MRUFileList.h

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// -*- C++ -*-

// PLearn (A C++ Machine Learning Library)
// Copyright (C) 1998 Pascal Vincent
// Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio and University of Montreal
//

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
// 
//  2. 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.
// 
//  3. The name of the authors may not be used to endorse or promote
//     products derived from this software without specific prior written
//     permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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// 
// This file is part of the PLearn library. For more information on the PLearn
// library, go to the PLearn Web site at www.plearn.org

// Julien Keable
 

#ifndef MRUFileQueue_H
#define MRUFileQueue_H

#include <fstream>
//#include <iostream>
//#include <string>
#include <list>

namespace PLearn{
using namespace std;

/* 
This class implements a MRU-type (most recently used) list of a maximum of 1000 opened ofstreams,
(so that on each call to 'getFile(string fname)', the file 'fname' is moved to the top of the list.)
If you try to open more than that, the least recently used file is closed beforehand

Typically, after contructing the object, user will only need to call getFile(...), and check errorMsg()
when the function returns NULL.
*/

class MRUFileList
{
public:

  typedef list<pair<string,ofstream*> > list_typ;

  MRUFileList(int _max_opened_files=1000, ios_base::openmode _mode = ios_base::out | ios_base::app);
  ~MRUFileList();

  ofstream * getFile(string fname);

  string errorMsg(){return error;}
  void clearError(){error="";}
  
  // return the cache miss percentage (the % of times the wanted file is not already opened)
  float misses(){return 100.0f * (float)tot_miss/(float)tot_access;}

protected:
  int max_opened_files;
  string error;
  list_typ mru_list;
  int tot_miss,tot_access;
  ios_base::openmode mode;
};

} // end of namespace PLearn  
#endif

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