_pthread_alloc.h

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Copyright (c) 1997
 * Moscow Center for SPARC Technology
 *
 * Copyright (c) 1999 
 * Boris Fomitchev
 *
 * This material is provided "as is", with absolutely no warranty expressed
 * or implied. Any use is at your own risk.
 *
 * Permission to use or copy this software for any purpose is hereby granted 
 * without fee, provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 *
 */

#ifndef _STLP_PTHREAD_ALLOC_H
#define _STLP_PTHREAD_ALLOC_H

// Pthread-specific node allocator.
// This is similar to the default allocator, except that free-list
// information is kept separately for each thread, avoiding locking.
// This should be reasonably fast even in the presence of threads.
// The down side is that storage may not be well-utilized.
// It is not an error to allocate memory in thread A and deallocate
// it in thread B.  But this effectively transfers ownership of the memory,
// so that it can only be reallocated by thread B.  Thus this can effectively
// result in a storage leak if it's done on a regular basis.
// It can also result in frequent sharing of
// cache lines among processors, with potentially serious performance
// consequences.

#ifndef _STLP_INTERNAL_ALLOC_H
#include <stl/_alloc.h>
#endif

#ifndef __RESTRICT
#  define __RESTRICT
#endif

_STLP_BEGIN_NAMESPACE

#define _STLP_DATA_ALIGNMENT 8

union _Pthread_alloc_obj {
    union _Pthread_alloc_obj * __free_list_link;
    char __client_data[_STLP_DATA_ALIGNMENT];    /* The client sees this.    */
};

// Pthread allocators don't appear to the client to have meaningful
// instances.  We do in fact need to associate some state with each
// thread.  That state is represented by
// _Pthread_alloc_per_thread_state<_Max_size>.

template<size_t _Max_size>
struct _Pthread_alloc_per_thread_state {
  typedef _Pthread_alloc_obj __obj;
  enum { _S_NFREELISTS = _Max_size/_STLP_DATA_ALIGNMENT };
  _Pthread_alloc_obj* volatile __free_list[_S_NFREELISTS]; 
  _Pthread_alloc_per_thread_state<_Max_size> * __next; 
        // Free list link for list of available per thread structures.
        // When one of these becomes available for reuse due to thread
        // termination, any objects in its free list remain associated
        // with it.  The whole structure may then be used by a newly
        // created thread.
  _Pthread_alloc_per_thread_state() : __next(0)
  {
    memset((void *)__free_list, 0, (size_t)_S_NFREELISTS * sizeof(__obj *));
  }
  // Returns an object of size __n, and possibly adds to size n free list.
  void *_M_refill(size_t __n);
};

// Pthread-specific allocator.
// The argument specifies the largest object size allocated from per-thread
// free lists.  Larger objects are allocated using malloc_alloc.
// Max_size must be a power of 2.
template < __DFL_NON_TYPE_PARAM(size_t, _Max_size, _MAX_BYTES) >
class _Pthread_alloc {

public: // but only for internal use:

  typedef _Pthread_alloc_obj __obj;

  // Allocates a chunk for nobjs of size size.  nobjs may be reduced
  // if it is inconvenient to allocate the requested number.
  static char *_S_chunk_alloc(size_t __size, int &__nobjs);

  enum {_S_ALIGN = _STLP_DATA_ALIGNMENT};

  static size_t _S_round_up(size_t __bytes) {
        return (((__bytes) + (int)_S_ALIGN-1) & ~((int)_S_ALIGN - 1));
  }
  static size_t _S_freelist_index(size_t __bytes) {
        return (((__bytes) + (int)_S_ALIGN-1)/(int)_S_ALIGN - 1);
  }

private:
  // Chunk allocation state. And other shared state.
  // Protected by _S_chunk_allocator_lock.
  static _STLP_mutex_base _S_chunk_allocator_lock;
  static char *_S_start_free;
  static char *_S_end_free;
  static size_t _S_heap_size;
  static _Pthread_alloc_per_thread_state<_Max_size>* _S_free_per_thread_states;
  static pthread_key_t _S_key;
  static bool _S_key_initialized;
        // Pthread key under which per thread state is stored. 
        // Allocator instances that are currently unclaimed by any thread.
  static void _S_destructor(void *instance);
        // Function to be called on thread exit to reclaim per thread
        // state.
  static _Pthread_alloc_per_thread_state<_Max_size> *_S_new_per_thread_state();
        // Return a recycled or new per thread state.
  static _Pthread_alloc_per_thread_state<_Max_size> *_S_get_per_thread_state();
        // ensure that the current thread has an associated
        // per thread state.
  class _M_lock;
  friend class _M_lock;
  class _M_lock {
      public:
        _M_lock () { _S_chunk_allocator_lock._M_acquire_lock(); }
        ~_M_lock () { _S_chunk_allocator_lock._M_release_lock(); }
  };

public:

  /* n must be > 0      */
  static void * allocate(size_t __n)
  {
    __obj * volatile * __my_free_list;
    __obj * __RESTRICT __result;
    _Pthread_alloc_per_thread_state<_Max_size>* __a;

    if (__n > _Max_size) {
        return(__malloc_alloc<0>::allocate(__n));
    }
    if (!_S_key_initialized ||
        !(__a = (_Pthread_alloc_per_thread_state<_Max_size>*)
                                 pthread_getspecific(_S_key))) {
        __a = _S_get_per_thread_state();
    }
    __my_free_list = __a -> __free_list + _S_freelist_index(__n);
    __result = *__my_free_list;
    if (__result == 0) {
        void *__r = __a -> _M_refill(_S_round_up(__n));
        return __r;
    }
    *__my_free_list = __result -> __free_list_link;
    return (__result);
  };

  /* p may not be 0 */
  static void deallocate(void *__p, size_t __n)
  {
    __obj *__q = (__obj *)__p;
    __obj * volatile * __my_free_list;
    _Pthread_alloc_per_thread_state<_Max_size>* __a;

    if (__n > _Max_size) {
        __malloc_alloc<0>::deallocate(__p, __n);
        return;
    }
    if (!_S_key_initialized ||
        !(__a = (_Pthread_alloc_per_thread_state<_Max_size> *)
                pthread_getspecific(_S_key))) {
        __a = _S_get_per_thread_state();
    }
    __my_free_list = __a->__free_list + _S_freelist_index(__n);
    __q -> __free_list_link = *__my_free_list;
    *__my_free_list = __q;
  }

  static void * reallocate(void *__p, size_t __old_sz, size_t __new_sz);

} ;

# if defined (_STLP_USE_TEMPLATE_EXPORT)
_STLP_EXPORT_TEMPLATE_CLASS _Pthread_alloc<_MAX_BYTES>;
# endif

typedef _Pthread_alloc<_MAX_BYTES> __pthread_alloc;
typedef __pthread_alloc pthread_alloc;

template <class _Tp>
class pthread_allocator {
  typedef pthread_alloc _S_Alloc;          // The underlying allocator.
public:
  typedef size_t     size_type;
  typedef ptrdiff_t  difference_type;
  typedef _Tp*       pointer;
  typedef const _Tp* const_pointer;
  typedef _Tp&       reference;
  typedef const _Tp& const_reference;
  typedef _Tp        value_type;

#ifdef _STLP_MEMBER_TEMPLATE_CLASSES
  template <class _NewType> struct rebind {
    typedef pthread_allocator<_NewType> other;
  };
#endif

  pthread_allocator() _STLP_NOTHROW {}
  pthread_allocator(const pthread_allocator<_Tp>& a) _STLP_NOTHROW {}

#if defined (_STLP_MEMBER_TEMPLATES) && defined (_STLP_FUNCTION_PARTIAL_ORDER)
  template <class _OtherType> pthread_allocator(const pthread_allocator<_OtherType>&)
                _STLP_NOTHROW {}
#endif

  ~pthread_allocator() _STLP_NOTHROW {}

  pointer address(reference __x) const { return &__x; }
  const_pointer address(const_reference __x) const { return &__x; }

  // __n is permitted to be 0.  The C++ standard says nothing about what
  // the return value is when __n == 0.
  _Tp* allocate(size_type __n, const void* = 0) {
    return __n != 0 ? __STATIC_CAST(_Tp*,_S_Alloc::allocate(__n * sizeof(_Tp)))
                    : 0;
  }

  // p is not permitted to be a null pointer.
  void deallocate(pointer __p, size_type __n)
    { _S_Alloc::deallocate(__p, __n * sizeof(_Tp)); }

  size_type max_size() const _STLP_NOTHROW 
    { return size_t(-1) / sizeof(_Tp); }

  void construct(pointer __p, const _Tp& __val) { _STLP_PLACEMENT_NEW (__p) _Tp(__val); }
  void destroy(pointer _p) { _p->~_Tp(); }
};

_STLP_TEMPLATE_NULL
class _STLP_CLASS_DECLSPEC pthread_allocator<void> {
public:
  typedef size_t      size_type;
  typedef ptrdiff_t   difference_type;
  typedef void*       pointer;
  typedef const void* const_pointer;
  typedef void        value_type;
#ifdef _STLP_MEMBER_TEMPLATE_CLASSES
  template <class _NewType> struct rebind {
    typedef pthread_allocator<_NewType> other;
  };
#endif
};

/*
template <size_t _Max_size>
inline bool operator==(const _Pthread_alloc<_Max_size>&,
                       const _Pthread_alloc<_Max_size>&)
{
  return true;
}
*/

template <class _T1, class _T2>
inline bool operator==(const pthread_allocator<_T1>&,
                       const pthread_allocator<_T2>& a2) 
{
  return true;
}

#ifdef _STLP_FUNCTION_TMPL_PARTIAL_ORDER
template <class _T1, class _T2>
inline bool operator!=(const pthread_allocator<_T1>&,
                       const pthread_allocator<_T2>&)
{
  return false;
}
#endif

#ifdef _STLP_CLASS_PARTIAL_SPECIALIZATION

template <class _Tp, size_t _Max_size>
struct _Alloc_traits<_Tp, _Pthread_alloc<_Max_size> >
{
  typedef __allocator<_Tp, _Pthread_alloc<_Max_size> > 
          allocator_type;
};

template <class _Tp, class _Atype>
struct _Alloc_traits<_Tp, pthread_allocator<_Atype> >
{
  typedef pthread_allocator<_Tp> allocator_type;
};

#endif

#if !defined (_STLP_MEMBER_TEMPLATE_CLASSES)

template <class _Tp1, class _Tp2>
inline pthread_allocator<_Tp2>&
__stl_alloc_rebind(pthread_allocator<_Tp1>& __x, const _Tp2*) {
  return (pthread_allocator<_Tp2>&)__x;
}

template <class _Tp1, class _Tp2>
inline pthread_allocator<_Tp2>
__stl_alloc_create(pthread_allocator<_Tp1>&, const _Tp2*) {
  return pthread_allocator<_Tp2>();
}

#endif /* _STLP_MEMBER_TEMPLATE_CLASSES */

_STLP_END_NAMESPACE

# if defined (_STLP_EXPOSE_GLOBALS_IMPLEMENTATION) && !defined (_STLP_LINK_TIME_INSTANTIATION)
#  include <stl/_pthread_alloc.c>
# endif

#endif /* _STLP_PTHREAD_ALLOC */

// Local Variables:
// mode:C++
// End:

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