javax.swing.text
Class GapContent

java.lang.Object
  extended byjavax.swing.text.GapVector
      extended byjavax.swing.text.GapContent
All Implemented Interfaces:
AbstractDocument.Content, Serializable

public class GapContent
extends GapVector
implements AbstractDocument.Content, Serializable

An implementation of the AbstractDocument.Content interface implemented using a gapped buffer similar to that used by emacs. The underlying storage is a array of unicode characters with a gap somewhere. The gap is moved to the location of changes to take advantage of common behavior where most changes are 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.

The positions tracking change are also generally cheap to maintain. The Position implementations (marks) store the array index and can easily calculate the sequential position from the current gap location. Changes only require update to the the marks between the old and new gap boundaries when the gap is moved, so generally updating the marks is pretty cheap. The marks are stored sorted so they can be located quickly with a binary search. This increases the cost of adding a mark, and decreases the cost of keeping the mark updated.

Author:
Timothy Prinzing
See Also:
Serialized Form

Nested Class Summary
(package private)  class GapContent.InsertUndo
          UnoableEdit created for inserts.
(package private)  class GapContent.MarkData
          Holds the data for a mark... separately from the real mark so that the real mark (Position that the caller of createPosition holds) can be collected if there are no more references to it.
(package private) static class GapContent.MarkVector
           
(package private)  class GapContent.RemoveUndo
          UndoableEdit created for removes.
(package private)  class GapContent.StickyPosition
           
(package private)  class GapContent.UndoPosRef
          Used to hold a reference to a Mark that is being reset as the result of removing from the content.
 
Field Summary
private static char[] empty
           
private  GapContent.MarkVector marks
           
private  ReferenceQueue queue
           
private  GapContent.MarkData search
          Record used for searching for the place to start updating mark indexs when the gap boundaries are moved.
private  int unusedMarks
          The number of unused mark entries
 
Constructor Summary
GapContent()
          Creates a new GapContent object.
GapContent(int initialLength)
          Creates a new GapContent object, with the initial size specified.
 
Method Summary
protected  Object allocateArray(int len)
          Allocate an array to store items of the type appropriate (which is determined by the subclass).
(package private)  void close(int position, int nItems)
          Delete nItems at position.
(package private)  int compare(GapContent.MarkData o1, GapContent.MarkData o2)
          Compares two marks.
 Position createPosition(int offset)
          Creates a position within the content that will track change as the content is mutated.
(package private)  int findMarkAdjustIndex(int searchIndex)
          Finds the index to start mark adjustments given some search index.
(package private)  int findSortIndex(GapContent.MarkData o)
          Finds the index of where to insert a new mark.
protected  Object getArray()
          Access to the array.
protected  int getArrayLength()
          Get the length of the allocated array.
 void getChars(int where, int len, Segment chars)
          Retrieves a portion of the content.
protected  int getGapEnd()
          Access to the end of the gap.
protected  int getGapStart()
          Access to the start of the gap.
protected  Vector getPositionsInRange(Vector v, int offset, int length)
          Returns a Vector containing instances of UndoPosRef for the Positions in the range offset to offset + length.
 String getString(int where, int len)
          Retrieves a portion of the content.
 UndoableEdit insertString(int where, String str)
          Inserts a string into the content.
 int length()
          Returns the length of the content.
(package private)  int open(int position, int nItems)
          Make space for the given number of items at the given location.
private  void readObject(ObjectInputStream s)
           
 UndoableEdit remove(int where, int nitems)
          Removes part of the content.
(package private)  void removeUnusedMarks()
          Remove all unused marks out of the sorted collection of marks.
protected  void replace(int position, int rmSize, Object addItems, int addSize)
          Replace the given logical position in the storage with the given new items.
protected  void resetMarksAtZero()
          Resets all the marks that have an offset of 0 to have an index of zero as well.
(package private)  void resize(int nsize)
          resize the underlying storage array to the given new size
protected  void shiftEnd(int newSize)
          Make the gap bigger, moving any necessary data and updating the appropriate marks
protected  void shiftGap(int newGapStart)
          Move the start of the gap to a new location, without changing the size of the gap.
protected  void shiftGapEndUp(int newGapEnd)
          Adjust the gap end upward.
protected  void shiftGapStartDown(int newGapStart)
          Adjust the gap end downward.
protected  void updateUndoPositions(Vector positions, int offset, int length)
          Resets the location for all the UndoPosRef instances in positions.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

empty

private static final char[] empty

marks

private transient GapContent.MarkVector marks

search

private transient GapContent.MarkData search
Record used for searching for the place to start updating mark indexs when the gap boundaries are moved.


unusedMarks

private transient int unusedMarks
The number of unused mark entries


queue

private transient ReferenceQueue queue
Constructor Detail

GapContent

public GapContent()
Creates a new GapContent object. Initial size defaults to 10.


GapContent

public GapContent(int initialLength)
Creates a new GapContent object, with the initial size specified. The initial size will not be allowed to go below 2, to give room for the implied break and the gap.

Parameters:
initialLength - the initial size
Method Detail

allocateArray

protected Object allocateArray(int len)
Allocate an array to store items of the type appropriate (which is determined by the subclass).

Specified by:
allocateArray in class GapVector

getArrayLength

protected int getArrayLength()
Get the length of the allocated array.

Specified by:
getArrayLength in class GapVector

length

public int length()
Returns the length of the content.

Specified by:
length in interface AbstractDocument.Content
Returns:
the length >= 1
See Also:
AbstractDocument.Content.length()

insertString

public UndoableEdit insertString(int where,
                                 String str)
                          throws BadLocationException
Inserts a string into the content.

Specified by:
insertString in interface AbstractDocument.Content
Parameters:
where - the starting position >= 0, < length()
str - the non-null string to insert
Returns:
an UndoableEdit object for undoing
Throws:
BadLocationException - if the specified position is invalid
See Also:
AbstractDocument.Content.insertString(int, java.lang.String)

remove

public UndoableEdit remove(int where,
                           int nitems)
                    throws BadLocationException
Removes part of the content.

Specified by:
remove in interface AbstractDocument.Content
Parameters:
where - the starting position >= 0, where + nitems < length()
nitems - the number of characters to remove >= 0
Returns:
an UndoableEdit object for undoing
Throws:
BadLocationException - if the specified position is invalid
See Also:
AbstractDocument.Content.remove(int, int)

getString

public String getString(int where,
                        int len)
                 throws BadLocationException
Retrieves a portion of the content.

Specified by:
getString in interface AbstractDocument.Content
Parameters:
where - the starting position >= 0
len - the length to retrieve >= 0
Returns:
a string representing the content
Throws:
BadLocationException - if the specified position is invalid
See Also:
AbstractDocument.Content.getString(int, int)

getChars

public void getChars(int where,
                     int len,
                     Segment chars)
              throws BadLocationException
Retrieves a portion of the content. If the desired content spans the gap, we copy the content. If the desired content does not span the gap, the actual store is returned to avoid the copy since it is contiguous.

Specified by:
getChars in interface AbstractDocument.Content
Parameters:
where - the starting position >= 0, where + len <= length()
len - the number of characters to retrieve >= 0
chars - the Segment object to return the characters in
Throws:
BadLocationException - if the specified position is invalid
See Also:
AbstractDocument.Content.getChars(int, int, javax.swing.text.Segment)

createPosition

public Position createPosition(int offset)
                        throws BadLocationException
Creates a position within the content that will track change as the content is mutated.

Specified by:
createPosition in interface AbstractDocument.Content
Parameters:
offset - the offset to track >= 0
Returns:
the position
Throws:
BadLocationException - if the specified position is invalid

shiftEnd

protected void shiftEnd(int newSize)
Make the gap bigger, moving any necessary data and updating the appropriate marks

Overrides:
shiftEnd in class GapVector

shiftGap

protected void shiftGap(int newGapStart)
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.

Overrides:
shiftGap in class GapVector

resetMarksAtZero

protected void resetMarksAtZero()
Resets all the marks that have an offset of 0 to have an index of zero as well.


shiftGapStartDown

protected void shiftGapStartDown(int newGapStart)
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).

Overrides:
shiftGapStartDown in class GapVector

shiftGapEndUp

protected void shiftGapEndUp(int newGapEnd)
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).

Overrides:
shiftGapEndUp in class GapVector

compare

final int compare(GapContent.MarkData o1,
                  GapContent.MarkData o2)
Compares two marks.

Parameters:
o1 - the first object
o2 - the second object
Returns:
< 0 if o1 < o2, 0 if the same, > 0 if o1 > o2

findMarkAdjustIndex

final int findMarkAdjustIndex(int searchIndex)
Finds the index to start mark adjustments given some search index.


findSortIndex

final int findSortIndex(GapContent.MarkData o)
Finds the index of where to insert a new mark.

Parameters:
o - the mark to insert
Returns:
the index

removeUnusedMarks

final void removeUnusedMarks()
Remove all unused marks out of the sorted collection of marks.


readObject

private void readObject(ObjectInputStream s)
                 throws ClassNotFoundException,
                        IOException
Throws:
ClassNotFoundException
IOException

getPositionsInRange

protected Vector getPositionsInRange(Vector v,
                                     int offset,
                                     int length)
Returns a Vector containing instances of UndoPosRef for the Positions in the range offset to offset + length. If v is not null the matching Positions are placed in there. The vector with the resulting Positions are returned.

Parameters:
v - the Vector to use, with a new one created on null
offset - the starting offset >= 0
length - the length >= 0
Returns:
the set of instances

updateUndoPositions

protected void updateUndoPositions(Vector positions,
                                   int offset,
                                   int length)
Resets the location for all the UndoPosRef instances in positions.

This is meant for internal usage, and is generally not of interest to subclasses.

Parameters:
positions - the UndoPosRef instances to reset

getArray

protected final Object getArray()
Access to the array. The actual type of the array is known only by the subclass.


getGapStart

protected final int getGapStart()
Access to the start of the gap.


getGapEnd

protected final int getGapEnd()
Access to the end of the gap.


replace

protected void replace(int position,
                       int rmSize,
                       Object addItems,
                       int addSize)
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.

Parameters:
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.
rmSize - the number of items to remove
addItems - the new items to place in storage.

close

void close(int position,
           int nItems)
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.


open

int open(int position,
         int nItems)
Make space for the given number of items at the given location.

Returns:
the location that the caller should fill in

resize

void resize(int nsize)
resize the underlying storage array to the given new size