[vmkit-commits] [vmkit] r145762 - in /vmkit/trunk: LICENSE.TXT lib/j3/ClassLib/OpenJDK/java/ lib/j3/ClassLib/OpenJDK/java/lang/ lib/j3/ClassLib/OpenJDK/java/lang/VMString.java

[Will Dietz]

Author: wdietz2
Date: Sat Dec  3 03:01:32 2011
New Revision: 145762

URL: http://llvm.org/viewvc/llvm-project?rev=145762&view=rev
Log:
Import VMString.java from GNU Classpath 0-97.2 for string interning in OpenJDK

Updated LICENSE.txt accordingly.

Added:
    vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/
    vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/
    vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/VMString.java
Modified:
    vmkit/trunk/LICENSE.TXT

Modified: vmkit/trunk/LICENSE.TXT
URL: http://llvm.org/viewvc/llvm-project/vmkit/trunk/LICENSE.TXT?rev=145762&r1=145761&r2=145762&view=diff
==============================================================================
--- vmkit/trunk/LICENSE.TXT (original)
+++ vmkit/trunk/LICENSE.TXT Sat Dec  3 03:01:32 2011
@@ -64,3 +64,4 @@
 MMTk                vmkit/mmtk/
 JNI                 vmkit/include/j3/
 OpenJDK             vmkit/include/j3/openjdk
+GNU Classpath       vmkit/lib/j3/ClassLib/OpenJDK/java

Added: vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/VMString.java
URL: http://llvm.org/viewvc/llvm-project/vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/VMString.java?rev=145762&view=auto
==============================================================================
--- vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/VMString.java (added)
+++ vmkit/trunk/lib/j3/ClassLib/OpenJDK/java/lang/VMString.java Sat Dec  3 03:01:32 2011
@@ -0,0 +1,91 @@
+/* VMString.java -- VM Specific String methods
+   Copyright (C) 2003 Free Software Foundation
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.lang;
+
+import java.lang.ref.WeakReference;
+import java.util.WeakHashMap;
+
+/*
+ * This class is a reference version, mainly for compiling a class library
+ * jar.  It is likely that VM implementers replace this with their own
+ * version that can communicate effectively with the VM.
+ */
+
+/**
+ * Code relocated from java.lang.String by 
+ * @author Dave Grove <groved at us.ibm.com>
+ */
+final class VMString
+{
+
+  /**
+   * Holds the references for each intern()'d String. If all references to
+   * the string disappear, and the VM properly supports weak references,
+   * the String will be GC'd.
+   */
+  private static final WeakHashMap internTable = new WeakHashMap();
+
+  /**
+   * Fetches this String from the intern hashtable. If two Strings are
+   * considered equal, by the equals() method, then intern() will return the
+   * same String instance. ie. if (s1.equals(s2)) then
+   * (s1.intern() == s2.intern()). All string literals and string-valued
+   * constant expressions are already interned.
+   *
+   * @param str the String to intern
+   * @return the interned String
+   */
+  static String intern(String str)
+  {
+    synchronized (internTable)
+      {
+        WeakReference ref = (WeakReference) internTable.get(str);
+        if (ref != null)
+          {
+            String s = (String) ref.get();
+            // If s is null, then no strong references exist to the String;
+            // the weak hash map will soon delete the key.
+            if (s != null)
+              return s;
+          }
+        internTable.put(str, new WeakReference(str));
+      }
+    return str;
+  }
+
+} // class VMString