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// Copyright (c) 2003-present, Jodd Team (http://jodd.org)
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

package jodd.util.buffer;

/**
 * Fast, fast double buffer.
 * This buffer implementation does not store all data
 * in single array, but in array of chunks.
 */
public class FastDoubleBuffer {

    private double[][] buffers = new double[16][];
    private int buffersCount;
    private int currentBufferIndex = -1;
    private double[] currentBuffer;
    private int offset;
    private int size;
    private final int minChunkLen;

    /**
     * Creates a new double buffer. The buffer capacity is
     * initially 1024 bytes, though its size increases if necessary.
     */
    public FastDoubleBuffer() {
        this.minChunkLen = 1024;
    }

    /**
     * Creates a new double buffer, with a buffer capacity of
     * the specified size, in bytes.
     *
     * @param size the initial size.
     * @throws IllegalArgumentException if size is negative.
     */
    public FastDoubleBuffer(int size) {
        if (size < 0) {
            throw new IllegalArgumentException("Invalid size: " + size);
        }
        this.minChunkLen = size;
    }

    /**
     * Prepares next chunk to match new size.
     * The minimal length of new chunk is minChunkLen.
     */
    private void needNewBuffer(int newSize) {
        int delta = newSize - size;
        int newBufferSize = Math.max(minChunkLen, delta);

        currentBufferIndex++;
        currentBuffer = new double[newBufferSize];
        offset = 0;

        // add buffer
        if (currentBufferIndex >= buffers.length) {
            int newLen = buffers.length << 1;
            double[][] newBuffers = new double[newLen][];
            System.arraycopy(buffers, 0, newBuffers, 0, buffers.length);
            buffers = newBuffers;
        }
        buffers[currentBufferIndex] = currentBuffer;
        buffersCount++;
    }

    /**
     * Appends double array to buffer.
     */
    public FastDoubleBuffer append(double[] array, int off, int len) {
        int end = off + len;
        if ((off < 0)
                || (len < 0)
                || (end > array.length)) {
            throw new IndexOutOfBoundsException();
        }
        if (len == 0) {
            return this;
        }
        int newSize = size + len;
        int remaining = len;

        if (currentBuffer != null) {
            // first try to fill current buffer
            int part = Math.min(remaining, currentBuffer.length - offset);
            System.arraycopy(array, end - remaining, currentBuffer, offset, part);
            remaining -= part;
            offset += part;
            size += part;
        }

        if (remaining > 0) {
            // still some data left
            // ask for new buffer
            needNewBuffer(newSize);

            // then copy remaining
            // but this time we are sure that it will fit
            int part = Math.min(remaining, currentBuffer.length - offset);
            System.arraycopy(array, end - remaining, currentBuffer, offset, part);
            offset += part;
            size += part;
        }

        return this;
    }

    /**
     * Appends double array to buffer.
     */
    public FastDoubleBuffer append(double[] array) {
        return append(array, 0, array.length);
    }

    /**
     * Appends single double to buffer.
     */
    public FastDoubleBuffer append(double element) {
        if ((currentBuffer == null) || (offset == currentBuffer.length)) {
            needNewBuffer(size + 1);
        }

        currentBuffer[offset] = element;
        offset++;
        size++;

        return this;
    }

    /**
     * Appends another fast buffer to this one.
     */
    public FastDoubleBuffer append(FastDoubleBuffer buff) {
        if (buff.size == 0) {
            return this;
        }
        for (int i = 0; i < buff.currentBufferIndex; i++) {
            append(buff.buffers[i]);
        }
        append(buff.currentBuffer, 0, buff.offset);
        return this;
    }

    /**
     * Returns buffer size.
     */
    public int size() {
        return size;
    }

    /**
     * Tests if this buffer has no elements.
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * Returns current index of inner double array chunk.
     * Represents the index of last used inner array chunk.
     */
    public int index() {
        return currentBufferIndex;
    }

    /**
     * Returns the offset of last used element in current inner array chunk.
     */
    public int offset() {
        return offset;
    }

    /**
     * Returns double inner array chunk at given index.
     * May be used for iterating inner chunks in fast manner.
     */
    public double[] array(int index) {
        return buffers[index];
    }

    /**
     * Resets the buffer content.
     */
    public void clear() {
        size = 0;
        offset = 0;
        currentBufferIndex = -1;
        currentBuffer = null;
        buffersCount = 0;
    }

    /**
     * Creates double array from buffered content.
     */
    public double[] toArray() {
        int pos = 0;
        double[] array = new double[size];

        if (currentBufferIndex == -1) {
            return array;
        }

        for (int i = 0; i < currentBufferIndex; i++) {
            int len = buffers[i].length;
            System.arraycopy(buffers[i], 0, array, pos, len);
            pos += len;
        }

        System.arraycopy(buffers[currentBufferIndex], 0, array, pos, offset);

        return array;
    }

    /**
     * Creates double subarray from buffered content.
     */
    public double[] toArray(int start, int len) {
        int remaining = len;
        int pos = 0;
        double[] array = new double[len];

        if (len == 0) {
            return array;
        }

        int i = 0;
        while (start >= buffers[i].length) {
            start -= buffers[i].length;
            i++;
        }

        while (i < buffersCount) {
            double[] buf = buffers[i];
            int c = Math.min(buf.length - start, remaining);
            System.arraycopy(buf, start, array, pos, c);
            pos += c;
            remaining -= c;
            if (remaining == 0) {
                break;
            }
            start = 0;
            i++;
        }
        return array;
    }

    /**
     * Returns double element at given index.
     */
    public double get(int index) {
        if ((index >= size) || (index < 0)) {
            throw new IndexOutOfBoundsException();
        }
        int ndx = 0;
        while (true) {
            double[] b = buffers[ndx];
            if (index < b.length) {
                return b[index];
            }
            ndx++;
            index -= b.length;
        }
    }

}