Add AbstractRegistration.notClosed()

[yangtools.git] / common / concepts / src / main / java / org / opendaylight / yangtools / concepts / AbstractRegistration.java

diff --git a/common/concepts/src/main/java/org/opendaylight/yangtools/concepts/AbstractRegistration.java b/common/concepts/src/main/java/org/opendaylight/yangtools/concepts/AbstractRegistration.java
index c07b38b3ff7515ba064ff63d1701e537616b4a11..ae2677b0e2b5d363fe7c578dde448579907cfe2e 100644 (file)
--- a/common/concepts/src/main/java/org/opendaylight/yangtools/concepts/AbstractRegistration.java
+++ b/common/concepts/src/main/java/org/opendaylight/yangtools/concepts/AbstractRegistration.java
@@ -7,40 +7,69 @@
  */
 package org.opendaylight.yangtools.concepts;
 
-import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
+import com.google.common.base.MoreObjects;
+import com.google.common.base.MoreObjects.ToStringHelper;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
 
 /**
- * Utility registration handle. It is a convenience for register-style method
- * which can return an AutoCloseable realized by a subclass of this class.
- * Invoking the close() method triggers unregistration of the state the method
- * installed.
+ * Utility registration handle. It is a convenience for register-style method which can return an AutoCloseable realized
+ * by a subclass of this class. Invoking the close() method triggers unregistration of the state the method installed.
  */
-public abstract class AbstractRegistration implements AutoCloseable {
-    private static final AtomicIntegerFieldUpdater<AbstractRegistration> CLOSED_UPDATER =
-            AtomicIntegerFieldUpdater.newUpdater(AbstractRegistration.class, "closed");
-    private volatile int closed = 0;
+public abstract class AbstractRegistration implements Registration {
+    private static final VarHandle CLOSED;
+
+    // All access needs to go through this handle
+    @SuppressWarnings("unused")
+    private volatile byte closed;
+
+    static {
+        try {
+            CLOSED = MethodHandles.lookup().findVarHandle(AbstractRegistration.class, "closed", byte.class);
+        } catch (ReflectiveOperationException e) {
+            throw new ExceptionInInitializerError(e);
+        }
+    }
 
     /**
-     * Remove the state referenced by this registration. This method is
-     * guaranteed to be called at most once. The referenced state must be
-     * retained until this method is invoked.
+     * Remove the state referenced by this registration. This method is guaranteed to be called at most once.
+     * Referenced state must be retained until this method is invoked.
      */
     protected abstract void removeRegistration();
 
     /**
-     * Query the state of this registration. Returns true if it was
-     * closed.
+     * Query the state of this registration. Returns true if it was closed. Equivalent of {@code !notClosed()}.
      *
      * @return true if the registration was closed, false otherwise.
      */
-    protected final boolean isClosed() {
-        return closed != 0;
+    public final boolean isClosed() {
+        return (byte) CLOSED.getAcquire(this) != 0;
+    }
+
+    /**
+     * Query the state of this registration. Returns false if it was closed. Equivalent of {@code !isClosed()}.
+     *
+     * @return false if the registration was closed, true otherwise.
+     */
+    public final boolean notClosed() {
+        return (byte) CLOSED.getAcquire(this) == 0;
     }
 
     @Override
     public final void close() {
-        if (CLOSED_UPDATER.compareAndSet(this, 0, 1)) {
+        // We want full setVolatile() memory semantics here, as all state before calling this method
+        // needs to be visible
+        if (CLOSED.compareAndSet(this, (byte) 0, (byte) 1)) {
             removeRegistration();
         }
     }
+
+    @Override
+    public final String toString() {
+        return addToStringAttributes(MoreObjects.toStringHelper(this).omitNullValues()).toString();
+    }
+
+    protected ToStringHelper addToStringAttributes(final ToStringHelper toStringHelper) {
+        return toStringHelper.add("closed", isClosed());
+    }
 }