1 //
2 // detail/thread_info_base.hpp
3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 //
5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
6 //
7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
9 //
10 
11 #ifndef BOOST_ASIO_DETAIL_THREAD_INFO_BASE_HPP
12 #define BOOST_ASIO_DETAIL_THREAD_INFO_BASE_HPP
13 
14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
15 # pragma once
16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
17 
18 #include <climits>
19 #include <cstddef>
20 #include <boost/asio/detail/noncopyable.hpp>
21 
22 #include <boost/asio/detail/push_options.hpp>
23 
24 namespace boost {
25 namespace asio {
26 namespace detail {
27 
28 class thread_info_base
29   : private noncopyable
30 {
31 public:
thread_info_base()32   thread_info_base()
33     : reusable_memory_(0)
34   {
35   }
36 
~thread_info_base()37   ~thread_info_base()
38   {
39     if (reusable_memory_)
40       ::operator delete(reusable_memory_);
41   }
42 
allocate(thread_info_base * this_thread,std::size_t size)43   static void* allocate(thread_info_base* this_thread, std::size_t size)
44   {
45     std::size_t chunks = (size + chunk_size - 1) / chunk_size;
46 
47     if (this_thread && this_thread->reusable_memory_)
48     {
49       void* const pointer = this_thread->reusable_memory_;
50       this_thread->reusable_memory_ = 0;
51 
52       unsigned char* const mem = static_cast<unsigned char*>(pointer);
53       if (static_cast<std::size_t>(mem[0]) >= chunks)
54       {
55         mem[size] = mem[0];
56         return pointer;
57       }
58 
59       ::operator delete(pointer);
60     }
61 
62     void* const pointer = ::operator new(chunks * chunk_size + 1);
63     unsigned char* const mem = static_cast<unsigned char*>(pointer);
64     mem[size] = (chunks <= UCHAR_MAX) ? static_cast<unsigned char>(chunks) : 0;
65     return pointer;
66   }
67 
deallocate(thread_info_base * this_thread,void * pointer,std::size_t size)68   static void deallocate(thread_info_base* this_thread,
69       void* pointer, std::size_t size)
70   {
71     if (size <= chunk_size * UCHAR_MAX)
72     {
73       if (this_thread && this_thread->reusable_memory_ == 0)
74       {
75         unsigned char* const mem = static_cast<unsigned char*>(pointer);
76         mem[0] = mem[size];
77         this_thread->reusable_memory_ = pointer;
78         return;
79       }
80     }
81 
82     ::operator delete(pointer);
83   }
84 
85 private:
86   enum { chunk_size = 4 };
87   void* reusable_memory_;
88 };
89 
90 } // namespace detail
91 } // namespace asio
92 } // namespace boost
93 
94 #include <boost/asio/detail/pop_options.hpp>
95 
96 #endif // BOOST_ASIO_DETAIL_THREAD_INFO_BASE_HPP
97