mm.h

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/****************************************************************************
 *
 *  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>
 
// GCC with C++98 and -fexceptions requires exception
// specifiers, however with C++11 and newer, using them causes an error.
#if __cplusplus < 201103L
#define GRASS_MM_USE_EXCEPTION_SPECIFIER
#endif /* __cplusplus < 201103L */
 
#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 designed 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();
 
    // make these members of MM_register
#ifdef GRASS_MM_USE_EXCEPTION_SPECIFIER
    void *operator new(size_t) throw(std::bad_alloc);
    void *operator new[](size_t) throw(std::bad_alloc);
    void operator delete(void *) throw();
    void operator delete[](void *) throw();
#else
    void *operator new(size_t);
    void *operator new[](size_t);
    void operator delete(void *) noexcept;
    void operator delete[](void *) noexcept;
#endif /* GRASS_MM_USE_EXCEPTION_SPECIFIER */
 
    friend class mm_register_init;
};
 
// 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