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diff --git a/Source/cmVariableWatch.h b/Source/cmVariableWatch.h
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+/*============================================================================
+  CMake - Cross Platform Makefile Generator
+  Copyright 2000-2009 Kitware, Inc., Insight Software Consortium
+
+  Distributed under the OSI-approved BSD License (the "License");
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+============================================================================*/
+#ifndef cmVariableWatch_h
+#define cmVariableWatch_h
+
+#include "cmStandardIncludes.h"
+
+class cmMakefile;
+
+/** \class cmVariableWatch
+ * \brief Helper class for watching of variable accesses.
+ *
+ * Calls function when variable is accessed
+ */
+class cmVariableWatch
+{
+public:
+  typedef void (*WatchMethod)(const std::string& variable, int access_type,
+    void* client_data, const char* newValue, const cmMakefile* mf);
+  typedef void (*DeleteData)(void* client_data);
+
+  cmVariableWatch();
+  ~cmVariableWatch();
+
+  /**
+   * Add watch to the variable
+   */
+  bool AddWatch(const std::string& variable, WatchMethod method,
+                void* client_data=0, DeleteData delete_data=0);
+  void RemoveWatch(const std::string& variable, WatchMethod method,
+                   void* client_data=0);
+
+  /**
+   * This method is called when variable is accessed
+   */
+  void VariableAccessed(const std::string& variable, int access_type,
+    const char* newValue, const cmMakefile* mf) const;
+
+  /**
+   * Different access types.
+   */
+  enum
+    {
+    VARIABLE_READ_ACCESS = 0,
+    UNKNOWN_VARIABLE_READ_ACCESS,
+    UNKNOWN_VARIABLE_DEFINED_ACCESS,
+    ALLOWED_UNKNOWN_VARIABLE_READ_ACCESS,
+    VARIABLE_MODIFIED_ACCESS,
+    VARIABLE_REMOVED_ACCESS,
+    NO_ACCESS
+    };
+
+  /**
+   * Return the access as string
+   */
+  static const char* GetAccessAsString(int access_type);
+
+protected:
+  struct Pair
+  {
+    WatchMethod Method;
+    void*        ClientData;
+    DeleteData   DeleteDataCall;
+    Pair() : Method(0), ClientData(0), DeleteDataCall(0) {}
+    ~Pair()
+      {
+      if (this->DeleteDataCall && this->ClientData)
+        {
+        this->DeleteDataCall(this->ClientData);
+        }
+      }
+  };
+
+  typedef std::vector< Pair* > VectorOfPairs;
+  typedef std::map<cmStdString, VectorOfPairs > StringToVectorOfPairs;
+
+  StringToVectorOfPairs WatchMap;
+};
+
+
+#endif