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/*
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* Copyright 1999-2006 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package javax.swing;
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/**
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* A <code>SizeSequence</code> object
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* efficiently maintains an ordered list
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* of sizes and corresponding positions.
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* One situation for which <code>SizeSequence</code>
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* might be appropriate is in a component
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* that displays multiple rows of unequal size.
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* In this case, a single <code>SizeSequence</code>
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* object could be used to track the heights
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* and Y positions of all rows.
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* <p>
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* Another example would be a multi-column component,
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* such as a <code>JTable</code>,
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* in which the column sizes are not all equal.
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* The <code>JTable</code> might use a single
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* <code>SizeSequence</code> object
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* to store the widths and X positions of all the columns.
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* The <code>JTable</code> could then use the
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* <code>SizeSequence</code> object
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* to find the column corresponding to a certain position.
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* The <code>JTable</code> could update the
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* <code>SizeSequence</code> object
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* whenever one or more column sizes changed.
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*
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* <p>
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* The following figure shows the relationship between size and position data
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* for a multi-column component.
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* <p>
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* <center>
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* <img src="doc-files/SizeSequence-1.gif" width=384 height = 100
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* alt="The first item begins at position 0, the second at the position equal
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to the size of the previous item, and so on.">
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* </center>
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* <p>
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* In the figure, the first index (0) corresponds to the first column,
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* the second index (1) to the second column, and so on.
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* The first column's position starts at 0,
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* and the column occupies <em>size<sub>0</sub></em> pixels,
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* where <em>size<sub>0</sub></em> is the value returned by
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* <code>getSize(0)</code>.
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* Thus, the first column ends at <em>size<sub>0</sub></em> - 1.
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* The second column then begins at
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* the position <em>size<sub>0</sub></em>
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* and occupies <em>size<sub>1</sub></em> (<code>getSize(1)</code>) pixels.
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* <p>
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* Note that a <code>SizeSequence</code> object simply represents intervals
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* along an axis.
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* In our examples, the intervals represent height or width in pixels.
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* However, any other unit of measure (for example, time in days)
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* could be just as valid.
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*
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* <p>
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*
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* <h4>Implementation Notes</h4>
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*
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* Normally when storing the size and position of entries,
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* one would choose between
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* storing the sizes or storing their positions
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* instead. The two common operations that are needed during
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* rendering are: <code>getIndex(position)</code>
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* and <code>setSize(index, size)</code>.
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* Whichever choice of internal format is made one of these
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* operations is costly when the number of entries becomes large.
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* If sizes are stored, finding the index of the entry
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* that encloses a particular position is linear in the
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* number of entries. If positions are stored instead, setting
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* the size of an entry at a particular index requires updating
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* the positions of the affected entries, which is also a linear
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* calculation.
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* <p>
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* Like the above techniques this class holds an array of N integers
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* internally but uses a hybrid encoding, which is halfway
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* between the size-based and positional-based approaches.
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* The result is a data structure that takes the same space to store
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* the information but can perform most operations in Log(N) time
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* instead of O(N), where N is the number of entries in the list.
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* <p>
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* Two operations that remain O(N) in the number of entries are
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* the <code>insertEntries</code>
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* and <code>removeEntries</code> methods, both
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* of which are implemented by converting the internal array to
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* a set of integer sizes, copying it into the new array, and then
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* reforming the hybrid representation in place.
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*
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* @author Philip Milne
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* @since 1.3
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*/
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/*
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* Each method is implemented by taking the minimum and
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* maximum of the range of integers that need to be operated
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* upon. All the algorithms work by dividing this range
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* into two smaller ranges and recursing. The recursion
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* is terminated when the upper and lower bounds are equal.
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*/
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public class SizeSequence {
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private static int[] emptyArray = new int[0];
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private int a[];
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/**
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* Creates a new <code>SizeSequence</code> object
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* that contains no entries. To add entries, you
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* can use <code>insertEntries</code> or <code>setSizes</code>.
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*
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* @see #insertEntries
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* @see #setSizes
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*/
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public SizeSequence() {
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a = emptyArray;
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}
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/**
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* Creates a new <code>SizeSequence</code> object
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* that contains the specified number of entries,
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* all initialized to have size 0.
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*
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* @param numEntries the number of sizes to track
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* @exception NegativeArraySizeException if
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* <code>numEntries < 0</code>
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*/
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public SizeSequence(int numEntries) {
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this(numEntries, 0);
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}
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/**
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* Creates a new <code>SizeSequence</code> object
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* that contains the specified number of entries,
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* all initialized to have size <code>value</code>.
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*
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* @param numEntries the number of sizes to track
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* @param value the initial value of each size
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*/
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public SizeSequence(int numEntries, int value) {
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this();
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insertEntries(0, numEntries, value);
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}
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/**
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* Creates a new <code>SizeSequence</code> object
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* that contains the specified sizes.
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*
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* @param sizes the array of sizes to be contained in
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* the <code>SizeSequence</code>
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*/
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public SizeSequence(int[] sizes) {
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this();
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setSizes(sizes);
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}
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/**
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* Resets the size sequence to contain <code>length</code> items
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* all with a size of <code>size</code>.
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*/
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void setSizes(int length, int size) {
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if (a.length != length) {
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a = new int[length];
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}
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setSizes(0, length, size);
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}
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private int setSizes(int from, int to, int size) {
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if (to <= from) {
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return 0;
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}
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int m = (from + to)/2;
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a[m] = size + setSizes(from, m, size);
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return a[m] + setSizes(m + 1, to, size);
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}
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/**
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* Resets this <code>SizeSequence</code> object,
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* using the data in the <code>sizes</code> argument.
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* This method reinitializes this object so that it
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* contains as many entries as the <code>sizes</code> array.
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* Each entry's size is initialized to the value of the
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* corresponding item in <code>sizes</code>.
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*
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* @param sizes the array of sizes to be contained in
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* this <code>SizeSequence</code>
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*/
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public void setSizes(int[] sizes) {
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if (a.length != sizes.length) {
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a = new int[sizes.length];
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}
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setSizes(0, a.length, sizes);
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}
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private int setSizes(int from, int to, int[] sizes) {
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if (to <= from) {
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return 0;
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}
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int m = (from + to)/2;
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a[m] = sizes[m] + setSizes(from, m, sizes);
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return a[m] + setSizes(m + 1, to, sizes);
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}
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/**
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* Returns the size of all entries.
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*
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* @return a new array containing the sizes in this object
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*/
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public int[] getSizes() {
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int n = a.length;
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int[] sizes = new int[n];
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getSizes(0, n, sizes);
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return sizes;
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}
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private int getSizes(int from, int to, int[] sizes) {
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if (to <= from) {
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return 0;
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}
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int m = (from + to)/2;
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sizes[m] = a[m] - getSizes(from, m, sizes);
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return a[m] + getSizes(m + 1, to, sizes);
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}
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/**
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* Returns the start position for the specified entry.
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* For example, <code>getPosition(0)</code> returns 0,
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* <code>getPosition(1)</code> is equal to
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* <code>getSize(0)</code>,
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* <code>getPosition(2)</code> is equal to
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* <code>getSize(0)</code> + <code>getSize(1)</code>,
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* and so on.
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* <p>Note that if <code>index</code> is greater than
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* <code>length</code> the value returned may
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* be meaningless.
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*
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* @param index the index of the entry whose position is desired
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* @return the starting position of the specified entry
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*/
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public int getPosition(int index) {
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return getPosition(0, a.length, index);
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}
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private int getPosition(int from, int to, int index) {
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if (to <= from) {
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return 0;
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}
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int m = (from + to)/2;
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if (index <= m) {
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return getPosition(from, m, index);
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}
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else {
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return a[m] + getPosition(m + 1, to, index);
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}
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}
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/**
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* Returns the index of the entry
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* that corresponds to the specified position.
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* For example, <code>getIndex(0)</code> is 0,
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* since the first entry always starts at position 0.
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*
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* @param position the position of the entry
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* @return the index of the entry that occupies the specified position
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*/
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public int getIndex(int position) {
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return getIndex(0, a.length, position);
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}
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private int getIndex(int from, int to, int position) {
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if (to <= from) {
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return from;
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}
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int m = (from + to)/2;
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int pivot = a[m];
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if (position < pivot) {
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return getIndex(from, m, position);
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}
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else {
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return getIndex(m + 1, to, position - pivot);
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}
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}
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/**
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* Returns the size of the specified entry.
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* If <code>index</code> is out of the range
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* <code>(0 <= index < getSizes().length)</code>
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* the behavior is unspecified.
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*
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* @param index the index corresponding to the entry
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* @return the size of the entry
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*/
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public int getSize(int index) {
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return getPosition(index + 1) - getPosition(index);
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}
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/**
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* Sets the size of the specified entry.
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* Note that if the value of <code>index</code>
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* does not fall in the range:
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* <code>(0 <= index < getSizes().length)</code>
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* the behavior is unspecified.
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*
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* @param index the index corresponding to the entry
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* @param size the size of the entry
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*/
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public void setSize(int index, int size) {
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changeSize(0, a.length, index, size - getSize(index));
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}
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private void changeSize(int from, int to, int index, int delta) {
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if (to <= from) {
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return;
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}
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int m = (from + to)/2;
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if (index <= m) {
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a[m] += delta;
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changeSize(from, m, index, delta);
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}
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else {
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changeSize(m + 1, to, index, delta);
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}
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}
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/**
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* Adds a contiguous group of entries to this <code>SizeSequence</code>.
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* Note that the values of <code>start</code> and
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* <code>length</code> must satisfy the following
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* conditions: <code>(0 <= start < getSizes().length)
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* AND (length >= 0)</code>. If these conditions are
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* not met, the behavior is unspecified and an exception
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* may be thrown.
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*
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* @param start the index to be assigned to the first entry
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* in the group
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* @param length the number of entries in the group
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* @param value the size to be assigned to each new entry
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* @exception ArrayIndexOutOfBoundsException if the parameters
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* are outside of the range:
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* (<code>0 <= start < (getSizes().length)) AND (length >= 0)</code>
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*/
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public void insertEntries(int start, int length, int value) {
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int sizes[] = getSizes();
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int end = start + length;
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int n = a.length + length;
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a = new int[n];
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for (int i = 0; i < start; i++) {
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a[i] = sizes[i] ;
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}
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for (int i = start; i < end; i++) {
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a[i] = value ;
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}
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for (int i = end; i < n; i++) {
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a[i] = sizes[i-length] ;
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}
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setSizes(a);
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}
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/**
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* Removes a contiguous group of entries
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* from this <code>SizeSequence</code>.
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* Note that the values of <code>start</code> and
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* <code>length</code> must satisfy the following
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* conditions: <code>(0 <= start < getSizes().length)
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* AND (length >= 0)</code>. If these conditions are
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* not met, the behavior is unspecified and an exception
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* may be thrown.
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*
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* @param start the index of the first entry to be removed
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* @param length the number of entries to be removed
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*/
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public void removeEntries(int start, int length) {
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int sizes[] = getSizes();
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int end = start + length;
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int n = a.length - length;
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a = new int[n];
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for (int i = 0; i < start; i++) {
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a[i] = sizes[i] ;
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}
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for (int i = start; i < n; i++) {
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a[i] = sizes[i+length] ;
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}
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setSizes(a);
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}
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}
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