{
int entryHash = generateHashCode(biome, blockState);
// try getting the existing Entry
Entry entry = ENTRY_BY_HASH.get(entryHash);
if (entry != null)
// check for existing entry
ConcurrentHashMap<IBlockStateWrapper, Entry> entryByBlockState = ENTRY_BY_BLOCKSTATE_BY_BIOMEWRAPPER.get(biome);
if (entryByBlockState != null)
{
return entry;
Entry entry = entryByBlockState.get(blockState);
if (entry != null)
{
return entry;
}
}
// create the missing entry
return ENTRY_BY_HASH.compute(entryHash, (Integer newHash, Entry currentEntry) ->
{
if (currentEntry != null)
{
return currentEntry;
}
return new Entry(biome, blockState);
});
// Lazily create the inner map and new Entry
return ENTRY_BY_BLOCKSTATE_BY_BIOMEWRAPPER
.computeIfAbsent(biome, newBiome -> new ConcurrentHashMap<>())
.computeIfAbsent(blockState, newBlockState -> new Entry(biome, blockState));
}
private Entry(IBiomeWrapper biome, IBlockStateWrapper blockState)
{
@@ -402,13 +396,18 @@ public class FullDataPointIdMap
// overrides //
//===========//
/**
* Reminder: this hash code won't always be unique, collisions can occur;
* because of that this hash shouldn't be the only unique identifier for this object.
*/
@Override
public int hashCode()
{
// cache the hash code to improve speed
if (this.hashCode == null)
if (!this.hashGenerated)
{
this.hashCode = generateHashCode(this);
this.hashGenerated = true;
}
return this.hashCode;
@@ -430,10 +429,14 @@ public class FullDataPointIdMap
public boolean equals(Object otherObj)
{
if (otherObj == this)
{
return true;
}
if (!(otherObj instanceof Entry))
{
return false;
}
Entry other = (Entry) otherObj;
return other.biome.getSerialString().equals(this.biome.getSerialString())