utils.cpp

   1 /*
   2         Skype Call Recorder
   3         Copyright (C) 2008 jlh (jlh at gmx dot ch)
   4
   5         This program is free software; you can redistribute it and/or modify it
   6         under the terms of the GNU General Public License as published by the
   7         Free Software Foundation; either version 2 of the License, version 3 of
   8         the License, or (at your option) any later version.
   9
  10         This program is distributed in the hope that it will be useful, but
  11         WITHOUT ANY WARRANTY; without even the implied warranty of
  12         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13         General Public License for more details.
  14
  15         You should have received a copy of the GNU General Public License along
  16         with this program; if not, write to the Free Software Foundation, Inc.,
  17         51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18
  19         The GNU General Public License version 2 is included with the source of
  20         this program under the file name COPYING.  You can also get a copy on
  21         http://www.fsf.org/
  22 */
  23
  24 #include <QFile>
  25 #include <sys/file.h>
  26 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #include <fcntl.h>
  29 #include <unistd.h>
  30
  31 #include "utils.h"
  32 #include "common.h"
  33
  34 LockFile::LockFile() :
  35         fd(-1)
  36 {
  37 }
  38
  39 LockFile::~LockFile() {
  40         unlock();
  41 }
  42
  43 bool LockFile::lock(const QString &fn) {
  44         fileName = fn;
  45         fd = open(QFile::encodeName(fileName).constData(), O_CREAT | O_WRONLY, 0644);
  46
  47         if (fd < 0) {
  48                 debug("ERROR: opening lock file failed");
  49                 return false;
  50         }
  51
  52         if (flock(fd, LOCK_EX | LOCK_NB) != 0) {
  53                 close(fd);
  54                 debug("ERROR: cannot get lock on lock file");
  55                 return false;
  56         }
  57
  58         // set the FD_CLOEXEC flag, so that when another process forks off of
  59         // us, it won't inherit the file descriptor and the lock.  see commit
  60         // ce6f838b4587528630784c1ea1ad272b64e78544 to see why we do this
  61
  62         int flags = fcntl(fd, F_GETFD, 0);
  63
  64         if (flags == -1) {
  65                 debug("ERROR: failed to fcntl() lock file");
  66                 unlock();
  67                 return false;
  68         }
  69
  70         flags |= FD_CLOEXEC;
  71         flags = fcntl(fd, F_SETFD, flags);
  72
  73         if (flags == -1) {
  74                 debug("ERROR: failed to set FD_CLOEXEC on lock file");
  75                 unlock();
  76                 return false;
  77         }
  78
  79         debug("Got lock on lock file");
  80         return true;
  81 }
  82
  83 void LockFile::unlock() {
  84         if (!isLocked())
  85                 return;
  86         QFile::remove(fileName);
  87         flock(fd, LOCK_UN);
  88         close(fd);
  89         fd = -1;
  90 }
  91
  92 bool LockFile::isLocked() const {
  93         return fd >= 0;
  94 }
  95