492977d9be
Motivation: Sometimes, we wish to operate on both buffers and anything that can produce a buffer. For instance, when making a composite buffer, we could compose either buffers or sends. Modification: Introduce a Deref interface, which is extended by both Rc and Send. A Deref can be used to acquire an Rc instance, and in doing so will also acquire a reference to the Rc. That is, dereferencing increases the reference count. For Rc itself, this just delegates to Rc.acquire, while for Send it delegates to Send.receive, and can only be called once. The Allocator.compose method has been changed to take Derefs. This allows us to compose either Bufs or Sends of bufs. Or a mix. Extra care and caution has been added to the code, to make sure the reference counts are managed correctly when composing buffers, now that it's a more complicated operation. A handful of convenience methods for working with Sends have also been added to the Send interface. Result: We can now build a composite buffer out of sends of buffers.
71 lines
2.2 KiB
Java
71 lines
2.2 KiB
Java
/*
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* Copyright 2020 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.buffer.api;
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import java.lang.invoke.VarHandle;
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import static io.netty.buffer.api.Statics.findVarHandle;
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import static java.lang.invoke.MethodHandles.lookup;
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class TransferSend<I extends Rc<I>, T extends Rc<I>> implements Send<I> {
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private static final VarHandle RECEIVED = findVarHandle(lookup(), TransferSend.class, "received", boolean.class);
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private final Owned<T> outgoing;
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private final Drop<T> drop;
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private final Class<?> concreteType;
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@SuppressWarnings("unused")
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private volatile boolean received; // Accessed via VarHandle
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TransferSend(Owned<T> outgoing, Drop<T> drop, Class<?> concreteType) {
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this.outgoing = outgoing;
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this.drop = drop;
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this.concreteType = concreteType;
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}
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@SuppressWarnings("unchecked")
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@Override
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public I receive() {
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gateReception();
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var copy = outgoing.transferOwnership(drop);
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drop.attach(copy);
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return (I) copy;
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}
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Owned<T> unsafeUnwrapOwned() {
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gateReception();
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return outgoing;
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}
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private void gateReception() {
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if ((boolean) RECEIVED.getAndSet(this, true)) {
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throw new IllegalStateException("This object has already been received.");
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}
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}
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@Override
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public boolean isInstanceOf(Class<?> cls) {
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return cls.isAssignableFrom(concreteType);
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}
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@Override
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public void discard() {
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if (!(boolean) RECEIVED.getAndSet(this, true)) {
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var copy = outgoing.transferOwnership(drop);
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drop.attach(copy);
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copy.close();
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}
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}
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}
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