contrib/libc++/include/__sso_allocator

   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