org.eclipse.text/src/org/eclipse/jface/text/GapTextStore.java - platform/eclipse.platform.text - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2008 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.jface.text;

 import org.eclipse.core.runtime.Assert;


 /**
  * Implements a gap managing text store. The gap text store relies on the assumption that
  * consecutive changes to a document are co-located. The start of the gap is always moved to the
  * location of the last change.
  * <p>
  * <strong>Performance:</strong> Typing-style changes perform in constant time unless re-allocation
  * becomes necessary. Generally, a change that does not cause re-allocation will cause at most one
  * {@linkplain System#arraycopy(Object, int, Object, int, int) arraycopy} operation of a length of
  * about <var>d</var>, where <var>d</var> is the distance from the previous change. Let <var>a(x)</var>
  * be the algorithmic performance of an <code>arraycopy</code> operation of the length <var>x</var>,
  * then such a change then performs in <i>O(a(x))</i>,
  * {@linkplain #get(int, int) get(int, <var>length</var>)} performs in <i>O(a(length))</i>,
  * {@link #get(int)} in <i>O(1)</i>.
  * <p>
  * How frequently the array needs re-allocation is controlled by the constructor parameters.
  * </p>
  * <p>
  * This class is not intended to be subclassed.
  * </p>
  *
  * @see CopyOnWriteTextStore for a copy-on-write text store wrapper
  * @noextend This class is not intended to be subclassed by clients.
  */
 public class GapTextStore implements ITextStore {
 	/**
 	 * The minimum gap size allocated when re-allocation occurs.
 	 * @since 3.3
 	 */
 	private final int fMinGapSize;
 	/**
 	 * The maximum gap size allocated when re-allocation occurs.
 	 * @since 3.3
 	 */
 	private final int fMaxGapSize;
 	/**
 	 * The multiplier to compute the array size from the content length
 	 * (1&nbsp;&lt;=&nbsp;fSizeMultiplier&nbsp;&lt;=&nbsp;2).
 	 *
 	 * @since 3.3
 	 */
 	private final float fSizeMultiplier;

 	/** The store's content */
 	private char[] fContent= new char[0];
 	/** Starting index of the gap */
 	private int fGapStart= 0;
 	/** End index of the gap */
 	private int fGapEnd= 0;
 	/**
 	 * The current high water mark. If a change would cause the gap to grow larger than this, the
 	 * array is re-allocated.
 	 * @since 3.3
 	 */
 	private int fThreshold= 0;

 	/**
 	 * Creates a new empty text store using the specified low and high watermarks.
 	 *
 	 * @param lowWatermark unused - at the lower bound, the array is only resized when the content
 	 *        does not fit
 	 * @param highWatermark if the gap is ever larger than this, it will automatically be shrunken
 	 *        (&gt;=&nbsp;0)
 	 * @deprecated use {@link GapTextStore#GapTextStore(int, int, float)} instead
 	 */
 	public GapTextStore(int lowWatermark, int highWatermark) {
 		/*
 		 * Legacy constructor. The API contract states that highWatermark is the upper bound for the
 		 * gap size. Albeit this contract was not previously adhered to, it is now: The allocated
 		 * gap size is fixed at half the highWatermark. Since the threshold is always twice the
 		 * allocated gap size, the gap will never grow larger than highWatermark. Previously, the
 		 * gap size was initialized to highWatermark, causing re-allocation if the content length
 		 * shrunk right after allocation. The fixed gap size is now only half of the previous value,
 		 * circumventing that problem (there was no API contract specifying the initial gap size).
 		 *
 		 * The previous implementation did not allow the gap size to become smaller than
 		 * lowWatermark, which doesn't make any sense: that area of the gap was simply never ever
 		 * used.
 		 */
 		this(highWatermark / 2, highWatermark / 2, 0f);
 	}

 	/**
 	 * Equivalent to
 	 * {@linkplain GapTextStore#GapTextStore(int, int, float) new GapTextStore(256, 4096, 0.1f)}.
 	 *
 	 * @since 3.3
 	 */
 	public GapTextStore() {
 		this(256, 4096, 0.1f);
 	}

 	/**
 	 * Creates an empty text store that uses re-allocation thresholds relative to the content
 	 * length. Re-allocation is controlled by the <em>gap factor</em>, which is the quotient of
 	 * the gap size and the array size. Re-allocation occurs if a change causes the gap factor to go
 	 * outside <code>[0,&nbsp;maxGapFactor]</code>. When re-allocation occurs, the array is sized
 	 * such that the gap factor is <code>0.5 * maxGapFactor</code>. The gap size computed in this
 	 * manner is bounded by the <code>minSize</code> and <code>maxSize</code> parameters.
 	 * <p>
 	 * A <code>maxGapFactor</code> of <code>0</code> creates a text store that never has a gap
 	 * at all (if <code>minSize</code> is 0); a <code>maxGapFactor</code> of <code>1</code>
 	 * creates a text store that doubles its size with every re-allocation and that never shrinks.
 	 * </p>
 	 * <p>
 	 * The <code>minSize</code> and <code>maxSize</code> parameters are absolute bounds to the
 	 * allocated gap size. Use <code>minSize</code> to avoid frequent re-allocation for small
 	 * documents. Use <code>maxSize</code> to avoid a huge gap being allocated for large
 	 * documents.
 	 * </p>
 	 *
 	 * @param minSize the minimum gap size to allocate (&gt;=&nbsp;0; use 0 for no minimum)
 	 * @param maxSize the maximum gap size to allocate (&gt;=&nbsp;minSize; use
 	 *        {@link Integer#MAX_VALUE} for no maximum)
 	 * @param maxGapFactor is the maximum fraction of the array that is occupied by the gap (<code>0&nbsp;&lt;=&nbsp;maxGapFactor&nbsp;&lt;=&nbsp;1</code>)
 	 * @since 3.3
 	 */
 	public GapTextStore(int minSize, int maxSize, float maxGapFactor) {
 		Assert.isLegal(0f <= maxGapFactor && maxGapFactor <= 1f);
 		Assert.isLegal(0 <= minSize && minSize <= maxSize);
 		fMinGapSize= minSize;
 		fMaxGapSize= maxSize;
 		fSizeMultiplier= 1 / (1 - maxGapFactor / 2);
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextStore#get(int)
 	 */
 	public final char get(int offset) {
 		if (offset < fGapStart)
 			return fContent[offset];

 		return fContent[offset + gapSize()];
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextStore#get(int, int)
 	 */
 	public final String get(int offset, int length) {
 		if (fGapStart <= offset)
 			return new String(fContent, offset + gapSize() , length);

 		final int end= offset + length;

 		if (end <= fGapStart)
 			return new String(fContent, offset, length);

 		StringBuffer buf= new StringBuffer(length);
 		buf.append(fContent, offset, fGapStart - offset);
 		buf.append(fContent, fGapEnd, end - fGapStart);
 		return buf.toString();
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextStore#getLength()
 	 */
 	public final int getLength() {
 		return fContent.length - gapSize();
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextStore#set(java.lang.String)
 	 */
 	public final void set(String text) {
 		/*
 		 * Moves the gap to the end of the content. There is no sensible prediction of where the
 		 * next change will occur, but at least the next change will not trigger re-allocation. This
 		 * is especially important when using the GapTextStore within a CopyOnWriteTextStore, where
 		 * the GTS is only initialized right before a modification.
 		 */
 		replace(0, getLength(), text);
 	}

 	/*
 	 * @see org.eclipse.jface.text.ITextStore#replace(int, int, java.lang.String)
 	 */
 	public final void replace(int offset, int length, String text) {
 		if (text == null) {
 			adjustGap(offset, length, 0);
 		} else {
 			int textLength= text.length();
 			adjustGap(offset, length, textLength);
 			if (textLength != 0)
 				text.getChars(0, textLength, fContent, offset);
 		}
 	}

 	/**
 	 * Moves the gap to <code>offset + add</code>, moving any content after
 	 * <code>offset + remove</code> behind the gap. The gap size is kept between 0 and
 	 * {@link #fThreshold}, leading to re-allocation if needed. The content between
 	 * <code>offset</code> and <code>offset + add</code> is undefined after this operation.
 	 *
 	 * @param offset the offset at which a change happens
 	 * @param remove the number of character which are removed or overwritten at <code>offset</code>
 	 * @param add the number of character which are inserted or overwriting at <code>offset</code>
 	 */
 	private void adjustGap(int offset, int remove, int add) {
 		final int oldGapSize= gapSize();
 		final int newGapSize= oldGapSize - add + remove;
 		final boolean reuseArray= 0 <= newGapSize && newGapSize <= fThreshold;

 		final int newGapStart= offset + add;
 		final int newGapEnd;

 		if (reuseArray)
 			newGapEnd= moveGap(offset, remove, oldGapSize, newGapSize, newGapStart);
 		else
 			newGapEnd= reallocate(offset, remove, oldGapSize, newGapSize, newGapStart);

 		fGapStart= newGapStart;
 		fGapEnd= newGapEnd;
 	}

 	/**
 	 * Moves the gap to <code>newGapStart</code>.
 	 *
 	 * @param offset the change offset
 	 * @param remove the number of removed / overwritten characters
 	 * @param oldGapSize the old gap size
 	 * @param newGapSize the gap size after the change
 	 * @param newGapStart the offset in the array to move the gap to
 	 * @return the new gap end
 	 * @since 3.3
 	 */
 	private int moveGap(int offset, int remove, int oldGapSize, int newGapSize, int newGapStart) {
 		/*
 		 * No re-allocation necessary. The area between the change offset and gap can be copied
 		 * in at most one operation. Don't copy parts that will be overwritten anyway.
 		 */
 		final int newGapEnd= newGapStart + newGapSize;
 		if (offset < fGapStart) {
 			int afterRemove= offset + remove;
 			if (afterRemove < fGapStart) {
 				final int betweenSize= fGapStart - afterRemove;
 				arrayCopy(afterRemove, fContent, newGapEnd, betweenSize);
 			}
 			// otherwise, only the gap gets enlarged
 		} else {
 			final int offsetShifted= offset + oldGapSize;
 			final int betweenSize= offsetShifted - fGapEnd; // in the typing case, betweenSize is 0
 			arrayCopy(fGapEnd, fContent, fGapStart, betweenSize);
 		}
 		return newGapEnd;
 	}

 	/**
 	 * Reallocates a new array and copies the data from the previous one.
 	 *
 	 * @param offset the change offset
 	 * @param remove the number of removed / overwritten characters
 	 * @param oldGapSize the old gap size
 	 * @param newGapSize the gap size after the change if no re-allocation would occur (can be negative)
 	 * @param newGapStart the offset in the array to move the gap to
 	 * @return the new gap end
 	 * @since 3.3
 	 */
 	private int reallocate(int offset, int remove, final int oldGapSize, int newGapSize, final int newGapStart) {
 		// the new content length (without any gap)
 		final int newLength= fContent.length - newGapSize;
 		// the new array size based on the gap factor
 		int newArraySize= (int) (newLength * fSizeMultiplier);
 		newGapSize= newArraySize - newLength;

 		// bound the gap size within min/max
 		if (newGapSize < fMinGapSize) {
 			newGapSize= fMinGapSize;
 			newArraySize= newLength + newGapSize;
 		} else if (newGapSize > fMaxGapSize) {
 			newGapSize= fMaxGapSize;
 			newArraySize= newLength + newGapSize;
 		}

 		// the upper threshold is always twice the gapsize
 		fThreshold= newGapSize * 2;
 		final char[] newContent= allocate(newArraySize);
 		final int newGapEnd= newGapStart + newGapSize;

 		/*
 		 * Re-allocation: The old content can be copied in at most 3 operations to the newly allocated
 		 * array. Either one of change offset and the gap may come first.
 		 * - unchanged area before the change offset / gap
 		 * - area between the change offset and the gap (either one may be first)
 		 * - rest area after the change offset / after the gap
 		 */
 		if (offset < fGapStart) {
 			// change comes before gap
 			arrayCopy(0, newContent, 0, offset);
 			int afterRemove= offset + remove;
 			if (afterRemove < fGapStart) {
 				// removal is completely before the gap
 				final int betweenSize= fGapStart - afterRemove;
 				arrayCopy(afterRemove, newContent, newGapEnd, betweenSize);
 				final int restSize= fContent.length - fGapEnd;
 				arrayCopy(fGapEnd, newContent, newGapEnd + betweenSize, restSize);
 			} else {
 				// removal encompasses the gap
 				afterRemove += oldGapSize;
 				final int restSize= fContent.length - afterRemove;
 				arrayCopy(afterRemove, newContent, newGapEnd, restSize);
 			}
 		} else {
 			// gap comes before change
 			arrayCopy(0, newContent, 0, fGapStart);
 			final int offsetShifted= offset + oldGapSize;
 			final int betweenSize= offsetShifted - fGapEnd;
 			arrayCopy(fGapEnd, newContent, fGapStart, betweenSize);
 			final int afterRemove= offsetShifted + remove;
 			final int restSize= fContent.length - afterRemove;
 			arrayCopy(afterRemove, newContent, newGapEnd, restSize);
 		}

 		fContent= newContent;
 		return newGapEnd;
 	}

 	/**
 	 * Allocates a new <code>char[size]</code>.
 	 *
 	 * @param size the length of the new array.
 	 * @return a newly allocated char array
 	 * @since 3.3
 	 */
 	private char[] allocate(int size) {
 	    return new char[size];
     }

 	/*
 	 * Executes System.arraycopy if length != 0. A length < 0 cannot happen -> don't hide coding
 	 * errors by checking for negative lengths.
 	 * @since 3.3
 	 */
 	private void arrayCopy(int srcPos, char[] dest, int destPos, int length) {
 		if (length != 0)
 			System.arraycopy(fContent, srcPos, dest, destPos, length);
 	}

 	/**
 	 * Returns the gap size.
 	 *
 	 * @return the gap size
 	 * @since 3.3
 	 */
 	private int gapSize() {
 		return fGapEnd - fGapStart;
 	}

 	/**
 	 * Returns a copy of the content of this text store.
 	 * For internal use only.
 	 *
 	 * @return a copy of the content of this text store
 	 */
 	protected String getContentAsString() {
 		return new String(fContent);
 	}

 	/**
 	 * Returns the start index of the gap managed by this text store.
 	 * For internal use only.
 	 *
 	 * @return the start index of the gap managed by this text store
 	 */
 	protected int getGapStartIndex() {
 		return fGapStart;
 	}

 	/**
 	 * Returns the end index of the gap managed by this text store.
 	 * For internal use only.
 	 *
 	 * @return the end index of the gap managed by this text store
 	 */
 	protected int getGapEndIndex() {
 		return fGapEnd;
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2000, 2008 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.jface.text;

	import org.eclipse.core.runtime.Assert;


	/**
	* Implements a gap managing text store. The gap text store relies on the assumption that
	* consecutive changes to a document are co-located. The start of the gap is always moved to the
	* location of the last change.
	* <p>
	* <strong>Performance:</strong> Typing-style changes perform in constant time unless re-allocation
	* becomes necessary. Generally, a change that does not cause re-allocation will cause at most one
	* {@linkplain System#arraycopy(Object, int, Object, int, int) arraycopy} operation of a length of
	* about <var>d</var>, where <var>d</var> is the distance from the previous change. Let <var>a(x)</var>
	* be the algorithmic performance of an <code>arraycopy</code> operation of the length <var>x</var>,
	* then such a change then performs in <i>O(a(x))</i>,
	* {@linkplain #get(int, int) get(int, <var>length</var>)} performs in <i>O(a(length))</i>,
	* {@link #get(int)} in <i>O(1)</i>.
	* <p>
	* How frequently the array needs re-allocation is controlled by the constructor parameters.
	* </p>
	* <p>
	* This class is not intended to be subclassed.
	* </p>
	*
	* @see CopyOnWriteTextStore for a copy-on-write text store wrapper
	* @noextend This class is not intended to be subclassed by clients.
	*/
	public class GapTextStore implements ITextStore {
	/**
	* The minimum gap size allocated when re-allocation occurs.
	* @since 3.3
	*/
	private final int fMinGapSize;
	/**
	* The maximum gap size allocated when re-allocation occurs.
	* @since 3.3
	*/
	private final int fMaxGapSize;
	/**
	* The multiplier to compute the array size from the content length
	* (1 <= fSizeMultiplier <= 2).
	*
	* @since 3.3
	*/
	private final float fSizeMultiplier;

	/** The store's content */
	private char[] fContent= new char[0];
	/** Starting index of the gap */
	private int fGapStart= 0;
	/** End index of the gap */
	private int fGapEnd= 0;
	/**
	* The current high water mark. If a change would cause the gap to grow larger than this, the
	* array is re-allocated.
	* @since 3.3
	*/
	private int fThreshold= 0;

	/**
	* Creates a new empty text store using the specified low and high watermarks.
	*
	* @param lowWatermark unused - at the lower bound, the array is only resized when the content
	* does not fit
	* @param highWatermark if the gap is ever larger than this, it will automatically be shrunken
	* (>= 0)
	* @deprecated use {@link GapTextStore#GapTextStore(int, int, float)} instead
	*/
	public GapTextStore(int lowWatermark, int highWatermark) {
	/*
	* Legacy constructor. The API contract states that highWatermark is the upper bound for the
	* gap size. Albeit this contract was not previously adhered to, it is now: The allocated
	* gap size is fixed at half the highWatermark. Since the threshold is always twice the
	* allocated gap size, the gap will never grow larger than highWatermark. Previously, the
	* gap size was initialized to highWatermark, causing re-allocation if the content length
	* shrunk right after allocation. The fixed gap size is now only half of the previous value,
	* circumventing that problem (there was no API contract specifying the initial gap size).
	*
	* The previous implementation did not allow the gap size to become smaller than
	* lowWatermark, which doesn't make any sense: that area of the gap was simply never ever
	* used.
	*/
	this(highWatermark / 2, highWatermark / 2, 0f);
	}

	/**
	* Equivalent to
	* {@linkplain GapTextStore#GapTextStore(int, int, float) new GapTextStore(256, 4096, 0.1f)}.
	*
	* @since 3.3
	*/
	public GapTextStore() {
	this(256, 4096, 0.1f);
	}

	/**
	* Creates an empty text store that uses re-allocation thresholds relative to the content
	* length. Re-allocation is controlled by the <em>gap factor</em>, which is the quotient of
	* the gap size and the array size. Re-allocation occurs if a change causes the gap factor to go
	* outside <code>[0, maxGapFactor]</code>. When re-allocation occurs, the array is sized
	* such that the gap factor is <code>0.5 * maxGapFactor</code>. The gap size computed in this
	* manner is bounded by the <code>minSize</code> and <code>maxSize</code> parameters.
	* <p>
	* A <code>maxGapFactor</code> of <code>0</code> creates a text store that never has a gap
	* at all (if <code>minSize</code> is 0); a <code>maxGapFactor</code> of <code>1</code>
	* creates a text store that doubles its size with every re-allocation and that never shrinks.
	* </p>
	* <p>
	* The <code>minSize</code> and <code>maxSize</code> parameters are absolute bounds to the
	* allocated gap size. Use <code>minSize</code> to avoid frequent re-allocation for small
	* documents. Use <code>maxSize</code> to avoid a huge gap being allocated for large
	* documents.
	* </p>
	*
	* @param minSize the minimum gap size to allocate (>= 0; use 0 for no minimum)
	* @param maxSize the maximum gap size to allocate (>= minSize; use
	* {@link Integer#MAX_VALUE} for no maximum)
	* @param maxGapFactor is the maximum fraction of the array that is occupied by the gap (<code>0 <= maxGapFactor <= 1</code>)
	* @since 3.3
	*/
	public GapTextStore(int minSize, int maxSize, float maxGapFactor) {
	Assert.isLegal(0f <= maxGapFactor && maxGapFactor <= 1f);
	Assert.isLegal(0 <= minSize && minSize <= maxSize);
	fMinGapSize= minSize;
	fMaxGapSize= maxSize;
	fSizeMultiplier= 1 / (1 - maxGapFactor / 2);
	}

	/*
	* @see org.eclipse.jface.text.ITextStore#get(int)
	*/
	public final char get(int offset) {
	if (offset < fGapStart)
	return fContent[offset];

	return fContent[offset + gapSize()];
	}

	/*
	* @see org.eclipse.jface.text.ITextStore#get(int, int)
	*/
	public final String get(int offset, int length) {
	if (fGapStart <= offset)
	return new String(fContent, offset + gapSize() , length);

	final int end= offset + length;

	if (end <= fGapStart)
	return new String(fContent, offset, length);

	StringBuffer buf= new StringBuffer(length);
	buf.append(fContent, offset, fGapStart - offset);
	buf.append(fContent, fGapEnd, end - fGapStart);
	return buf.toString();
	}

	/*
	* @see org.eclipse.jface.text.ITextStore#getLength()
	*/
	public final int getLength() {
	return fContent.length - gapSize();
	}

	/*
	* @see org.eclipse.jface.text.ITextStore#set(java.lang.String)
	*/
	public final void set(String text) {
	/*
	* Moves the gap to the end of the content. There is no sensible prediction of where the
	* next change will occur, but at least the next change will not trigger re-allocation. This
	* is especially important when using the GapTextStore within a CopyOnWriteTextStore, where
	* the GTS is only initialized right before a modification.
	*/
	replace(0, getLength(), text);
	}

	/*
	* @see org.eclipse.jface.text.ITextStore#replace(int, int, java.lang.String)
	*/
	public final void replace(int offset, int length, String text) {
	if (text == null) {
	adjustGap(offset, length, 0);
	} else {
	int textLength= text.length();
	adjustGap(offset, length, textLength);
	if (textLength != 0)
	text.getChars(0, textLength, fContent, offset);
	}
	}

	/**
	* Moves the gap to <code>offset + add</code>, moving any content after
	* <code>offset + remove</code> behind the gap. The gap size is kept between 0 and
	* {@link #fThreshold}, leading to re-allocation if needed. The content between
	* <code>offset</code> and <code>offset + add</code> is undefined after this operation.
	*
	* @param offset the offset at which a change happens
	* @param remove the number of character which are removed or overwritten at <code>offset</code>
	* @param add the number of character which are inserted or overwriting at <code>offset</code>
	*/
	private void adjustGap(int offset, int remove, int add) {
	final int oldGapSize= gapSize();
	final int newGapSize= oldGapSize - add + remove;
	final boolean reuseArray= 0 <= newGapSize && newGapSize <= fThreshold;

	final int newGapStart= offset + add;
	final int newGapEnd;

	if (reuseArray)
	newGapEnd= moveGap(offset, remove, oldGapSize, newGapSize, newGapStart);
	else
	newGapEnd= reallocate(offset, remove, oldGapSize, newGapSize, newGapStart);

	fGapStart= newGapStart;
	fGapEnd= newGapEnd;
	}

	/**
	* Moves the gap to <code>newGapStart</code>.
	*
	* @param offset the change offset
	* @param remove the number of removed / overwritten characters
	* @param oldGapSize the old gap size
	* @param newGapSize the gap size after the change
	* @param newGapStart the offset in the array to move the gap to
	* @return the new gap end
	* @since 3.3
	*/
	private int moveGap(int offset, int remove, int oldGapSize, int newGapSize, int newGapStart) {
	/*
	* No re-allocation necessary. The area between the change offset and gap can be copied
	* in at most one operation. Don't copy parts that will be overwritten anyway.
	*/
	final int newGapEnd= newGapStart + newGapSize;
	if (offset < fGapStart) {
	int afterRemove= offset + remove;
	if (afterRemove < fGapStart) {
	final int betweenSize= fGapStart - afterRemove;
	arrayCopy(afterRemove, fContent, newGapEnd, betweenSize);
	}
	// otherwise, only the gap gets enlarged
	} else {
	final int offsetShifted= offset + oldGapSize;
	final int betweenSize= offsetShifted - fGapEnd; // in the typing case, betweenSize is 0
	arrayCopy(fGapEnd, fContent, fGapStart, betweenSize);
	}
	return newGapEnd;
	}

	/**
	* Reallocates a new array and copies the data from the previous one.
	*
	* @param offset the change offset
	* @param remove the number of removed / overwritten characters
	* @param oldGapSize the old gap size
	* @param newGapSize the gap size after the change if no re-allocation would occur (can be negative)
	* @param newGapStart the offset in the array to move the gap to
	* @return the new gap end
	* @since 3.3
	*/
	private int reallocate(int offset, int remove, final int oldGapSize, int newGapSize, final int newGapStart) {
	// the new content length (without any gap)
	final int newLength= fContent.length - newGapSize;
	// the new array size based on the gap factor
	int newArraySize= (int) (newLength * fSizeMultiplier);
	newGapSize= newArraySize - newLength;

	// bound the gap size within min/max
	if (newGapSize < fMinGapSize) {
	newGapSize= fMinGapSize;
	newArraySize= newLength + newGapSize;
	} else if (newGapSize > fMaxGapSize) {
	newGapSize= fMaxGapSize;
	newArraySize= newLength + newGapSize;
	}

	// the upper threshold is always twice the gapsize
	fThreshold= newGapSize * 2;
	final char[] newContent= allocate(newArraySize);
	final int newGapEnd= newGapStart + newGapSize;

	/*
	* Re-allocation: The old content can be copied in at most 3 operations to the newly allocated
	* array. Either one of change offset and the gap may come first.
	* - unchanged area before the change offset / gap
	* - area between the change offset and the gap (either one may be first)
	* - rest area after the change offset / after the gap
	*/
	if (offset < fGapStart) {
	// change comes before gap
	arrayCopy(0, newContent, 0, offset);
	int afterRemove= offset + remove;
	if (afterRemove < fGapStart) {
	// removal is completely before the gap
	final int betweenSize= fGapStart - afterRemove;
	arrayCopy(afterRemove, newContent, newGapEnd, betweenSize);
	final int restSize= fContent.length - fGapEnd;
	arrayCopy(fGapEnd, newContent, newGapEnd + betweenSize, restSize);
	} else {
	// removal encompasses the gap
	afterRemove += oldGapSize;
	final int restSize= fContent.length - afterRemove;
	arrayCopy(afterRemove, newContent, newGapEnd, restSize);
	}
	} else {
	// gap comes before change
	arrayCopy(0, newContent, 0, fGapStart);
	final int offsetShifted= offset + oldGapSize;
	final int betweenSize= offsetShifted - fGapEnd;
	arrayCopy(fGapEnd, newContent, fGapStart, betweenSize);
	final int afterRemove= offsetShifted + remove;
	final int restSize= fContent.length - afterRemove;
	arrayCopy(afterRemove, newContent, newGapEnd, restSize);
	}

	fContent= newContent;
	return newGapEnd;
	}

	/**
	* Allocates a new <code>char[size]</code>.
	*
	* @param size the length of the new array.
	* @return a newly allocated char array
	* @since 3.3
	*/
	private char[] allocate(int size) {
	return new char[size];
	}

	/*
	* Executes System.arraycopy if length != 0. A length < 0 cannot happen -> don't hide coding
	* errors by checking for negative lengths.
	* @since 3.3
	*/
	private void arrayCopy(int srcPos, char[] dest, int destPos, int length) {
	if (length != 0)
	System.arraycopy(fContent, srcPos, dest, destPos, length);
	}

	/**
	* Returns the gap size.
	*
	* @return the gap size
	* @since 3.3
	*/
	private int gapSize() {
	return fGapEnd - fGapStart;
	}

	/**
	* Returns a copy of the content of this text store.
	* For internal use only.
	*
	* @return a copy of the content of this text store
	*/
	protected String getContentAsString() {
	return new String(fContent);
	}

	/**
	* Returns the start index of the gap managed by this text store.
	* For internal use only.
	*
	* @return the start index of the gap managed by this text store
	*/
	protected int getGapStartIndex() {
	return fGapStart;
	}

	/**
	* Returns the end index of the gap managed by this text store.
	* For internal use only.
	*
	* @return the end index of the gap managed by this text store
	*/
	protected int getGapEndIndex() {
	return fGapEnd;
	}
	}