io.atomix.catalyst.buffer.util.MappedMemoryAllocator Maven / Gradle / Ivy
/*
* Copyright 2015 the original author or authors.
*
* 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
*
* http://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.atomix.catalyst.buffer.util;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Mapped memory allocator.
*
* The mapped memory allocator provides direct memory access to memory mapped from a file on disk. The mapped allocator
* supports allocating memory in any {@link java.nio.channels.FileChannel.MapMode}. Once the file is mapped and the
* memory has been allocated, the mapped allocator provides the memory address of the underlying
* {@link java.nio.MappedByteBuffer} for access via {@link sun.misc.Unsafe}.
*
* @author Jordan Halterman
*/
public class MappedMemoryAllocator implements MemoryAllocator {
public static final FileChannel.MapMode DEFAULT_MAP_MODE = FileChannel.MapMode.READ_WRITE;
private final AtomicInteger referenceCount = new AtomicInteger();
private final RandomAccessFile file;
private final FileChannel channel;
private final FileChannel.MapMode mode;
private final long offset;
public MappedMemoryAllocator(File file) {
this(file, DEFAULT_MAP_MODE, 0);
}
public MappedMemoryAllocator(File file, FileChannel.MapMode mode) {
this(file, mode, 0);
}
public MappedMemoryAllocator(File file, FileChannel.MapMode mode, long offset) {
this(createFile(file, mode), mode, offset);
}
public MappedMemoryAllocator(RandomAccessFile file, FileChannel.MapMode mode, long offset) {
if (file == null)
throw new NullPointerException("file cannot be null");
if (mode == null)
throw new NullPointerException("mode cannot be null");
if (offset < 0)
throw new IllegalArgumentException("offset cannot be negative");
this.file = file;
this.channel = this.file.getChannel();
this.mode = mode;
this.offset = offset;
}
private static RandomAccessFile createFile(File file, FileChannel.MapMode mode) {
if (file == null)
throw new NullPointerException("file cannot be null");
if (mode == null)
mode = DEFAULT_MAP_MODE;
try {
return new RandomAccessFile(file, parseMode(mode));
} catch (IOException e) {
throw new RuntimeException(e);
}
}
private static String parseMode(FileChannel.MapMode mode) {
if (mode == FileChannel.MapMode.READ_ONLY) {
return "r";
} else if (mode == FileChannel.MapMode.READ_WRITE) {
return "rw";
}
throw new IllegalArgumentException("unsupported map mode");
}
@Override
public MappedMemory allocate(long size) {
if (size > MappedMemory.MAX_SIZE)
throw new IllegalArgumentException("mapped memory size cannot be greater than " + MappedMemory.MAX_SIZE);
try {
if (file.length() < size)
file.setLength(size);
referenceCount.incrementAndGet();
return new MappedMemory(channel.map(mode, offset, size), this);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
@Override
public MappedMemory reallocate(MappedMemory memory, long size) {
MappedMemory newMemory = allocate(size);
memory.free();
return newMemory;
}
/**
* Releases a reference from the allocator.
*/
void release() {
if (referenceCount.decrementAndGet() == 0) {
try {
file.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
}