ArenaBlock.h

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// This file's extension implies that it's C, but it's really -*- C++ -*-.
/*
  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
*/
#ifndef ATLALLOCATORS_ARENABLOCK_H
#define ATLALLOCATORS_ARENABLOCK_H
 
 
#include <cstdlib>
#include <atomic>
#include "AthAllocators/ArenaBlockAlignDetail.h"
 
namespace SG {
 
 
 
class ArenaAllocatorBase;
 
class ArenaBlock
{
public:
  typedef char* pointer;
  typedef const char* const_pointer;
 
  typedef void func_t (pointer);
 
 
  static ArenaBlock* newBlock (size_t n, size_t elt_size, func_t* ctor);
 
 
  static void destroy (ArenaBlock* p, func_t* dtor);
 
 
  static void destroyList (ArenaBlock* p, func_t* dtor);
 
 
  static void appendList (ArenaBlock** headp, ArenaBlock* tail);
 
 
  static void applyList (ArenaBlock* p, func_t* func, size_t n);
 
 
  size_t size() const;
 
 
  size_t eltSize() const;
 
 
  ArenaBlock* & link();
 
 
  const ArenaBlock* link() const;
 
 
  pointer index (size_t i);
 
 
  const_pointer index (size_t i) const;
 
 
  pointer index (size_t i, size_t elt_size);
 
 
  const_pointer index (size_t i, size_t elt_size) const;
 
 
  static size_t overhead();
 
 
  static size_t nactive();
 
 
  void protect();
 
 
  void unprotect();
 
 
  static void protectList (ArenaBlock* p);
 
 
  static void unprotectList (ArenaBlock* p);
 
private:
  ArenaBlock (size_t n, size_t elt_size);
  ~ArenaBlock() {}
  ArenaBlock (const ArenaBlock&);
  ArenaBlock& operator= (const ArenaBlock&);
 
  // This is not really needed.  It's just to squelch the g++ warning
  // about classes with all private ctors/dtors and no friends.
  friend class ArenaAllocatorBase;
 
  ArenaBlock* m_link;
 
  size_t m_size;
 
  size_t m_elt_size;
 
  // The start of the block body.
  // Try to make sure it's aligned.
  ArenaBlockAlignDetail::padForAlign m_dummy;
 
  static std::atomic<size_t> s_nactive;
};
 
 
static const int ArenaBlockBodyOffset =
  sizeof (ArenaBlock) - sizeof (ArenaBlockAlignDetail::padForAlign);
 
 
} // namespace SG
 
 
#include "AthAllocators/ArenaBlock.icc"
 
 
#endif // not ATLALLOCATORS_ARENABLOCK_H