org.lmdbjava.ByteBufferProxy Maven / Gradle / Ivy
/*-
* #%L
* LmdbJava
* %%
* Copyright (C) 2016 The LmdbJava Open Source Project
* %%
* 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.
* #L%
*/
package org.lmdbjava;
import static java.lang.ThreadLocal.withInitial;
import java.lang.reflect.Field;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import static java.nio.ByteBuffer.allocateDirect;
import java.util.ArrayDeque;
import jnr.ffi.Pointer;
import static org.lmdbjava.Env.SHOULD_CHECK;
import static org.lmdbjava.UnsafeAccess.UNSAFE;
/**
* {@link ByteBuffer}-based proxy.
*
*
* There are two concrete {@link ByteBuffer} proxy implementations available:
*
* - A "fast" implementation: {@link UnsafeProxy}
* - A "safe" implementation: {@link ReflectiveProxy}
*
*
*
* Users nominate which implementation they prefer by referencing the
* {@link #PROXY_OPTIMAL} or {@link #PROXY_SAFE} field when invoking
* {@link Env#create(org.lmdbjava.BufferProxy)}.
*/
public final class ByteBufferProxy {
/**
* The fastest {@link ByteBuffer} proxy that is available on this platform.
* This will always be the same instance as {@link #PROXY_SAFE} if the
* {@link UnsafeAccess#DISABLE_UNSAFE_PROP} has been set to true
* and/or {@link UnsafeAccess} is unavailable. Guaranteed to never be null.
*/
public static final BufferProxy PROXY_OPTIMAL;
/**
* The safe, reflective {@link ByteBuffer} proxy for this system. Guaranteed
* to never be null.
*/
public static final BufferProxy PROXY_SAFE;
static {
PROXY_SAFE = new ReflectiveProxy();
PROXY_OPTIMAL = getProxyOptimal();
}
private ByteBufferProxy() {
}
private static BufferProxy getProxyOptimal() {
try {
return new UnsafeProxy();
} catch (final RuntimeException e) { // NOPMD
return PROXY_SAFE;
}
}
/**
* The buffer must be a direct buffer (not heap allocated).
*/
public static final class BufferMustBeDirectException extends LmdbException {
private static final long serialVersionUID = 1L;
/**
* Creates a new instance.
*/
public BufferMustBeDirectException() {
super("The buffer must be a direct buffer (not heap allocated");
}
}
/**
* Provides {@link ByteBuffer} pooling and address resolution for concrete
* {@link BufferProxy} implementations.
*/
abstract static class AbstractByteBufferProxy extends BufferProxy {
protected static final String FIELD_NAME_ADDRESS = "address";
protected static final String FIELD_NAME_CAPACITY = "capacity";
/**
* A thread-safe pool for a given length. If the buffer found is valid (ie
* not of a negative length) then that buffer is used. If no valid buffer is
* found, a new buffer is created.
*/
private static final ThreadLocal> BUFFERS
= withInitial(() -> new ArrayDeque<>(16));
static Field findField(final Class c, final String name) {
Class clazz = c;
do {
try {
final Field field = clazz.getDeclaredField(name);
field.setAccessible(true);
return field;
} catch (final NoSuchFieldException e) {
clazz = clazz.getSuperclass();
}
} while (clazz != null);
throw new LmdbException(name + " not found");
}
protected final long address(final ByteBuffer buffer) {
if (SHOULD_CHECK && !buffer.isDirect()) {
throw new BufferMustBeDirectException();
}
return ((sun.nio.ch.DirectBuffer) buffer).address() + buffer.position();
}
@Override
protected final ByteBuffer allocate() {
final ArrayDeque queue = BUFFERS.get();
final ByteBuffer buffer = queue.poll();
if (buffer != null && buffer.capacity() >= 0) {
return buffer;
} else {
return allocateDirect(0);
}
}
@Override
protected final void deallocate(final ByteBuffer buff) {
final ArrayDeque queue = BUFFERS.get();
queue.offer(buff);
}
}
/**
* A proxy that uses Java reflection to modify byte buffer fields, and
* official JNR-FFF methods to manipulate native pointers.
*/
private static final class ReflectiveProxy extends AbstractByteBufferProxy {
private static final Field ADDRESS_FIELD;
private static final Field CAPACITY_FIELD;
static {
ADDRESS_FIELD = findField(Buffer.class, FIELD_NAME_ADDRESS);
CAPACITY_FIELD = findField(Buffer.class, FIELD_NAME_CAPACITY);
}
@Override
protected void in(final ByteBuffer buffer, final Pointer ptr,
final long ptrAddr) {
ptr.putLong(STRUCT_FIELD_OFFSET_DATA, address(buffer));
ptr.putLong(STRUCT_FIELD_OFFSET_SIZE, buffer.remaining());
}
@Override
protected void in(final ByteBuffer buffer, final int size, final Pointer ptr,
final long ptrAddr) {
ptr.putLong(STRUCT_FIELD_OFFSET_SIZE, size);
ptr.putLong(STRUCT_FIELD_OFFSET_DATA, address(buffer));
}
@Override
protected void out(final ByteBuffer buffer, final Pointer ptr,
final long ptrAddr) {
final long addr = ptr.getLong(STRUCT_FIELD_OFFSET_DATA);
final long size = ptr.getLong(STRUCT_FIELD_OFFSET_SIZE);
try {
ADDRESS_FIELD.set(buffer, addr);
CAPACITY_FIELD.set(buffer, (int) size);
} catch (final IllegalArgumentException | IllegalAccessException e) {
throw new LmdbException("Cannot modify buffer", e);
}
buffer.clear();
}
}
/**
* A proxy that uses Java's "unsafe" class to directly manipulate byte buffer
* fields and JNR-FFF allocated memory pointers.
*/
private static final class UnsafeProxy extends AbstractByteBufferProxy {
private static final long ADDRESS_OFFSET;
private static final long CAPACITY_OFFSET;
static {
try {
final Field address = findField(Buffer.class, FIELD_NAME_ADDRESS);
final Field capacity = findField(Buffer.class, FIELD_NAME_CAPACITY);
ADDRESS_OFFSET = UNSAFE.objectFieldOffset(address);
CAPACITY_OFFSET = UNSAFE.objectFieldOffset(capacity);
} catch (final SecurityException e) {
throw new LmdbException("Field access error", e);
}
}
@Override
protected void in(final ByteBuffer buffer, final Pointer ptr,
final long ptrAddr) {
UNSAFE.putLong(ptrAddr + STRUCT_FIELD_OFFSET_SIZE, buffer.remaining());
UNSAFE.putLong(ptrAddr + STRUCT_FIELD_OFFSET_DATA, address(buffer));
}
@Override
protected void in(final ByteBuffer buffer, final int size, final Pointer ptr,
final long ptrAddr) {
UNSAFE.putLong(ptrAddr + STRUCT_FIELD_OFFSET_SIZE, size);
UNSAFE.putLong(ptrAddr + STRUCT_FIELD_OFFSET_DATA, address(buffer));
}
@Override
protected void out(final ByteBuffer buffer, final Pointer ptr,
final long ptrAddr) {
final long addr = UNSAFE.getLong(ptrAddr + STRUCT_FIELD_OFFSET_DATA);
final long size = UNSAFE.getLong(ptrAddr + STRUCT_FIELD_OFFSET_SIZE);
UNSAFE.putLong(buffer, ADDRESS_OFFSET, addr);
UNSAFE.putInt(buffer, CAPACITY_OFFSET, (int) size);
buffer.clear();
}
}
}