Question

我按照这个提升示例构建了一个自定义处理程序分配器：http://www.boost.org/doc/libs/1_56_0/doc/html/boost_asio/example/cpp03/allocation/server.cpp
在自定义处理程序上调用io_service.post（）会给出错误： No matching function for call to object of type 'custom_alloc_handler<void (*)()>

以下是一些示例代码：

#include <iostream>
#include "boost/asio.hpp"
#include "boost/bind.hpp"
#include "boost/asio/handler_alloc_hook.hpp"
#include <boost/aligned_storage.hpp>

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();
        }
        else
        {
            return ::operator new(size);
        }
    }

    void deallocate(void* pointer)
    {
        if (pointer == storage_.address())
        {
            in_use_ = false;
        }
        else
        {
            ::operator delete(pointer);
        }
    }

private:
    boost::aligned_storage<1024> storage_;
    bool in_use_;
};

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_;
};

template <typename Handler>
inline custom_alloc_handler<Handler> make_custom_alloc_handler(
                                           handler_allocator& a, Handler h)
{
    return custom_alloc_handler<Handler>(a, h);
}

void handler()
{
    std::cout << "handler called" << std::endl;
}

int main(int argc, const char * argv[])
{

    boost::asio::io_service ioService;
    handler_allocator allocator;

    ioService.post(
        make_custom_alloc_handler(allocator, &handler)
    );

    return 0;
}

问题似乎是由于BOOST_ASIO_COMPLETION_HANDLER_CHECK失败。我找不到办法让它发挥作用。

Answer 1

原因是你必须在custom_alloc_handler中拥有正确的模板功能！

void operator()()
{
   handler_();
}

使用自定义处理程序分配器发布到boost :: io_service

1 个答案: