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diff --git a/src/delta.cpp b/src/delta.cpp
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+/* $Id: delta.cpp,v 1.4 2006-11-05 04:42:43 ganzhorn Exp $
+ * This file is part of lfhex.
+ * Copyright (C) 2006 Salem Ganzhorn <eyekode@yahoo.com>
+ *
+ * This program 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 version 2.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include "delta.hpp"
+
+//
+// DeltaMap class implimentation:
+//
+
+DeltaMap::DeltaMap() {} // noop
+DeltaMap::~DeltaMap()
+{
+  // just free all of the Delta's
+  clear();
+}
+
+// Free all the Delta's
+// Note: this invalidates all pointers to Delta's returned through search()
+// do NOT keep returned pointers arround for long.
+//
+void DeltaMap::clear()
+{
+  _map.erase(_map.begin(),_map.end());
+  
+  // note: the union of _undo and _redo should contain ALL of the Delta's
+  // in the map. The intersection of _undo and _redo should be the empty set.
+  while ( !_undo.empty() ) {
+    delete _undo.top();
+    _undo.pop();
+  }
+  while ( !_redo.empty() ) {
+    delete _redo.top();
+    _redo.pop();
+  }
+}
+
+// returns const ptr to the most recent delta on offset off_t
+const Delta * DeltaMap::search( off_t offset ) const
+{
+  delta_map_t::const_iterator itr = _map.find(offset);
+  if ( itr != _map.end() && (itr->second).size() )
+    return itr->second.back();
+  else
+    return 0;
+}
+
+size_t DeltaMap::insert( off_t offset, 
+		      const vector<uchar>& oldData, 
+		      const vector<uchar>& newData )
+{
+  //
+  // only modify the newData of the top undo iff the offsets match
+  // and the redo stack is empty.
+  //
+  if( _undo.size() && _undo.top()->offset() == offset && _redo.empty() ) {
+    //just modify the newData of the top delta
+    _undo.top()->setNewData( newData );
+
+    // _map[offset] _should_ exist
+    return _map[offset].size();
+  } else {
+    // create a new delta
+    Delta * tmp = new Delta(offset, oldData, newData);
+    _map[offset].push_back( tmp );
+    _undo.push( tmp );
+    return _map[offset].size();
+  }
+}
+
+bool DeltaMap::undo()
+{
+  if( _undo.empty() )
+    return false;
+
+  Delta* d = _undo.top();
+  _undo.pop();
+  // find the delta in the delta list indexed by d->offset and remove it.
+  map<off_t,list<Delta*> >::iterator itr = _map.find(d->offset());
+  itr->second.remove(d);
+  // remove the entry iff the list is empty
+  if( itr->second.empty() ) {
+    _map.erase(itr);
+  }
+  // push the delta back onto the redo stack.
+  _redo.push( d );
+  return true;
+}
+
+bool DeltaMap::redo()
+{
+  if( _redo.empty() )
+    return false;
+
+  // insert the delta back into the modification list
+  Delta *d = _redo.top();
+  _redo.pop();
+  _map[d->offset()].push_back( d );
+  _undo.push( d );
+  return true;
+}
+
+// methods for iterating over all the modifications in the tree
+off_t DeltaMap::lower_bound(off_t lb) const
+{
+  delta_map_t::const_iterator itr = _map.lower_bound(lb);
+  if( itr == _map.end() ) {
+    return -1;
+  } else {
+    return itr->first;
+  }
+}