Java example source code file (AbstractSpinedBuffer.java)

This example Java source code file (AbstractSpinedBuffer.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractspinedbuffer, capacity, illegal, illegalargumentexception, max_chunk_power, min_chunk_power, min_chunk_size, min_spine_size

The AbstractSpinedBuffer.java Java example source code

/*
 * Copyright (c) 2012, 2013, 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 java.util.stream;

/**
 * Base class for a data structure for gathering elements into a buffer and then
 * iterating them. Maintains an array of increasingly sized arrays, so there is
 * no copying cost associated with growing the data structure.
 * @since 1.8
 */
abstract class AbstractSpinedBuffer {
    /**
     * Minimum power-of-two for the first chunk.
     */
    public static final int MIN_CHUNK_POWER = 4;

    /**
     * Minimum size for the first chunk.
     */
    public static final int MIN_CHUNK_SIZE = 1 << MIN_CHUNK_POWER;

    /**
     * Max power-of-two for chunks.
     */
    public static final int MAX_CHUNK_POWER = 30;

    /**
     * Minimum array size for array-of-chunks.
     */
    public static final int MIN_SPINE_SIZE = 8;


    /**
     * log2 of the size of the first chunk.
     */
    protected final int initialChunkPower;

    /**
     * Index of the *next* element to write; may point into, or just outside of,
     * the current chunk.
     */
    protected int elementIndex;

    /**
     * Index of the *current* chunk in the spine array, if the spine array is
     * non-null.
     */
    protected int spineIndex;

    /**
     * Count of elements in all prior chunks.
     */
    protected long[] priorElementCount;

    /**
     * Construct with an initial capacity of 16.
     */
    protected AbstractSpinedBuffer() {
        this.initialChunkPower = MIN_CHUNK_POWER;
    }

    /**
     * Construct with a specified initial capacity.
     *
     * @param initialCapacity The minimum expected number of elements
     */
    protected AbstractSpinedBuffer(int initialCapacity) {
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity);

        this.initialChunkPower = Math.max(MIN_CHUNK_POWER,
                                          Integer.SIZE - Integer.numberOfLeadingZeros(initialCapacity - 1));
    }

    /**
     * Is the buffer currently empty?
     */
    public boolean isEmpty() {
        return (spineIndex == 0) && (elementIndex == 0);
    }

    /**
     * How many elements are currently in the buffer?
     */
    public long count() {
        return (spineIndex == 0)
               ? elementIndex
               : priorElementCount[spineIndex] + elementIndex;
    }

    /**
     * How big should the nth chunk be?
     */
    protected int chunkSize(int n) {
        int power = (n == 0 || n == 1)
                    ? initialChunkPower
                    : Math.min(initialChunkPower + n - 1, AbstractSpinedBuffer.MAX_CHUNK_POWER);
        return 1 << power;
    }

    /**
     * Remove all data from the buffer
     */
    public abstract void clear();
}