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+//
+// detail/thread_info_base.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef ASIO_DETAIL_THREAD_INFO_BASE_HPP
+#define ASIO_DETAIL_THREAD_INFO_BASE_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <climits>
+#include <cstddef>
+#include "asio/detail/noncopyable.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+class thread_info_base
+ : private noncopyable
+{
+public:
+ struct default_tag
+ {
+ enum { mem_index = 0 };
+ };
+
+ struct awaitee_tag
+ {
+ enum { mem_index = 1 };
+ };
+
+ thread_info_base()
+ {
+ for (int i = 0; i < max_mem_index; ++i)
+ reusable_memory_[i] = 0;
+ }
+
+ ~thread_info_base()
+ {
+ for (int i = 0; i < max_mem_index; ++i)
+ if (reusable_memory_[i])
+ ::operator delete(reusable_memory_[i]);
+ }
+
+ static void* allocate(thread_info_base* this_thread, std::size_t size)
+ {
+ return allocate(default_tag(), this_thread, size);
+ }
+
+ static void deallocate(thread_info_base* this_thread,
+ void* pointer, std::size_t size)
+ {
+ deallocate(default_tag(), this_thread, pointer, size);
+ }
+
+ template <typename Purpose>
+ static void* allocate(Purpose, thread_info_base* this_thread,
+ std::size_t size)
+ {
+ std::size_t chunks = (size + chunk_size - 1) / chunk_size;
+
+ if (this_thread && this_thread->reusable_memory_[Purpose::mem_index])
+ {
+ void* const pointer = this_thread->reusable_memory_[Purpose::mem_index];
+ this_thread->reusable_memory_[Purpose::mem_index] = 0;
+
+ unsigned char* const mem = static_cast<unsigned char*>(pointer);
+ if (static_cast<std::size_t>(mem[0]) >= chunks)
+ {
+ mem[size] = mem[0];
+ return pointer;
+ }
+
+ ::operator delete(pointer);
+ }
+
+ void* const pointer = ::operator new(chunks * chunk_size + 1);
+ unsigned char* const mem = static_cast<unsigned char*>(pointer);
+ mem[size] = (chunks <= UCHAR_MAX) ? static_cast<unsigned char>(chunks) : 0;
+ return pointer;
+ }
+
+ template <typename Purpose>
+ static void deallocate(Purpose, thread_info_base* this_thread,
+ void* pointer, std::size_t size)
+ {
+ if (size <= chunk_size * UCHAR_MAX)
+ {
+ if (this_thread && this_thread->reusable_memory_[Purpose::mem_index] == 0)
+ {
+ unsigned char* const mem = static_cast<unsigned char*>(pointer);
+ mem[0] = mem[size];
+ this_thread->reusable_memory_[Purpose::mem_index] = pointer;
+ return;
+ }
+ }
+
+ ::operator delete(pointer);
+ }
+
+private:
+ enum { chunk_size = 4 };
+ enum { max_mem_index = 2 };
+ void* reusable_memory_[max_mem_index];
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_THREAD_INFO_BASE_HPP