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diff --git a/src/delta.hpp b/src/delta.hpp
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+/* $Id: delta.hpp,v 1.5 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.
+ */
+
+#ifndef _DELTA_MAP_
+#define _DELTA_MAP_
+
+#include <sys/types.h>
+#include <list>
+#include <map>
+#include <vector>
+#include <stack>
+
+#include <iostream>
+
+#include "local.h"
+
+class Delta {
+public:
+  Delta( off_t i, const vector<uchar>& oldData, const vector<uchar>& newData) :
+    _offset(i), _old(oldData), _new(newData) {}
+
+  void setNewData( const vector<uchar>& ndata ) { _new = ndata; }
+
+  off_t          offset()  const { return _offset; }
+  const vector<uchar>& newData() const { return _new;}
+  const vector<uchar>& oldData() const { return _old;}
+protected:
+  off_t                 _offset;
+  vector<uchar>               _old;
+  vector<uchar>               _new;
+};
+
+
+// allocation for all delta's is dynamic, but it is all handled 
+// within the class.
+// the user of the class does not need to worry about memory 
+// allocation/deallocation.
+class DeltaMap {
+public:
+  DeltaMap();
+  ~DeltaMap();
+
+public:
+  // insert a new delta
+  size_t insert(off_t offset, 
+	     const vector<uchar>& oldData,
+	     const vector<uchar>& newData);
+  // return the offset of the last inserted Delta.
+  off_t lastOffset() const;
+  // set the last delta's newData to data
+  void setLastData( const vector<uchar>& data);
+  int  numEdits() const { return _undo.size(); }
+  // find the most recent delta
+  const Delta*  search(off_t offset) const;
+
+  // cleans undo/redo stacks and frees memory for all deltas.
+  // Makes references to delta's invalid.
+  void clear();
+
+  bool undo(); //undo last insert
+  bool redo(); //redo last insert
+
+  // method for iterating over all of the modifications
+  // finds the first offset that is is not less than lb
+  // so lower_bound(0) returns the offset of the first delta
+  // (off_t) -1 is returned on failure
+  off_t lower_bound(off_t lb) const;
+
+protected:
+  typedef map<off_t,list<Delta*> > delta_map_t;
+  // notes:
+  // the back of the delta list is always the most recent/non undone delta.
+  map<off_t,list<Delta*> > _map;
+  stack<Delta*>   _undo;
+  stack<Delta*>   _redo;
+};
+
+#endif