ceph/src/boost/boost/asio/detail/call_stack.hpp

   1 //
   2 // detail/call_stack.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2019 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_CALL_STACK_HPP
  12 #define BOOST_ASIO_DETAIL_CALL_STACK_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/config.hpp>
  19 #include <boost/asio/detail/noncopyable.hpp>
  20 #include <boost/asio/detail/tss_ptr.hpp>
  21
  22 #include <boost/asio/detail/push_options.hpp>
  23
  24 namespace boost {
  25 namespace asio {
  26 namespace detail {
  27
  28 // Helper class to determine whether or not the current thread is inside an
  29 // invocation of io_context::run() for a specified io_context object.
  30 template <typename Key, typename Value = unsigned char>
  31 class call_stack
  32 {
  33 public:
  34   // Context class automatically pushes the key/value pair on to the stack.
  35   class context
  36     : private noncopyable
  37   {
  38   public:
  39     // Push the key on to the stack.
  40     explicit context(Key* k)
  41       : key_(k),
  42         next_(call_stack<Key, Value>::top_)
  43     {
  44       value_ = reinterpret_cast<unsigned char*>(this);
  45       call_stack<Key, Value>::top_ = this;
  46     }
  47
  48     // Push the key/value pair on to the stack.
  49     context(Key* k, Value& v)
  50       : key_(k),
  51         value_(&v),
  52         next_(call_stack<Key, Value>::top_)
  53     {
  54       call_stack<Key, Value>::top_ = this;
  55     }
  56
  57     // Pop the key/value pair from the stack.
  58     ~context()
  59     {
  60       call_stack<Key, Value>::top_ = next_;
  61     }
  62
  63     // Find the next context with the same key.
  64     Value* next_by_key() const
  65     {
  66       context* elem = next_;
  67       while (elem)
  68       {
  69         if (elem->key_ == key_)
  70           return elem->value_;
  71         elem = elem->next_;
  72       }
  73       return 0;
  74     }
  75
  76   private:
  77     friend class call_stack<Key, Value>;
  78
  79     // The key associated with the context.
  80     Key* key_;
  81
  82     // The value associated with the context.
  83     Value* value_;
  84
  85     // The next element in the stack.
  86     context* next_;
  87   };
  88
  89   friend class context;
  90
  91   // Determine whether the specified owner is on the stack. Returns address of
  92   // key if present, 0 otherwise.
  93   static Value* contains(Key* k)
  94   {
  95     context* elem = top_;
  96     while (elem)
  97     {
  98       if (elem->key_ == k)
  99         return elem->value_;
 100       elem = elem->next_;
 101     }
 102     return 0;
 103   }
 104
 105   // Obtain the value at the top of the stack.
 106   static Value* top()
 107   {
 108     context* elem = top_;
 109     return elem ? elem->value_ : 0;
 110   }
 111
 112 private:
 113   // The top of the stack of calls for the current thread.
 114   static tss_ptr<context> top_;
 115 };
 116
 117 template <typename Key, typename Value>
 118 tss_ptr<typename call_stack<Key, Value>::context>
 119 call_stack<Key, Value>::top_;
 120
 121 } // namespace detail
 122 } // namespace asio
 123 } // namespace boost
 124
 125 #include <boost/asio/detail/pop_options.hpp>
 126
 127 #endif // BOOST_ASIO_DETAIL_CALL_STACK_HPP