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.
53 lines
2.1 KiB
Java
53 lines
2.1 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.util.function.Supplier;
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/**
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* A Deref provides the capability to acquire a reference to a {@linkplain Rc reference counted} object.
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* <p>
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* <strong>Note:</strong> Callers must ensure that they close any references they obtain.
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* <p>
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* Deref itself does not specify if a reference can be obtained more than once.
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* For instance, any {@link Send} object is also a {@code Deref}, but the reference can only be acquired once.
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* Meanwhile, {@link Rc} objects are themselves their own {@code Derefs}, and permit references to be acquired multiple
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* times.
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*
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* @param <T> The concrete type of reference counted object that can be obtained.
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*/
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public interface Deref<T extends Rc<T>> extends Supplier<T> {
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/**
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* Acquire a reference to the reference counted object.
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* <p>
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* <strong>Note:</strong> This call increments the reference count of the acquired object, and must be paired with
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* a {@link Rc#close()} call.
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* Using a try-with-resources clause is the easiest way to ensure this.
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*
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* @return A reference to the reference counted object.
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*/
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@Override
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T get();
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/**
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* Determine if the object in this {@code Deref} is an instance of the given class.
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*
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* @param cls The type to check.
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* @return {@code true} if the object in this {@code Deref} can be assigned fields or variables of the given type.
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*/
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boolean isInstanceOf(Class<?> cls);
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}
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