vrpn_SendTextMessageStreamProxy.h

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/** @file
    @brief Header allowing use of a output stream-style method of sending
    text messages from devices. Contains the operator<< overload needed to
    stream into a vrpn_BaseClassUnique::SendTextMessageBoundCall, and the
    proxy object containing an ostringstream that executes the bound call
    when it's done having data streamed in to it.
 
    This is a separate header to avoid including <sstream> in vrpn_BaseClass.h
    since the functionality is only used by device implementations themselves,
    and not even all of them. Further, since we create the stream proxy
    only once we've seen an operator<< (rather than as a part of the bound
   call),
    we know that if a stream proxy exists, it has a message to send.
 
    @date 2011
 
    @author
    Ryan Pavlik
    <rpavlik@iastate.edu> and <abiryan@ryand.net>
    http://academic.cleardefinition.com/
    Iowa State University Virtual Reality Applications Center
    Human-Computer Interaction Graduate Program
*/
 
//          Copyright Iowa State University 2011.
// 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)
 
#pragma once
 
// Internal Includes
#include "vrpn_BaseClass.h"
 
// Library/third-party includes
// - none
 
// Standard includes
#include <sstream>
 
class vrpn_SendTextMessageStreamProxy {
private:
    /// Functor allowing us to perform a send_text_message call on
    /// a device's behalf once we're done having data streamed in.
 vrpn_BaseClassUnique::SendTextMessageBoundCall const& _call;
 
    /// Stream that will accumulate the message
    std::ostringstream _s;
 
    /// assignment operator disabled
 vrpn_SendTextMessageStreamProxy&
    operator=(vrpn_SendTextMessageStreamProxy const&);
 
public:
    /// Templated constructor taking anything streamable.
 template <typename T>
 vrpn_SendTextMessageStreamProxy(
 vrpn_BaseClassUnique::SendTextMessageBoundCall const& call,
        T const& firstData)
        : _call(call)
    {
        _s << firstData;
    }
 
    /// Constructor taking a std::string, since we can use the ostringstream's
    /// std::string constructor in this case.
 vrpn_SendTextMessageStreamProxy(
 vrpn_BaseClassUnique::SendTextMessageBoundCall const& call,
        std::string const& firstData)
        : _call(call)
        , _s(firstData)
    {
    }
 
    /// Copy constructor - required for return by value (?)
 vrpn_SendTextMessageStreamProxy(
 vrpn_SendTextMessageStreamProxy const& other)
        : _call(other._call)
        , _s(other._s.str())
    {
    }
 
    /// Destructor performs the send_text_message call with all contents
    /// streamed into it.
 ~vrpn_SendTextMessageStreamProxy() { _call(_s.str().c_str()); }
 
    /// Template operator<<, used for the second item streamed into the results
    /// of a BoundCall-returning send_text_message() call. The first one is
    /// handled below, and creates this temporary proxy object. Now, we can
    /// return a reference to the internal ostream, and we'll still
    /// stick around until the end of the statement to make the call
    /// once it's all done.
 template <typename T> std::ostream& operator<<(T const& other)
    {
        _s << other;
 return _s;
    }
};
 
/// Templated operator << that takes a
/// vrpn_BaseClassUnique::SendTextMessageBoundCall on the left, and some data on
/// the
/// right, and uses that to initialize and return a temporary
/// vrpn_SendTextMessageStreamProxy who will be able to accept
/// additional streamed data before making the send_text_message call in its
/// destructor at the
/// end of the statement.
template <typename T>
vrpn_SendTextMessageStreamProxy
operator<<(vrpn_BaseClassUnique::SendTextMessageBoundCall const& call,
           T const& firstData)
{
 return vrpn_SendTextMessageStreamProxy(call, firstData);
}