ENH: add caching for the input CMakeList.txt files, 2X speed up

Source/cmListFileCache.h

@@ -0,0 +1,88 @@
+/*=========================================================================
+
+  Program:   Insight Segmentation & Registration Toolkit
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+Copyright (c) 2001 Insight Consortium
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * The name of the Insight Consortium, nor the names of any consortium members,
+   nor of any contributors, may be used to endorse or promote products derived
+   from this software without specific prior written permission.
+
+  * Modified source versions must be plainly marked as such, and must not be
+    misrepresented as being the original software.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS ``AS IS''
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+=========================================================================*/
+#ifndef cmListFileCache_h
+#define cmListFileCache_h
+
+#include "cmStandardIncludes.h"
+
+/** \class cmListFileCache
+ * \brief A class to cache list file contents.
+ *
+ * cmListFileCache is a class used to cache the contents of parsed
+ * cmake list files.
+ */
+
+struct cmListFileFunction
+{
+  std::string m_Name;
+  std::vector<std::string> m_Arguments;
+};
+
+struct cmListFile
+{
+  long int m_ModifiedTime;
+  std::vector<cmListFileFunction> m_Functions;
+};
+
+class cmListFileCache
+{
+public:
+  static cmListFileCache* GetInstance();
+  static void ClearCache();
+
+
+  /** Return the cached version of the given file.
+   *  If the file is not already in the cache, a cache entry
+   *  will be made.  If there is an error loading the file,
+   *  NULL is returned.
+   */
+  cmListFile* GetFileCache(const char* path);
+private:
+  // Cache the file
+  bool cmListFileCache::CacheFile(const char* path);
+  // private data
+  typedef std::map<cmStdString, cmListFile> ListFileMap;
+  ListFileMap m_ListFileCache;  // file name to ListFile map
+  static cmListFileCache* Instance; // singelton pointer
+};
+
+
+#endif