/*

 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * 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).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.vm.ci.hotspot;

import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime;

import java.io.ByteArrayOutputStream;

import java.io.PrintStream;

import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.Option;

import jdk.vm.ci.meta.JavaConstant;

/**

 * Encapsulates a JNI reference to an object in the HotSpot heap.

 *

 * {@link IndirectHotSpotObjectConstantImpl} objects are only allocated in the shared library heap.

 *

 * @see HotSpotObjectConstantScope

 */

final class IndirectHotSpotObjectConstantImpl extends HotSpotObjectConstantImpl {

    /**

     * An object handle in {@code JVMCI::_object_handles}.

     */

    private long objectHandle;

    /**

     * Lazily computed hash code.

     */

    private int hashCode;

    final IndirectHotSpotObjectConstantImpl base;

    private static class Audit {

        final Object scope;

        final long handle;

        final Throwable origin;

        Audit(Object scope, long handle, Throwable origin) {

            this.scope = scope;

            this.handle = handle;

            this.origin = origin;

        }

    }

    /**

     * Details useful to audit a scoped handle used after its creating scope closes. Set to an

     * {@link Audit} object if {@link HotSpotJVMCIRuntime.Option#AuditHandles} is true otherwise to

     * {@link HotSpotObjectConstantScope#localScopeDescription}.

     */

    private Object rawAudit;

    @SuppressWarnings("serial")

    @VMEntryPoint

    private IndirectHotSpotObjectConstantImpl(long objectHandle, boolean compressed, boolean skipRegister) {

        super(compressed);

        assert objectHandle != 0 && UnsafeAccess.UNSAFE.getLong(objectHandle) != 0;

        this.objectHandle = objectHandle;

        this.base = null;

        if (!skipRegister) {

            HotSpotObjectConstantScope scope = HotSpotObjectConstantScope.CURRENT.get();

            if (scope != null && !scope.isGlobal()) {

                scope.add(this);

                if (HotSpotJVMCIRuntime.Option.AuditHandles.getBoolean()) {

                    rawAudit = new Audit(scope.localScopeDescription, objectHandle, new Throwable() {

                        @Override

                        public String toString() {

                            return "Created " + objectHandle;

                        }

                    });

                }

            } else {

                HandleCleaner.create(this, objectHandle);

            }

        }

    }

    private IndirectHotSpotObjectConstantImpl(IndirectHotSpotObjectConstantImpl base, boolean compressed) {

        super(compressed);

        // This is a variant of an original object that only varies in compress vs uncompressed.

        // Instead of creating a new handle, reference that object and objectHandle.

        this.objectHandle = base.getHandle();

        // There should only be one level of indirection to the base object.

        assert base.base == null || base.base.base == null;

        this.base = base.base != null ? base.base : base;

    }

    long getHandle() {

        checkHandle();

        return objectHandle;

    }

    private void checkHandle() {

        if (objectHandle == 0L) {

            String message;

            if (rawAudit instanceof Audit) {

                Audit audit = (Audit) rawAudit;

                ByteArrayOutputStream baos = new ByteArrayOutputStream();

                PrintStream ps = new PrintStream(baos);

                ps.println("Foreign object reference " + audit.handle + " created in scope '" + audit.scope + "' is no longer valid. Origin: {");

                audit.origin.printStackTrace(ps);

                ps.print('}');

                ps.flush();

                message = baos.toString();

            } else {

                message = "Foreign object reference created in scope '" + rawAudit + "' is no longer valid. " +

                                "Set property " + Option.AuditHandles.getPropertyName() + "=true to show origin of invalid foreign references.";

            }

            throw new NullPointerException(message);

        }

    }

    boolean isValid() {

        return objectHandle != 0L;

    }

    @Override

    public HotSpotResolvedObjectType getType() {

        checkHandle();

        return super.getType();

    }

    /**

     * Clears the foreign object reference.

     */

    void clear(Object scopeDescription) {

        checkHandle();

        CompilerToVM.compilerToVM().deleteGlobalHandle(objectHandle);

        if (rawAudit == null) {

            rawAudit = scopeDescription;

        }

        objectHandle = 0L;

    }

    @Override

    public JavaConstant compress() {

        assert !compressed;

        return new IndirectHotSpotObjectConstantImpl(this, true);

    }

    @Override

    public JavaConstant uncompress() {

        assert compressed;

        return new IndirectHotSpotObjectConstantImpl(this, false);

    }

    @Override

    public int getIdentityHashCode() {

        checkHandle();

        int hash = hashCode;

        if (hash == 0) {

            hash = runtime().compilerToVm.getIdentityHashCode(this);

            if (hash == 0) {

                hash = 31;

            }

            hashCode = hash;

        }

        return hash;

    }

}