src/java.base/share/classes/jdk/internal/foreign/GlobalSession.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package jdk.internal.foreign;

import jdk.internal.vm.annotation.ForceInline;

import java.util.Objects;

/**
 * The global, non-closeable, shared session. Similar to a shared session, but its {@link #close()} method throws unconditionally.
 * Adding new resources to the global session, does nothing: as the session can never become not-alive, there is nothing to track.
 * Acquiring and or releasing a memory session similarly does nothing.
 */
non-sealed class GlobalSession extends MemorySessionImpl {

    public GlobalSession() {
        super(null, null);
        this.state = NONCLOSEABLE;
    }

    @Override
    @ForceInline
    public void release0() {
        // do nothing
    }

    @Override
    @ForceInline
    public void acquire0() {
        // do nothing
    }

    @Override
    void addInternal(ResourceList.ResourceCleanup resource) {
        // do nothing
    }

    @Override
    public void justClose() {
        throw nonCloseable();
    }

    /**
     * This is a global session that wraps a heap object. Possible objects are: Java arrays, buffers and
     * class loaders. Objects of two heap sessions are compared by identity. That is, if the wrapped object is the same,
     * then the resulting heap sessions are also considered equals. We do not compare the objects using
     * {@link Object#equals(Object)}, as that would be problematic when comparing buffers, whose equality and
     * hash codes are content-dependent.
     */
    static class HeapSession extends GlobalSession {

        final Object ref;

        public HeapSession(Object ref) {
            super();
            this.ref = Objects.requireNonNull(ref);
        }

        @Override
        public boolean equals(Object obj) {
            return obj instanceof HeapSession session &&
                    ref == session.ref;
        }

        @Override
        public int hashCode() {
            return System.identityHashCode(ref);
        }
    }
}