Mixing Qt with STL and Boost - are there any bridges to make it easy?

Question

Are there any bridges to make mixing Qt with STL and Boost as seamless and easy as possible?

This is a followup to Mixing Qt and Boost, where no specific answers how to accomplish this were given.

Answer 1

What bridges do you need?

You can use all the Qt container classes with std algorithms. Most of the time I prefer the Qt container classes because I'm sure they use the copy-on-write idiom (constant time operation). Qt's foreach function creates a copy of the container so its nice that you know for sure it is a constant time operation.

If the Qt signal slot mechanism is to slow you can switch to the boost alternative. The great thing about Qt signal/slot is the signal/slot connection between two threads.

QtConcurrent works great with BOOST.Lambda

---

For "shared" child-parent relationship I use this helper function.

template <class Object>
static boost::shared_ptr<Object> makeSharedObject()
{
    using namespace boost;
    using namespace boost::lambda;
    return boost::shared_ptr<Object>( 
        new Object(),
        bind( &Object::deleteLater, _1 ) );
}

---

Qt containers are not supported by Boost.serialize, you'll have to write the serialize functions yourself. I would love a bridge between the Qt streaming classes and Boost.archive.

Here is my QList serialization template you can figure out the rest of them ...

///\file document is based on "boost/serialization/list.hpp"

namespace boost { 
    namespace serialization {

        //---------------------------------------------------------------------------
        /// Saves a QList object to a collection 
        template<class Archive, class U >
        inline void save(Archive &ar, const QList< U > &t, const uint /* file_version */ )
        {
            boost::serialization::stl::save_collection< Archive, QList<U> >(ar, t);
        }

        //---------------------------------------------------------------------------
        /// Loads a QList object from a collection 
        template<class Archive, class U>
        inline void load(Archive &ar, QList<U > &t, const uint /* file_version */ )
        {
                boost::serialization::stl::load_collection< 
                    Archive, 
                    QList<U>, 
                    boost::serialization::stl::archive_input_seq<Archive, QList<U> >,
                    boost::serialization::stl::no_reserve_imp< QList<U> > >(ar, t);
        }

        //---------------------------------------------------------------------------
        /// split non-intrusive serialization function member into separate
        /// non intrusive save/load member functions
        template<class Archive, class U >
        inline void serialize(Archive &ar, QList<U> &t, const uint file_version )
        {
            boost::serialization::split_free( ar, t, file_version);
        }

    } // namespace serialization
} // namespace boost

BOOST_SERIALIZATION_COLLECTION_TRAITS(QList)

---

If you want Boost.Bind to handle QPointer as a normal pointer (like shared_ptr):

namespace boost {

    template<typename T> T * get_pointer(QPointer<T> const& qPointer)
    {
        return qPointer;
    }
}

---

Using QIODevice where a std::stream is needed

namespace boost {
    namespace iostreams {

        class IoDeviceSource 
        {
        public:
            typedef char char_type;
            typedef source_tag category;

            explicit IoDeviceSource(QIODevice& source) 
                : m_source(source) 
            {
            }

            std::streamsize read(char* buffer, std::streamsize n)
            {
                return return m_source.read(buffer, n);
            }   
        private:
            QIODevice& m_source;
        };

        class IoDeviceSink {

        public:
            typedef char char_type;
            typedef sink_tag category;

            explicit IoDeviceSink(QIODevice& sink)
                : m_sink(sink)
            {
            }

            std::streamsize write(const char_type* buffer, std::streamsize n) 
            {
                return m_sink.write(buffer, n);
            }

        private:
            QIODevice &m_sink;
        };

        class IoDeviceDevice {

        public:
            typedef char char_type;
            typedef seekable_device_tag category;

            explicit IoDeviceDevice(QIODevice& device)
                :m_device(device) {
            }

            std::streamsize write(const char_type *buffer, std::streamsize n)
            {
                return m_device.write(buffer, n);
            }

            std::streamsize read(char* buffer, std::streamsize n)
            {
                return m_device.read(buffer, n);
            }

            stream_offset seek(stream_offset off, std::ios_base::seekdir way)
            {
                using namespace std;
                stream_offset next(0);

                if(way==ios_base::beg)
                {
                    next = m_device.pos();
                } 
                else if(way==ios_base::cur)
                {
                    next = m_device.pos() + offset;
                } 
                else if(way==ios_base::end)
                {
                    next = m_device.size() -1 + offset;
                }
                else
                {
                    throw ios_base::failure("bad seek direction");
                }

                if( !m_device.seek(next) )
                {
                    throw ios_base::failure("bad seek offset");
                }
                return m_device.pos();
            }

        private:    
            QIODevice &m_device;
        };
    }
}

Example

#include <iostream>
#include <QFile>
#include <boost/iostreams/stream.hpp>
#include "iodevicestream.h"

int main(int argc, char *argv[])
{
    namespace io = boost::iostreams;

    QVector<int> data;

    QFile fl("temp.bin");
    fl.open(QIODevice::ReadWrite);
    io::stream<io::IoDeviceDevice> inoutput( fl );  

    std::copy(data.begin(), data.end(), std::ostream_iterator<int>(inoutput, "\n"));
    inoutput.flush();
    inoutput.seekg(0, std::ios_base::beg);
    std::cout << inoutput;
    return 0;
}

Answer 2

What exactly is the problem?
You can ignore all the Qt collection classes if you want and use STL equivalents.
Similarly you can use Boost's cross platform file/network libs.

The main reason to use Qt's own is probably that boost isn't necessarily that widely available, especially on mobile devices. Some of Boost's libs are a little more complicated to use than the Qt ones for simple tasks.