lock.cpp

00001 /*
00002     This file is part of libkabc.
00003     Copyright (c) 2001,2003 Cornelius Schumacher <schumacher@kde.org>
00004 
00005     This library is free software; you can redistribute it and/or
00006     modify it under the terms of the GNU Library General Public
00007     License as published by the Free Software Foundation; either
00008     version 2 of the License, or (at your option) any later version.
00009 
00010     This library is distributed in the hope that it will be useful,
00011     but WITHOUT ANY WARRANTY; without even the implied warranty of
00012     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013     Library General Public License for more details.
00014 
00015     You should have received a copy of the GNU Library General Public License
00016     along with this library; see the file COPYING.LIB.  If not, write to
00017     the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
00018     Boston, MA 02110-1301, USA.
00019 */
00020 
00021 #include "lock.h"
00022 
00023 #include <kapplication.h>
00024 #include <kdebug.h>
00025 #include <klocale.h>
00026 #include <kstandarddirs.h>
00027 #include <ktempfile.h>
00028 
00029 #include <qfile.h>
00030 
00031 #include <signal.h>
00032 #include <sys/types.h>
00033 #include <sys/stat.h>
00034 #include <unistd.h>
00035 
00036 using namespace KABC;
00037 
00038 Lock::Lock( const QString &identifier )
00039   : mIdentifier( identifier )
00040 {
00041   mIdentifier.replace( "/", "_" );
00042 }
00043 
00044 Lock::~Lock()
00045 {
00046   unlock();
00047 }
00048 
00049 QString Lock::locksDir()
00050 {
00051   return locateLocal( "data", "kabc/lock/" );
00052 }
00053 
00054 bool Lock::readLockFile( const QString &filename, int &pid, QString &app )
00055 {
00056   QFile file( filename );
00057   if ( !file.open( IO_ReadOnly ) ) return false;
00058 
00059   QTextStream t( &file );
00060   pid = t.readLine().toInt();
00061   app = t.readLine();
00062 
00063   return true;
00064 }
00065 
00066 bool Lock::writeLockFile( const QString &filename )
00067 {
00068   QFile file( filename );
00069   if ( !file.open( IO_WriteOnly ) ) return false;
00070   QTextStream t( &file );
00071   t << ::getpid() << endl << QString( KGlobal::instance()->instanceName() );
00072 
00073   return true;
00074 }
00075 
00076 QString Lock::lockFileName() const
00077 {
00078   return locksDir() + mIdentifier + ".lock";
00079 }
00080 
00081 bool Lock::lock()
00082 {
00083   kdDebug(5700) << "Lock::lock()" << endl;
00084 
00085   QString lockName = lockFileName();
00086   kdDebug(5700) << "-- lock name: " << lockName << endl;
00087 
00088   if ( QFile::exists( lockName ) ) {  // check if it is a stale lock file
00089     int pid;
00090     QString app;
00091 
00092     if ( !readLockFile( lockFileName(), pid, app ) ) {
00093       mError = i18n("Unable to open lock file.");
00094       return false;
00095     }
00096 
00097     int retval = ::kill( pid, 0 );
00098     if ( retval == -1 && errno == ESRCH ) { // process doesn't exists anymore
00099       QFile::remove( lockName );
00100       kdWarning(5700) << "Removed stale lock file from process '" << app << "'"
00101                       << endl;
00102     } else {
00103       QString identifier( mIdentifier );
00104       identifier.replace( '_', '/' );
00105 
00106       mError = i18n("The address book '%1' is locked by application '%2'.\nIf you believe this is incorrect, just remove the lock file from '%3'")
00107                .arg( identifier ).arg( app ).arg( locateLocal( "data", "kabc/lock/*.lock" ) );
00108       return false;
00109     }
00110   }
00111 
00112   QString lockUniqueName;
00113   lockUniqueName = mIdentifier + kapp->randomString( 8 );
00114   mLockUniqueName = locateLocal( "data", "kabc/lock/" + lockUniqueName );
00115   kdDebug(5700) << "-- lock unique name: " << mLockUniqueName << endl;
00116 
00117   // Create unique file
00118   writeLockFile( mLockUniqueName );
00119 
00120   // Create lock file
00121   int result = ::link( QFile::encodeName( mLockUniqueName ),
00122                        QFile::encodeName( lockName ) );
00123 
00124   if ( result == 0 ) {
00125     mError = "";
00126     emit locked();
00127     return true;
00128   }
00129 
00130   // TODO: check stat
00131 
00132   mError = i18n("Error");
00133   return false;
00134 }
00135 
00136 bool Lock::unlock()
00137 {
00138   int pid;
00139   QString app;
00140   if ( readLockFile( lockFileName(), pid, app ) ) {
00141     if ( pid == getpid() ) {
00142       QFile::remove( lockFileName() );
00143       QFile::remove( mLockUniqueName );
00144       emit unlocked();
00145     } else {
00146       mError = i18n("Unlock failed. Lock file is owned by other process: %1 (%2)")
00147                .arg( app ).arg( QString::number( pid ) );
00148       kdDebug() << "Lock::unlock(): " << mError << endl;
00149       return false;
00150     }
00151   }
00152 
00153   mError = "";
00154   return true;
00155 }
00156 
00157 QString Lock::error() const
00158 {
00159   return mError;
00160 }
00161 
00162 #include "lock.moc"
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