contrib/libc++/include/__sso_allocator

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___SSO_ALLOCATOR
  11 #define _LIBCPP___SSO_ALLOCATOR
  12
  13 #include <__config>
  14 #include <type_traits>
  15 #include <new>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 template <class _Tp, size_t _Np> class _LIBCPP_HIDDEN __sso_allocator;
  24
  25 template <size_t _Np>
  26 class _LIBCPP_HIDDEN __sso_allocator<void, _Np>
  27 {
  28 public:
  29     typedef const void*       const_pointer;
  30     typedef void              value_type;
  31 };
  32
  33 template <class _Tp, size_t _Np>
  34 class _LIBCPP_HIDDEN __sso_allocator
  35 {
  36     typename aligned_storage<sizeof(_Tp) * _Np>::type buf_;
  37     bool __allocated_;
  38 public:
  39     typedef size_t            size_type;
  40     typedef _Tp*              pointer;
  41     typedef _Tp               value_type;
  42
  43     _LIBCPP_INLINE_VISIBILITY __sso_allocator() throw() : __allocated_(false) {}
  44     _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}
  45     template <class _Up> _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator<_Up, _Np>&) throw()
  46          : __allocated_(false) {}
  47 private:
  48     __sso_allocator& operator=(const __sso_allocator&);
  49 public:
  50     _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = 0)
  51     {
  52         if (!__allocated_ && __n <= _Np)
  53         {
  54             __allocated_ = true;
  55             return (pointer)&buf_;
  56         }
  57         return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
  58     }
  59     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n)
  60     {
  61         if (__p == (pointer)&buf_)
  62             __allocated_ = false;
  63         else
  64             _VSTD::__libcpp_deallocate(__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
  65     }
  66     _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);}
  67
  68     _LIBCPP_INLINE_VISIBILITY
  69     bool operator==(__sso_allocator& __a) const {return &buf_ == &__a.buf_;}
  70     _LIBCPP_INLINE_VISIBILITY
  71     bool operator!=(__sso_allocator& __a) const {return &buf_ != &__a.buf_;}
  72 };
  73
  74 _LIBCPP_END_NAMESPACE_STD
  75
  76 #endif  // _LIBCPP___SSO_ALLOCATOR