diff -u -r1.2 -r1.3
--- IIdentifierHelper.java	4 May 2007 10:23:38 -0000	1.2
+++ IIdentifierHelper.java	10 May 2007 00:12:24 -0000	1.3
@@ -1,17 +1,129 @@

 package org.lcsim.detector.identifier;
 
 /**

- * COMMENT

+ * This class has a reference to a single {@IIdentifierDictionary}
+ * that specifies the fields for a 64-bit [log in to unmask]
+ * 
+ * The {{@link #pack(IExpandedIdentifier)} method is used to turn
+ * an {@link IExpandedIdentifier} of field values into a compact,
+ * or packed, identifier.
+ * 
+ * The {@link #unpack(IIdentifier)} method does the reverse, 
+ * taking a packed {@link IIdentifier} and turning into a 
+ * list of field values.
+ * 
+ * The {@link #getValue( IIdentifier compact, IIdentifierField desc )} method
+ * is used to unpack a single field value.  There are similar, overloaded methods 
+ * for using an index in the dictionary or a field label to retrieve a single
+ * field value.
+ * 
+ * @see org.lcsim.detector.identifier;
+ * @see IIdentifier
+ * @see IExpandedIdentifier
+ * @see IIdentifierDictionary

  *
  * @author Jeremy McCormick

- * @version $Id: IIdentifierHelper.java,v 1.2 2007/05/04 10:23:38 jeremy Exp $

+ * @version $Id: IIdentifierHelper.java,v 1.3 2007/05/10 00:12:24 jeremy Exp $

  */
 
 public interface IIdentifierHelper
 {

+    /**
+     * Get the {@link IIdentifierDictionary} associated 
+     * with this helper.
+     * 
+     * @return The IdentifierDictionary.
+     */

     public IIdentifierDictionary getIdentifierDictionary();

-    public IIdentifier pack(IExpandedIdentifier id);
-    //public IIdentifier pack(IExpandedIdentifier id, int start);
-    //public IIdentifier pack(IExpandedIdentifier id, int start, int nfields);

+    
+    /**
+     * Pack an {@link IExpandedIdentifier} into a compact {@link IIdentifier}. 
+     * 
+     * @param id The ExpandedIdentifier to be packed.
+     * @return The compact identfier.
+     */
+    public IIdentifier pack( IExpandedIdentifier id );
+        
+    /**
+     * Get a single field value using an [log in to unmask] 
+     * 
+     * @param compact The compact Identifier.
+     * @param desc    The field description.
+     * @return        The field value.
+     */
+    public int getValue( IIdentifier compact, IIdentifierField desc ); 
+    
+    /**
+     * Get a single field value by index. 
+     * 
+     * @param compact The compact Identifier.
+     * @param field   The field index in the dictionary.
+     * @return        The field value.
+     */
+    public int getValue( IIdentifier compact, int field );
+    
+    /**
+     * Get a single field value by name. 
+     * 
+     * @param compact The compact Identifier.
+     * @param field   The field index in the dictionary.
+     * @return        The field value.
+     */    
+    public int getValue( IIdentifier compact, String field );
+            
+    /**
+     * Pack a subset of fields in an {@link IExpandedIdentifier}.
+     * 
+     * @param id    An ExpandedIdentifier to pack.
+     * @param start The start index in the ExpandedIdentifier.
+     * @return      An Identifier with the packed fields.
+     */
+    public IIdentifier pack(IExpandedIdentifier id, int start);
+    
+    /**
+     * Pack a subset of fields in an {@link IExpandedIdentifier}.
+     * 
+     * @param id         An ExpandedIdentifier to pack.
+     * @param startIndex Starting index.
+     * @param endIndex   End index.
+     * @return           An Identifier with the packed fields.
+     */    
+    public IIdentifier pack(IExpandedIdentifier id, int startIndex, int endIndex );   
+    
+    /**
+     * Upack the {@link IIdentifier} into an {@link IExpandedIdentifer}
+     * containing field values.
+     * 
+     * @param id The Identifier.
+     * @return An ExpandedIdentifier.
+     */

     public IExpandedIdentifier unpack(IIdentifier id);

-}

+    
+    /**
+     * 
+     * Upack the {@link IIdentifier} into an {@link IExpandedIdentifer}
+     * containing the fields starting at index start and 
+     * unpacking nfields fields.  The {@link IExpandedIdentifier} is
+     * padded with zero values to match the full specification in the
+     * [log in to unmask]
+     * 
+     * @param id          The identifier.
+     * @param startIndex  The start index.
+     * @param endIndex    The end index. 
+     * @return            An ExpandedIdentifier with the unpacked values.
+     */
+    public IExpandedIdentifier unpack(IIdentifier id, int startIndex, int endIndex );
+ 
+   /**
+    * Upack the {@link IIdentifier} into an {@link IExpandedIdentifer}
+    * containing the fields starting at index start and 
+    * unpacking all fields to the end.  The {@link IExpandedIdentifier} is
+    * padded with zero values to match the full specification in the
+    * [log in to unmask]
+    * 
+    * @param id          The identifier.
+    * @param startIndex  The start field index.
+    * @return            An ExpandedIdentifier with the unpacked values.
+    */
+    public IExpandedIdentifier unpack(IIdentifier id, int startIndex);     
+}

\ No newline at end of file

diff -u -r1.1 -r1.2
--- IdentifierUtil.java	2 May 2007 23:44:57 -0000	1.1
+++ IdentifierUtil.java	10 May 2007 00:12:24 -0000	1.2
@@ -1,59 +1,180 @@

 package org.lcsim.detector.identifier;
 
 /**

- * Identifier utility methods.

+ * Identifier utility methods for packing {@IIdentifier}s and 
+ * unpacking {@IExpandedIdentifier}s using information from an 
+ * [log in to unmask]
+ * 
+ * Most of the methods in {@IIdentifierHelper} use the static 
+ * utility functions defined here.
+ * 
+ * @see org.lcsim.detector.identifier
+ * @see IIdentifierDictionary
+ * @see IIdentifierField
+ * @see IIdentifier
+ * @see IExpandedIdentifier

  *
  * @author Jeremy McCormick

- * @version $Id: IdentifierUtil.java,v 1.1 2007/05/02 23:44:57 jeremy Exp $

+ * @version $Id: IdentifierUtil.java,v 1.2 2007/05/10 00:12:24 jeremy Exp $

  */

-

 public final class IdentifierUtil
 {

+    /**
+     * Class should not be instantiated.  All methods are static.
+     */

     private IdentifierUtil()
     {}

-    
-    public static IIdentifier pack( IExpandedIdentifier id, IIdentifierDictionary iddict )
-    {        
-        long result = 0;
-        int idx = 0;
-        for ( int value : id.getValues() )
-        {                       
-            IIdentifierField field = iddict.getField(idx);
-                        
-            int start = field.getOffset();
-            int length = field.getNumberOfBits();
-            long mask = ((1L<<length) - 1) << start;
-            result &= ~mask;
-            result |= (((long) value)<<start) & mask;
-                        
-            ++idx;
-        }              
-       
-        return new Identifier( result );

+               
+    public static IExpandedIdentifier unpack( IIdentifierDictionary iddict, IIdentifier compact, int startIndex )
+    {     
+        return IdentifierUtil.unpack( iddict, compact, startIndex, -1 );

     }

-
-    public static IExpandedIdentifier unpack( IIdentifier compact, IIdentifierDictionary iddict )

+    
+    public static IExpandedIdentifier unpack( IIdentifierDictionary iddict, IIdentifier compact )
+    {     
+        return IdentifierUtil.unpack( iddict, compact, 0 );
+    }           
+    
+    public static IExpandedIdentifier unpack( IIdentifierDictionary iddict, IIdentifier compact, int startIndex, int endIndex )

     {        
         ExpandedIdentifier buffer = new ExpandedIdentifier();

-

+        

         long id = compact.getValue();
         

-        for ( IIdentifierField field : iddict.getFields().values() )
-        {                       
-            int start = field.getOffset();
-            int length = field.getNumberOfBits();
-            int mask = (1<<length) - 1;
-            
-            int result = (int) ((id >> start) & mask);
-            if (field.isSigned())

+        int maxIndex = iddict.getMaxIndex();
+                
+        if ( startIndex > maxIndex )
+        {
+            throw new RuntimeException("Start index <" + startIndex + "> is not a valid index in <" + iddict.getName() + ">.");
+        }
+               
+        if ( endIndex > iddict.getNumberOfFields() )
+        {
+            throw new RuntimeException("End index <" + endIndex + "> is not a valid index in <" + iddict.getName() + ">.");
+        }
+              
+        if ( endIndex == -1 )
+        {
+            endIndex = iddict.getMaxIndex();
+        }
+        else
+        {
+            if ( startIndex > endIndex )
+            {
+                throw new IllegalArgumentException("Start index <" + startIndex + "> is bigger than end index <" + endIndex + ">.");
+            }
+        }            
+        
+        for ( int i=0; i<iddict.getNumberOfFields(); i++)
+        {            
+            if ( i >= startIndex  && i <= endIndex )

             {

-                int signBit = 1<<(length-1);
-                if ((result & signBit) != 0) result -= (1<<length);

+                //System.out.println(i);
+                
+                IIdentifierField field = iddict.getField(i);
+
+                int start = field.getOffset();
+                int length = field.getNumberOfBits();
+                int mask = (1<<length) - 1;            
+
+                int result = (int) ((id >> start) & mask);
+                if (field.isSigned())
+                {
+                    int signBit = 1<<(length-1);
+                    if ((result & signBit) != 0) result -= (1<<length);
+                }
+
+                buffer.addValue(result);
+            }
+            else
+            {
+                buffer.addValue(0);

             }

-                        
-            buffer.addValue(result);                       

         }
                
         return buffer;

-    }              

+    }           
+    
+    
+    public static int getValue( IIdentifierDictionary iddict, IIdentifier compact, IIdentifierField desc )
+    {                
+        int start = desc.getOffset();
+        int length = desc.getNumberOfBits();
+        long mask = desc.getMaskOn();
+                
+        int result = (int) ((compact.getValue() >> start) & mask);
+        
+        if ( desc.isSigned() ) 
+        {
+            int signBit = 1<<(length-1);
+            if ((result & signBit) != 0) result -= (1<<length);
+        }
+        return result;        
+    }
+    
+    public static int getValue( IIdentifierDictionary iddict, IIdentifier compact, int field )
+    {        
+        return IdentifierUtil.getValue( iddict, compact, iddict.getField( field ) );
+    }
+    
+    public static int getValue( IIdentifierDictionary iddict, IIdentifier compact, String field )
+    {
+        int idx = iddict.getFieldIndex( field );
+        return IdentifierUtil.getValue( iddict, compact, idx );
+    }
+    
+    public static IIdentifier pack( IIdentifierDictionary iddict, IExpandedIdentifier id, int startIndex, int endIndex )
+    {
+        long result=0;
+              
+        if ( startIndex > iddict.getNumberOfFields() )
+        {
+            throw new IllegalArgumentException("Start index <" + startIndex + "> is not a valid index in <" + iddict.getName() + ">.");
+        }
+                                       
+        if ( endIndex > iddict.getMaxIndex() )
+        {
+            throw new IllegalArgumentException("End index <" + endIndex + "> is not a valid index in <" + iddict.getName() + ">.");
+        }
+        
+        if ( endIndex > startIndex )
+        {
+            throw new IllegalArgumentException("Start index is bigger than end index.");
+        }
+        
+        if ( endIndex == -1 )
+        {
+            endIndex = iddict.getMaxIndex();
+        }
+        else
+        {
+            if ( startIndex > endIndex )
+            {
+                throw new IllegalArgumentException("Start index <" + startIndex + "> is bigger than end index <" + endIndex + ">.");
+            }
+        }            
+                
+        for ( int i=startIndex; i<=endIndex; i++ )
+        {            
+            IIdentifierField field = iddict.getField(i);
+            
+            int offset = field.getOffset();
+            int length = field.getNumberOfBits();
+            long mask = ((1L<<length) - 1) << offset;
+            result &= ~mask;
+            result |= (((long) id.getValue(i))<<offset) & mask;
+        }
+        
+        return new Identifier( result );
+    }
+    
+    public static IIdentifier pack( IIdentifierDictionary iddict, IExpandedIdentifier id )
+    {        
+        return IdentifierUtil.pack( iddict, id, 0 );
+    }
+        
+    public static IIdentifier pack( IIdentifierDictionary iddict, IExpandedIdentifier id, int startIndex )
+    {
+        return IdentifierUtil.pack( iddict, id, startIndex, -1 );
+    }    

 }

\ No newline at end of file