#include <qlibrary.h>
Public Methods | |
QLibrary (const QString &filename) | |
Constructor of QLibrary. More... | |
virtual | ~QLibrary () |
Deletes the QLibrary object. More... | |
void* | resolve (const char *) |
Returns the address of the exported symbol symb. More... | |
bool | load () |
Loads the library. More... | |
virtual bool | unload () |
Unloads the library and returns TRUE if the library could be unloaded; otherwise returns FALSE. More... | |
bool | isLoaded () const |
Returns TRUE if the library is loaded; otherwise returns FALSE. More... | |
bool | autoUnload () const |
Returns TRUE if the library will be automatically unloaded when this wrapper object is destructed; otherwise returns FALSE. More... | |
void | setAutoUnload (bool enable) |
If enabled is TRUE (the default), the wrapper object is set to automatically unload the library upon destruction. More... | |
QString | library () const |
Returns the filename of the shared library this QLibrary object handles, including the platform specific file extension. More... | |
QRESULT | queryInterface (const QUuid &request, QUnknownInterface **iface) |
Forwards the query to the component and returns the result. More... | |
Static Public Methods | |
void* | resolve (const QString &filename, const char *) |
This is an overloaded member function, provided for convenience. More... |
An instance of a QLibrary object can handle a single shared library and provide access to the functionality in the library in a platform independent way. If the library is a component server, QLibrary provides access to the exported component and can directly query this component for interfaces.
QLibrary ensures that the shared library is loaded and stays in memory whilst it is in use. QLibrary can also unload the library on destruction and release unused resources.
A typical use of QLibrary is to resolve an exported symbol in a shared object, and to call the function that this symbol represents. This is called "explicit linking" in contrast to "implicit linking", which is done by the link step in the build process when linking an executable against a library.
The following code snippet loads a library, resolves the symbol "mysymbol", and calls the function if everything succeeded. If something went wrong, e.g. the library file does not exist or the symbol is not defined, the function pointer will be 0 and won't be called. When the QLibrary object is destroyed the library will be unloaded, making all references to memory allocated in the library invalid.
typedef void (*MyPrototype)(); MyPrototype myFunction; QLibrary myLib( "mylib" ); myFunction = (MyProtoype) myLib.resolve( "mysymbol" ); if ( myFunction ) { myFunction(); }
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Constructor of QLibrary. Creates a QLibrary object for the shared library filename. The library will be unloaded in the destructor.
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Deletes the QLibrary object. The library will be unloaded if autoUnload() is TRUE (the default), otherwise it stays in memory until the application exits.
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Returns TRUE if the library will be automatically unloaded when this wrapper object is destructed; otherwise returns FALSE. The default is TRUE. |
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Returns TRUE if the library is loaded; otherwise returns FALSE.
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Returns the filename of the shared library this QLibrary object handles, including the platform specific file extension.
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Loads the library. Since resolve() always calls this function before resolving any symbols it is not necessary to call it explicitly. In some situations you might want the library loaded in advance, in which case you would use this function. |
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Forwards the query to the component and returns the result. request and iface are propagated to the component's queryInterface implementation. The library gets loaded if necessary. |
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This is an overloaded member function, provided for convenience. It behaves essentially like the above function. Loads the library filename and returns the address of the exported symbol symb. The function returns 0 if the symbol could not be resolved or the library could not be loaded. This function is useful only if you want to resolve a single symbol, e.g. a function pointer from a specific library once:
typedef void (*FunctionType)(); static FunctionType *ptrFunction = 0; static bool triedResolve = FALSE; if ( !ptrFunction && !triedResolve ) ptrFunction = QLibrary::resolve( "mylib", "mysymb" ); if ( ptrFunction ) ptrFunction(); else ...
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Returns the address of the exported symbol symb. The library is loaded if necessary. The function returns 0 if the symbol could not be resolved or the library could not be loaded.
typedef int (*avgProc)( int, int ); avgProc avg = (avgProc) library->resolve( "avg" ); if ( avg ) { return avg( 5, 8 ); } else { return -1; } |
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If enabled is TRUE (the default), the wrapper object is set to automatically unload the library upon destruction. If enabled is FALSE, the wrapper object is not unloaded unless you explicitly call unload(). |
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Unloads the library and returns TRUE if the library could be unloaded; otherwise returns FALSE. This function is called by the destructor if autoUnload() is enabled. |