src/unix/snglinst.cpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        unix/snglinst.cpp
   3 // Purpose:     implements wxSingleInstanceChecker class for Unix using
   4 //              lock files with fcntl(2) or flock(2)
   5 // Author:      Vadim Zeitlin
   6 // Modified by:
   7 // Created:     09.06.01
   8 // RCS-ID:      $Id$
   9 // Copyright:   (c) 2001 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
  10 // License:     wxWindows license
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 // ============================================================================
  14 // declarations
  15 // ============================================================================
  16
  17 // ----------------------------------------------------------------------------
  18 // headers
  19 // ----------------------------------------------------------------------------
  20
  21 #ifdef __GNUG__
  22     #pragma implementation "snglinst.h"
  23 #endif
  24
  25 // For compilers that support precompilation, includes "wx.h".
  26 #include "wx/wxprec.h"
  27
  28 #ifdef __BORLANDC__
  29     #pragma hdrstop
  30 #endif
  31
  32 #if wxUSE_SNGLINST_CHECKER
  33
  34 #ifndef WX_PRECOMP
  35     #include "wx/string.h"
  36     #include "wx/log.h"
  37     #include "wx/intl.h"
  38     #include "wx/file.h"
  39 #endif //WX_PRECOMP
  40
  41 #include "wx/utils.h"           // wxGetHomeDir()
  42
  43 #include "wx/snglinst.h"
  44
  45 #include <unistd.h>
  46 #include <sys/types.h>
  47 #include <sys/stat.h>           // for S_I[RW]USR
  48 #include <signal.h>             // for kill()
  49 #include <errno.h>
  50
  51 #ifdef HAVE_FCNTL
  52     #include <fcntl.h>
  53 #elif defined(HAVE_FLOCK)
  54     #include <sys/file.h>
  55 #else
  56     // normally, wxUSE_SNGLINST_CHECKER must have been reset by configure
  57     #error "wxSingleInstanceChecker can't be compiled on this platform"
  58 #endif // fcntl()/flock()
  59
  60 // ----------------------------------------------------------------------------
  61 // constants
  62 // ----------------------------------------------------------------------------
  63
  64 // argument of wxLockFile()
  65 enum LockOperation
  66 {
  67     LOCK,
  68     UNLOCK
  69 };
  70
  71 // return value of CreateLockFile()
  72 enum LockResult
  73 {
  74     LOCK_ERROR = -1,
  75     LOCK_EXISTS,
  76     LOCK_CREATED
  77 };
  78
  79 // ----------------------------------------------------------------------------
  80 // private functions: (exclusively) lock/unlock the file
  81 // ----------------------------------------------------------------------------
  82
  83 #ifdef HAVE_FCNTL
  84
  85 static int wxLockFile(int fd, LockOperation lock)
  86 {
  87     // init the flock parameter struct
  88     struct flock fl;
  89     fl.l_type = lock == LOCK ? F_WRLCK : F_UNLCK;
  90
  91     // lock the entire file
  92     fl.l_whence =
  93     fl.l_start =
  94     fl.l_len = 0;
  95
  96     // is this needed?
  97     fl.l_pid = getpid();
  98
  99     return fcntl(fd, F_SETLK, &fl);
 100 }
 101
 102 #else // HAVE_FLOCK
 103
 104 static int wxLockFile(int fd, LockOperation lock)
 105 {
 106     return flock(fd, lock == LOCK ? LOCK_EX | LOCK_NB : LOCK_UN);
 107 }
 108
 109 #endif // fcntl()/flock()
 110
 111 // ----------------------------------------------------------------------------
 112 // wxSingleInstanceCheckerImpl: the real implementation class
 113 // ----------------------------------------------------------------------------
 114
 115 class wxSingleInstanceCheckerImpl
 116 {
 117 public:
 118     wxSingleInstanceCheckerImpl()
 119     {
 120         m_fdLock = -1;
 121         m_pidLocker = 0;
 122     }
 123
 124     bool Create(const wxString& name);
 125
 126     pid_t GetLockerPID() const { return m_pidLocker; }
 127
 128     ~wxSingleInstanceCheckerImpl() { Unlock(); }
 129
 130 private:
 131     // try to create and lock the file
 132     LockResult CreateLockFile();
 133
 134     // unlock and remove the lock file
 135     void Unlock();
 136
 137     // the descriptor of our lock file, -1 if none
 138     int m_fdLock;
 139
 140     // pid of the process owning the lock file
 141     pid_t m_pidLocker;
 142
 143     // the name of the lock file
 144     wxString m_nameLock;
 145 };
 146
 147 // ============================================================================
 148 // wxSingleInstanceCheckerImpl implementation
 149 // ============================================================================
 150
 151 LockResult wxSingleInstanceCheckerImpl::CreateLockFile()
 152 {
 153     // try to open the file
 154     m_fdLock = open(m_nameLock.fn_str(),
 155                     O_WRONLY | O_CREAT | O_EXCL,
 156                     S_IRUSR | S_IWUSR);
 157
 158     if ( m_fdLock != -1 )
 159     {
 160         // try to lock it
 161         if ( wxLockFile(m_fdLock, LOCK) == 0 )
 162         {
 163             // fine, we have the exclusive lock to the file, write our PID
 164             // into it
 165             m_pidLocker = getpid();
 166
 167             // use char here, not wxChar!
 168             char buf[256]; // enough for any PID size
 169             int len = sprintf(buf, "%d", (int)m_pidLocker) + 1;
 170
 171             if ( write(m_fdLock, buf, len) != len )
 172             {
 173                 wxLogSysError(_("Failed to write to lock file '%s'"),
 174                               m_nameLock.c_str());
 175
 176                 Unlock();
 177
 178                 return LOCK_ERROR;
 179             }
 180
 181             fsync(m_fdLock);
 182
 183             return LOCK_CREATED;
 184         }
 185         else // failure: see what exactly happened
 186         {
 187             close(m_fdLock);
 188             m_fdLock = -1;
 189
 190             if ( errno != EACCES && errno != EAGAIN )
 191             {
 192                 wxLogSysError(_("Failed to lock the lock file '%s'"),
 193                               m_nameLock.c_str());
 194
 195                 unlink(m_nameLock.fn_str());
 196
 197                 return LOCK_ERROR;
 198             }
 199             //else: couldn't lock because the lock is held by another process:
 200             //      this might have happened because of a race condition:
 201             //      maybe another instance opened and locked the file between
 202             //      our calls to open() and flock(), so don't give an error
 203         }
 204     }
 205
 206     // we didn't create and lock the file
 207     return LOCK_EXISTS;
 208 }
 209
 210 bool wxSingleInstanceCheckerImpl::Create(const wxString& name)
 211 {
 212     m_nameLock = name;
 213
 214     switch ( CreateLockFile() )
 215     {
 216         case LOCK_EXISTS:
 217             // there is a lock file, check below if it is still valid
 218             break;
 219
 220         case LOCK_CREATED:
 221             // nothing more to do
 222             return TRUE;
 223
 224         case LOCK_ERROR:
 225             // oops...
 226             return FALSE;
 227     }
 228
 229     // try to open the file for reading and get the PID of the process
 230     // which has it
 231     wxFile file(name, wxFile::read);
 232     if ( !file.IsOpened() )
 233     {
 234         // well, this is really weird - file doesn't exist and we can't
 235         // create it
 236         //
 237         // normally, this just means that we don't have write access to
 238         // the directory where we try to create it, so return failure,
 239         // even it might also be a rare case of a race condition when
 240         // another process managed to open and lock the file and terminate
 241         // (erasing it) before we got here, but this should happen so
 242         // rarely in practice that we don't care
 243         wxLogError(_("Failed to access lock file."));
 244
 245         return FALSE;
 246     }
 247
 248     char buf[256];
 249     off_t count = file.Read(buf, WXSIZEOF(buf));
 250     if ( count == wxInvalidOffset )
 251     {
 252         wxLogError(_("Failed to read PID from lock file."));
 253     }
 254     else
 255     {
 256         if ( sscanf(buf, "%d", (int *)&m_pidLocker) == 1 )
 257         {
 258             if ( kill(m_pidLocker, 0) != 0 )
 259             {
 260                 if ( unlink(name.fn_str()) != 0 )
 261                 {
 262                     wxLogError(_("Failed to remove stale lock file '%s'."),
 263                                name.c_str());
 264
 265                     // return TRUE in this case for now...
 266                 }
 267                 else
 268                 {
 269                     wxLogMessage(_("Deleted stale lock file '%s'."),
 270                                  name.c_str());
 271
 272                     // retry now
 273                     (void)CreateLockFile();
 274                 }
 275             }
 276             //else: the other process is running
 277         }
 278         else
 279         {
 280             wxLogWarning(_("Invalid lock file '%s'."), name.c_str());
 281         }
 282     }
 283
 284     // return TRUE if we could get the PID of the process owning the lock file
 285     // (whether it is still running or not), FALSE otherwise as it is
 286     // unexpected
 287     return m_pidLocker != 0;
 288 }
 289
 290 void wxSingleInstanceCheckerImpl::Unlock()
 291 {
 292     if ( m_fdLock != -1 )
 293     {
 294         if ( unlink(m_nameLock.fn_str()) != 0 )
 295         {
 296             wxLogSysError(_("Failed to remove lock file '%s'"),
 297                           m_nameLock.c_str());
 298         }
 299
 300         if ( wxLockFile(m_fdLock, UNLOCK) != 0 )
 301         {
 302             wxLogSysError(_("Failed to unlock lock file '%s'"),
 303                           m_nameLock.c_str());
 304         }
 305
 306         if ( close(m_fdLock) != 0 )
 307         {
 308             wxLogSysError(_("Failed to close lock file '%s'"),
 309                           m_nameLock.c_str());
 310         }
 311     }
 312
 313     m_pidLocker = 0;
 314 }
 315
 316 // ============================================================================
 317 // wxSingleInstanceChecker implementation
 318 // ============================================================================
 319
 320 bool wxSingleInstanceChecker::Create(const wxString& name,
 321                                      const wxString& path)
 322 {
 323     wxASSERT_MSG( !m_impl,
 324                   _T("calling wxSingleInstanceChecker::Create() twice?") );
 325
 326     // must have the file name to create a lock file
 327     wxASSERT_MSG( !name.empty(), _T("lock file name can't be empty") );
 328
 329     m_impl = new wxSingleInstanceCheckerImpl;
 330
 331     wxString fullname = path;
 332     if ( fullname.empty() )
 333     {
 334         fullname = wxGetHomeDir();
 335     }
 336
 337     if ( fullname.Last() != _T('/') )
 338     {
 339         fullname += _T('/');
 340     }
 341
 342     fullname << name;
 343
 344     return m_impl->Create(fullname);
 345 }
 346
 347 bool wxSingleInstanceChecker::IsAnotherRunning() const
 348 {
 349     wxCHECK_MSG( m_impl, FALSE, _T("must call Create() first") );
 350
 351     // if another instance is running, it must own the lock file - otherwise
 352     // we have it and the locker PID is ours one
 353     return m_impl->GetLockerPID() != getpid();
 354 }
 355
 356 wxSingleInstanceChecker::~wxSingleInstanceChecker()
 357 {
 358     delete m_impl;
 359 }
 360
 361 #endif // wxUSE_SNGLINST_CHECKER
 362