path: root/library/qlibrary.cpp

/**********************************************************************
** Copyright (C) 2000-2002 Trolltech AS.  All rights reserved.
**
** This file is part of the Qtopia Environment.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
** See http://www.trolltech.com/gpl/ for GPL licensing information.
**
** Contact info@trolltech.com if any conditions of this licensing are
** not clear to you.
**
**********************************************************************/


#include "qlibrary_p.h"

// uncomment this to get error messages
//#define QT_DEBUG_COMPONENT 1 
// uncomment this to get error and success messages
//#define QT_DEBUG_COMPONENT 2

#ifndef QT_DEBUG_COMPONENT
# if defined(QT_DEBUG)
#  define QT_DEBUG_COMPONENT 1
# endif
#endif

#ifndef QT_NO_COMPONENT

// KAI C++ has at the moment problems with unloading the Qt plugins. So don't
// unload them as a workaround for now.
#if defined(Q_CC_KAI) || defined(Q_OS_MAC)
#define QT_NO_LIBRARY_UNLOAD
#endif

#if defined(Q_WS_WIN) && !defined(QT_MAKEDLL)
#define QT_NO_LIBRARY_UNLOAD
#endif

/* Platform independent QLibraryPrivate implementations */
#ifndef QT_LITE_COMPONENT

#include "qtimer.h"

extern Q_EXPORT QApplication *qApp;

QLibraryPrivate::QLibraryPrivate( QLibrary *lib )
    : QObject( 0, lib->library().latin1() ), pHnd( 0 ), libIface( 0 ), unloadTimer( 0 ), library( lib )
{
}

QLibraryPrivate::~QLibraryPrivate()
{
    if ( libIface )
	libIface->release();
    killTimer();
}

/*
  Only components that implement the QLibraryInterface can
  be unloaded automatically.
*/
void QLibraryPrivate::tryUnload()
{
    if ( library->policy() == QLibrary::Manual || !pHnd || !libIface )
	return;

    if ( !libIface->canUnload() )
	return;

#if defined(QT_DEBUG_COMPONENT) && QT_DEBUG_COMPONENT == 2
    if ( library->unload() )
	qDebug( "%s has been automatically unloaded", library->library().latin1() );
#else
    library->unload();
#endif
}

#else // QT_LITE_COMPOINENT

QLibraryPrivate::QLibraryPrivate( QLibrary *lib )
    : pHnd( 0 ), libIface( 0 ), library( lib )
{
}

#endif // QT_LITE_COMPOINENT

void QLibraryPrivate::startTimer()
{
#ifndef QT_LITE_COMPONENT
    unloadTimer = new QTimer( this );
    connect( unloadTimer, SIGNAL( timeout() ), this, SLOT( tryUnload() ) );
    unloadTimer->start( 5000, FALSE );
#endif
}

void QLibraryPrivate::killTimer()
{
#ifndef QT_LITE_COMPONENT
    delete unloadTimer;
    unloadTimer = 0;
#endif
}

/*!
  \class QLibrary qlibrary.h

  \brief The QLibrary class provides a wrapper for handling shared libraries.

  This class is temporarily copied from Qt 3.0.
*/

/*!
  \enum QLibrary::Policy

  This enum type defines the various policies a QLibrary can have with respect to
  loading and unloading the shared library.

  The \e policy can be:

  \value Delayed  The library get's loaded as soon as needed and unloaded in the destructor
  \value Immediately  The library is loaded immediately and unloaded in the destructor
  \value Manual  Like delayed, and library has to be unloaded manually
*/

/*!
  Creates a QLibrary object for the shared library \a filename.
  The library get's loaded if \a pol is Immediately.

  Note that \a filename does not need to include the (platform specific)
  file extension, so calling

  \code
  QLibrary lib( "mylib" );
  \endcode

  would be equivalent to

  \code
  QLibrary lib( "mylib.dll" );
  \endcode

  on Windows. But \e "mylib.dll" will obviously not work on other platforms.

  \sa setPolicy(), unload()
*/
QLibrary::QLibrary( const QString& filename, Policy pol )
    : libfile( filename ), libPol( pol ), entry( 0 )
{
    d = new QLibraryPrivate( this );
    if ( pol == Immediately )
	load();
}

/*!
  Deletes the QLibrary object.
  The library will be unloaded if the policy is not Manual.

  \sa unload(), setPolicy()
*/
QLibrary::~QLibrary()
{
    if ( libPol == Manual || !unload() ) {
	if ( entry ) {
	    entry->release();
	    entry = 0;
	}
    }
    delete d;
}

void QLibrary::createInstanceInternal()
{
    if ( libfile.isEmpty() )
	return;

    if ( !d->pHnd ) {
	ASSERT( entry == 0 );
	load();
    }

    if ( d->pHnd && !entry ) {
#if defined(QT_DEBUG_COMPONENT) && QT_DEBUG_COMPONENT == 2
	qWarning( "%s has been loaded.", library().latin1() );
#endif
	typedef QUnknownInterface* (*UCMInstanceProc)();
	UCMInstanceProc ucmInstanceProc;
	ucmInstanceProc = (UCMInstanceProc) resolve( "ucm_instantiate" );
	entry = ucmInstanceProc ? ucmInstanceProc() : 0;
	if ( entry ) {
	    entry->queryInterface( IID_QLibrary, (QUnknownInterface**)&d->libIface);
	    if ( d->libIface ) {
		if ( !d->libIface->init() ) {
#if defined(QT_DEBUG_COMPONENT)
		    qWarning( "%s: QLibraryInterface::init() failed.", library().latin1() );
#endif
		    unload();
		    return;
		}

		d->killTimer();
		if ( libPol != Manual )
		    d->startTimer();
	    }
	} else {
#if defined(QT_DEBUG_COMPONENT)
	    qWarning( "%s: No interface implemented.", library().latin1() );
#endif
	    unload();
	}
    }
}

/*!
  Returns the address of the exported symbol \a symb. The library gets
  loaded if necessary. The function returns NULL if the symbol could
  not be resolved, or if loading the library failed.

  \code
  typedef int (*addProc)( int, int );

  addProc add = (addProc) library->resolve( "add" );
  if ( add )
      return add( 5, 8 );
  else
      return 5 + 8;
  \endcode

  \sa queryInterface()
*/
void *QLibrary::resolve( const char* symb )
{
    if ( !d->pHnd )
	load();
    if ( !d->pHnd )
	return 0;

    void *address = d->resolveSymbol( symb );
    if ( !address ) {
#if defined(QT_DEBUG_COMPONENT)
	// resolveSymbol() might give a warning; so let that warning look so fatal
	qWarning( QString("Trying to resolve symbol \"_%1\" instead").arg( symb ) );
#endif
	address = d->resolveSymbol( QString( "_" ) + symb );
    }
    return address;
}

/*!
    \overload

  Loads the library \a filename and returns the address of the exported symbol \a symb.
  Note that like for the constructor, \a filename does not need to include the (platform specific)
  file extension. The library staying loaded until the process exits.

  The function returns a null pointer if the symbol could not be resolved or if loading
  the library failed.
*/
void *QLibrary::resolve( const QString &filename, const char *symb )
{
    QLibrary lib( filename, Manual );
    return lib.resolve( symb );
}

/*!
  Returns whether the library is loaded.

  \sa unload()
*/
bool QLibrary::isLoaded() const
{
    return d->pHnd != 0;
}

/*!
  Loads the library.
*/
bool QLibrary::load()
{
    return d->loadLibrary();
}

/*!
  Releases the component and unloads the library when successful.
  Returns TRUE if the library could be unloaded, otherwise FALSE.
  If the component implements the QLibraryInterface, the cleanup()
  function of this interface will be called. The unloading will be
  cancelled if the subsequent call to canUnload() returns FALSE.

  This function gets called automatically in the destructor if
  the policy is not Manual.

  \warning
  If \a force is set to TRUE, the library gets unloaded at any cost,
  which is in most cases a segmentation fault, so you should know what
  you're doing!

  \sa queryInterface(), resolve()
*/
bool QLibrary::unload( bool force )
{
    if ( !d->pHnd )
	return TRUE;

    if ( entry ) {
	if ( d->libIface ) {
	    d->libIface->cleanup();

	    bool can = d->libIface->canUnload();
	    can = ( d->libIface->release() <= 1 ) && can;
	    // the "entry" member must be the last reference to the component
	    if ( can || force ) {
		d->libIface = 0;
	    } else {
#if defined(QT_DEBUG_COMPONENT)
		qWarning( "%s prevents unloading!", library().latin1() );
#endif
		d->libIface->addRef();
		return FALSE;
	    }
	}

	if ( entry->release() ) {
#if defined(QT_DEBUG_COMPONENT)
	    qWarning( "%s is still in use!", library().latin1() );
#endif
	    if ( force ) {
		delete entry;
	    } else {
		entry->addRef();
		return FALSE;
	    }
	}
	d->killTimer();

	entry = 0;
    }

// ### this is a hack to solve problems with plugin unloading und KAI C++
// (other compilers may have the same problem)
#if !defined(QT_NO_LIBRARY_UNLOAD)
    if ( !d->freeLibrary() ) {
#if defined(QT_DEBUG_COMPONENT)
	qWarning( "%s could not be unloaded.", library().latin1() );
#endif
	return FALSE;
#else
	return TRUE;
#endif
#if !defined(QT_NO_LIBRARY_UNLOAD)
    }

#if defined(QT_DEBUG_COMPONENT) && QT_DEBUG_COMPONENT == 2
    qWarning( "%s has been unloaded.", library().latin1() );
#endif

    d->pHnd = 0;
    return TRUE;
#endif
}

/*!
  Sets the current policy to \a pol.
  The library is loaded if \a pol is set to Immediately.
*/
void QLibrary::setPolicy( Policy pol )
{
    libPol = pol;

    if ( libPol == Immediately && !d->pHnd )
	load();
}

/*!
  Returns the current policy.

  \sa setPolicy()
*/
QLibrary::Policy QLibrary::policy() const
{
    return libPol;
}

/*!
  Returns the filename of the shared library this QLibrary object handles,
  including the platform specific file extension.

  \code
  QLibrary lib( "mylib" );
  QString str = lib.library();
  \endcode

  will set \e str to "mylib.dll" on Windows, and "libmylib.so" on Linux.
*/
QString QLibrary::library() const
{
    if ( libfile.isEmpty() )
	return libfile;

    QString filename = libfile;
#if defined(Q_WS_WIN)
    if ( filename.find( ".dll" ) == -1 )
	filename += ".dll";
#elif defined(Q_OS_MACX)
    if ( filename.find( ".dylib" ) == -1 )
	filename += ".dylib";
#else
    if ( filename.find( ".so" ) == -1 )
	filename = QString( "lib%1.so" ).arg( filename );
#endif

    return filename;
}

/*!
  Forwards the query to the component and returns the result. \a request and \a iface
  are propagated to the component's queryInterface implementation.

  The library gets loaded if necessary.
*/
QRESULT QLibrary::queryInterface( const QUuid& request, QUnknownInterface** iface )
{
    if ( !entry ) {
	createInstanceInternal();
    }

    return entry ? entry->queryInterface( request, iface ) : QE_NOINTERFACE;
}

#endif // QT_NO_COMPONENT