Start line:  
End line:  

Snippet Preview

Snippet HTML Code

Stack Overflow Questions
  /*
   ***** BEGIN LICENSE BLOCK *****
   * Version: EPL 1.0/GPL 2.0/LGPL 2.1
   *
   * The contents of this file are subject to the Eclipse Public
   * License Version 1.0 (the "License"); you may not use this file
   * except in compliance with the License. You may obtain a copy of
   * the License at http://www.eclipse.org/legal/epl-v10.html
   *
  * Software distributed under the License is distributed on an "AS
  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
  * implied. See the License for the specific language governing
  * rights and limitations under the License.
  * 
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  * in which case the provisions of the GPL or the LGPL are applicable instead
  * of those above. If you wish to allow use of your version of this file only
  * under the terms of either the GPL or the LGPL, and not to allow others to
  * use your version of this file under the terms of the EPL, indicate your
  * decision by deleting the provisions above and replace them with the notice
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the EPL, the GPL or the LGPL.
  ***** END LICENSE BLOCK *****/
 package org.jruby.runtime.ivars;
 
A variable accessor that uses a stamped volatile int and Unsafe methods to ensure thread-friendly table updating.
 
 public class StampedVariableAccessor extends VariableAccessor {
    
Construct a new StampedVariableAccessor for the given "real" class, variable name, variable index, and class ID.

Parameters:
realClass the "real" class
name the variable's name
index the variable's index
classId the class's ID
 
     public StampedVariableAccessor(RubyClass realClassString nameint indexint classId) {
         super(realClassnameindexclassId);
     }

    
Set this variable into the given object using Unsafe to ensure safe updating of the variable table.

Parameters:
object the object into which to set this variable
value the variable's value
 
     public void set(Object objectObject value) {
         ((RubyBasicObject)object).ensureInstanceVariablesSettable();
         setVariable((RubyBasicObject)objectvalue);
     }
    
    
Set the given variable index into the specified object. The "real" class and index are pass in to provide functional access. This version checks if self has been frozen before proceeding to set the variable.

Parameters:
self the object into which to set the variable
realClass the "real" class for the object
index the index of the variable
value the variable's value
 
     public static void setVariableChecked(RubyBasicObject selfRubyClass realClassint indexObject value) {
         self.ensureInstanceVariablesSettable();
         setVariable(selfrealClassindexvalue);
     }
    
    
Set the given variable index into the specified object. The "real" class and index are pass in to provide functional access.

Parameters:
self the object into which to set the variable
realClass the "real" class for the object
index the index of the variable
value the variable's value
 
     public static void setVariable(RubyBasicObject selfRubyClass realClassint indexObject value) {
         while (true) {
             int currentStamp = self.varTableStamp;
             // spin-wait if odd
             if((currentStamp & 0x01) != 0)
                continue;
             
             Object[] currentTable = (Object[]) ..getObjectVolatile(self.);
             
             if (currentTable == null || index >= currentTable.length) {
                 if (!createTableUnsafe(selfcurrentStamprealClasscurrentTableindexvalue)) continue;
             } else {
                 if (!updateTableUnsafe(selfcurrentStampcurrentTableindexvalue)) continue;
            }
            
            break;
        }
    }

    
Create or exapand a table for the given object, using Unsafe CAS and ordering operations to ensure visibility.

Parameters:
self the object into which to set the variable
currentStamp the current variable table stamp
realClass the "real" class for the object
currentTable the current table
index the index of the variable
value the variable's value
Returns:
whether the update was successful, for CAS retrying
    private static boolean createTableUnsafe(RubyBasicObject selfint currentStampRubyClass realClassObject[] currentTableint indexObject value) {
        // try to acquire exclusive access to the varTable field
        if (!..compareAndSwapInt(self.currentStamp, ++currentStamp)) {
            return false;
        }
        
        Object[] newTable = new Object[realClass.getVariableTableSizeWithExtras()];
        
        if(currentTable != null) {
            System.arraycopy(currentTable, 0, newTable, 0, currentTable.length);
        }
        
        newTable[index] = value;
        
        
        // release exclusive access
        self.varTableStamp = currentStamp + 1;
        
        return true;
    }

    
Update the given table table for the given object, using Unsafe fence or volatile operations to ensure visibility.

Parameters:
self the object into which to set the variable
currentStamp the current variable table stamp
currentTable the current table
index the index of the variable
value the variable's value
Returns:
whether the update was successful, for CAS retrying
    private static boolean updateTableUnsafe(RubyBasicObject selfint currentStampObject[] currentTableint indexObject value) {
        // shared access to varTable field.
        if(.) {
            currentTable[index] = value;
            UnsafeHolder.fullFence();
        } else {
            // TODO: maybe optimize by read and checking current value before setting
        }
        // validate stamp. redo on concurrent modification
        return self.varTableStamp == currentStamp;
    }
New to GrepCode? Check out our FAQ X