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

src/java.base/share/classes/jdk/internal/foreign/SlicingAllocator.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) 2021, 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.lang.foreign.MemorySegment;
import java.lang.foreign.SegmentAllocator;

public final class SlicingAllocator implements SegmentAllocator {

    private final MemorySegment segment;
    private final long maxAlign;

    private long sp = 0L;

    public SlicingAllocator(MemorySegment segment) {
        this.segment = segment;
        this.maxAlign = ((AbstractMemorySegmentImpl)segment).maxAlignMask();
    }

    MemorySegment trySlice(long byteSize, long byteAlignment) {
        long min = segment.address();
        long start = Utils.alignUp(min + sp, byteAlignment) - min;
        MemorySegment slice = segment.asSlice(start, byteSize, byteAlignment);
        sp = start + byteSize;
        return slice;
    }

    @Override
    public MemorySegment allocate(long byteSize, long byteAlignment) {
        Utils.checkAllocationSizeAndAlign(byteSize, byteAlignment);
        // try to slice from current segment first...
        return trySlice(byteSize, byteAlignment);
    }
}