| // |
| // handler_allocator.cpp |
| // ~~~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2016 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 HANDLER_ALLOCATOR_HPP |
| #define HANDLER_ALLOCATOR_HPP |
| |
| #include "asio.hpp" |
| #include <boost/aligned_storage.hpp> |
| #include <boost/noncopyable.hpp> |
| |
| // Class to manage the memory to be used for handler-based custom allocation. |
| // It contains a single block of memory which may be returned for allocation |
| // requests. If the memory is in use when an allocation request is made, the |
| // allocator delegates allocation to the global heap. |
| class handler_allocator |
| : private boost::noncopyable |
| { |
| public: |
| handler_allocator() |
| : in_use_(false) |
| { |
| } |
| |
| void* allocate(std::size_t size) |
| { |
| if (!in_use_ && size < storage_.size) |
| { |
| in_use_ = true; |
| return storage_.address(); |
| } |
| |
| return ::operator new(size); |
| } |
| |
| void deallocate(void* pointer) |
| { |
| if (pointer == storage_.address()) |
| { |
| in_use_ = false; |
| } |
| else |
| { |
| ::operator delete(pointer); |
| } |
| } |
| |
| private: |
| // Storage space used for handler-based custom memory allocation. |
| boost::aligned_storage<1024> storage_; |
| |
| // Whether the handler-based custom allocation storage has been used. |
| bool in_use_; |
| }; |
| |
| // Wrapper class template for handler objects to allow handler memory |
| // allocation to be customised. Calls to operator() are forwarded to the |
| // encapsulated handler. |
| template <typename Handler> |
| class custom_alloc_handler |
| { |
| public: |
| custom_alloc_handler(handler_allocator& a, Handler h) |
| : allocator_(a), |
| handler_(h) |
| { |
| } |
| |
| template <typename Arg1> |
| void operator()(Arg1 arg1) |
| { |
| handler_(arg1); |
| } |
| |
| template <typename Arg1, typename Arg2> |
| void operator()(Arg1 arg1, Arg2 arg2) |
| { |
| handler_(arg1, arg2); |
| } |
| |
| friend void* asio_handler_allocate(std::size_t size, |
| custom_alloc_handler<Handler>* this_handler) |
| { |
| return this_handler->allocator_.allocate(size); |
| } |
| |
| friend void asio_handler_deallocate(void* pointer, std::size_t /*size*/, |
| custom_alloc_handler<Handler>* this_handler) |
| { |
| this_handler->allocator_.deallocate(pointer); |
| } |
| |
| private: |
| handler_allocator& allocator_; |
| Handler handler_; |
| }; |
| |
| // Helper function to wrap a handler object to add custom allocation. |
| template <typename Handler> |
| inline custom_alloc_handler<Handler> make_custom_alloc_handler( |
| handler_allocator& a, Handler h) |
| { |
| return custom_alloc_handler<Handler>(a, h); |
| } |
| |
| #endif // HANDLER_ALLOCATOR_HPP |