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,
 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         int rc = wxLockFile(m_fdLock, LOCK);
 162         if ( rc == 0 )
 163         {
 164             // fine, we have the exclusive lock to the file, write our PID
 165             // into it
 166             m_pidLocker = getpid();
 167
 168             // use char here, not wxChar!
 169             char buf[256]; // enough for any PID size
 170             int len = sprintf(buf, "%d", (int)m_pidLocker) + 1;
 171
 172             if ( write(m_fdLock, buf, len) != len )
 173             {
 174                 wxLogSysError(_("Failed to write to lock file '%s'"),
 175                               m_nameLock.c_str());
 176
 177                 Unlock();
 178
 179                 return LOCK_ERROR;
 180             }
 181
 182             fsync(m_fdLock);
 183
 184             return LOCK_CREATED;
 185         }
 186         else // failure: see what exactly happened
 187         {
 188             close(m_fdLock);
 189             m_fdLock = -1;
 190
 191             if ( rc != EACCES && rc != EAGAIN )
 192             {
 193                 wxLogSysError(_("Failed to lock the lock file '%s'"),
 194                               m_nameLock.c_str());
 195
 196                 unlink(m_nameLock);
 197
 198                 return LOCK_ERROR;
 199             }
 200             //else: couldn't lock because the lock is held by another process:
 201             //      this might have happened because of a race condition:
 202             //      maybe another instance opened and locked the file between
 203             //      our calls to open() and flock(), so don't give an error
 204         }
 205     }
 206
 207     // we didn't create and lock the file
 208     return LOCK_EXISTS;
 209 }
 210
 211 bool wxSingleInstanceCheckerImpl::Create(const wxString& name)
 212 {
 213     m_nameLock = name;
 214
 215     switch ( CreateLockFile() )
 216     {
 217         case LOCK_EXISTS:
 218             // there is a lock file, check below if it is still valid
 219             break;
 220
 221         case LOCK_CREATED:
 222             // nothing more to do
 223             return TRUE;
 224
 225         case LOCK_ERROR:
 226             // oops...
 227             return FALSE;
 228     }
 229
 230     // try to open the file for reading and get the PID of the process
 231     // which has it
 232     wxFile file(name, wxFile::read);
 233     if ( !file.IsOpened() )
 234     {
 235         // well, this is really weird - file doesn't exist and we can't
 236         // create it
 237         //
 238         // normally, this just means that we don't have write access to
 239         // the directory where we try to create it, so return failure,
 240         // even it might also be a rare case of a race condition when
 241         // another process managed to open and lock the file and terminate
 242         // (erasing it) before we got here, but this should happen so
 243         // rarely in practice that we don't care
 244         wxLogError(_("Failed to access lock file."));
 245
 246         return FALSE;
 247     }
 248
 249     char buf[256];
 250     off_t count = file.Read(buf, WXSIZEOF(buf));
 251     if ( count == wxInvalidOffset )
 252     {
 253         wxLogError(_("Failed to read PID from lock file."));
 254     }
 255     else
 256     {
 257         if ( sscanf(buf, "%d", (int *)&m_pidLocker) == 1 )
 258         {
 259             if ( kill(m_pidLocker, 0) != 0 )
 260             {
 261                 if ( unlink(name) != 0 )
 262                 {
 263                     wxLogError(_("Failed to remove stale lock file '%s'."),
 264                                name.c_str());
 265
 266                     // return TRUE in this case for now...
 267                 }
 268                 else
 269                 {
 270                     wxLogMessage(_("Deleted stale lock file '%s'."),
 271                                  name.c_str());
 272
 273                     // retry now
 274                     (void)CreateLockFile();
 275                 }
 276             }
 277             //else: the other process is running
 278         }
 279         else
 280         {
 281             wxLogWarning(_("Invalid lock file '%s'."), name.c_str());
 282         }
 283     }
 284
 285     // return TRUE if we could get the PID of the process owning the lock file
 286     // (whether it is still running or not), FALSE otherwise as it is
 287     // unexpected
 288     return m_pidLocker != 0;
 289 }
 290
 291 void wxSingleInstanceCheckerImpl::Unlock()
 292 {
 293     if ( m_fdLock != -1 )
 294     {
 295         if ( unlink(m_nameLock) != 0 )
 296         {
 297             wxLogSysError(_("Failed to remove lock file '%s'"),
 298                           m_nameLock.c_str());
 299         }
 300
 301         if ( wxLockFile(m_fdLock, UNLOCK) != 0 )
 302         {
 303             wxLogSysError(_("Failed to unlock lock file '%s'"),
 304                           m_nameLock.c_str());
 305         }
 306
 307         if ( close(m_fdLock) != 0 )
 308         {
 309             wxLogSysError(_("Failed to close lock file '%s'"),
 310                           m_nameLock.c_str());
 311         }
 312     }
 313
 314     m_pidLocker = 0;
 315 }
 316
 317 // ============================================================================
 318 // wxSingleInstanceChecker implementation
 319 // ============================================================================
 320
 321 bool wxSingleInstanceChecker::Create(const wxString& name,
 322                                      const wxString& path)
 323 {
 324     wxASSERT_MSG( !m_impl,
 325                   _T("calling wxSingleInstanceChecker::Create() twice?") );
 326
 327     // must have the file name to create a lock file
 328     wxASSERT_MSG( !name.empty(), _T("lock file name can't be empty") );
 329
 330     m_impl = new wxSingleInstanceCheckerImpl;
 331
 332     wxString fullname = path;
 333     if ( fullname.empty() )
 334     {
 335         fullname << wxGetHomeDir() << _T('/');
 336     }
 337
 338     fullname << name;
 339
 340     return m_impl->Create(fullname);
 341 }
 342
 343 bool wxSingleInstanceChecker::IsAnotherRunning() const
 344 {
 345     wxCHECK_MSG( m_impl, FALSE, _T("must call Create() first") );
 346
 347     // if another instance is running, it must own the lock file - otherwise
 348     // we have it and the locker PID is ours one
 349     return m_impl->GetLockerPID() != getpid();
 350 }
 351
 352 wxSingleInstanceChecker::~wxSingleInstanceChecker()
 353 {
 354     delete m_impl;
 355 }
 356
 357 #endif // wxUSE_SNGLINST_CHECKER
 358