/*
 * Copyright (C) 2015 by Multi-Tech Systems
 *
 * This file is part of libmts-io.
 *
 * libmts-io 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 2 of the License, or
 * (at your option) any later version.
 *
 * libmts-io 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 libmts-io.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

/*!
 \file MTS_IO_LockFile.cpp
 \brief A brief description
 \date Oct 8, 2014
 \author sgodinez

 A more elaborate description
*/

#include <mts/MTS_IO_LockFile.h>
#include <mts/MTS_Timer.h>
#include <sys/file.h>
#include <unistd.h>

using namespace MTS::IO;

LockFile::LockFile(const std::string& sFile)
: m_sFile(sFile)
, m_iLockFd(-1)
, m_iLockErr(-1)
{
}

LockFile::~LockFile()
{
    unlock();
}

bool LockFile::lock(uint32_t attemptMillis)
{
    if (isLocked()) {
        return true;
    }

    m_iLockFd = ::open(m_sFile.c_str(), O_CREAT | O_RDWR, 0644);
    if (m_iLockFd >= 0) {
        MTS::Timer timer;
        timer.start();
        while (timer.getMillis() < attemptMillis) {
            m_iLockErr = ::flock(m_iLockFd, LOCK_EX | LOCK_NB);
            if (m_iLockErr == 0) {
                return true;
            } else if (errno != EWOULDBLOCK) {
                break;
            }
            ::usleep(((rand() % 10) + 1) * 100000); //Sleep from 100ms to 1 Second
        }
        ::close(m_iLockFd);
    }
    m_iLockFd = -1;
    return false;
}

void LockFile::unlock()
{
    ::flock(m_iLockFd, LOCK_UN);
    ::close(m_iLockFd);
    m_iLockFd = -1;
    m_iLockErr = -1;
}

bool LockFile::isLocked()
{
    return m_iLockErr == 0;
}