/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2010 The Boeing Company

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Tom Goff <thomas.goff@boeing.com>

 */

#include <cerrno>

#include <cstring>

#include <unistd.h>

#include <fcntl.h>

#include "log.h"

#include "fatal-error.h"

#include "simple-ref-count.h"

#include "system-thread.h"

#include "simulator.h"

#include "unix-fd-reader.h"

NS_LOG_COMPONENT_DEFINE ("FdReader");

namespace ns3 {

FdReader::FdReader ()

  : m_fd (-1), m_readCallback (0), m_readThread (0), m_stop (false),

    m_destroyEvent ()

{

  m_evpipe[0] = -1;

  m_evpipe[1] = -1;

}

FdReader::~FdReader ()

{

  Stop ();

}

void FdReader::Start (int fd, Callback<void, uint8_t *, ssize_t> readCallback)

{

  int tmp;

  NS_ASSERT_MSG (m_readThread == 0, "read thread already exists");

  // create a pipe for inter-thread event notification

  tmp = pipe (m_evpipe);

  if (tmp == -1)

    {

      NS_FATAL_ERROR ("pipe() failed: " << std::strerror (errno));

    }

  // make the read end non-blocking

  tmp = fcntl (m_evpipe[0], F_GETFL);

  if (tmp == -1)

    {

      NS_FATAL_ERROR ("fcntl() failed: " << std::strerror (errno));

    }

  if (fcntl (m_evpipe[0], F_SETFL, tmp | O_NONBLOCK) == -1)

    {

      NS_FATAL_ERROR ("fcntl() failed: " << std::strerror (errno));

    }

  m_fd = fd;

  m_readCallback = readCallback;

  //

  // We're going to spin up a thread soon, so we need to make sure we have

  // a way to tear down that thread when the simulation stops.  Do this by

  // scheduling a "destroy time" method to make sure the thread exits before

  // proceeding.

  //

  if (!m_destroyEvent.IsRunning ())

    {

      // hold a reference to ensure that this object is not

      // deallocated before the destroy-time event fires

      this->Ref ();

      m_destroyEvent =

        Simulator::ScheduleDestroy (&FdReader::DestroyEvent, this);

    }

  //

  // Now spin up a thread to read from the fd

  //

  NS_LOG_LOGIC ("Spinning up read thread");

  m_readThread = Create<SystemThread> (MakeCallback (&FdReader::Run, this));

  m_readThread->Start ();

}

void FdReader::DestroyEvent (void)

{

  Stop ();

  this->Unref ();

}

void FdReader::Stop (void)

{

  m_stop = true;

  // signal the read thread

  if (m_evpipe[1] != -1)

    {

      char zero = 0;

      ssize_t len = write (m_evpipe[1], &zero, sizeof (zero));

      if (len != sizeof (zero))

        NS_LOG_WARN ("incomplete write(): " << std::strerror (errno));

    }

  // join the read thread

  if (m_readThread != 0)

    {

      m_readThread->Join ();

      m_readThread = 0;

    }

  // close the write end of the event pipe

  if (m_evpipe[1] != -1)

    {

      close (m_evpipe[1]);

      m_evpipe[1] = -1;

    }

  // close the read end of the event pipe

  if (m_evpipe[0] != -1)

    {

      close (m_evpipe[0]);

      m_evpipe[0] = -1;

    }

  // reset everything else

  m_fd = -1;

  m_readCallback.Nullify ();

  m_stop = false;

}

// This runs in a separate thread

void FdReader::Run (void)

{

  int nfds;

  fd_set rfds;

  nfds = (m_fd > m_evpipe[0] ? m_fd : m_evpipe[0]) + 1;

  FD_ZERO (&rfds);

  FD_SET (m_fd, &rfds);

  FD_SET (m_evpipe[0], &rfds);

  for (;;)

    {

      int r;

      fd_set readfds = rfds;

      r = select (nfds, &readfds, NULL, NULL, NULL);

      if (r == -1 && errno != EINTR)

        {

          NS_FATAL_ERROR ("select() failed: " << std::strerror (errno));

        }

      if (FD_ISSET (m_evpipe[0], &readfds))

        {

          // drain the event pipe

          for (;;)

            {

              char buf[1024];

              ssize_t len = read (m_evpipe[0], buf, sizeof (buf));

              if (len == 0)

                {

                  NS_FATAL_ERROR ("event pipe closed");

                }

              if (len < 0)

                {

                  if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK)

                    {

                      break;

                    }

                  else

                    {

                      NS_FATAL_ERROR ("read() failed: " << std::strerror (errno));

                    }

                }

            }

        }

      if (m_stop)

        {

          // this thread is done

          break;

        }

      if (FD_ISSET (m_fd, &readfds))

        {

          struct FdReader::Data data = DoRead ();

          // reading stops when m_len is zero

          if (data.m_len == 0)

            {

              break;

            }

          // the callback is only called when m_len is positive (data

          // is ignored if m_len is negative)

          else if (data.m_len > 0)

            {

              m_readCallback (data.m_buf, data.m_len);

            }

        }

    }

}

} // namespace ns3