Re: [Boost-users] boost::asio::read_until w/ boost::function

Subject: Re: [Boost-users] boost::asio::read_until w/ boost::function
From: marty (marty_at_[hidden])
Date: 2010-02-23 15:32:43

Thanks for your input.  Unfortunately; no dice.  It still doesn't 
compile (below), and the error(also below) provides little insight in my 
relatively inexperienced assessment.  I have a feeling that the 
enable_if mechanism is not behaving properly on my particular system.

(the fact that others have successfully compiled this implies that the 
boost::function must have the correct signature to satisfy the 
enable_if....)

----error
/usr/local/include/boost/asio/read_until.hpp: In instantiation of 
`boost::asio::detail::has_result_type<boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)> >':
/usr/local/include/boost/asio/read_until.hpp:75:   instantiated from 
`boost::asio::is_match_condition<boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)> >'
/usr/local/include/boost/utility/enable_if.hpp:36:   instantiated from 
`boost::enable_if<boost::asio::is_match_condition<boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)> >, 
void>'
../src/temp.cpp:56:   instantiated from here
/usr/local/include/boost/asio/read_until.hpp:60: error: call of 
overloaded `helper(const 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>&)' 
is ambiguous
/usr/local/include/boost/asio/read_until.hpp:57: note: candidates are: 
static boost::asio::detail::has_result_type<T>::big 
boost::asio::detail::has_result_type<T>::helper(U, ...) [with U = 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>, T = 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>]
/usr/local/include/boost/asio/read_until.hpp:58: note:                 
static char boost::asio::detail::has_result_type<T>::helper(U, typename 
U::result_type*) [with U = 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>, T = 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>]
/usr/local/include/boost/asio/read_until.hpp:60: error: enumerator value 
for `value' not integer constant
../src/temp.cpp: In constructor `MyClass::MyClass()':
../src/temp.cpp:56: error: no matching function for call to 
`read_until(boost::asio::serial_port&, boost::asio::streambuf&, 
boost::function<std::pair<boost::asio::buffers_iterator<boost::asio::const_buffers_1, 
char>, bool> 
()(boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>, 
boost::asio::buffers_iterator<boost::asio::const_buffers_1, char>)>&)'

----temp.cpp
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/function.hpp>

using namespace std;

class MyClass {
private:
    boost::asio::serial_port _port;
    boost::asio::io_service _service;
    boost::asio::streambuf _readBuffer;

    typedef 
boost::asio::buffers_iterator<boost::asio::streambuf::const_buffers_type> 
t_Iterator;
    typedef std::pair<t_Iterator, bool> t_ConditionPair;

    t_ConditionPair customCondition(t_Iterator i1, t_Iterator i2)
    {
        t_ConditionPair cond;
        return cond;
    }

public:
    MyClass() :
        _port(_service, "/dev/ttyS0")
    {
        boost::function<t_ConditionPair(t_Iterator,t_Iterator)> cond =
            boost::bind(
                &MyClass::customCondition,
                this,
                _1,
                _2
                );

        boost::asio::read_until(
            _port,
            _readBuffer,
            cond
            );
    };

    virtual ~MyClass()
    { };
};

> On Sat, Feb 20, 2010 at 10:56 AM, Igor R <boost.lists_at_[hidden] 
> <mailto:boost.lists_at_[hidden]>> wrote:
>
>     > I'm having some trouble resolving the call to read_until
>     > (see snippet below)
>     >
>     > Is there some reason I am not be able to use a boost::function
>     > as the MatchCondition object?
>
>     It compiles well with MSVC9.0
>
>  
> As a workaround, try assigning the result of the bind to a 
> boost::function<> object of the appropriate type first, and then 
> passing that boost::function<> object by value into the asio method
>
> Not sure if it will work, but if nothing else it might get the 
> compiler to give you a different error and you can figure something out.
>  
> ------------------------------------------------------------------------
>
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