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    • dev.tauri.choam.internal.mcas.PaddedMemoryLocation Maven / Gradle / Ivy

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    /*
 * SPDX-License-Identifier: Apache-2.0
 * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
 *
 * 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 dev.tauri.choam.internal.mcas;

import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.lang.ref.WeakReference;

import dev.tauri.choam.internal.VarHandleHelper;

final class PaddedMemoryLocation
  extends PaddedMemoryLocationPadding
  implements MemoryLocation {

  private static final VarHandle VALUE;
  private static final VarHandle VERSION;
  private static final VarHandle MARKER;

  static {
    try {
      MethodHandles.Lookup l = MethodHandles.lookup();
      VALUE = VarHandleHelper.withInvokeExactBehavior(l.findVarHandle(PaddedMemoryLocation.class, "value", Object.class));
      VERSION = VarHandleHelper.withInvokeExactBehavior(l.findVarHandle(PaddedMemoryLocation.class, "version", long.class));
      MARKER = VarHandleHelper.withInvokeExactBehavior(l.findVarHandle(PaddedMemoryLocation.class, "marker", WeakReference.class));
    } catch (ReflectiveOperationException e) {
      throw new ExceptionInInitializerError(e);
    }
  }

  private final long _id;

  private volatile A value;

  private volatile long version = Version.Start;

  private volatile WeakReference marker; // = null

  PaddedMemoryLocation(A a, long id) {
    this.value = a;
    this._id = id;
  }

  @Override
  public final long id() {
    return this._id;
  }

  @Override
  public final int hashCode() {
    // `RefIdGen` generates IDs with
    // Fibonacci hashing, so no need
    // to hash them here even further.
    // IDs are globally unique, so the
    // default `equals` (based on object
    // identity) is fine for us.
    return (int) this.id();
  }

  @Override
  public final A unsafeGetV() {
    return this.value;
  }

  @Override
  public final A unsafeGetP() {
    return (A) VALUE.get(this);
  }

  @Override
  public final void unsafeSetV(A a) {
    this.value = a;
  }

  @Override
  public final void unsafeSetP(A a) {
    VALUE.set(this, a);
  }

  @Override
  public final boolean unsafeCasV(A ov, A nv) {
    return VALUE.compareAndSet(this, ov, nv);
  }

  @Override
  public final A unsafeCmpxchgV(A ov, A nv) {
    return (A) VALUE.compareAndExchange(this, ov, nv);
  }

  @Override
  public final A unsafeCmpxchgR(A ov, A nv) {
    return (A) VALUE.compareAndExchangeRelease(this, ov, nv);
  }

  @Override
  public final long unsafeGetVersionV() {
    return this.version;
  }

  @Override
  public final long unsafeCmpxchgVersionV(long ov, long nv) {
    return (long) VERSION.compareAndExchange(this, ov, nv);
  }

  @Override
  public final WeakReference unsafeGetMarkerV() {
    return this.marker;
  }

  @Override
  public final boolean unsafeCasMarkerV(WeakReference ov, WeakReference nv) {
    return MARKER.compareAndSet(this, ov, nv);
  }

  @Override
  public final WeakReference unsafeCmpxchgMarkerR(WeakReference ov, WeakReference nv) {
    return (WeakReference) MARKER.compareAndExchangeRelease(this, ov, nv);
  }

  public final long dummy() {
    return this.dummyImpl(42L);
  }
}
    
    
    
    

    




    
    
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