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wxWindows-2.4.0
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snglinst.cpp
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2002-08-05
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363 lines
///////////////////////////////////////////////////////////////////////////////
// Name: unix/snglinst.cpp
// Purpose: implements wxSingleInstanceChecker class for Unix using
// lock files with fcntl(2) or flock(2)
// Author: Vadim Zeitlin
// Modified by:
// Created: 09.06.01
// RCS-ID: $Id: snglinst.cpp,v 1.6 2002/08/05 18:04:08 RR Exp $
// Copyright: (c) 2001 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
// License: wxWindows license
///////////////////////////////////////////////////////////////////////////////
// ============================================================================
// declarations
// ============================================================================
// ----------------------------------------------------------------------------
// headers
// ----------------------------------------------------------------------------
#ifdef __GNUG__
#pragma implementation "snglinst.h"
#endif
// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"
#ifdef __BORLANDC__
#pragma hdrstop
#endif
#if wxUSE_SNGLINST_CHECKER
#ifndef WX_PRECOMP
#include "wx/string.h"
#include "wx/log.h"
#include "wx/intl.h"
#include "wx/file.h"
#endif //WX_PRECOMP
#include "wx/utils.h" // wxGetHomeDir()
#include "wx/snglinst.h"
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h> // for S_I[RW]USR
#include <signal.h> // for kill()
#include <errno.h>
#ifdef HAVE_FCNTL
#include <fcntl.h>
#elif defined(HAVE_FLOCK)
#include <sys/file.h>
#else
// normally, wxUSE_SNGLINST_CHECKER must have been reset by configure
#error "wxSingleInstanceChecker can't be compiled on this platform"
#endif // fcntl()/flock()
// ----------------------------------------------------------------------------
// constants
// ----------------------------------------------------------------------------
// argument of wxLockFile()
enum LockOperation
{
LOCK,
UNLOCK
};
// return value of CreateLockFile()
enum LockResult
{
LOCK_ERROR = -1,
LOCK_EXISTS,
LOCK_CREATED
};
// ----------------------------------------------------------------------------
// private functions: (exclusively) lock/unlock the file
// ----------------------------------------------------------------------------
#ifdef HAVE_FCNTL
static int wxLockFile(int fd, LockOperation lock)
{
// init the flock parameter struct
struct flock fl;
fl.l_type = lock == LOCK ? F_WRLCK : F_UNLCK;
// lock the entire file
fl.l_whence =
fl.l_start =
fl.l_len = 0;
// is this needed?
fl.l_pid = getpid();
return fcntl(fd, F_SETLK, &fl);
}
#else // HAVE_FLOCK
static int wxLockFile(int fd, LockOperation lock)
{
return flock(fd, lock == LOCK ? LOCK_EX | LOCK_NB : LOCK_UN);
}
#endif // fcntl()/flock()
// ----------------------------------------------------------------------------
// wxSingleInstanceCheckerImpl: the real implementation class
// ----------------------------------------------------------------------------
class wxSingleInstanceCheckerImpl
{
public:
wxSingleInstanceCheckerImpl()
{
m_fdLock = -1;
m_pidLocker = 0;
}
bool Create(const wxString& name);
pid_t GetLockerPID() const { return m_pidLocker; }
~wxSingleInstanceCheckerImpl() { Unlock(); }
private:
// try to create and lock the file
LockResult CreateLockFile();
// unlock and remove the lock file
void Unlock();
// the descriptor of our lock file, -1 if none
int m_fdLock;
// pid of the process owning the lock file
pid_t m_pidLocker;
// the name of the lock file
wxString m_nameLock;
};
// ============================================================================
// wxSingleInstanceCheckerImpl implementation
// ============================================================================
LockResult wxSingleInstanceCheckerImpl::CreateLockFile()
{
// try to open the file
m_fdLock = open(m_nameLock.fn_str(),
O_WRONLY | O_CREAT | O_EXCL,
S_IRUSR | S_IWUSR);
if ( m_fdLock != -1 )
{
// try to lock it
if ( wxLockFile(m_fdLock, LOCK) == 0 )
{
// fine, we have the exclusive lock to the file, write our PID
// into it
m_pidLocker = getpid();
// use char here, not wxChar!
char buf[256]; // enough for any PID size
int len = sprintf(buf, "%d", (int)m_pidLocker) + 1;
if ( write(m_fdLock, buf, len) != len )
{
wxLogSysError(_("Failed to write to lock file '%s'"),
m_nameLock.c_str());
Unlock();
return LOCK_ERROR;
}
fsync(m_fdLock);
return LOCK_CREATED;
}
else // failure: see what exactly happened
{
close(m_fdLock);
m_fdLock = -1;
if ( errno != EACCES && errno != EAGAIN )
{
wxLogSysError(_("Failed to lock the lock file '%s'"),
m_nameLock.c_str());
unlink(m_nameLock.fn_str());
return LOCK_ERROR;
}
//else: couldn't lock because the lock is held by another process:
// this might have happened because of a race condition:
// maybe another instance opened and locked the file between
// our calls to open() and flock(), so don't give an error
}
}
// we didn't create and lock the file
return LOCK_EXISTS;
}
bool wxSingleInstanceCheckerImpl::Create(const wxString& name)
{
m_nameLock = name;
switch ( CreateLockFile() )
{
case LOCK_EXISTS:
// there is a lock file, check below if it is still valid
break;
case LOCK_CREATED:
// nothing more to do
return TRUE;
case LOCK_ERROR:
// oops...
return FALSE;
}
// try to open the file for reading and get the PID of the process
// which has it
wxFile file(name, wxFile::read);
if ( !file.IsOpened() )
{
// well, this is really weird - file doesn't exist and we can't
// create it
//
// normally, this just means that we don't have write access to
// the directory where we try to create it, so return failure,
// even it might also be a rare case of a race condition when
// another process managed to open and lock the file and terminate
// (erasing it) before we got here, but this should happen so
// rarely in practice that we don't care
wxLogError(_("Failed to access lock file."));
return FALSE;
}
char buf[256];
off_t count = file.Read(buf, WXSIZEOF(buf));
if ( count == wxInvalidOffset )
{
wxLogError(_("Failed to read PID from lock file."));
}
else
{
if ( sscanf(buf, "%d", (int *)&m_pidLocker) == 1 )
{
if ( kill(m_pidLocker, 0) != 0 )
{
if ( unlink(name.fn_str()) != 0 )
{
wxLogError(_("Failed to remove stale lock file '%s'."),
name.c_str());
// return TRUE in this case for now...
}
else
{
wxLogMessage(_("Deleted stale lock file '%s'."),
name.c_str());
// retry now
(void)CreateLockFile();
}
}
//else: the other process is running
}
else
{
wxLogWarning(_("Invalid lock file '%s'."), name.c_str());
}
}
// return TRUE if we could get the PID of the process owning the lock file
// (whether it is still running or not), FALSE otherwise as it is
// unexpected
return m_pidLocker != 0;
}
void wxSingleInstanceCheckerImpl::Unlock()
{
if ( m_fdLock != -1 )
{
if ( unlink(m_nameLock.fn_str()) != 0 )
{
wxLogSysError(_("Failed to remove lock file '%s'"),
m_nameLock.c_str());
}
if ( wxLockFile(m_fdLock, UNLOCK) != 0 )
{
wxLogSysError(_("Failed to unlock lock file '%s'"),
m_nameLock.c_str());
}
if ( close(m_fdLock) != 0 )
{
wxLogSysError(_("Failed to close lock file '%s'"),
m_nameLock.c_str());
}
}
m_pidLocker = 0;
}
// ============================================================================
// wxSingleInstanceChecker implementation
// ============================================================================
bool wxSingleInstanceChecker::Create(const wxString& name,
const wxString& path)
{
wxASSERT_MSG( !m_impl,
_T("calling wxSingleInstanceChecker::Create() twice?") );
// must have the file name to create a lock file
wxASSERT_MSG( !name.empty(), _T("lock file name can't be empty") );
m_impl = new wxSingleInstanceCheckerImpl;
wxString fullname = path;
if ( fullname.empty() )
{
fullname = wxGetHomeDir();
}
if ( fullname.Last() != _T('/') )
{
fullname += _T('/');
}
fullname << name;
return m_impl->Create(fullname);
}
bool wxSingleInstanceChecker::IsAnotherRunning() const
{
wxCHECK_MSG( m_impl, FALSE, _T("must call Create() first") );
// if another instance is running, it must own the lock file - otherwise
// we have it and the locker PID is ours one
return m_impl->GetLockerPID() != getpid();
}
wxSingleInstanceChecker::~wxSingleInstanceChecker()
{
delete m_impl;
}
#endif // wxUSE_SNGLINST_CHECKER