1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
#include "singleapplication.h"
#include <QSharedMemory>
#include <QLocalSocket>
#include <QLocalServer>
#include <QMutex>
#include <cstdlib>
#ifdef Q_OS_UNIX
#include <signal.h>
#include <unistd.h>
#endif
class SingleApplicationPrivate {
public:
SingleApplicationPrivate(SingleApplication *q_ptr) : q_ptr(q_ptr) { }
void startServer(QString &serverName)
{
// Start a QLocalServer to listen for connections
server = new QLocalServer();
server->removeServer(serverName);
server->listen(serverName);
QObject::connect(server, SIGNAL(newConnection()), q_ptr, SLOT(slotConnectionEstablished()));
}
#ifdef Q_OS_UNIX
void crashHandler()
{
// This guarantees the program will work even with multiple
// instances of SingleApplication in different threads
// Which in my opinion is idiotic, but lets handle that too
{
sharedMemMutex.lock();
sharedMem.append(memory);
sharedMemMutex.unlock();
}
// Handle any further termination signals to ensure the
// QSharedMemory block is deleted even if the process crashes
signal(SIGSEGV, SingleApplicationPrivate::terminate);
signal(SIGABRT, SingleApplicationPrivate::terminate);
signal(SIGFPE, SingleApplicationPrivate::terminate);
signal(SIGILL, SingleApplicationPrivate::terminate);
signal(SIGINT, SingleApplicationPrivate::terminate);
signal(SIGTERM, SingleApplicationPrivate::terminate);
}
static void terminate(int signum)
{
while( ! sharedMem.empty() ) {
delete sharedMem.back();
sharedMem.pop_back();
}
::exit(128 + signum);
}
static QList<QSharedMemory*> sharedMem;
static QMutex sharedMemMutex;
#endif
QSharedMemory *memory;
SingleApplication *q_ptr;
QLocalServer *server;
QLocalSocket *socket;
};
#ifdef Q_OS_UNIX
QList<QSharedMemory*> SingleApplicationPrivate::sharedMem;
QMutex SingleApplicationPrivate::sharedMemMutex;
#endif
/**
* @brief Constructor. Checks and fires up LocalServer or closes the program
* if another instance already exists
* @param argc
* @param argv
*/
SingleApplication::SingleApplication(int &argc, char *argv[])
: QApplication(argc, argv), d_ptr(new SingleApplicationPrivate(this))
{
QString serverName = QApplication::organizationName() + QApplication::applicationName();
serverName.replace(QRegExp("[^\\w\\-. ]"), "");
// Garantee thread safe behaviour with a shared memory block
d_ptr->memory = new QSharedMemory(serverName);
// Create a shared memory block with a minimum size of 1 byte
if( d_ptr->memory->create(1, QSharedMemory::ReadOnly) )
{
#ifdef Q_OS_UNIX
// Handle any further termination signals to ensure the
// QSharedMemory block is deleted even if the process crashes
d_ptr->crashHandler();
#endif
// Successful creation means that no main process exists
// So we start a Local Server to listen for connections
d_ptr->startServer(serverName);
} else {
// Connect to the Local Server of the main process to notify it
// that a new process had been started
d_ptr->socket = new QLocalSocket();
d_ptr->socket->connectToServer(serverName);
// Even though a shared memory block exists, the original application might have crashed
// So only after a successful connection is the second instance terminated
if( d_ptr->socket->waitForConnected(100) )
{
::exit(EXIT_SUCCESS); // Terminate the program using STDLib's exit function
} else {
delete d_ptr->memory;
::exit(EXIT_SUCCESS);
}
}
}
/**
* @brief Destructor
*/
SingleApplication::~SingleApplication()
{
delete d_ptr->memory;
d_ptr->server->close();
}
/**
* @brief Executed when the showUp command is sent to LocalServer
*/
void SingleApplication::slotConnectionEstablished()
{
QLocalSocket *socket = d_ptr->server->nextPendingConnection();
socket->close();
delete socket;
emit showUp();
}
|
