/****************************************************************************
 * 
 *  MODULE:     iostream
 *

 *  COPYRIGHT (C) 2007 Laura Toma
 *   
 * 

 *  Iostream is a library that implements streams, external memory
 *  sorting on streams, and an external memory priority queue on
 *  streams. These are the fundamental components used in external
 *  memory algorithms.  

 * Credits: The library was developed by Laura Toma.  The kernel of
 * class STREAM is based on the similar class existent in the GPL TPIE
 * project developed at Duke University. The sorting and priority
 * queue have been developed by Laura Toma based on communications
 * with Rajiv Wickremesinghe. The library was developed as part of
 * porting Terraflow to GRASS in 2001.  PEARL upgrades in 2003 by
 * Rajiv Wickremesinghe as part of the Terracost project.

 * 
 *  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; either version 2 of the License, or
 *  (at your option) any later version.
 *

 *  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.  *
 *  **************************************************************************/


#ifndef _MM_H
#define _MM_H

#include <sys/types.h>


#define MM_REGISTER_VERSION 2

// The default amount of memory we will allow to be allocated (40MB).
#define MM_DEFAULT_MM_SIZE (40<<20)


// MM accounting modes
typedef enum {
  MM_IGNORE_MEMORY_EXCEEDED=0,
  MM_ABORT_ON_MEMORY_EXCEEDED,
  MM_WARN_ON_MEMORY_EXCEEDED
} MM_mode;


// MM Error codes
enum MM_err {
  MM_ERROR_NO_ERROR = 0,
  MM_ERROR_INSUFFICIENT_SPACE,
  MM_ERROR_UNDERFLOW,
  MM_ERROR_EXCESSIVE_ALLOCATION
};


// types of memory usage queries we can make on streams
enum MM_stream_usage {
  // Overhead of the object without the buffer
  MM_STREAM_USAGE_OVERHEAD = 1,

  // amount used by a buffer
  MM_STREAM_USAGE_BUFFER,

  // Amount currently in use.
  MM_STREAM_USAGE_CURRENT,

  // Maximum amount possibly in use.
  MM_STREAM_USAGE_MAXIMUM
};




// Declarations of a very simple memory manager desgined to work with
// BTEs that rely on the underlying OS to manage physical memory.
class MM_register {
private:
  // The number of instances of this class and descendents that exist.
  static int instances;
  
  // The amount of space remaining to be allocated.
  size_t   remaining;
  
  // The user-specified limit on memory. 
  size_t   user_limit;
  
  // the amount that has been allocated.
  size_t   used;
  
  // flag indicates how we are keeping track of memory 
  static MM_mode register_new;

//protected: 
//  // private methods, only called by operators new and delete.

public: //  Need to be accessible from pqueue constructor
  MM_err register_allocation  (size_t sz);
  MM_err register_deallocation(size_t sz);

  
public:
  MM_register();
  ~MM_register(void);

  MM_err set_memory_limit(size_t sz);  
  void   enforce_memory_limit ();    
  void   ignore_memory_limit ();     
  void   warn_memory_limit ();       
  MM_mode get_limit_mode();
  void print_limit_mode();

  size_t memory_available ();        
  size_t memory_used ();             
  size_t memory_limit ();            

  int    space_overhead ();          
 
  void print();

  friend class mm_register_init;
  friend void * operator new(size_t) throw(std::bad_alloc);
  friend void * operator new[](size_t) throw(std::bad_alloc);
  friend void operator delete(void *) throw();
  friend void operator delete[](void *) throw();
};




// A class to make sure that MM_manager gets set up properly (only one
// instance) .
class mm_register_init {
private:
  // The number of mm_register_init objects that exist.
  static unsigned int count;
  
public:
  mm_register_init(void);
  ~mm_register_init(void);
};

static mm_register_init source_file_mm_register_init;





// Here is the single memory management object (defined in mm.C).
extern MM_register MM_manager;



#endif // _MM_H 
