/*
* @(#)GapVector.java 1.12 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.swing.text;
import java.util.Vector;
import java.io.Serializable;
import javax.swing.undo.UndoableEdit;
/**
* An implementation of a gapped buffer similar to that used by
* emacs. The underlying storage is a java array of some type,
* which is known only by the subclass of this class. The array
* has a gap somewhere. The gap is moved to the location of changes
* to take advantage of common behavior where most changes occur
* in the same location. Changes that occur at a gap boundary are
* generally cheap and moving the gap is generally cheaper than
* moving the array contents directly to accomodate the change.
*
* @author Timothy Prinzing
* @version 1.12 12/19/03
* @see GapContent
*/
abstract class GapVector implements Serializable {
/**
* Creates a new GapVector object. Initial size defaults to 10.
*/
public GapVector() {
this(10);
}
/**
* Creates a new GapVector object, with the initial
* size specified.
*
* @param initialLength the initial size
*/
public GapVector(int initialLength) {
array = allocateArray(initialLength);
g0 = 0;
g1 = initialLength;
}
/**
* Allocate an array to store items of the type
* appropriate (which is determined by the subclass).
*/
protected abstract Object allocateArray(int len);
/**
* Get the length of the allocated array
*/
protected abstract int getArrayLength();
/**
* Access to the array. The actual type
* of the array is known only by the subclass.
*/
protected final Object getArray() {
return array;
}
/**
* Access to the start of the gap.
*/
protected final int getGapStart() {
return g0;
}
/**
* Access to the end of the gap.
*/
protected final int getGapEnd() {
return g1;
}
// ---- variables -----------------------------------
/**
* The array of items. The type is determined by the subclass.
*/
private Object array;
/**
* start of gap in the array
*/
private int g0;
/**
* end of gap in the array
*/
private int g1;
// --- gap management -------------------------------
/**
* Replace the given logical position in the storage with
* the given new items. This will move the gap to the area
* being changed if the gap is not currently located at the
* change location.
*
* @param position the location to make the replacement. This
* is not the location in the underlying storage array, but
* the location in the contiguous space being modeled.
* @param rmSize the number of items to remove
* @param addItems the new items to place in storage.
*/
protected void replace(int position, int rmSize, Object addItems, int addSize) {
int addOffset = 0;
if (addSize == 0) {
close(position, rmSize);
return;
} else if (rmSize > addSize) {
/* Shrink the end. */
close(position+addSize, rmSize-addSize);
} else {
/* Grow the end, do two chunks. */
int endSize = addSize - rmSize;
int end = open(position + rmSize, endSize);
System.arraycopy(addItems, rmSize, array, end, endSize);
addSize = rmSize;
}
System.arraycopy(addItems, addOffset, array, position, addSize);
}
/**
* Delete nItems at position. Squeezes any marks
* within the deleted area to position. This moves
* the gap to the best place by minimizing it's
* overall movement. The gap must intersect the
* target block.
*/
void close(int position, int nItems) {
if (nItems == 0) return;
int end = position + nItems;
int new_gs = (g1 - g0) + nItems;
if (end <= g0) {
// Move gap to end of block.
if (g0 != end) {
shiftGap(end);
}
// Adjust g0.
shiftGapStartDown(g0 - nItems);
} else if (position >= g0) {
// Move gap to beginning of block.
if (g0 != position) {
shiftGap(position);
}
// Adjust g1.
shiftGapEndUp(g0 + new_gs);
} else {
// The gap is properly inside the target block.
// No data movement necessary, simply move both gap pointers.
shiftGapStartDown(position);
shiftGapEndUp(g0 + new_gs);
}
}
/**
* Make space for the given number of items at the given
* location.
*
* @return the location that the caller should fill in
*/
int open(int position, int nItems) {
int gapSize = g1 - g0;
if (nItems == 0) {
if (position > g0)
position += gapSize;
return position;
}
// Expand the array if the gap is too small.
shiftGap(position);
if (nItems >= gapSize) {
// Pre-shift the gap, to reduce total movement.
shiftEnd(getArrayLength() - gapSize + nItems);
gapSize = g1 - g0;
}
g0 = g0 + nItems;
return position;
}
/**
* resize the underlying storage array to the
* given new size
*/
void resize(int nsize) {
Object narray = allocateArray(nsize);
System.arraycopy(array, 0, narray, 0, Math.min(nsize, getArrayLength()));
array = narray;
}
/**
* Make the gap bigger, moving any necessary data and updating
* the appropriate marks
*/
protected void shiftEnd(int newSize) {
int oldSize = getArrayLength();
int oldGapEnd = g1;
int upperSize = oldSize - oldGapEnd;
int arrayLength = getNewArraySize(newSize);
int newGapEnd = arrayLength - upperSize;
resize(arrayLength);
g1 = newGapEnd;
if (upperSize != 0) {
// Copy array items to new end of array.
System.arraycopy(array, oldGapEnd, array, newGapEnd, upperSize);
}
}
/**
* Calculates a new size of the storage array depending on required
* capacity.
* @param reqSize the size which is necessary for new content
* @return the new size of the storage array
*/
int getNewArraySize(int reqSize) {
return (reqSize + 1) * 2;
}
/**
* Move the start of the gap to a new location,
* without changing the size of the gap. This
* moves the data in the array and updates the
* marks accordingly.
*/
protected void shiftGap(int newGapStart) {
if (newGapStart == g0) {
return;
}
int oldGapStart = g0;
int dg = newGapStart - oldGapStart;
int oldGapEnd = g1;
int newGapEnd = oldGapEnd + dg;
int gapSize = oldGapEnd - oldGapStart;
g0 = newGapStart;
g1 = newGapEnd;
if (dg > 0) {
// Move gap up, move data down.
System.arraycopy(array, oldGapEnd, array, oldGapStart, dg);
} else if (dg < 0) {
// Move gap down, move data up.
System.arraycopy(array, newGapStart, array, newGapEnd, -dg);
}
}
/**
* Adjust the gap end downward. This doesn't move
* any data, but it does update any marks affected
* by the boundary change. All marks from the old
* gap start down to the new gap start are squeezed
* to the end of the gap (their location has been
* removed).
*/
protected void shiftGapStartDown(int newGapStart) {
g0 = newGapStart;
}
/**
* Adjust the gap end upward. This doesn't move
* any data, but it does update any marks affected
* by the boundary change. All marks from the old
* gap end up to the new gap end are squeezed
* to the end of the gap (their location has been
* removed).
*/
protected void shiftGapEndUp(int newGapEnd) {
g1 = newGapEnd;
}
}
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