netty-incubator-buffer-api/src/main/java/io/netty/buffer/api/MemoryManagers.java
Chris Vest 95709828bf Add a ByteBuffer based implementation of Buffer
Motivation:
We need a new implementation of our new API that supports Java 11, since that is what Netty 5 will most likely baseline on.
We also need an implementation that does not rely on Unsafe.
This leaves us with ByteBuffer as the underlying currency of memory.

Modification:
- Add a NioBuffer implementation and associated supporting classes.
- The entry-point for this is a new MemoryManagers API, which is used to pick the implementation and provide the on-/off-heap MemoryManager implementations.
- Add a mechanism to configure/override which MemoryManagers implementation to use.
- The MemoryManagers implementations are service-loadable, so new ones can be discovered at runtime.
- The existing MemorySegment based implementation also get a MemoryManagers implementation.
- Expand the BufferTest to include all combinations of all implementations. We now run 360.000 tests in BufferTest.
- Some common infrastructure, like ArcDrop, is moved to its own package.
- Add a module-info.java to control the service loading, and the visibility in the various packages.
- Some pom.xml file updates to support our now module based project.

Result:
We have an implementation that should work on Java 11, but we currently don't build or test on 11.
More work needs to happen before that is a reality.
2021-03-18 15:18:22 +01:00

76 lines
2.7 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.netty.buffer.api;
import java.util.ServiceLoader;
import java.util.function.Supplier;
import java.util.stream.Stream;
/**
* The MemoryManagers interface is the handle through which {@link BufferAllocator buffer allocators} access the low
* level memory management APIs.
* <p>
* This is hidden behind this interface in order to make allocation and pool agnostic and reusable across buffer and
* memory implementations.
*/
public interface MemoryManagers {
/**
* Get the default, or currently configured, memory managers instance.
* @return A MemoryManagers instance.
*/
static MemoryManagers getManagers() {
return MemoryManagersOverride.getManagers();
}
/**
* Temporarily override the default configured memory managers instance.
* <p>
* Calls to {@link #getManagers()} from within the given supplier will get the given managers instance.
*
* @param managers Override the default configured managers instance with this instance.
* @param supplier The supplier function to be called while the override is in place.
* @param <T> The result type from the supplier.
* @return The result from the supplier.
*/
static <T> T using(MemoryManagers managers, Supplier<T> supplier) {
return MemoryManagersOverride.using(managers, supplier);
}
/**
* Get a lazy-loading stream of all available memory managers.
*
* @return A stream of providers of memory managers instances.
*/
static Stream<ServiceLoader.Provider<MemoryManagers>> getAllManagers() {
var loader = ServiceLoader.load(MemoryManagers.class);
return loader.stream();
}
/**
* Get a {@link MemoryManager} instance that is suitable for allocating on-heap {@link Buffer} instances.
*
* @return An on-heap {@link MemoryManager}.
*/
MemoryManager getHeapMemoryManager();
/**
* Get a {@link MemoryManager} instance that is suitable for allocating off-heap {@link Buffer} instances.
*
* @return An off-heap {@link MemoryManager}.
*/
MemoryManager getNativeMemoryManager();
}