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Rework Neighbor Cache to use Weak References #2828

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Merged
Zorbatron merged 3 commits into from
Aug 7, 2025
Merged

Rework Neighbor Cache to use Weak References #2828

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f0c0235
make neighbor cache use weak refs
ghzdude Jun 10, 2025
a5b266d
use list instead of rawtype array
ghzdude Jun 11, 2025
9706d67
fix possible loss of referent (?)
ghzdude Jun 18, 2025
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47 changes: 36 additions & 11 deletions src/main/java/gregtech/api/metatileentity/NeighborCacheTileEntityBase.java
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Original file line number Diff line number Diff line change
Expand Up @@ -11,11 +11,17 @@
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.List;

public abstract class NeighborCacheTileEntityBase extends SyncedTileEntityBase implements INeighborCache {

private final TileEntity[] neighbors = new TileEntity[6];
private static final WeakReference<TileEntity> NULL = new WeakReference<>(null);
private static final WeakReference<TileEntity> INVALID = new WeakReference<>(null);

private final List<WeakReference<TileEntity>> neighbors = Arrays.asList(
INVALID, INVALID, INVALID, INVALID, INVALID, INVALID);
private boolean neighborsInvalidated = false;

public NeighborCacheTileEntityBase() {
Expand All @@ -24,7 +30,9 @@ public NeighborCacheTileEntityBase() {

protected void invalidateNeighbors() {
if (!this.neighborsInvalidated) {
Arrays.fill(this.neighbors, this);
for (EnumFacing value : EnumFacing.VALUES) {
this.neighbors.set(value.getIndex(), INVALID);
}
this.neighborsInvalidated = true;
}
}
Expand Down Expand Up @@ -60,17 +68,34 @@ public void onChunkUnload() {
@Override
public @Nullable TileEntity getNeighbor(@NotNull EnumFacing facing) {
if (world == null || pos == null) return null;
int i = facing.getIndex();
TileEntity neighbor = this.neighbors[i];
if (neighbor == this || (neighbor != null && neighbor.isInvalid())) {
neighbor = world.getTileEntity(pos.offset(facing));
this.neighbors[i] = neighbor;
this.neighborsInvalidated = false;
}
return neighbor;
// if the ref is INVALID, compute neighbor, otherwise, return TE or null
WeakReference<TileEntity> ref = invalidRef(facing) ? computeNeighbor(facing) : getRef(facing);
return ref.get();
}

private boolean invalidRef(EnumFacing facing) {
WeakReference<TileEntity> ref = getRef(facing);
if (ref == INVALID) return true;
TileEntity te = ref.get();
return te != null && te.isInvalid();
}

@NotNull
private WeakReference<TileEntity> computeNeighbor(EnumFacing facing) {
TileEntity te = super.getNeighbor(facing);
// avoid making new references to null TEs
WeakReference<TileEntity> ref = te == null ? NULL : new WeakReference<>(te);
this.neighbors.set(facing.getIndex(), ref);
this.neighborsInvalidated = false;
return ref;
}

@NotNull
private WeakReference<TileEntity> getRef(EnumFacing facing) {
return this.neighbors.get(facing.getIndex());
}

public void onNeighborChanged(@NotNull EnumFacing facing) {
this.neighbors[facing.getIndex()] = this;
this.neighbors.set(facing.getIndex(), INVALID);
}
}
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