Re: [cp-patches] StringBuilder and Appendable for CVS HEAD

[Tom Tromey]

Jeroen> Doesn't help. If StringBuilder is busy modifying the character
Jeroen> array in one thread (after it checked the shared flag) and on
Jeroen> another thread a new String is constructed from that
Jeroen> StringBuilder object, you now have a mutable String.

I don't know why I've been so dense about this.
I'm checking in the appended to the generics branch.

Tom

Index: ChangeLog
from  Tom Tromey  <address@hidden>

        * java/lang/String.java (String(StringBuilder)): Rewrote.
        * java/lang/StringBuilder.java (shared): Removed.
        (ensureCapacity): Updated.
        (substrinng): Likewise.
        (toString): Likewise.

Index: java/lang/String.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/String.java,v
retrieving revision 1.58.2.2
diff -u -r1.58.2.2 String.java
--- java/lang/String.java 9 Oct 2004 23:39:06 -0000 1.58.2.2
+++ java/lang/String.java 19 Dec 2004 06:31:38 -0000
@@ -449,22 +449,7 @@
    */
   public String(StringBuilder buffer)
   {
-    synchronized (buffer)
-      {
-        offset = 0;
-        count = buffer.count;
-        // Share unless buffer is 3/4 empty.
-        if ((count << 2) < buffer.value.length)
-          {
-            value = new char[count];
-            System.arraycopy(buffer.value, 0, value, 0, count);
-          }
-        else
-          {
-            buffer.shared = true;
-            value = buffer.value;
-          }
-      }
+    this(buffer.value, 0, buffer.count);
   }
 
   /**
Index: java/lang/StringBuilder.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/lang/Attic/StringBuilder.java,v
retrieving revision 1.1.2.3
diff -u -r1.1.2.3 StringBuilder.java
--- java/lang/StringBuilder.java 15 Oct 2004 00:55:26 -0000 1.1.2.3
+++ java/lang/StringBuilder.java 19 Dec 2004 06:31:38 -0000
@@ -103,16 +103,6 @@
   char[] value;
 
   /**
-   * True if the buffer is shared with another object (StringBuilder or
-   * String); this means the buffer must be copied before writing to it again.
-   * Note that this has permissions set this way so that String can get the
-   * value.
-   *
-   * @serial whether the buffer is shared
-   */
-  boolean shared;
-
-  /**
    * The default capacity of a buffer.
    */
   private final static int DEFAULT_CAPACITY = 16;
@@ -211,19 +201,13 @@
    */
   public void ensureCapacity(int minimumCapacity)
   {
-    if (shared || minimumCapacity > value.length)
+    if (minimumCapacity > value.length)
       {
-        // We don't want to make a larger vector when `shared' is
-        // set.  If we do, then setLength becomes very inefficient
-        // when repeatedly reusing a StringBuilder in a loop.
-        int max = (minimumCapacity > value.length
-                   ? value.length * 2 + 2
-                   : value.length);
+        int max = value.length * 2 + 2;
         minimumCapacity = (minimumCapacity < max ? max : minimumCapacity);
         char[] nb = new char[minimumCapacity];
         System.arraycopy(value, 0, nb, 0, count);
         value = nb;
-        shared = false;
       }
   }
 
@@ -661,12 +645,7 @@
       throw new StringIndexOutOfBoundsException();
     if (len == 0)
       return "";
-    // Don't copy unless substring is smaller than 1/4 of the buffer.
-    boolean share_buffer = ((len << 2) >= value.length);
-    if (share_buffer)
-      this.shared = true;
-    // Package constructor avoids an array copy.
-    return new String(value, beginIndex, len, share_buffer);
+    return new String(value, beginIndex, len);
   }
 
   /**
@@ -951,7 +930,6 @@
    */
   public String toString()
   {
-    // The string will set this.shared = true.
     return new String(this);
   }