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      1 // -*- C++ -*-
      2 //===----------------------------------------------------------------------===//
      3 //
      4 //                     The LLVM Compiler Infrastructure
      5 //
      6 // This file is dual licensed under the MIT and the University of Illinois Open
      7 // Source Licenses. See LICENSE.TXT for details.
      8 //
      9 //===----------------------------------------------------------------------===//
     10 
     11 #ifndef _LIBCPP___SSO_ALLOCATOR
     12 #define _LIBCPP___SSO_ALLOCATOR
     13 
     14 #include <__config>
     15 #include <type_traits>
     16 #include <new>
     17 
     18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
     19 #pragma GCC system_header
     20 #endif
     21 
     22 _LIBCPP_BEGIN_NAMESPACE_STD
     23 
     24 template <class _Tp, size_t _Np> class _LIBCPP_HIDDEN __sso_allocator;
     25 
     26 template <size_t _Np>
     27 class _LIBCPP_HIDDEN __sso_allocator<void, _Np>
     28 {
     29 public:
     30     typedef const void*       const_pointer;
     31     typedef void              value_type;
     32 };
     33 
     34 template <class _Tp, size_t _Np>
     35 class _LIBCPP_HIDDEN __sso_allocator
     36 {
     37     typename aligned_storage<sizeof(_Tp) * _Np>::type buf_;
     38     bool __allocated_;
     39 public:
     40     typedef size_t            size_type;
     41     typedef _Tp*              pointer;
     42     typedef _Tp               value_type;
     43 
     44     _LIBCPP_INLINE_VISIBILITY __sso_allocator() throw() : __allocated_(false) {}
     45     _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}
     46     template <class _Up> _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator<_Up, _Np>&) throw()
     47          : __allocated_(false) {}
     48 private:
     49     __sso_allocator& operator=(const __sso_allocator&);
     50 public:
     51     _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = 0)
     52     {
     53         if (!__allocated_ && __n <= _Np)
     54         {
     55             __allocated_ = true;
     56             return (pointer)&buf_;
     57         }
     58         return static_cast<pointer>(::operator new(__n * sizeof(_Tp)));
     59     }
     60     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type)
     61     {
     62         if (__p == (pointer)&buf_)
     63             __allocated_ = false;
     64         else
     65             ::operator delete(__p);
     66     }
     67     _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);}
     68 
     69     _LIBCPP_INLINE_VISIBILITY
     70     bool operator==(__sso_allocator& __a) const {return &buf_ == &__a.buf_;}
     71     _LIBCPP_INLINE_VISIBILITY
     72     bool operator!=(__sso_allocator& __a) const {return &buf_ != &__a.buf_;}
     73 };
     74 
     75 _LIBCPP_END_NAMESPACE_STD
     76 
     77 #endif  // _LIBCPP___SSO_ALLOCATOR
     78