diff --git a/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/api/tag/TagRegistry.java b/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/api/tag/TagRegistry.java index 1ec17ee90..a4754ec51 100644 --- a/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/api/tag/TagRegistry.java +++ b/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/api/tag/TagRegistry.java @@ -41,19 +41,7 @@ public final class TagRegistry { private TagRegistry() { } public static Tag create(Identifier id, Supplier> containerSupplier) { - return new TagDelegate(id, null) { - private TagContainer container; - - @Override - protected void onAccess() { - TagContainer currContainer = containerSupplier.get(); - - if (container != currContainer) { - container = currContainer; - delegate = container.getOrCreate(this.getId()); - } - } - }; + return new TagDelegate<>(id, containerSupplier); } public static Tag block(Identifier id) { diff --git a/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/impl/tag/extension/TagDelegate.java b/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/impl/tag/extension/TagDelegate.java index e0c0d338e..2f3d077ab 100644 --- a/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/impl/tag/extension/TagDelegate.java +++ b/fabric-tag-extensions-v0/src/main/java/net/fabricmc/fabric/impl/tag/extension/TagDelegate.java @@ -17,35 +17,68 @@ package net.fabricmc.fabric.impl.tag.extension; import java.util.Collection; +import java.util.function.Supplier; import net.minecraft.tag.Tag; +import net.minecraft.tag.TagContainer; import net.minecraft.util.Identifier; -public class TagDelegate extends Tag { - protected Tag delegate; +public final class TagDelegate extends Tag { + private final Supplier> containerSupplier; + private volatile Target target; - public TagDelegate(Identifier id, Tag delegate) { + public TagDelegate(Identifier id, Supplier> containerSupplier) { super(id); - this.delegate = delegate; - } - protected void onAccess() { } + this.containerSupplier = containerSupplier; + } @Override public boolean contains(T var1) { - onAccess(); - return delegate.contains(var1); + return getTag().contains(var1); } @Override public Collection values() { - onAccess(); - return delegate.values(); + return getTag().values(); } @Override public Collection> entries() { - onAccess(); - return delegate.entries(); + return getTag().entries(); + } + + /** + * Retrieve the tag this delegate is pointing to, computing it if missing or outdated. + * + *

Thread safety is being ensured by using an immutable holder object for consistently retrieving both result + * and condition, volatile for safe publishing and assuming TagContainer.getOrCreate is safe to call concurrently. + * + *

It should be possible to exploit a benign data race on this.target by removing volatile, but this option + * hasn't been chosen yet since a performance problem in the area is yet to be proven. + */ + private Tag getTag() { + Target target = this.target; + TagContainer reqContainer = containerSupplier.get(); + Tag ret; + + if (target == null || target.container != reqContainer) { + ret = reqContainer.getOrCreate(getId()); + this.target = new Target<>(reqContainer, ret); + } else { + ret = target.tag; + } + + return ret; + } + + private static final class Target { + Target(TagContainer container, Tag tag) { + this.container = container; + this.tag = tag; + } + + final TagContainer container; + final Tag tag; } }