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/*
Copyright (c) 2009-2012 250bpm s.r.o.
Copyright (c) 2007-2009 iMatix Corporation
Copyright (c) 2011 VMware, Inc.
Copyright (c) 2007-2011 Other contributors as noted in the AUTHORS file
This file is part of Crossroads I/O project.
Crossroads I/O 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.
Crossroads 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 "fq.hpp"
#include "pipe.hpp"
#include "err.hpp"
#include "msg.hpp"
xs::fq_t::fq_t () :
active (0),
current (0),
more (false)
{
}
xs::fq_t::~fq_t ()
{
xs_assert (pipes.empty ());
}
void xs::fq_t::attach (pipe_t *pipe_)
{
pipes.push_back (pipe_);
pipes.swap (active, pipes.size () - 1);
active++;
}
void xs::fq_t::terminated (pipe_t *pipe_)
{
// Remove the pipe from the list; adjust number of active pipes
// accordingly.
if (pipes.index (pipe_) < active) {
active--;
if (current == active)
current = 0;
}
pipes.erase (pipe_);
}
void xs::fq_t::activated (pipe_t *pipe_)
{
// Move the pipe to the list of active pipes.
pipes.swap (pipes.index (pipe_), active);
active++;
}
int xs::fq_t::recv (msg_t *msg_, int flags_)
{
return recvpipe (msg_, flags_, NULL);
}
int xs::fq_t::recvpipe (msg_t *msg_, int flags_, pipe_t **pipe_)
{
// Deallocate old content of the message.
int rc = msg_->close ();
errno_assert (rc == 0);
// Round-robin over the pipes to get the next message.
for (pipes_t::size_type count = active; count != 0; count--) {
// Try to fetch new message. If we've already read part of the message
// subsequent part should be immediately available.
bool fetched = pipes [current]->read (msg_);
// Check the atomicity of the message. If we've already received the
// first part of the message we should get the remaining parts
// without blocking.
xs_assert (!(more && !fetched));
// Note that when message is not fetched, current pipe is deactivated
// and replaced by another active pipe. Thus we don't have to increase
// the 'current' pointer.
if (fetched) {
if (pipe_)
*pipe_ = pipes [current];
more =
msg_->flags () & msg_t::more ? true : false;
if (!more) {
current++;
if (current >= active)
current = 0;
}
return 0;
}
else {
active--;
pipes.swap (current, active);
if (current == active)
current = 0;
}
}
// No message is available. Initialise the output parameter
// to be a 0-byte message.
rc = msg_->init ();
errno_assert (rc == 0);
errno = EAGAIN;
return -1;
}
bool xs::fq_t::has_in ()
{
// There are subsequent parts of the partly-read message available.
if (more)
return true;
// Note that messing with current doesn't break the fairness of fair
// queueing algorithm. If there are no messages available current will
// get back to its original value. Otherwise it'll point to the first
// pipe holding messages, skipping only pipes with no messages available.
for (pipes_t::size_type count = active; count != 0; count--) {
if (pipes [current]->check_read ())
return true;
// Deactivate the pipe.
active--;
pipes.swap (current, active);
if (current == active)
current = 0;
}
return false;
}
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