gapcontent.java

gcc的组建

   * Fetches a piece of content and stores it in a {@link Segment} object.
   * 
   * If the requested piece of text spans the gap, the content is copied into a
   * new array. If it doesn't then it is contiguous and the actual content
   * store is returned.
   * 
   * @param where the start location of the fragment
   * @param len the length of the fragment
   * @param txt the Segment object to store the fragment in
   * 
   * @throws BadLocationException if <code>where</code> or
   *         <code>where + len</code> are no valid locations in the buffer
   */
  public void getChars(int where, int len, Segment txt)
      throws BadLocationException
  {
    // check arguments
    int length = length();
    if (where >= length)
      throw new BadLocationException("the where argument cannot be greater"
          + " than the content length", where);
    if ((where + len) > length)
      throw new BadLocationException("len plus where cannot be greater"
          + " than the content length", len + where);

    // check if requested segment is contiguous
    if ((where < gapStart) && ((gapStart - where) < len))
    {
      // requested segment is not contiguous -> copy the pieces together
      char[] copy = new char[len];
      int lenFirst = gapStart - where; // the length of the first segment
      System.arraycopy(buffer, where, copy, 0, lenFirst);
      System.arraycopy(buffer, gapEnd, copy, lenFirst, len - lenFirst);
      txt.array = copy;
      txt.offset = 0;
      txt.count = len;
    }
    else
    {
      // requested segment is contiguous -> we can simply return the
      // actual content
      txt.array = buffer;
      if (where < gapStart)
        txt.offset = where;
      else
        txt.offset = where + (gapEnd - gapStart);
      txt.count = len;
    }
  }

  /**
   * Creates and returns a mark at the specified position.
   * 
   * @param offset the position at which to create the mark
   * 
   * @return the create Position object for the mark
   * 
   * @throws BadLocationException if the offset is not a valid position in the
   *         buffer
   */
  public Position createPosition(final int offset) throws BadLocationException
  {
    if (offset < 0 || offset > length())
      throw new BadLocationException("The offset was out of the bounds of this"
          + " buffer", offset);

    // We store the actual array index in the GapContentPosition. The real
    // offset is then calculated in the GapContentPosition.
    int mark = offset;
    if (offset > gapStart)
      mark += gapEnd - gapStart;
    GapContentPosition pos = new GapContentPosition(mark);

    // Add this into our list in a sorted fashion.
    int index = Collections.binarySearch(positions, pos);
    if (index < 0)
      index = -(index + 1);
    positions.add(index, pos);
    return pos;
  }

  /**
   * Enlarges the gap. This allocates a new bigger buffer array, copy the
   * segment before the gap as it is and the segment after the gap at the end
   * of the new buffer array. This does change the gapEnd mark but not the
   * gapStart mark.
   * 
   * @param newSize the new size of the gap
   */
  protected void shiftEnd(int newSize)
  {
    assert newSize > (gapEnd - gapStart) : "The new gap size must be greater "
                                           + "than the old gap size";

    int delta = newSize - gapEnd + gapStart;
    // Update the marks after the gapEnd.
    adjustPositionsInRange(gapEnd, buffer.length - gapEnd, delta);

    // Copy the data around.
    char[] newBuf = (char[]) allocateArray(length() + newSize);
    System.arraycopy(buffer, 0, newBuf, 0, gapStart);
    System.arraycopy(buffer, gapEnd, newBuf, gapStart + newSize, buffer.length
        - gapEnd);
    gapEnd = gapStart + newSize;
    buffer = newBuf;

  }

  /**
   * Shifts the gap to the specified position.
   * 
   * @param newGapStart the new start position of the gap
   */
  protected void shiftGap(int newGapStart)
  {
    if (newGapStart == gapStart)
      return;

    int newGapEnd = newGapStart + gapEnd - gapStart;
    if (newGapStart < gapStart)
      {
        // Update the positions between newGapStart and (old) gapStart. The marks
        // must be shifted by (gapEnd - gapStart).
        adjustPositionsInRange(newGapStart, gapStart - newGapStart, gapEnd - gapStart);
        System.arraycopy(buffer, newGapStart, buffer, newGapEnd, gapStart
                         - newGapStart);
        gapStart = newGapStart;
        gapEnd = newGapEnd;
      }
    else
      {
        // Update the positions between newGapEnd and (old) gapEnd. The marks
        // must be shifted by (gapEnd - gapStart).
        adjustPositionsInRange(gapEnd, newGapEnd - gapEnd, -(gapEnd - gapStart));
        System.arraycopy(buffer, gapEnd, buffer, gapStart, newGapStart
                         - gapStart);
        gapStart = newGapStart;
        gapEnd = newGapEnd;
      }
    if (gapStart == 0)
      resetMarksAtZero();
  }

  /**
   * Shifts the gap start downwards. This does not affect the content of the
   * buffer. This only updates the gap start and all the marks that are between
   * the old gap start and the new gap start. They all are squeezed to the start
   * of the gap, because their location has been removed.
   *
   * @param newGapStart the new gap start
   */
  protected void shiftGapStartDown(int newGapStart)
  {
    if (newGapStart == gapStart)
      return;

    assert newGapStart < gapStart : "The new gap start must be less than the "
                                    + "old gap start.";
    setPositionsInRange(newGapStart, gapStart - newGapStart, gapStart);
    gapStart = newGapStart;
  }

  /**
   * Shifts the gap end upwards. This does not affect the content of the
   * buffer. This only updates the gap end and all the marks that are between
   * the old gap end and the new end start. They all are squeezed to the end
   * of the gap, because their location has been removed.
   *
   * @param newGapEnd the new gap start
   */
  protected void shiftGapEndUp(int newGapEnd)
  {
    if (newGapEnd == gapEnd)
      return;

    assert newGapEnd > gapEnd : "The new gap end must be greater than the "
                                + "old gap end.";
    setPositionsInRange(gapEnd, newGapEnd - gapEnd, newGapEnd + 1);
    gapEnd = newGapEnd;
  }

  /**
   * Returns the allocated buffer array.
   * 
   * @return the allocated buffer array
   */
  protected Object getArray()
  {
    return buffer;
  }

  /**
   * Replaces a portion of the storage with the specified items.
   * 
   * @param position the position at which to remove items
   * @param rmSize the number of items to remove
   * @param addItems the items to add at location
   * @param addSize the number of items to add
   */
  protected void replace(int position, int rmSize, Object addItems,
                         int addSize)
  {
    if (gapStart != position)
      shiftGap(position);
    // Remove content
    if (rmSize > 0)
      shiftGapEndUp(gapEnd + rmSize);

    // If gap is too small, enlarge the gap.
    if ((gapEnd - gapStart) <= addSize)
      shiftEnd((addSize - gapEnd + gapStart + 1) * 2 + gapEnd + DEFAULT_BUFSIZE);

    // Add new items to the buffer.
    if (addItems != null)
      {
        System.arraycopy(addItems, 0, buffer, gapStart, addSize);
        gapStart += addSize;
      }
  }

  /**
   * Returns the start index of the gap within the buffer array.
   *
   * @return the start index of the gap within the buffer array
   */
  protected final int getGapStart()
  {
    return gapStart;
  }

  /**
   * Returns the end index of the gap within the buffer array.
   *
   * @return the end index of the gap within the buffer array
   */
  protected final int getGapEnd()
  {
    return gapEnd;
  }

  /**
   * Returns all <code>Position</code>s that are in the range specified by
   * <code>offset</code> and </code>length</code> within the buffer array.
   *
   * @param v the vector to use; if <code>null</code>, a new Vector is allocated
   * @param offset the start offset of the range to search
   * @param length the length of the range to search
   *
   * @return the positions within the specified range
   */
  protected Vector getPositionsInRange(Vector v, int offset, int length)
  {
    Vector res = v;
    if (res == null)
      res = new Vector();
    else
      res.clear();

    int endOffset = offset + length;

    int index1 = Collections.binarySearch(positions,
                                          new GapContentPosition(offset));
    if (index1 < 0)
      index1 = -(index1 + 1);
    for (ListIterator i = positions.listIterator(index1); i.hasNext();)
      {
        GapContentPosition p = (GapContentPosition) i.next();
        if (p.mark > endOffset)
          break;
        if (p.mark >= offset && p.mark <= endOffset)
          res.add(p);
      }
    return res;
  }
  
  /**
   * Sets the mark of all <code>Position</code>s that are in the range 
   * specified by <code>offset</code> and </code>length</code> within 
   * the buffer array to <code>value</code>
   *
   * @param offset the start offset of the range to search
   * @param length the length of the range to search
   * @param value the new value for each mark
   */
  void setPositionsInRange(int offset, int length, int value)
  {
    int endOffset = offset + length;

    int index1 = Collections.binarySearch(positions,
                                          new GapContentPosition(offset));
    if (index1 < 0)
      index1 = -(index1 + 1);
    for (ListIterator i = positions.listIterator(index1); i.hasNext();)
      {
        GapContentPosition p = (GapContentPosition) i.next();
        if (p.mark > endOffset)
          break;
        
        if (p.mark >= offset && p.mark <= endOffset)
          p.mark = value;
      }
  }
  
  /**
   * Adjusts the mark of all <code>Position</code>s that are in the range 
   * specified by <code>offset</code> and </code>length</code> within 
   * the buffer array by <code>increment</code>
   *
   * @param offset the start offset of the range to search
   * @param length the length of the range to search
   * @param incr the increment
   */
  void adjustPositionsInRange(int offset, int length, int incr)
  {
    int endOffset = offset + length;

    int index1 = Collections.binarySearch(positions,
                                          new GapContentPosition(offset));
    if (index1 < 0)
      index1 = -(index1 + 1);
    for (ListIterator i = positions.listIterator(index1); i.hasNext();)
      {
        GapContentPosition p = (GapContentPosition) i.next();
        if (p.mark > endOffset)
          break;

        if (p.mark >= offset && p.mark <= endOffset)
          p.mark += incr;
      }
  }

  /**
   * Resets all <code>Position</code> that have an offset of <code>0</code>,
   * to also have an array index of <code>0</code>. This might be necessary
   * after a call to <code>shiftGap(0)</code>, since then the marks at offset
   * <code>0</code> get shifted to <code>gapEnd</code>.
   */
  protected void resetMarksAtZero()
  {
    if (gapStart != 0)
      return;

    setPositionsInRange(gapEnd, 0, 0);
  }

  /**
   * Outputs debugging info to System.err. It prints out the buffer array,
   * the gapStart is marked by a &lt; sign, the gapEnd is marked by a &gt;
   * sign and each position is marked by a # sign.
   */
  private void dump()
  {
    System.err.println("GapContent debug information");
    System.err.println("buffer length: " + buffer.length);
    System.err.println("gap start: " + gapStart);
    System.err.println("gap end: " + gapEnd);
    for (int i = 0; i < buffer.length; i++)
      {
        if (i == gapStart)
          System.err.print('<');
        if (i == gapEnd)
          System.err.print('>');

        if (!Character.isISOControl(buffer[i]))
          System.err.print(buffer[i]);
        else
          System.err.print('.');
      }
    System.err.println();
  }

  private void dumpPositions()
  {
    for (Iterator i = positions.iterator(); i.hasNext();)
      {
        GapContentPosition pos = (GapContentPosition) i.next();
        System.err.println("position at: " + pos.mark);
      }
  }
}