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 * Copyright (c) 2007 Sun Microsystems, Inc. All Rights Reserved.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
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 * INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
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package net.java.joglutils.msg.collections;

import java.nio.FloatBuffer;

import net.java.joglutils.msg.impl.BufferFactory;
import net.java.joglutils.msg.math.Vec2f;

/** Provides the abstraction of a collection of Vec2f objects while
    allowing access to the backing store in the form of a direct
    FloatBuffer to make it easy to pass down to OpenGL. */

public class Vec2fCollection {
  // Data is stored as a direct FloatBuffer
  private FloatBuffer data;

  private static final int ELEMENT_SIZE = 2;

  /** Creates an empty Vec2fCollection. */
  public Vec2fCollection() {
    // Assume you'll probably want at least four vertices
    this(4);
  }

  /** Creates an empty Vec2fCollection with the backing store sized to
      hold roughly the given number of vectors. */
  public Vec2fCollection(int estimatedSize) {
    data = BufferFactory.newFloatBuffer(ELEMENT_SIZE * estimatedSize);
    data.limit(0);
  }

  /** Returns the number of Vec2fs currently in this collection. */
  public int size() {
    return data.limit() / ELEMENT_SIZE;
  }

  /** Stores the given Vec2f at the given index. If the collection has
      not grown to the given size, throws an exception. */
  public void set(int index, Vec2f value) throws IndexOutOfBoundsException {
    if (index >= size()) {
      throw new IndexOutOfBoundsException("" + index + " >= " + size());
    }
    int base = index * ELEMENT_SIZE;
    FloatBuffer buf = data;
    buf.put(base,     value.x());
    buf.put(base + 1, value.y());
  }

  /** Fetches the Vec2f at the given index. If the collection has not
      grown to the given size, throws an exception. */
  public Vec2f get(int index) throws IndexOutOfBoundsException {
    if (index >= size()) {
      throw new IndexOutOfBoundsException("" + index + " >= " + size());
    }
    int base = index * ELEMENT_SIZE;
    // Note: could use a small pool of Vec2fs here if allocation rate
    // is an issue. However, escape analysis should eventually take
    // care of this.
    FloatBuffer buf = data;
    return new Vec2f(buf.get(base), buf.get(base + 1));
  }

  /** Adds the given Vec2f to this collection, expanding it if
      necessary. */
  public void add(Vec2f value) {
    FloatBuffer buf = data;
    if (buf.limit() == buf.capacity()) {
      FloatBuffer newBuf = BufferFactory.newFloatBuffer(Math.max(buf.capacity() + ELEMENT_SIZE,
                                                                 round((int) (buf.capacity() * 1.5f))));
      newBuf.put(buf);
      newBuf.rewind();
      newBuf.limit(buf.limit());
      data = newBuf;
      buf = newBuf;
    }
    int pos = buf.limit();
    buf.limit(pos + ELEMENT_SIZE);
    buf.put(pos,     value.x());
    buf.put(pos + 1, value.y());
  }

  /** Removes the given Vec2f from this collection. Moves all Vec2fs
      above it down one slot. */
  public Vec2f remove(int index) throws IndexOutOfBoundsException {
    if (index >= size()) {
      throw new IndexOutOfBoundsException("" + index + " >= " + size());
    }
    FloatBuffer buf = data;
    int pos = index * ELEMENT_SIZE;
    Vec2f res = new Vec2f(buf.get(pos), buf.get(pos + 1));
    if (index == size() - 1) {
      // Simply lower the limit
      buf.limit(buf.limit() - ELEMENT_SIZE);
    } else {
      buf.position(pos + ELEMENT_SIZE);
      FloatBuffer rest = buf.slice();
      buf.position(pos);
      buf.put(rest);
      buf.limit(buf.limit() - ELEMENT_SIZE);
      buf.rewind();
    }
    return res;
  }
  
  /** Returns the backing buffer of this collection. */
  public FloatBuffer getData() {
    FloatBuffer buf = data;
    buf.position(0);
    return buf.slice();
  }

  //----------------------------------------------------------------------
  // Internals only below this point
  //

  private static int round(int size) {
    return size - (size % ELEMENT_SIZE);
  }
}