AllocatorPool.h

Go to the documentation of this file.

/***********************************************************************************\
* (c) Copyright 1998-2025 CERN for the benefit of the LHCb and ATLAS collaborations *
*                                                                                   *
* This software is distributed under the terms of the Apache version 2 licence,     *
* copied verbatim in the file "LICENSE".                                            *
*                                                                                   *
* In applying this licence, CERN does not waive the privileges and immunities       *
* granted to it by virtue of its status as an Intergovernmental Organization        *
* or submit itself to any jurisdiction.                                             *
\***********************************************************************************/
// ============================================================================
// ============================================================================
 
//
// ********************************************************************
// * DISCLAIMER                                                       *
// *                                                                  *
// * The following disclaimer summarizes all the specific disclaimers *
// * of contributors to this software. The specific disclaimers,which *
// * govern, are listed with their locations in:                      *
// *   http://cern.ch/geant4/license                                  *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.                                                             *
// *                                                                  *
// * This  code  implementation is the  intellectual property  of the *
// * GEANT4 collaboration.                                            *
// * By copying,  distributing  or modifying the Program (or any work *
// * based  on  the Program)  you indicate  your  acceptance of  this *
// * statement, and all its terms.                                    *
// ********************************************************************
//
// -------------------------------------------------------------------
//      GEANT 4 class header file
//
// Class description:
//
// Class implementing a memory pool for fast allocation and deallocation
// of memory chunks.  The size of the chunks for small allocated objects
// is fixed to 1Kb and takes into account of memory alignment; for large
// objects it is set to 10 times the object's size.
// The implementation is derived from: B.Stroustrup, The C++ Programming
// Language, Third Edition.
 
//           -------------- G4AllocatorPool ----------------
//
// Author: G.Cosmo (CERN), November 2000
// -------------------------------------------------------------------
 
#pragma once
 
#include <GaudiKernel/Kernel.h>
#include <memory>
 
namespace GaudiUtils {
  class GAUDI_API AllocatorPool final {
  public:
    explicit AllocatorPool( unsigned int n = 0 );
    ~AllocatorPool();
    AllocatorPool( const AllocatorPool& right );
    inline void* Alloc();
    inline void Free( void* b );
    inline unsigned int Size() const;
    void Reset();
 
  private:
    AllocatorPool& operator=( const AllocatorPool& right );
 
  private:
    struct PoolLink final {
      PoolLink* next = nullptr;
    };
    class PoolChunk final {
    public:
      explicit PoolChunk( unsigned int sz ) : size( sz ), mem{ new char[size] } {}
      const unsigned int      size;
      std::unique_ptr<char[]> mem;
      PoolChunk*              next = nullptr;
    };
 
    void Grow();
 
  private:
    const unsigned int esize;
    const unsigned int csize;
    PoolChunk*         chunks  = nullptr;
    PoolLink*          head    = nullptr;
    int                nchunks = 0;
  };
 
} // namespace GaudiUtils
 
// ************************************************************
// Alloc
// ************************************************************
//
inline void* GaudiUtils::AllocatorPool::Alloc() {
  if ( head == 0 ) { Grow(); }
  PoolLink* p = head; // return first element
  head        = p->next;
  return p;
}
 
// ************************************************************
// Free
// ************************************************************
//
inline void GaudiUtils::AllocatorPool::Free( void* b ) {
  PoolLink* p = static_cast<PoolLink*>( b );
  p->next     = head; // put b back as first element
  head        = p;
}
 
// ************************************************************
// Size
// ************************************************************
//
inline unsigned int GaudiUtils::AllocatorPool::Size() const { return nchunks * csize; }