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/*
 * Copyright (C) 2006-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see .
 */

package org.filesys.server.memory;

/**
 * Byte buffer Pool Class
 *
 * Memory pool of different sized byte buffers.
 *
 * @author gkspencer
 */
public class ByteBufferPool {

    // List of byte buffer pools
    private ByteBufferList[] m_bufferLists;

    // Buffer sizes, initial allocation and maximum allocation
    private int[] m_bufSizes;
    private int[] m_initAlloc;
    private int[] m_maxAlloc;

    /**
     * Class constuctor
     *
     * @param bufSizes  Buffer sizes int[]
     * @param initAlloc Initial allocations for each size int[]
     * @param maxAlloc  Maximim allocations for each size int[]
     */
    public ByteBufferPool(int[] bufSizes, int[] initAlloc, int[] maxAlloc) {

        // Validate the buffer size, initial allocation and max allocation arrays
        if ((bufSizes.length != initAlloc.length) && (bufSizes.length != maxAlloc.length))
            throw new RuntimeException("Invalid ByteBufferPool parameters");

        // Save the buffer details
        m_bufSizes = bufSizes;
        m_initAlloc = initAlloc;
        m_maxAlloc = maxAlloc;

        // Allocate the buffer list
        m_bufferLists = new ByteBufferList[m_bufSizes.length];

        // Allocate the byte buffer lists
        for (int i = 0; i < m_bufSizes.length; i++) {

            // Allocate a byte buffer list for the current buffer size
            ByteBufferList bufList = new ByteBufferList(m_bufSizes[i], m_initAlloc[i], m_maxAlloc[i]);
            m_bufferLists[i] = bufList;
        }
    }

    /**
     * Allocate a byte buffer from the appropriate buffer list, if there are buffers available then do not wait
     *
     * @param siz int
     * @return byte[]
     */
    public final byte[] allocateBuffer(int siz) {

        // Allocate a buffer, do not wait if there are no buffers available
        return allocateBuffer(siz, 0);
    }

    /**
     * Allocate a byte buffer from the appropriate buffer list
     *
     * @param siz      int
     * @param waitTime long
     * @return byte[]
     */
    public final byte[] allocateBuffer(int siz, long waitTime) {

        // Allocate the buffer from the appropriate list
        int idx = 0;

        while (idx < m_bufSizes.length && siz > m_bufSizes[idx])
            idx++;

        if (idx == m_bufSizes.length)
            throw new RuntimeException("Requested allocation size too long for pool, " + siz);

        // Allocate a buffer
        return m_bufferLists[idx].allocateBuffer(waitTime);
    }

    /**
     * Release a buffer
     *
     * @param buf byte[]
     */
    public final void releaseBuffer(byte[] buf) {

        // Find the buffer list the buffer was allocated from
        int idx = 0;

        while (idx < m_bufSizes.length && buf.length != m_bufSizes[idx])
            idx++;

        if (idx == m_bufSizes.length)
            throw new RuntimeException("Released buffer does not match any buffer sizes, " + buf.length);

        // Release the buffer
        m_bufferLists[idx].releaseBuffer(buf);
    }

    /**
     * Shrink the buffer lists back to their initial allocation sizes
     */
    public final void shrinkLists() {
        for (int i = 0; i < m_bufferLists.length; i++)
            m_bufferLists[i].shrinkList();
    }

    /**
     * Return the length of the smallest packet size available
     *
     * @return int
     */
    public final int getSmallestSize() {
        return m_bufSizes[0];
    }

    /**
     * Return the length of the largest packet size available
     *
     * @return int
     */
    public final int getLargestSize() {
        return m_bufSizes[m_bufSizes.length - 1];
    }

    /**
     * Return the buffer list
     *
     * @return ByteBufferList[]
     */
    public final ByteBufferList[] getBufferList() {
        return m_bufferLists;
    }

    /**
     * Return the byte buffer pool details as a string
     *
     * @return String
     */
    public String toString() {
        StringBuilder str = new StringBuilder();

        str.append("[BufferLists:\n");

        for (int i = 0; i < m_bufferLists.length; i++) {
            str.append("  ");
            str.append(m_bufferLists[i].toString());
            str.append("\n");
        }

        str.append("]");

        return str.toString();
    }
}