150 lines
5.6 KiB
Java
150 lines
5.6 KiB
Java
/*
|
|
* Copyright 2021 The Netty Project
|
|
*
|
|
* The Netty Project licenses this file to you 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.
|
|
*/
|
|
package io.net5.buffer.api;
|
|
|
|
import io.net5.buffer.api.internal.ResourceSupport;
|
|
import io.net5.buffer.api.internal.Statics;
|
|
|
|
import java.lang.invoke.VarHandle;
|
|
import java.util.Objects;
|
|
|
|
import static java.lang.invoke.MethodHandles.lookup;
|
|
|
|
/**
|
|
* The {@link BufferHolder} is an abstract class that simplifies the implementation of objects that themselves contain
|
|
* a {@link Buffer} instance.
|
|
* <p>
|
|
* The {@link BufferHolder} can only hold on to a single buffer, so objects and classes that need to hold on to multiple
|
|
* buffers will have to do their implementation from scratch, though they can use the code of the {@link BufferHolder}
|
|
* as inspiration. Alternatively, multiple buffers can be
|
|
* {@linkplain CompositeBuffer#compose(BufferAllocator, Send[]) composed} into a single buffer, which can then be put
|
|
* in a buffer holder.
|
|
* <p>
|
|
* If you just want an object that is a reference to a buffer, then the {@link BufferRef} can be used for that purpose.
|
|
* If you have an advanced use case where you wish to implement {@link Resource}, and tightly control lifetimes, then
|
|
* {@link ResourceSupport} can be of help.
|
|
*
|
|
* @param <T> The concrete {@link BufferHolder} type.
|
|
*/
|
|
public abstract class BufferHolder<T extends BufferHolder<T>> implements Resource<T> {
|
|
private static final VarHandle BUF = Statics.findVarHandle(lookup(), BufferHolder.class, "buf", Buffer.class);
|
|
private Buffer buf;
|
|
|
|
/**
|
|
* Create a new {@link BufferHolder} to hold the given {@linkplain Buffer buffer}.
|
|
*
|
|
* @param buf The {@linkplain Buffer buffer} to be held by this holder.
|
|
*/
|
|
protected BufferHolder(Buffer buf) {
|
|
this.buf = Objects.requireNonNull(buf, "The buffer cannot be null.");
|
|
}
|
|
|
|
/**
|
|
* Create a new {@link BufferHolder} to hold the {@linkplain Buffer buffer} received from the given {@link Send}.
|
|
* <p>
|
|
* The {@link BufferHolder} will then be holding exclusive ownership of the buffer.
|
|
*
|
|
* @param send The {@linkplain Buffer buffer} to be held by this holder.
|
|
*/
|
|
protected BufferHolder(Send<Buffer> send) {
|
|
buf = Objects.requireNonNull(send, "The Send-object cannot be null.").receive();
|
|
}
|
|
|
|
@Override
|
|
public void close() {
|
|
buf.close();
|
|
}
|
|
|
|
@SuppressWarnings("unchecked")
|
|
@Override
|
|
public Send<T> send() {
|
|
return buf.send().map((Class<T>) getClass(), this::receive);
|
|
}
|
|
|
|
/**
|
|
* Called when a {@linkplain #send() sent} {@link BufferHolder} is received by the recipient.
|
|
* The {@link BufferHolder} should return a new concrete instance, that wraps the given {@link Buffer} object.
|
|
*
|
|
* @param buf The {@link Buffer} that is {@linkplain Send#receive() received} by the recipient,
|
|
* and needs to be wrapped in a new {@link BufferHolder} instance.
|
|
* @return A new {@linkplain T buffer holder} instance, containing the given {@linkplain Buffer buffer}.
|
|
*/
|
|
protected abstract T receive(Buffer buf);
|
|
|
|
/**
|
|
* Replace the underlying referenced buffer with the given buffer.
|
|
* <p>
|
|
* This method is protected to permit advanced use cases of {@link BufferHolder} sub-class implementations.
|
|
* <p>
|
|
* <strong>Note:</strong> This method closes the current buffer,
|
|
* and takes exclusive ownership of the received buffer.
|
|
* <p>
|
|
* The buffer assignment is performed using a plain store.
|
|
*
|
|
* @param send The new {@link Buffer} instance that is replacing the currently held buffer.
|
|
*/
|
|
protected final void replaceBuffer(Send<Buffer> send) {
|
|
Buffer received = send.receive();
|
|
buf.close();
|
|
buf = received;
|
|
}
|
|
|
|
/**
|
|
* Replace the underlying referenced buffer with the given buffer.
|
|
* <p>
|
|
* This method is protected to permit advanced use cases of {@link BufferHolder} sub-class implementations.
|
|
* <p>
|
|
* <strong>Note:</strong> this method closes the current buffer,
|
|
* and takes exclusive ownership of the received buffer.
|
|
* <p>
|
|
* The buffer assignment is performed using a volatile store.
|
|
*
|
|
* @param send The {@link Send} with the new {@link Buffer} instance that is replacing the currently held buffer.
|
|
*/
|
|
protected final void replaceBufferVolatile(Send<Buffer> send) {
|
|
Buffer received = send.receive();
|
|
var prev = (Buffer) BUF.getAndSet(this, received);
|
|
prev.close();
|
|
}
|
|
|
|
/**
|
|
* Access the held {@link Buffer} instance.
|
|
* <p>
|
|
* The access is performed using a plain load.
|
|
*
|
|
* @return The {@link Buffer} instance being held by this {@linkplain T buffer holder}.
|
|
*/
|
|
protected final Buffer getBuffer() {
|
|
return buf;
|
|
}
|
|
|
|
/**
|
|
* Access the held {@link Buffer} instance.
|
|
* <p>
|
|
* The access is performed using a volatile load.
|
|
*
|
|
* @return The {@link Buffer} instance being held by this {@linkplain T buffer holder}.
|
|
*/
|
|
protected final Buffer getBufferVolatile() {
|
|
return (Buffer) BUF.getVolatile(this);
|
|
}
|
|
|
|
@Override
|
|
public boolean isAccessible() {
|
|
return buf.isAccessible();
|
|
}
|
|
}
|