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/***** BEGIN LICENSE BLOCK *****
 * Version: EPL 1.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/epl-v10.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2011 Wayne Meissner
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
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 * decision by deleting the provisions above and replace them with the notice
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package org.jruby.ext.ffi.jffi;

import com.kenai.jffi.PageManager;
import org.jruby.Ruby;
import org.jruby.ext.ffi.MemoryIO;
import org.jruby.util.PhantomReferenceReaper;

import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

final class TransientNativeMemoryIO extends BoundedNativeMemoryIO {
    /** Keeps strong references to the memory bucket until cleanup */
    private static final Map referenceSet = new ConcurrentHashMap();
    private static final ThreadLocal> currentMagazine = new ThreadLocal>();
    private static final int PAGES_PER_MAGAZINE = 1;
    private final Object sentinel;

    /**
     * Allocates native memory, aligned to a minimum boundary.
     *
     * @param runtime The Ruby runtime
     * @param size The number of bytes to allocate
     * @param align The minimum alignment of the memory
     * @param clear Whether the memory should be cleared (zeroed)
     * @return A new {@link org.jruby.ext.ffi.AllocatedDirectMemoryIO}
     */
    static MemoryIO allocateAligned(Ruby runtime, int size, int align, boolean clear) {
        if (size > 1024) {
            return AllocatedNativeMemoryIO.allocateAligned(runtime, size, align, clear);
        }

        Reference magazineReference = currentMagazine.get();
        Magazine magazine = magazineReference != null ? magazineReference.get() : null;
        Object sentinel = magazine != null ? magazine.sentinel() : null;
        long address;

        if (sentinel == null || (address = magazine.allocate(size, align)) == 0) {
            PageManager pm = PageManager.getInstance();
            long memory;
            int pageCount = PAGES_PER_MAGAZINE;
            do {
                memory = pm.allocatePages(pageCount, PageManager.PROT_READ | PageManager.PROT_WRITE);
                if (memory != 0L && memory != -1L) {
                    break;
                }

                // No available pages; trigger a full GC to reclaim some memory
                System.gc();
            } while (true);

            referenceSet.put(magazine = new Magazine(sentinel = new Object(), pm, memory, pageCount), Boolean.TRUE);
            currentMagazine.set(new SoftReference(magazine));
            address = magazine.allocate(size, align);
        }
        

        return new TransientNativeMemoryIO(runtime, sentinel, address, size);
    }

    private TransientNativeMemoryIO(Ruby runtime, Object sentinel, long address, int size) {
        super(runtime, address, size);
        this.sentinel = sentinel;
    }
    
    private static long align(long offset, long align) {
        return (offset + align - 1L) & ~(align - 1L);
    }

    /**
     * Holder for a group of memory allocations.
     */
    private static final class Magazine extends PhantomReferenceReaper