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Add support for automatic remote object disposal.
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright 2024 Cojen.org | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * https://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| package org.cojen.dirmi; | ||
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| import java.lang.annotation.*; | ||
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| /** | ||
| * Designates a remote interface as supporting automatic disposal when the client-side object | ||
| * is reclaimed by the garbage collector. Automatic disposal doesn't work for the {@link | ||
| * Session#root root} object, and it doesn't work when a reference cycle is formed between | ||
| * client-side and remote-side objects. | ||
| * | ||
| * @author Brian S. O'Neill | ||
| * @see Disposer | ||
| * @see Session#dispose | ||
| */ | ||
| @Documented | ||
| @Retention(RetentionPolicy.RUNTIME) | ||
| @Target({ElementType.TYPE}) | ||
| public @interface AutoDispose { | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,166 @@ | ||
| /* | ||
| * Copyright 2024 Cojen.org | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * https://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| package org.cojen.dirmi.core; | ||
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| import java.lang.invoke.MethodHandles; | ||
| import java.lang.invoke.VarHandle; | ||
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| import java.lang.ref.Reference; | ||
| import java.lang.ref.ReferenceQueue; | ||
| import java.lang.ref.WeakReference; | ||
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| /** | ||
| * | ||
| * | ||
| * @author Brian S. O'Neill | ||
| */ | ||
| public final class AutoDisposer extends ReferenceQueue<Stub> implements Runnable { | ||
| private static AutoDisposer cInstance; | ||
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| private static AutoDisposer access() { | ||
| AutoDisposer instance; | ||
| synchronized (AutoDisposer.class) { | ||
| instance = cInstance; | ||
| if (instance == null) { | ||
| cInstance = instance = new AutoDisposer(); | ||
| } | ||
| instance.mRegistered++; | ||
| } | ||
| return instance; | ||
| } | ||
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| private long mRegistered; | ||
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| private AutoDisposer() { | ||
| Thread t = new Thread(this, getClass().getSimpleName()); | ||
| t.setDaemon(true); | ||
| t.start(); | ||
| } | ||
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| public void run() { | ||
| // Infinite timeout. | ||
| long timeout = 0; | ||
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| while (true) { | ||
| Reference<? extends Stub> ref; | ||
| try { | ||
| ref = remove(timeout); | ||
| } catch (InterruptedException e) { | ||
| // Clear the interrupted status. | ||
| Thread.interrupted(); | ||
| ref = null; | ||
| } | ||
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| if (ref == null) { | ||
| // Timed out waiting, which implies that the timeout isn't infinite. | ||
| synchronized (AutoDisposer.class) { | ||
| if (mRegistered == 0) { | ||
| // Still idle, so exit. | ||
| if (cInstance == this) { | ||
| cInstance = null; | ||
| } | ||
| return; | ||
| } | ||
| } | ||
| continue; | ||
| } | ||
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| long removed = 1; | ||
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| while (true) { | ||
| if (ref instanceof BasicRef br) { | ||
| br.removed(); | ||
| } | ||
| ref = poll(); | ||
| if (ref == null) { | ||
| break; | ||
| } | ||
| removed++; | ||
| } | ||
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| synchronized (AutoDisposer.class) { | ||
| if ((mRegistered -= removed) == 0) { | ||
| // If still idle after one minute, then exit. | ||
| timeout = 60_000; | ||
| } else { | ||
| // Queue still has registered refs, so use an infinite timeout. There's no | ||
| // point in waking up this thread unless it has something to do. | ||
| timeout = 0; | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| public static sealed class BasicRef extends WeakReference<StubWrapper> { | ||
| private final StubInvoker mInvoker; | ||
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| public BasicRef(StubWrapper wrapper, StubInvoker invoker) { | ||
| super(wrapper, access()); | ||
| mInvoker = invoker; | ||
| } | ||
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| void removed() { | ||
| if (mInvoker.support().session() instanceof CoreSession session) { | ||
| // Note: Although the pipe isn't flushed immediately, this operation might | ||
| // still block. If it does, then no dispose messages will be sent for any | ||
| // sessions until the blocked one automatically disconnects. This can be | ||
| // prevented by running a task in a separate thread, but that would end up | ||
| // creating a new temporary object. Ideally, the task option should only be | ||
| // used when the pipe's output buffer is full. | ||
| session.stubDisposeAndNotify(mInvoker, null, false); | ||
| } | ||
| } | ||
| } | ||
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| public static final class CountedRef extends BasicRef { | ||
| private static final VarHandle cRefCountHandle; | ||
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| static { | ||
| try { | ||
| var lookup = MethodHandles.lookup(); | ||
| cRefCountHandle = lookup.findVarHandle(CountedRef.class, "mRefCount", long.class); | ||
| } catch (Throwable e) { | ||
| throw CoreUtils.rethrow(e); | ||
| } | ||
| } | ||
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| private long mRefCount; | ||
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| public CountedRef(StubWrapper wrapper, StubInvoker invoker) { | ||
| super(wrapper, invoker); | ||
| mRefCount = 1; | ||
| } | ||
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| @Override | ||
| void removed() { | ||
| decRefCount(1); | ||
| } | ||
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| public void incRefCount() { | ||
| cRefCountHandle.getAndAdd(this, 1L); | ||
| } | ||
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| /** | ||
| * Note: Calling this method might block if a notification needs to be written. | ||
| */ | ||
| public void decRefCount(long amount) { | ||
| if (((long) cRefCountHandle.getAndAdd(this, -amount)) <= amount) { | ||
| super.removed(); | ||
| } | ||
| } | ||
| } | ||
| } |
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