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+/****************************************************************************
+**
+** Definition of TQLock class. This manages interprocess locking
+**
+** Created : 20000406
+**
+** Copyright (C) 2000-2008 Trolltech ASA. All rights reserved.
+**
+** This file is part of the kernel module of the TQt GUI Toolkit.
+**
+** This file may be used under the terms of the GNU General
+** Public License versions 2.0 or 3.0 as published by the Free
+** Software Foundation and appearing in the files LICENSE.GPL2
+** and LICENSE.GPL3 included in the packaging of this file.
+** Alternatively you may (at your option) use any later version
+** of the GNU General Public License if such license has been
+** publicly approved by Trolltech ASA (or its successors, if any)
+** and the KDE Free TQt Foundation.
+**
+** Please review the following information to ensure GNU General
+** Public Licensing requirements will be met:
+** http://trolltech.com/products/qt/licenses/licensing/opensource/.
+** If you are unsure which license is appropriate for your use, please
+** review the following information:
+** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
+** or contact the sales department at sales@trolltech.com.
+**
+** Licensees holding valid TQt Commercial licenses may use this file in
+** accordance with the TQt Commercial License Agreement provided with
+** the Software.
+**
+** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
+** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
+** herein.
+**
+**********************************************************************/
+
+#include "tqlock_p.h"
+
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+
+#include <unistd.h>
+#include <sys/types.h>
+#if defined(TQ_OS_MACX)
+#define TQ_NO_SEMAPHORE
+#include <sys/stat.h>
+#include <sys/file.h>
+#else
+#include <sys/sem.h>
+#if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED) \
+ || defined(TQ_OS_FREEBSD) || defined(TQ_OS_OPENBSD) || defined(TQ_OS_NETBSD) || defined(TQ_OS_BSDI)
+/* union semun is defined by including <sys/sem.h> */
+#else
+/* according to X/OPEN we have to define it ourselves */
+union semun {
+ int val; /* value for SETVAL */
+ struct semid_ds *buf; /* buffer for IPC_STAT, IPC_SET */
+ unsigned short *array; /* array for GETALL, SETALL */
+};
+#endif
+#endif
+#include <sys/ipc.h>
+#include <string.h>
+#include <errno.h>
+
+#define MAX_LOCKS 200 // maximum simultaneous read locks
+
+class TQLockData
+{
+public:
+#ifdef TQ_NO_SEMAPHORE
+ TQCString file;
+#endif
+ int id;
+ int count;
+ bool owned;
+};
+
+#endif
+
+/*!
+ \class TQLock qlock_p.h
+ \brief The TQLock class is a wrapper for a System V shared semaphore.
+
+ \ingroup qws
+ \ingroup io
+
+ \internal
+
+ It is used by TQt/Embedded for synchronizing access to the graphics
+ card and shared memory region between processes.
+*/
+
+/*!
+ \enum TQLock::Type
+
+ \value Read
+ \value Write
+*/
+
+/*!
+ \fn TQLock::TQLock( const TQString &filename, char id, bool create )
+
+ Creates a lock. \a filename is the file path of the Unix-domain
+ socket the TQt/Embedded client is using. \a id is the name of the
+ particular lock to be created on that socket. If \a create is TRUE
+ the lock is to be created (as the TQt/Embedded server does); if \a
+ create is FALSE the lock should exist already (as the TQt/Embedded
+ client expects).
+*/
+
+TQLock::TQLock( const TQString &filename, char id, bool create )
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ data = new TQLockData;
+ data->count = 0;
+#ifdef TQ_NO_SEMAPHORE
+ data->file = TQString(filename+id).local8Bit();
+ for(int x = 0; x < 2; x++) {
+ data->id = open(data->file, O_RDWR | (x ? O_CREAT : 0), S_IRWXU);
+ if(data->id != -1 || !create) {
+ data->owned = x;
+ break;
+ }
+ }
+#else
+ key_t semkey = ftok(filename, id);
+ data->id = semget(semkey,0,0);
+ data->owned = create;
+ if ( create ) {
+ semun arg; arg.val = 0;
+ if ( data->id != -1 )
+ semctl(data->id,0,IPC_RMID,arg);
+ data->id = semget(semkey,1,IPC_CREAT|0600);
+ arg.val = MAX_LOCKS;
+ semctl(data->id,0,SETVAL,arg);
+ }
+#endif
+ if ( data->id == -1 ) {
+ qWarning( "Cannot %s semaphore %s \'%c\'",
+ create ? "create" : "get", filename.latin1(), id );
+ qDebug("Error %d %s\n",errno,strerror(errno));
+ }
+#endif
+}
+
+/*!
+ \fn TQLock::~TQLock()
+
+ Destroys a lock
+*/
+
+TQLock::~TQLock()
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ if ( locked() )
+ unlock();
+#ifdef TQ_NO_SEMAPHORE
+ if(isValid()) {
+ close(data->id);
+ if( data->owned )
+ unlink( data->file );
+ }
+#else
+ if(data->owned) {
+ semun arg; arg.val = 0;
+ semctl( data->id, 0, IPC_RMID, arg );
+ }
+#endif
+ delete data;
+#endif
+}
+
+/*!
+ \fn bool TQLock::isValid() const
+
+ Returns TRUE if the lock constructor was succesful; returns FALSE if
+ the lock could not be created or was not available to connect to.
+*/
+
+bool TQLock::isValid() const
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ return (data->id != -1);
+#else
+ return TRUE;
+#endif
+}
+
+/*!
+ Locks the semaphore with a lock of type \a t. Locks can either be
+ \c Read or \c Write. If a lock is \c Read, attempts by other
+ processes to obtain \c Read locks will succeed, and \c Write
+ attempts will block until the lock is unlocked. If locked as \c
+ Write, all attempts to lock by other processes will block until
+ the lock is unlocked. Locks are stacked: i.e. a given TQLock can be
+ locked multiple times by the same process without blocking, and
+ will only be unlocked after a corresponding number of unlock()
+ calls.
+*/
+
+void TQLock::lock( Type t )
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ if ( !data->count ) {
+#ifdef TQ_NO_SEMAPHORE
+ int op = LOCK_SH;
+ if(t == Write)
+ op = LOCK_EX;
+ for( int rv=1; rv; ) {
+ rv = flock(data->id, op);
+ if (rv == -1 && errno != EINTR)
+ qDebug("Semop lock failure %s",strerror(errno));
+ }
+#else
+ sembuf sops;
+ sops.sem_num = 0;
+ sops.sem_flg = SEM_UNDO;
+
+ if ( t == Write ) {
+ sops.sem_op = -MAX_LOCKS;
+ type = Write;
+ } else {
+ sops.sem_op = -1;
+ type = Read;
+ }
+
+ int rv;
+ do {
+ rv = semop(data->id,&sops,1);
+ if (rv == -1 && errno != EINTR)
+ qDebug("Semop lock failure %s",strerror(errno));
+ } while ( rv == -1 && errno == EINTR );
+#endif
+ }
+ data->count++;
+#endif
+}
+
+/*!
+ \fn void TQLock::unlock()
+
+ Unlocks the semaphore. If other processes were blocking waiting to
+ lock() the semaphore, one of them will wake up and succeed in
+ lock()ing.
+*/
+
+void TQLock::unlock()
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ if( data->count ) {
+ data->count--;
+ if( !data->count ) {
+#ifdef TQ_NO_SEMAPHORE
+ for( int rv=1; rv; ) {
+ rv = flock(data->id, LOCK_UN);
+ if (rv == -1 && errno != EINTR)
+ qDebug("Semop lock failure %s",strerror(errno));
+ }
+#else
+ sembuf sops;
+ sops.sem_num = 0;
+ sops.sem_op = 1;
+ sops.sem_flg = SEM_UNDO;
+ if ( type == Write )
+ sops.sem_op = MAX_LOCKS;
+
+ int rv;
+ do {
+ rv = semop(data->id,&sops,1);
+ if (rv == -1 && errno != EINTR)
+ qDebug("Semop unlock failure %s",strerror(errno));
+ } while ( rv == -1 && errno == EINTR );
+#endif
+ }
+ } else {
+ qDebug("Unlock without corresponding lock");
+ }
+#endif
+}
+
+/*!
+ \fn bool TQLock::locked() const
+
+ Returns TRUE if the lock is currently held by the current process;
+ otherwise returns FALSE.
+*/
+
+bool TQLock::locked() const
+{
+#ifndef TQT_NO_TQWS_MULTIPROCESS
+ return (data->count > 0);
+#else
+ return FALSE;
+#endif
+}
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