JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2005, 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 com.sun.xml.internal.stream.util;

import java.lang.ref.*;

/**
 * Buffer allocator for buffers of sizes 128 B, 2 KB and 8 KB. Includes
 * methods for allocating and freeing buffers.
 *
 * @author Binu John
 * @author Santiago PericasGeertsen
 */
public class BufferAllocator {
    private static final int SMALL_SIZE_LIMIT = 128;
    private static final int MEDIUM_SIZE_LIMIT = 2048;
    private static final int LARGE_SIZE_LIMIT = 8192;

    char[] smallCharBuffer;
    char[] mediumCharBuffer;
    char[] largeCharBuffer;

    byte[] smallByteBuffer;
    byte[] mediumByteBuffer;
    byte[] largeByteBuffer;

    public BufferAllocator() {
    }

    public char[] getCharBuffer(int size) {
        if (size <= SMALL_SIZE_LIMIT) {
            char[] buffer = smallCharBuffer;
            smallCharBuffer = null;
            return buffer;
        }
        else if (size <= MEDIUM_SIZE_LIMIT) {
            char[] buffer = mediumCharBuffer;
            mediumCharBuffer = null;
            return buffer;
        }
        else if (size <= LARGE_SIZE_LIMIT) {
            char[] buffer = largeCharBuffer;
            largeCharBuffer = null;
            return buffer;
        }
        return null;
    }

    public void returnCharBuffer(char[] c) {
        if (c == null) {
            return;
        }
        if (c.length <= SMALL_SIZE_LIMIT) {
            smallCharBuffer = c;
        }
        else if (c.length <= MEDIUM_SIZE_LIMIT) {
            mediumCharBuffer = c;
        }
        else if (c.length <= LARGE_SIZE_LIMIT) {
            largeCharBuffer = c;
        }
    }

    public byte[] getByteBuffer(int size) {
        if (size <= SMALL_SIZE_LIMIT) {
            byte[] buffer = smallByteBuffer;
            smallByteBuffer = null;
            return buffer;
        }
        else if (size <= MEDIUM_SIZE_LIMIT) {
            byte[] buffer = mediumByteBuffer;
            mediumByteBuffer = null;
            return buffer;
        }
        else if (size <= LARGE_SIZE_LIMIT) {
            byte[] buffer = largeByteBuffer;
            largeByteBuffer = null;
            return buffer;
        }
        return null;
    }


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