Faster undo operations (#2898)

worldedit-core/src/main/java/com/fastasyncworldedit/core/configuration/Settings.java

@@ -622,6 +622,13 @@ public class Settings extends Config {
     })
     public static class EXPERIMENTAL {
 
+        @Comment({
+                "Undo operation batch size",
+                " - The size defines the number of changes read at once.",
+                " - Larger numbers might reduce overhead but increase latency for edits with only few changes.",
+                " - 0 means undo operations are not batched."})
+        public int UNDO_BATCH_SIZE = 128;
+
         @Comment({
                 "[UNSAFE] Directly modify the region files. (OBSOLETE - USE ANVIL COMMANDS)",
                 " - IMPROPER USE CAN CAUSE WORLD CORRUPTION!",

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/change/ChangePopulator.java

@@ -0,0 +1,65 @@
+package com.fastasyncworldedit.core.history.change;
+
+import com.sk89q.worldedit.history.change.Change;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * @since TODO
+ */
+@ApiStatus.Internal
+public interface ChangePopulator<C extends Change> {
+
+    static <C extends Change> ChangePopulator<C> empty() {
+        class Empty implements ChangePopulator<C> {
+            private static final Empty EMPTY = new Empty();
+
+            @Override
+            public @NotNull C create() {
+                throw new UnsupportedOperationException("empty");
+            }
+
+            @Override
+            public @Nullable C populate(@NotNull final C change) {
+                return null;
+            }
+
+            @Override
+            public @Nullable C updateOrCreate(@Nullable final Change change) {
+                return null;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return false;
+            }
+        }
+        return Empty.EMPTY;
+    }
+
+    @SuppressWarnings("unchecked")
+    default @NotNull C update(@Nullable Change before) {
+        if (accepts(before)) {
+            return (C) before;
+        }
+        return create();
+    }
+
+    @NotNull
+    C create();
+
+    @Nullable
+    default C updateOrCreate(@Nullable Change change) {
+        C u = update(change);
+        return populate(u);
+    }
+
+    @Nullable
+    C populate(@NotNull C change);
+
+    @Contract("null->false")
+    boolean accepts(Change change);
+
+}

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/changeset/AbstractChangeSet.java

@@ -32,6 +32,7 @@ import com.sk89q.worldedit.world.block.BaseBlock;
 import com.sk89q.worldedit.world.block.BlockState;
 import com.sk89q.worldedit.world.block.BlockTypesCache;
 import org.apache.logging.log4j.Logger;
+import org.jetbrains.annotations.ApiStatus;
 
 import java.io.IOException;
 import java.util.Iterator;
@@ -250,6 +251,13 @@ public abstract class AbstractChangeSet implements ChangeSet, IBatchProcessor {
         return getIterator(redo);
     }
 
+    /**
+     * {@return a coordinator to exchange sets of changes between a producer and a consumer}
+     * @since TODO
+     */
+    @ApiStatus.Internal
+    public abstract ChangeExchangeCoordinator getCoordinatedChanges(BlockBag blockBag, int mode, boolean dir);
+
     public abstract Iterator<Change> getIterator(boolean redo);
 
     public EditSession toEditSession(Actor actor) {

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/changeset/AbstractDelegateChangeSet.java

@@ -76,6 +76,11 @@ public class AbstractDelegateChangeSet extends AbstractChangeSet {
         return parent.getIterator(blockBag, mode, redo);
     }
 
+    @Override
+    public ChangeExchangeCoordinator getCoordinatedChanges(final BlockBag blockBag, final int mode, final boolean dir) {
+        return parent.getCoordinatedChanges(blockBag, mode, dir);
+    }
+
     @Override
     public Iterator<Change> getIterator(boolean redo) {
         return parent.getIterator(redo);

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/changeset/ChangeExchangeCoordinator.java

@@ -0,0 +1,50 @@
+package com.fastasyncworldedit.core.history.changeset;
+
+import com.sk89q.worldedit.history.change.Change;
+import org.jetbrains.annotations.ApiStatus;
+
+import java.util.concurrent.Exchanger;
+import java.util.function.BiConsumer;
+
+/**
+ * @since TODO
+ */
+@ApiStatus.Internal
+public class ChangeExchangeCoordinator implements AutoCloseable {
+
+    private static final Thread.Builder.OfVirtual UNDO_VIRTUAL_THREAD_BUILDER = Thread.ofVirtual()
+            .name("FAWE undo", 0);
+    private final Exchanger<Change[]> exchanger;
+    private final BiConsumer<Exchanger<Change[]>, Change[]> runnerTask;
+    private boolean started = false;
+    private Thread runner;
+
+    public ChangeExchangeCoordinator(BiConsumer<Exchanger<Change[]>, Change[]> runner) {
+        this.runnerTask = runner;
+        this.exchanger = new Exchanger<>();
+    }
+
+    public Change[] take(Change[] consumed) {
+        if (!this.started) {
+            this.started = true;
+            final int length = consumed.length;
+            this.runner = UNDO_VIRTUAL_THREAD_BUILDER
+                    .start(() -> this.runnerTask.accept(this.exchanger, new Change[length]));
+        }
+        try {
+            return exchanger.exchange(consumed);
+        } catch (InterruptedException e) {
+            this.runner.interrupt();
+            Thread.currentThread().interrupt();
+            return null;
+        }
+    }
+
+    @Override
+    public void close() {
+        if (this.runner != null) {
+            this.runner.interrupt();
+        }
+    }
+
+}

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/changeset/FaweStreamChangeSet.java

@@ -1,6 +1,7 @@
 package com.fastasyncworldedit.core.history.changeset;
 
 import com.fastasyncworldedit.core.configuration.Settings;
+import com.fastasyncworldedit.core.history.change.ChangePopulator;
 import com.fastasyncworldedit.core.history.change.MutableBiomeChange;
 import com.fastasyncworldedit.core.history.change.MutableBlockChange;
 import com.fastasyncworldedit.core.history.change.MutableEntityChange;
@@ -20,15 +21,22 @@ import com.sk89q.worldedit.regions.Region;
 import com.sk89q.worldedit.world.World;
 import com.sk89q.worldedit.world.biome.BiomeType;
 import com.sk89q.worldedit.world.block.BlockTypes;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.util.ArrayDeque;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
+import java.util.List;
 import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.concurrent.Exchanger;
+import java.util.function.BiConsumer;
 
 /**
  * FAWE stream ChangeSet offering support for extended-height worlds
@@ -711,6 +719,284 @@ public abstract class FaweStreamChangeSet extends AbstractChangeSet {
         }
     }
 
+    @Override
+    public ChangeExchangeCoordinator getCoordinatedChanges(BlockBag blockBag, int mode, boolean dir) {
+        try {
+            return coordinatedChanges(blockBag, mode, dir);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private ChangeExchangeCoordinator coordinatedChanges(final BlockBag blockBag, final int mode, boolean dir) throws IOException {
+        close();
+        var tileCreate = tileChangePopulator(getTileCreateIS(), true);
+        var tileRemove = tileChangePopulator(getTileRemoveIS(), false);
+
+        var entityCreate = entityChangePopulator(getEntityCreateIS(), true);
+        var entityRemove = entityChangePopulator(getEntityRemoveIS(), false);
+
+        var blockChange = blockBag != null && mode > 0 ? fullBlockChangePopulator(blockBag, mode, dir) : blockChangePopulator(dir);
+
+        var biomeChange = biomeChangePopulator(dir);
+
+        Queue<ChangePopulator<?>> populators = new ArrayDeque<>(List.of(
+                tileCreate,
+                tileRemove,
+                entityCreate,
+                entityRemove,
+                blockChange,
+                biomeChange
+        ));
+        BiConsumer<Exchanger<Change[]>, Change[]> task = (exchanger, array) -> {
+            while (fillArray(array, populators)) {
+                try {
+                    array = exchanger.exchange(array);
+                } catch (InterruptedException e) {
+                    return;
+                }
+            }
+        };
+        return new ChangeExchangeCoordinator(task);
+    }
+
+    private boolean fillArray(Change[] changes, Queue<ChangePopulator<?>> populators) {
+        ChangePopulator<?> populator = populators.peek();
+        if (populator == null) {
+            return false;
+        }
+        for (int i = 0; i < changes.length; i++) {
+            Change change = changes[i];
+            do {
+                change = populator.updateOrCreate(change);
+                if (change == null) {
+                    populators.remove();
+                    populator = populators.peek();
+                    if (populator == null) {
+                        changes[i] = null; // mark end
+                        return true; // still needs to consume the elements of the current round
+                    }
+                } else {
+                    break;
+                }
+            } while (true);
+            changes[i] = change;
+        }
+        return true;
+    }
+
+    private static abstract class CompoundTagPopulator<C extends Change> implements ChangePopulator<C> {
+        private final NBTInputStream inputStream;
+
+        private CompoundTagPopulator(final NBTInputStream stream) {
+            inputStream = stream;
+        }
+
+        @Override
+        public @Nullable C populate(final @NotNull C change) {
+            try {
+                write(change, (CompoundTag) inputStream.readTag());
+                return change;
+            } catch (Exception ignored) {
+            }
+            try {
+                inputStream.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+            return null;
+        }
+
+        protected abstract void write(C change, CompoundTag tag);
+    }
+
+    private ChangePopulator<MutableTileChange> tileChangePopulator(NBTInputStream is, boolean create) {
+        if (is == null) {
+            return ChangePopulator.empty();
+        }
+        class Populator extends CompoundTagPopulator<MutableTileChange> {
+
+            private Populator() {
+                super(is);
+            }
+
+            @Override
+            public @NotNull MutableTileChange create() {
+                return new MutableTileChange(null, create);
+            }
+
+            @Override
+            protected void write(final MutableTileChange change, final CompoundTag tag) {
+                change.tag = tag;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return change instanceof MutableTileChange;
+            }
+
+        }
+        return new Populator();
+    }
+    private ChangePopulator<MutableEntityChange> entityChangePopulator(NBTInputStream is, boolean create) {
+        if (is == null) {
+            return ChangePopulator.empty();
+        }
+        class Populator extends CompoundTagPopulator<MutableEntityChange> {
+
+            private Populator() {
+                super(is);
+            }
+
+            @Override
+            public @NotNull MutableEntityChange create() {
+                return new MutableEntityChange(null, create);
+            }
+
+            @Override
+            protected void write(final MutableEntityChange change, final CompoundTag tag) {
+                change.tag = tag;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return change instanceof MutableTileChange;
+            }
+
+        }
+        return new Populator();
+    }
+
+    private ChangePopulator<MutableFullBlockChange> fullBlockChangePopulator(BlockBag blockBag, int mode, boolean dir) throws
+            IOException {
+        final FaweInputStream is = getBlockIS();
+        if (is == null) {
+            return ChangePopulator.empty();
+        }
+        class Populator implements ChangePopulator<MutableFullBlockChange> {
+
+            @Override
+            public @NotNull MutableFullBlockChange create() {
+                return new MutableFullBlockChange(blockBag, mode, dir);
+            }
+
+            @Override
+            public @Nullable MutableFullBlockChange populate(@NotNull final MutableFullBlockChange change) {
+                try {
+                    change.x = posDel.readX(is) + originX;
+                    change.y = posDel.readY(is);
+                    change.z = posDel.readZ(is) + originZ;
+                    idDel.readCombined(is, change);
+                    return change;
+                } catch (EOFException ignored) {
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+                try {
+                    is.close();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+                return null;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return change instanceof MutableFullBlockChange;
+            }
+
+        }
+        return new Populator();
+
+    }
+
+    private ChangePopulator<MutableBlockChange> blockChangePopulator(boolean dir) throws IOException {
+        final FaweInputStream is = getBlockIS();
+        if (is == null) {
+            return ChangePopulator.empty();
+        }
+        class Populator implements ChangePopulator<MutableBlockChange> {
+
+            @Override
+            public @NotNull MutableBlockChange create() {
+                return new MutableBlockChange(0, 0, 0, BlockTypes.AIR.getInternalId());
+            }
+
+            @Override
+            public @Nullable MutableBlockChange populate(@NotNull final MutableBlockChange change) {
+                try {
+                    change.x = posDel.readX(is) + originX;
+                    change.y = posDel.readY(is);
+                    change.z = posDel.readZ(is) + originZ;
+                    idDel.readCombined(is, change, dir);
+                    return change;
+                } catch (EOFException ignored) {
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+                try {
+                    is.close();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+                return null;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return change instanceof MutableBlockChange;
+            }
+
+        }
+        return new Populator();
+    }
+
+    private ChangePopulator<MutableBiomeChange> biomeChangePopulator(boolean dir) throws IOException {
+        final FaweInputStream is = getBiomeIS();
+        if (is == null) {
+            return ChangePopulator.empty();
+        }
+        class Populator implements ChangePopulator<MutableBiomeChange> {
+
+            @Override
+            public @NotNull MutableBiomeChange create() {
+                return new MutableBiomeChange();
+            }
+
+            @Override
+            public @Nullable MutableBiomeChange populate(@NotNull final MutableBiomeChange change) {
+                try {
+                    int int1 = is.read();
+                    if (int1 != -1) {
+                        int x = ((int1 << 24) + (is.read() << 16) + (is.read() << 8) + is.read()) << 2;
+                        int z = ((is.read() << 24) + (is.read() << 16) + (is.read() << 8) + is.read()) << 2;
+                        int y = (is.read() - 128) << 2;
+                        int from = is.readVarInt();
+                        int to = is.readVarInt();
+                        change.setBiome(x, y, z, from, to);
+                        return change;
+                    }
+                } catch (EOFException ignored) {
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+                try {
+                    is.close();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+                return null;
+            }
+
+            @Override
+            public boolean accepts(final Change change) {
+                return change instanceof MutableBiomeChange;
+            }
+
+        }
+        return new Populator();
+    }
+
     @Override
     public Iterator<Change> getIterator(final boolean dir) {
         try {

worldedit-core/src/main/java/com/fastasyncworldedit/core/history/changeset/NullChangeSet.java

@@ -54,6 +54,17 @@ public class NullChangeSet extends AbstractChangeSet {
         return getIterator(redo);
     }
 
+    @Override
+    public ChangeExchangeCoordinator getCoordinatedChanges(final BlockBag blockBag, final int mode, final boolean dir) {
+        return new ChangeExchangeCoordinator(((exchanger, changes) -> {
+            try {
+                exchanger.exchange(null);
+            } catch (InterruptedException ignored) {
+                Thread.currentThread().interrupt();
+            }
+        }));
+    }
+
     @Override
     public final Iterator<Change> getIterator(boolean undo) {
         return Collections.emptyIterator();

worldedit-core/src/main/java/com/sk89q/worldedit/function/operation/ChangeSetExecutor.java

@@ -19,7 +19,9 @@
 
 package com.sk89q.worldedit.function.operation;
 
+import com.fastasyncworldedit.core.configuration.Settings;
 import com.fastasyncworldedit.core.history.changeset.AbstractChangeSet;
+import com.fastasyncworldedit.core.history.changeset.ChangeExchangeCoordinator;
 import com.sk89q.worldedit.WorldEditException;
 import com.sk89q.worldedit.extent.inventory.BlockBag;
 import com.sk89q.worldedit.history.UndoContext;
@@ -56,6 +58,7 @@ public class ChangeSetExecutor implements Operation {
     //FAWE end
 
     private final Iterator<Change> iterator;
+    private final ChangeExchangeCoordinator changeExchangeCoordinator;
     private final Type type;
     private final UndoContext context;
 
@@ -74,18 +77,42 @@ public class ChangeSetExecutor implements Operation {
 
         this.type = type;
         this.context = context;
-        if (changeSet instanceof AbstractChangeSet) {
+        if (changeSet instanceof AbstractChangeSet abstractChangeSet) {
-            iterator = ((AbstractChangeSet) changeSet).getIterator(blockBag, inventory, type == Type.REDO);
+            if (Settings.settings().EXPERIMENTAL.UNDO_BATCH_SIZE > 0) {
+                this.changeExchangeCoordinator = abstractChangeSet.getCoordinatedChanges(blockBag, inventory, type == Type.REDO);
+                this.iterator = null;
+            } else {
+                this.iterator = abstractChangeSet.getIterator(blockBag, inventory, type == Type.REDO);
+                this.changeExchangeCoordinator = null;
+            }
         } else if (type == Type.UNDO) {
             iterator = changeSet.backwardIterator();
+            this.changeExchangeCoordinator = null;
         } else {
             iterator = changeSet.forwardIterator();
+            this.changeExchangeCoordinator = null;
         }
     }
     //FAWE end
 
     @Override
     public Operation resume(RunContext run) throws WorldEditException {
+        // FAWE start - ChangeExchangeCoordinator
+        if (this.changeExchangeCoordinator != null) {
+            try (this.changeExchangeCoordinator) {
+                Change[] changes = new Change[Settings.settings().EXPERIMENTAL.UNDO_BATCH_SIZE];
+                while ((changes = this.changeExchangeCoordinator.take(changes)) != null) {
+                    for (final Change change : changes) {
+                        if (change == null) {
+                            return null; // end
+                        }
+                        type.perform(change, context);
+                    }
+                }
+                return null;
+            }
+        }
+        // FAWE end
         while (iterator.hasNext()) {
             Change change = iterator.next();
             //FAWE start - types > individual history step