libzmq/src/msg.cpp

/*
    Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "msg.hpp"
#include "../include/zmq.h"

#include <string.h>
#include <stdlib.h>
#include <new>

#include "stdint.hpp"
#include "likely.hpp"
#include "err.hpp"

//  Check whether the sizes of public representation of the message (zmq_msg_t)
//  and private representation of the message (zmq::msg_t) match.
typedef char zmq_msg_size_check
    [2 * ((sizeof (zmq::msg_t) == sizeof (zmq_msg_t)) != 0) - 1];

bool zmq::msg_t::check ()
{
     return u.base.type >= type_min && u.base.type <= type_max;
}

int zmq::msg_t::init ()
{
    u.vsm.type = type_vsm;
    u.vsm.flags = 0;
    u.vsm.size = 0;
    return 0;
}

int zmq::msg_t::init_size (size_t size_)
{
    if (size_ <= max_vsm_size) {
        u.vsm.type = type_vsm;
        u.vsm.flags = 0;
        u.vsm.size = (unsigned char) size_;
    }
    else {
        u.lmsg.type = type_lmsg;
        u.lmsg.flags = 0;
        u.lmsg.content =
            (content_t*) malloc (sizeof (content_t) + size_);
        if (!u.lmsg.content) {
            errno = ENOMEM;
            return -1;
        }

        u.lmsg.content->data = u.lmsg.content + 1;
        u.lmsg.content->size = size_;
        u.lmsg.content->ffn = NULL;
        u.lmsg.content->hint = NULL;
        new (&u.lmsg.content->refcnt) zmq::atomic_counter_t ();
    }
    return 0;
}

int zmq::msg_t::init_data (void *data_, size_t size_, msg_free_fn *ffn_,
    void *hint_)
{
    u.lmsg.type = type_lmsg;
    u.lmsg.flags = 0;
    u.lmsg.content = (content_t*) malloc (sizeof (content_t));
    if (!u.lmsg.content) {
        errno = ENOMEM;
        return -1;
    }

    u.lmsg.content->data = data_;
    u.lmsg.content->size = size_;
    u.lmsg.content->ffn = ffn_;
    u.lmsg.content->hint = hint_;
    new (&u.lmsg.content->refcnt) zmq::atomic_counter_t ();
    return 0;

}

int zmq::msg_t::init_delimiter ()
{
    u.delimiter.type = type_delimiter;
    u.delimiter.flags = 0;
    return 0;
}

int zmq::msg_t::close ()
{
    //  Check the validity of the message.
    if (unlikely (!check ())) {
        errno = EFAULT;
        return -1;
    }

    if (u.base.type == type_lmsg) {

        //  If the content is not shared, or if it is shared and the reference
        //  count has dropped to zero, deallocate it.
        if (!(u.lmsg.flags & msg_t::shared) ||
              !u.lmsg.content->refcnt.sub (1)) {

            //  We used "placement new" operator to initialize the reference
            //  counter so we call the destructor explicitly now.
            u.lmsg.content->refcnt.~atomic_counter_t ();

            if (u.lmsg.content->ffn)
                u.lmsg.content->ffn (u.lmsg.content->data,
                    u.lmsg.content->hint);
            free (u.lmsg.content);
        }
    }

    //  Make the message invalid.
    u.base.type = 0;

    return 0;

}

int zmq::msg_t::move (msg_t &src_)
{
    //  Check the validity of the source.
    if (unlikely (!src_.check ())) {
        errno = EFAULT;
        return -1;
    }

    int rc = close ();
    if (unlikely (rc < 0))
        return rc;

    *this = src_;

    rc = src_.init ();
    if (unlikely (rc < 0))
        return rc;

    return 0;
}

int zmq::msg_t::copy (msg_t &src_)
{
    //  Check the validity of the source.
    if (unlikely (!src_.check ())) {
        errno = EFAULT;
        return -1;
    }

    int rc = close ();
    if (unlikely (rc < 0))
        return rc;

    if (src_.u.base.type == type_lmsg) {

        //  One reference is added to shared messages. Non-shared messages
        //  are turned into shared messages and reference count is set to 2.
        if (src_.u.lmsg.flags & msg_t::shared)
            src_.u.lmsg.content->refcnt.add (1);
        else {
            src_.u.lmsg.flags |= msg_t::shared;
            src_.u.lmsg.content->refcnt.set (2);
        }
    }

    *this = src_;

    return 0;

}

void *zmq::msg_t::data ()
{
    //  Check the validity of the message.
    zmq_assert (check ());

    switch (u.base.type) {
    case type_vsm:
        return u.vsm.data;
    case type_lmsg:
        return u.lmsg.content->data;
    default:
        zmq_assert (false);
        return NULL;
    }
}

size_t zmq::msg_t::size ()
{
    //  Check the validity of the message.
    zmq_assert (check ());

    switch (u.base.type) {
    case type_vsm:
        return u.vsm.size;
    case type_lmsg:
        return u.lmsg.content->size;
    default:
        zmq_assert (false);
        return 0;
    }
}

unsigned char zmq::msg_t::flags ()
{
    return u.base.flags;
}

void zmq::msg_t::set_flags (unsigned char flags_)
{
    u.base.flags |= flags_;
}

void zmq::msg_t::reset_flags (unsigned char flags_)
{
    u.base.flags &= ~flags_;
}

bool zmq::msg_t::is_identity () const
{
    return (u.base.flags & identity) == identity;
}

bool zmq::msg_t::is_delimiter ()
{
    return u.base.type == type_delimiter;
}

bool zmq::msg_t::is_vsm ()
{
    return u.base.type == type_vsm;
}

void zmq::msg_t::add_refs (int refs_)
{
    zmq_assert (refs_ >= 0);

    //  No copies required.
    if (!refs_)
        return;

    //  VSMs and delimiters can be copied straight away. The only message type
    //  that needs special care are long messages.
    if (u.base.type == type_lmsg) {
        if (u.lmsg.flags & msg_t::shared)
            u.lmsg.content->refcnt.add (refs_);
        else {
            u.lmsg.content->refcnt.set (refs_ + 1);
            u.lmsg.flags |= msg_t::shared;
        }
    }
}

bool zmq::msg_t::rm_refs (int refs_)
{
    zmq_assert (refs_ >= 0);

    //  No copies required.
    if (!refs_)
        return true;

    //  If there's only one reference close the message.
    if (u.base.type != type_lmsg || !(u.lmsg.flags & msg_t::shared)) {
        close ();
        return false;
    }

    //  The only message type that needs special care are long messages.
    if (!u.lmsg.content->refcnt.sub (refs_)) {
        //  We used "placement new" operator to initialize the reference
        //  counter so we call the destructor explicitly now.
        u.lmsg.content->refcnt.~atomic_counter_t ();

        if (u.lmsg.content->ffn)
            u.lmsg.content->ffn (u.lmsg.content->data, u.lmsg.content->hint);
        free (u.lmsg.content);

        return false;
    }

    return true;
}