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zeromq
ErniBrown
ErniBrown

Reputation: 1372

Zero-Copy messaging with zmqpp

ZeroCopy messaging is something that can be implemented in zeromq, but is it possible to use it with the zmqpp c++ bindings? There is almost no documentation, and I was not able to find anything in the examples...

Upvotes: 2

Views: 1352

Answers (2)

Fang DaHong
Fang DaHong

Reputation: 59

Just simply use zmqpp::message::copy().

In the zmqpp source code we can see:

void message::copy(message const& source)
{
    _parts.resize( source._parts.size() );
    for(size_t i = 0; i < source._parts.size(); ++i)
    {
        _parts[i] = source._parts[i].copy();
    }

    // we don't need a copy of the releasers as we did data copies of the internal data,
    //_releasers = source._releasers;
    //_strings = source._strings
}

the _parts which defined as:

private:
    typedef std::vector<frame> parts_type;
    parts_type _parts;

so, source._parts[i].copy() actually call zmqpp::frame::copy() which defined here:

frame frame::copy() const
{
    frame other( size() );
    other._sent = _sent;

    if( 0 != zmq_msg_copy( &other._msg, const_cast<zmq_msg_t*>(&_msg) ) )
    {
        throw zmq_internal_exception();
    }

    return other;
}

zmqpp::frame::_msg in the code snippet is defined as zmq_msg_t. All zmq_msg_t object in the frame objects of source zmqpp::message object been zero copied by zmq_msg_copy to new zmqpp::message object.

so, zmqpp::message::copy() help us get a new zmqpp::message object which it's all frame is zero copied from the source zmqpp::message object.

Upvotes: 0

jamesdillonharvey
jamesdillonharvey

Reputation: 1042

I would switch to cppzmq.

It's a more active project and maintained by some of the core libzmq people.

It's header only and has support for zero copy.

Upvotes: 2

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