[cp-patches] FYI: javax.swing.text.GapContent implemented

[Roman Kennke]

Hi,

I have rewritten the class javax.swing.text.GapContent to implement a 
real GapContent buffer. I've done lots of tests and it seems to behave 
correctly. There is still a problem though when deleting characters in 
Textfields, but AFAICS this is not a problem in this class but in one of 
the other swing.text classes. There is still no UndoableEdit support 
implemented.

2005-05-03  Roman Kennke  <address@hidden>

       * javax/swing/text/GapContent.java:
       Implemented a real GapContent. Only the public methods have
       been implemented so far and still no UndoableEdit support.

/Roman

Index: javax/swing/text/GapContent.java
===================================================================
RCS file: /cvsroot/classpath/classpath/javax/swing/text/GapContent.java,v
retrieving revision 1.9
retrieving revision 1.10
diff -u -r1.9 -r1.10
--- javax/swing/text/GapContent.java    27 Apr 2005 08:31:34 -0000      1.9
+++ javax/swing/text/GapContent.java    3 May 2005 10:07:42 -0000       1.10
@@ -40,8 +40,6 @@
 
 import java.io.Serializable;
 
-// too lazy to make a real gapcontent.
-// lets just use a stringbuffer instead.
 import javax.swing.undo.UndoableEdit;
 
 /**
@@ -53,20 +51,41 @@
  * has to be shifted around when the insertion point moves (then the gap also
  * moves and one array copy is necessary) or when the gap is filled up and
  * the buffer has to be enlarged.
+ *
+ * TODO: Implement UndoableEdit support stuff
  */
 public class GapContent
   implements AbstractDocument.Content, Serializable
 {
   private static final long serialVersionUID = 8374645204155842629L;
-    
-  StringBuffer buf = new StringBuffer();
+
+  /**
+   * This is the default buffer size and the amount of bytes that
+   * a buffer is extended if it is full.
+   */
+  static final int DEFAULT_BUFSIZE = 64;
+
+  /**
+   * The text buffer.
+   */
+  char[] buffer;
+
+  /**
+   * The index of the first character of the gap.
+   */
+  int gapStart;
+
+  /**
+   * The index of the character after the last character of the gap.
+   */
+  int gapEnd;
 
   /**
    * Creates a new GapContent object.
    */
   public GapContent()
   {
-    this(10);
+    this(DEFAULT_BUFSIZE);
   }
 
   /**
@@ -76,30 +95,33 @@
    */
   public GapContent(int size)
   {
-    buf.append("\n");
+    buffer = (char[]) allocateArray(size);
+    gapStart = 0;
+    gapEnd = size - 1;
+    buffer[size - 1] = '\n';
   }
 
   /**
-   * Creates and returns a mark at the specified position.
+   * Allocates an array of the specified length that can then be used as
+   * buffer.
    *
-   * @param offset the position at which to create the mark
-   *
-   * @return the create Position object for the mark
+   * @param size the size of the array to be allocated
    *
-   * @throws BadLocationException if the offset is not a valid position in
-   *         the buffer
+   * @return the allocated array
    */
-  public Position createPosition(final int offset) throws BadLocationException
+  protected Object allocateArray(int size)
   {
-    return new Position()
-      {
-       int off = offset;
+    return new char[size];
+  }
 
-       public int getOffset()
-       {
-         return off;
-       }
-      };
+  /**
+   * Returns the length of the allocated buffer array.
+   *
+   * @return the length of the allocated buffer array
+   */
+  protected int getArrayLength()
+  {
+    return buffer.length;
   }
 
   /**
@@ -109,7 +131,7 @@
    */
   public int length()
   {
-    return buf.length();
+    return buffer.length - (gapEnd - gapStart);
   }
 
   /**
@@ -127,7 +149,28 @@
   public UndoableEdit insertString(int where, String str)
     throws BadLocationException
   {
-    buf.insert(where, str);
+    // check arguments
+    int length = length();
+    int strLen = str.length();
+
+    if (where >= length)
+      throw new BadLocationException("the where argument cannot be greater"
+                                     + " than the content length", where);
+
+    // check if the gap is big enough to hold the string
+    if ((gapEnd - gapStart) < strLen)
+      // make room for this string and some more
+      shiftEnd(strLen + DEFAULT_BUFSIZE);
+
+    // are we at the gap boundary?
+    if (where != gapStart)
+      shiftGap(where);
+
+    // now we can simple copy the string into the gap and adjust the
+    // gap boundaries
+    System.arraycopy(str.toCharArray(), 0, buffer, gapStart, strLen);
+    gapStart += strLen;
+    dumpArray();
     return null;
   }
 
@@ -146,10 +189,37 @@
   public UndoableEdit remove(int where, int nitems)
     throws BadLocationException
   {
-    buf.delete(where, where + nitems);
+    // check arguments
+    int length = length();
+
+    if (where >= length)
+      throw new BadLocationException("the where argument cannot be greater"
+                                     + " than the content length", where);
+    if ((where + nitems) > length)
+      throw new BadLocationException("where + nitems cannot be greater"
+                                     + " than the content length",
+                                     where + nitems);
+
+    // check if we are at the gap boundary
+    if (where != gapStart)
+      shiftGap(where);
+
+    // now we simply have to enlarge the gap
+    gapEnd += nitems;
+    dumpArray();
     return null;
   }
 
+  private void dumpArray() 
+  {
+    for (int i = 0; i < buffer.length; i++) {
+      if (i == gapStart) System.err.print('<');
+      if (i == gapEnd) System.err.print('>');
+      
+      System.err.print("'" + buffer[i] + "' ");
+    }
+  }
+
   /**
    * Returns a piece of content as String.
    *
@@ -161,12 +231,18 @@
    */
   public String getString(int where, int len) throws BadLocationException
   {
-    return buf.substring(where, where+len);
+    Segment seg = new Segment();
+    getChars(where, len, seg);
+    return new String(seg.array, seg.offset, seg.count);
   }
 
   /**
    * Fetches a piece of content and stores it in a address@hidden 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
@@ -177,11 +253,116 @@
   public void getChars(int where, int len, Segment txt)
     throws BadLocationException
   {
-    txt.array = new char[len];
+    // 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
+  {
+    return new Position()
+      {
+       int off = offset;
 
-    System.arraycopy(buf.toString().toCharArray(), where, txt.array, 0, len);
+       public int getOffset()
+       {
+         return off;
+       }
+      };
+  }
+
+  /**
+   * 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)
+  {
+    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)
+  {
+    int newGapEnd = newGapStart + (gapEnd - gapStart);
+
+    if (newGapStart == gapStart)
+      return;
+    else if (newGapStart < gapStart)
+      {
+        System.arraycopy(buffer, newGapStart, buffer, newGapEnd,
+                         gapStart - newGapStart);
+        gapStart = newGapStart;
+        gapEnd = newGapEnd;
+      }
+    else
+      {
+        System.arraycopy(buffer, gapEnd, buffer, gapStart,
+                         newGapStart - gapStart);
+        gapStart = newGapStart;
+        gapEnd = newGapEnd;
+      }
+  }
 
-    txt.count = len;
-    txt.offset = 0;
+  /**
+   * Returns the allocated buffer array.
+   *
+   * @return the allocated buffer array
+   */
+  protected Object getArray()
+  {
+    return buffer;
   }
 }