src/java.base/share/classes/jdk/internal/foreign/MappedMemorySegmentImpl.java - master - niceSOFT/openjdk21

src/java.base/share/classes/jdk/internal/foreign/MappedMemorySegmentImpl.java
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8304265: Implementation of Foreign Function and Memory API (Third Preview)
27 апр 2023, 12:00
27 апр 2023, 12:00cbccc4c
/*
 * Copyright (c) 2020, 2023, 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.  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).
 *
 * 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.internal.foreign;

import java.nio.ByteBuffer;
import jdk.internal.access.foreign.UnmapperProxy;
import jdk.internal.misc.ScopedMemoryAccess;

/**
 * Implementation for a mapped memory segments. A mapped memory segment is a native memory segment, which
 * additionally features an {@link UnmapperProxy} object. This object provides detailed information about the
 * memory mapped segment, such as the file descriptor associated with the mapping. This information is crucial
 * in order to correctly reconstruct a byte buffer object from the segment (see {@link #makeByteBuffer()}).
 */
public final class MappedMemorySegmentImpl extends NativeMemorySegmentImpl {

    private final UnmapperProxy unmapper;

    static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();

    public MappedMemorySegmentImpl(long min, UnmapperProxy unmapper, long length, boolean readOnly, MemorySessionImpl scope) {
        super(min, length, readOnly, scope);
        this.unmapper = unmapper;
    }

    @Override
    ByteBuffer makeByteBuffer() {
        return NIO_ACCESS.newMappedByteBuffer(unmapper, min, (int)length, null,
                scope == MemorySessionImpl.GLOBAL ? null : this);
    }

    @Override
    MappedMemorySegmentImpl dup(long offset, long size, boolean readOnly, MemorySessionImpl scope) {
        return new MappedMemorySegmentImpl(min + offset, unmapper, size, readOnly, scope);
    }

    // mapped segment methods

    @Override
    public MappedMemorySegmentImpl asSlice(long offset, long newSize) {
        return (MappedMemorySegmentImpl)super.asSlice(offset, newSize);
    }

    @Override
    public boolean isMapped() {
        return true;
    }

    // support for mapped segments

    public void load() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.load(sessionImpl(), min, unmapper.isSync(), length);
        }
    }

    public void unload() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.unload(sessionImpl(), min, unmapper.isSync(), length);
        }
    }

    public boolean isLoaded() {
        return unmapper == null || SCOPED_MEMORY_ACCESS.isLoaded(sessionImpl(), min, unmapper.isSync(), length);
    }

    public void force() {
        if (unmapper != null) {
            SCOPED_MEMORY_ACCESS.force(sessionImpl(), unmapper.fileDescriptor(), min, unmapper.isSync(), 0, length);
        }
    }

}