src/app/qtlocalpeer/qtlockedfile_unix.cpp

   1 /*
   2  * Bittorrent Client using Qt and libtorrent.
   3  * Copyright (C) 2019  Mike Tzou (Chocobo1)
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18  *
  19  * In addition, as a special exception, the copyright holders give permission to
  20  * link this program with the OpenSSL project's "OpenSSL" library (or with
  21  * modified versions of it that use the same license as the "OpenSSL" library),
  22  * and distribute the linked executables. You must obey the GNU General Public
  23  * License in all respects for all of the code used other than "OpenSSL".  If you
  24  * modify file(s), you may extend this exception to your version of the file(s),
  25  * but you are not obligated to do so. If you do not wish to do so, delete this
  26  * exception statement from your version.
  27  *
  28 ****************************************************************************
  29 **
  30 ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
  31 ** Contact: http://www.qt-project.org/legal
  32 **
  33 ** This file is part of the Qt Solutions component.
  34 **
  35 ** $QT_BEGIN_LICENSE:BSD$
  36 ** You may use this file under the terms of the BSD license as follows:
  37 **
  38 ** "Redistribution and use in source and binary forms, with or without
  39 ** modification, are permitted provided that the following conditions are
  40 ** met:
  41 **   * Redistributions of source code must retain the above copyright
  42 **     notice, this list of conditions and the following disclaimer.
  43 **   * Redistributions in binary form must reproduce the above copyright
  44 **     notice, this list of conditions and the following disclaimer in
  45 **     the documentation and/or other materials provided with the
  46 **     distribution.
  47 **   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
  48 **     of its contributors may be used to endorse or promote products derived
  49 **     from this software without specific prior written permission.
  50 **
  51 **
  52 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  53 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  54 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  55 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  56 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  57 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  58 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  59 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  60 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  61 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  62 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
  63 **
  64 ** $QT_END_LICENSE$
  65 **
  66 ****************************************************************************
  67 */
  68
  69 #include "qtlockedfile.h"
  70
  71 #include <errno.h>
  72 #include <fcntl.h>
  73 #include <string.h>
  74 #include <unistd.h>
  75
  76 bool QtLockedFile::lock(const LockMode mode, const bool block)
  77 {
  78     if (!isOpen())
  79     {
  80         qWarning("QtLockedFile::lock(): file is not opened");
  81         return false;
  82     }
  83
  84     if (mode == NoLock)
  85         return unlock();
  86
  87     if (mode == m_lockMode)
  88         return true;
  89
  90     if (m_lockMode != NoLock)
  91         unlock();
  92
  93     struct flock fl;
  94     fl.l_whence = SEEK_SET;
  95     fl.l_start = 0;
  96     fl.l_len = 0;
  97     fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;
  98     int cmd = block ? F_SETLKW : F_SETLK;
  99     int ret = fcntl(handle(), cmd, &fl);
 100
 101     if (ret == -1)
 102     {
 103         if (errno != EINTR && errno != EAGAIN)
 104             qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
 105         return false;
 106     }
 107
 108     m_lockMode = mode;
 109     return true;
 110 }
 111
 112 bool QtLockedFile::unlock()
 113 {
 114     if (!isOpen())
 115     {
 116         qWarning("QtLockedFile::unlock(): file is not opened");
 117         return false;
 118     }
 119
 120     if (!isLocked())
 121         return true;
 122
 123     struct flock fl;
 124     fl.l_whence = SEEK_SET;
 125     fl.l_start = 0;
 126     fl.l_len = 0;
 127     fl.l_type = F_UNLCK;
 128     int ret = fcntl(handle(), F_SETLKW, &fl);
 129
 130     if (ret == -1)
 131     {
 132         qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
 133         return false;
 134     }
 135
 136     m_lockMode = NoLock;
 137     return true;
 138 }
 139
 140 QtLockedFile::~QtLockedFile()
 141 {
 142     if (isOpen())
 143         unlock();
 144 }