summaryrefslogtreecommitdiffstats
path: root/src/corelib/plugin/qpluginloader.cpp
blob: 4ef36afceac2a3c95445c1a417166f97e20aa12e (plain)
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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** GNU Lesser General Public License Usage
** This file may be used under the terms of the GNU Lesser General Public
** License version 2.1 as published by the Free Software Foundation and
** appearing in the file LICENSE.LGPL included in the packaging of this
** file. Please review the following information to ensure the GNU Lesser
** General Public License version 2.1 requirements will be met:
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of this
** file. Please review the following information to ensure the GNU General
** Public License version 3.0 requirements will be met:
** http://www.gnu.org/copyleft/gpl.html.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms and
** conditions contained in a signed written agreement between you and Nokia.
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qplatformdefs.h"

#include "qplugin.h"
#include "qpluginloader.h"
#include <qfileinfo.h>
#include "qlibrary_p.h"
#include "qdebug.h"
#include "qdir.h"

#ifndef QT_NO_LIBRARY

QT_BEGIN_NAMESPACE

/*!
    \class QPluginLoader
    \inmodule QtCore
    \reentrant
    \brief The QPluginLoader class loads a plugin at run-time.


    \ingroup plugins

    QPluginLoader provides access to a \l{How to Create Qt
    Plugins}{Qt plugin}. A Qt plugin is stored in a shared library (a
    DLL) and offers these benefits over shared libraries accessed
    using QLibrary:

    \list
    \li QPluginLoader checks that a plugin is linked against the same
       version of Qt as the application.
    \li QPluginLoader provides direct access to a root component object
       (instance()), instead of forcing you to resolve a C function manually.
    \endlist

    An instance of a QPluginLoader object operates on a single shared
    library file, which we call a plugin. It provides access to the
    functionality in the plugin in a platform-independent way. To
    specify which plugin to load, either pass a file name in
    the constructor or set it with setFileName().

    The most important functions are load() to dynamically load the
    plugin file, isLoaded() to check whether loading was successful,
    and instance() to access the root component in the plugin. The
    instance() function implicitly tries to load the plugin if it has
    not been loaded yet. Multiple instances of QPluginLoader can be
    used to access the same physical plugin.

    Once loaded, plugins remain in memory until all instances of
    QPluginLoader has been unloaded, or until the application
    terminates. You can attempt to unload a plugin using unload(),
    but if other instances of QPluginLoader are using the same
    library, the call will fail, and unloading will only happen when
    every instance has called unload(). Right before the unloading
    happen, the root component will also be deleted.

    See \l{How to Create Qt Plugins} for more information about
    how to make your application extensible through plugins.

    Note that the QPluginLoader cannot be used if your application is
    statically linked against Qt. In this case, you will also have to
    link to plugins statically. You can use QLibrary if you need to
    load dynamic libraries in a statically linked application.

    \sa QLibrary, {Plug & Paint Example}
*/

/*!
    Constructs a plugin loader with the given \a parent.
*/
QPluginLoader::QPluginLoader(QObject *parent)
    : QObject(parent), d(0), did_load(false)
{
}

/*!
    Constructs a plugin loader with the given \a parent that will
    load the plugin specified by \a fileName.

    To be loadable, the file's suffix must be a valid suffix for a
    loadable library in accordance with the platform, e.g. \c .so on
    Unix, - \c .dylib on Mac OS X, and \c .dll on Windows. The suffix
    can be verified with QLibrary::isLibrary().

    \sa setFileName()
*/
QPluginLoader::QPluginLoader(const QString &fileName, QObject *parent)
    : QObject(parent), d(0), did_load(false)
{
    setFileName(fileName);
}

/*!
    Destroys the QPluginLoader object.

    Unless unload() was called explicitly, the plugin stays in memory
    until the application terminates.

    \sa isLoaded(), unload()
*/
QPluginLoader::~QPluginLoader()
{
    if (d)
        d->release();
}

/*!
    Returns the root component object of the plugin. The plugin is
    loaded if necessary. The function returns 0 if the plugin could
    not be loaded or if the root component object could not be
    instantiated.

    If the root component object was destroyed, calling this function
    creates a new instance.

    The root component, returned by this function, is not deleted when
    the QPluginLoader is destroyed. If you want to ensure that the root
    component is deleted, you should call unload() as soon you don't
    need to access the core component anymore.  When the library is
    finally unloaded, the root component will automatically be deleted.

    The component object is a QObject. Use qobject_cast() to access
    interfaces you are interested in.

    \sa load()
*/
QObject *QPluginLoader::instance()
{
    if (!isLoaded() && !load())
        return 0;
    if (!d->inst && d->instance)
        d->inst = d->instance();
    return d->inst.data();
}

/*!
    Returns the meta data for this plugin. The meta data is data specified
    in a json format using the Q_PLUGIN_METADATA() macro when compiling
    the plugin.

    The meta data can be queried in a fast and inexpensive way without
    actually loading the plugin. This makes it possible to e.g. store
    capabilities of the plugin in there, and make the decision whether to
    load the plugin dependent on this meta data.
 */
QJsonObject QPluginLoader::metaData() const
{
    if (!d)
        return QJsonObject();
    return d->metaData;
}

/*!
    Loads the plugin and returns true if the plugin was loaded
    successfully; otherwise returns false. Since instance() always
    calls this function before resolving any symbols it is not
    necessary to call it explicitly. In some situations you might want
    the plugin loaded in advance, in which case you would use this
    function.

    \sa unload()
*/
bool QPluginLoader::load()
{
    if (!d || d->fileName.isEmpty())
        return false;
    if (did_load)
        return d->pHnd && d->instance;
    if (!d->isPlugin())
        return false;
    did_load = true;
    return d->loadPlugin();
}


/*!
    Unloads the plugin and returns true if the plugin could be
    unloaded; otherwise returns false.

    This happens automatically on application termination, so you
    shouldn't normally need to call this function.

    If other instances of QPluginLoader are using the same plugin, the
    call will fail, and unloading will only happen when every instance
    has called unload().

    Don't try to delete the root component. Instead rely on
    that unload() will automatically delete it when needed.

    \sa instance(), load()
*/
bool QPluginLoader::unload()
{
    if (did_load) {
        did_load = false;
        return d->unload();
    }
    if (d)  // Ouch
        d->errorString = tr("The plugin was not loaded.");
    return false;
}

/*!
    Returns true if the plugin is loaded; otherwise returns false.

    \sa load()
 */
bool QPluginLoader::isLoaded() const
{
    return d && d->pHnd && d->instance;
}

/*!
    \property QPluginLoader::fileName
    \brief the file name of the plugin

    To be loadable, the file's suffix must be a valid suffix for a
    loadable library in accordance with the platform, e.g. \c .so on
    Unix, \c .dylib on Mac OS X, and \c .dll on Windows. The suffix
    can be verified with QLibrary::isLibrary().

    If the file name does not exist, it will not be set. This property
    will then contain an empty string.

    By default, this property contains an empty string.

    \sa load()
*/
void QPluginLoader::setFileName(const QString &fileName)
{
#if defined(QT_SHARED)
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints;
        d->release();
        d = 0;
        did_load = false;
    }

    QString fn = QFileInfo(fileName).canonicalFilePath();

    d = QLibraryPrivate::findOrCreate(fn);
    d->loadHints = lh;
    if (fn.isEmpty())
        d->errorString = QLibrary::tr("The shared library was not found.");
#else
    if (qt_debug_component()) {
        qWarning("Cannot load %s into a statically linked Qt library.",
            (const char*)QFile::encodeName(fileName));
    }
    Q_UNUSED(fileName);
#endif
}

QString QPluginLoader::fileName() const
{
    if (d)
        return d->fileName;
    return QString();
}

/*!
    \since 4.2

    Returns a text string with the description of the last error that occurred.
*/
QString QPluginLoader::errorString() const
{
    return (!d || d->errorString.isEmpty()) ? tr("Unknown error") : d->errorString;
}

typedef QVector<QStaticPlugin> StaticPluginList;
Q_GLOBAL_STATIC(StaticPluginList, staticPluginList)

/*! \since 4.4

    \property QPluginLoader::loadHints
    \brief Give the load() function some hints on how it should behave.

    You can give hints on how the symbols in the plugin are
    resolved. By default, none of the hints are set.

    See the documentation of QLibrary::loadHints for a complete
    description of how this property works.

    \sa QLibrary::loadHints
*/

void QPluginLoader::setLoadHints(QLibrary::LoadHints loadHints)
{
    if (!d) {
        d = QLibraryPrivate::findOrCreate(QString());   // ugly, but we need a d-ptr
        d->errorString.clear();
    }
    d->loadHints = loadHints;
}

QLibrary::LoadHints QPluginLoader::loadHints() const
{
    if (!d) {
        QPluginLoader *that = const_cast<QPluginLoader *>(this);
        that->d = QLibraryPrivate::findOrCreate(QString());   // ugly, but we need a d-ptr
        that->d->errorString.clear();
    }
    return d->loadHints;
}

/*!
    \relates QPluginLoader
    \since 5.0

    Registers the given \a plugin with the plugin loader.
*/
void Q_CORE_EXPORT qRegisterStaticPluginFunction(QStaticPlugin plugin)
{
    staticPluginList()->append(plugin);
}

/*!
    Returns a list of static plugin instances (root components) held
    by the plugin loader.
*/
QObjectList QPluginLoader::staticInstances()
{
    QObjectList instances;
    const StaticPluginList *plugins = staticPluginList();
    if (plugins) {
        for (int i = 0; i < plugins->size(); ++i)
            instances += plugins->at(i).instance();
    }
    return instances;
}


QVector<QStaticPlugin> QLibraryPrivate::staticPlugins()
{
    StaticPluginList *plugins = staticPluginList();
    if (plugins)
        return *plugins;
    return QVector<QStaticPlugin>();
}

QT_END_NAMESPACE

#endif // QT_NO_LIBRARY