libzmq/src/v2_decoder.cpp

/*
    Copyright (c) 2007-2015 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 <stdlib.h>
#include <string.h>

#include "platform.hpp"
#ifdef ZMQ_HAVE_WINDOWS
#include "windows.hpp"
#endif

#include "v2_protocol.hpp"
#include "v2_decoder.hpp"
#include "likely.hpp"
#include "wire.hpp"
#include "err.hpp"

zmq::v2_decoder_t::v2_decoder_t (size_t bufsize_, int64_t maxmsgsize_) :
    decoder_base_t <v2_decoder_t> (bufsize_),
    msg_flags (0),
    maxmsgsize (maxmsgsize_)
{
    int rc = in_progress.init ();
    errno_assert (rc == 0);

    //  At the beginning, read one byte and go to flags_ready state.
    next_step (tmpbuf, 1, &v2_decoder_t::flags_ready);
}

zmq::v2_decoder_t::~v2_decoder_t ()
{
    int rc = in_progress.close ();
    errno_assert (rc == 0);
}

int zmq::v2_decoder_t::flags_ready ()
{
    msg_flags = 0;
    if (tmpbuf [0] & v2_protocol_t::more_flag)
        msg_flags |= msg_t::more;
    if (tmpbuf [0] & v2_protocol_t::command_flag)
        msg_flags |= msg_t::command;

    //  The payload length is either one or eight bytes,
    //  depending on whether the 'large' bit is set.
    if (tmpbuf [0] & v2_protocol_t::large_flag)
        next_step (tmpbuf, 8, &v2_decoder_t::eight_byte_size_ready);
    else
        next_step (tmpbuf, 1, &v2_decoder_t::one_byte_size_ready);

    return 0;
}

int zmq::v2_decoder_t::one_byte_size_ready ()
{
    //  Message size must not exceed the maximum allowed size.
    if (maxmsgsize >= 0)
        if (unlikely (tmpbuf [0] > static_cast <uint64_t> (maxmsgsize))) {
            errno = EMSGSIZE;
            return -1;
        }

    //  in_progress is initialised at this point so in theory we should
    //  close it before calling zmq_msg_init_size, however, it's a 0-byte
    //  message and thus we can treat it as uninitialised...
    int rc = in_progress.init_size (tmpbuf [0]);
    if (unlikely (rc)) {
        errno_assert (errno == ENOMEM);
        rc = in_progress.init ();
        errno_assert (rc == 0);
        errno = ENOMEM;
        return -1;
    }

    in_progress.set_flags (msg_flags);
    next_step (in_progress.data (), in_progress.size (),
        &v2_decoder_t::message_ready);

    return 0;
}

int zmq::v2_decoder_t::eight_byte_size_ready ()
{
    //  The payload size is encoded as 64-bit unsigned integer.
    //  The most significant byte comes first.
    const uint64_t msg_size = get_uint64 (tmpbuf);

    //  Message size must not exceed the maximum allowed size.
    if (maxmsgsize >= 0)
        if (unlikely (msg_size > static_cast <uint64_t> (maxmsgsize))) {
            errno = EMSGSIZE;
            return -1;
        }

    //  Message size must fit into size_t data type.
    if (unlikely (msg_size != static_cast <size_t> (msg_size))) {
        errno = EMSGSIZE;
        return -1;
    }

    //  in_progress is initialised at this point so in theory we should
    //  close it before calling init_size, however, it's a 0-byte
    //  message and thus we can treat it as uninitialised.
    int rc = in_progress.init_size (static_cast <size_t> (msg_size));
    if (unlikely (rc)) {
        errno_assert (errno == ENOMEM);
        rc = in_progress.init ();
        errno_assert (rc == 0);
        errno = ENOMEM;
        return -1;
    }

    in_progress.set_flags (msg_flags);
    next_step (in_progress.data (), in_progress.size (),
        &v2_decoder_t::message_ready);

    return 0;
}

int zmq::v2_decoder_t::message_ready ()
{
    //  Message is completely read. Signal this to the caller
    //  and prepare to decode next message.
    next_step (tmpbuf, 1, &v2_decoder_t::flags_ready);
    return 1;
}