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      1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "chrome/browser/importer/firefox_profile_lock.h"
      6 
      7 #include <errno.h>
      8 #include <fcntl.h>
      9 #include <sys/stat.h>
     10 #include <sys/types.h>
     11 
     12 #include "base/files/file_util.h"
     13 
     14 // This class is based on Firefox code in:
     15 //   profile/dirserviceprovider/src/nsProfileLock.cpp
     16 // The license block is:
     17 
     18 /* ***** BEGIN LICENSE BLOCK *****
     19 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
     20 *
     21 * The contents of this file are subject to the Mozilla Public License Version
     22 * 1.1 (the "License"); you may not use this file except in compliance with
     23 * the License. You may obtain a copy of the License at
     24 * http://www.mozilla.org/MPL/
     25 *
     26 * Software distributed under the License is distributed on an "AS IS" basis,
     27 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
     28 * for the specific language governing rights and limitations under the
     29 * License.
     30 *
     31 * The Original Code is mozilla.org code.
     32 *
     33 * The Initial Developer of the Original Code is
     34 * Netscape Communications Corporation.
     35 * Portions created by the Initial Developer are Copyright (C) 2002
     36 * the Initial Developer. All Rights Reserved.
     37 *
     38 * Contributor(s):
     39 *   Conrad Carlen <ccarlen (at) netscape.com>
     40 *   Brendan Eich <brendan (at) mozilla.org>
     41 *   Colin Blake <colin (at) theblakes.com>
     42 *   Javier Pedemonte <pedemont (at) us.ibm.com>
     43 *   Mats Palmgren <mats.palmgren (at) bredband.net>
     44 *
     45 * Alternatively, the contents of this file may be used under the terms of
     46 * either the GNU General Public License Version 2 or later (the "GPL"), or
     47 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
     48 * in which case the provisions of the GPL or the LGPL are applicable instead
     49 * of those above. If you wish to allow use of your version of this file only
     50 * under the terms of either the GPL or the LGPL, and not to allow others to
     51 * use your version of this file under the terms of the MPL, indicate your
     52 * decision by deleting the provisions above and replace them with the notice
     53 * and other provisions required by the GPL or the LGPL. If you do not delete
     54 * the provisions above, a recipient may use your version of this file under
     55 * the terms of any one of the MPL, the GPL or the LGPL.
     56 *
     57 * ***** END LICENSE BLOCK ***** */
     58 
     59 void FirefoxProfileLock::Init() {
     60   lock_fd_ = -1;
     61 }
     62 
     63 void FirefoxProfileLock::Lock() {
     64   if (HasAcquired())
     65     return;
     66 
     67   bool fcntl_lock = LockWithFcntl();
     68   if (!fcntl_lock) {
     69     return;
     70   } else if (!HasAcquired()) {
     71     old_lock_file_ = lock_file_.DirName().Append(kOldLockFileName);
     72     lock_fd_ = open(old_lock_file_.value().c_str(), O_CREAT | O_EXCL, 0644);
     73   }
     74 }
     75 
     76 void FirefoxProfileLock::Unlock() {
     77   if (!HasAcquired())
     78     return;
     79   close(lock_fd_);
     80   lock_fd_ = -1;
     81   base::DeleteFile(old_lock_file_, false);
     82 }
     83 
     84 bool FirefoxProfileLock::HasAcquired() {
     85   return (lock_fd_ >= 0);
     86 }
     87 
     88 // This function tries to lock Firefox profile using fcntl(). The return
     89 // value of this function together with HasAcquired() tells the current status
     90 // of lock.
     91 // if return == false: Another process has lock to the profile.
     92 // if return == true && HasAcquired() == true: successfully acquired the lock.
     93 // if return == false && HasAcquired() == false: Failed to acquire lock due
     94 // to some error (so that we can try alternate method of profile lock).
     95 bool FirefoxProfileLock::LockWithFcntl() {
     96   lock_fd_ = open(lock_file_.value().c_str(), O_WRONLY | O_CREAT | O_TRUNC,
     97                   0666);
     98   if (lock_fd_ == -1)
     99     return true;
    100 
    101   struct flock lock;
    102   lock.l_start = 0;
    103   lock.l_len = 0;
    104   lock.l_type = F_WRLCK;
    105   lock.l_whence = SEEK_SET;
    106   lock.l_pid = 0;
    107 
    108   struct flock testlock = lock;
    109   if (fcntl(lock_fd_, F_GETLK, &testlock) == -1) {
    110     close(lock_fd_);
    111     lock_fd_ = -1;
    112     return true;
    113   } else if (fcntl(lock_fd_, F_SETLK, &lock) == -1) {
    114     close(lock_fd_);
    115     lock_fd_ = -1;
    116     if (errno == EAGAIN || errno == EACCES)
    117       return false;
    118     else
    119       return true;
    120   } else {
    121     // We have the lock.
    122     return true;
    123   }
    124 }
    125