| Message ID | 20210711170359.300-2-laurent.pinchart@ideasonboard.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series |
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| Related | show |
On Sun, Jul 11, 2021 at 08:03:57PM +0300, Laurent Pinchart wrote: > Despite sharing the same name, the private data class created by the > Extensible design pattern and the C++ private access specifier have > different goals. The latter specifies class members private to the > class, while the former stores data not visible to the application. > > There are use cases for accessing the private data class from other > classes inside libcamera. Make this possible by exposing public _d() > functions in the class deriving from Extensible. This won't allow access > to the private data by applications as the definition of the Private > class isn't visible outside of libcamera. > > The _d() functions need to be defined as template functions to delay > their evaluation, as the static_cast() operator in the Extensible::_d() > functions needs the Private class to be fully defined. This should read The _d() functions need to be defined as template functions to delay their evaluation, as the static_cast() operator in the Extensible::_d() functions needs the Private class to be fully defined. The template argument is defaulted an ignored, as only its presence is required to delay evaluation. > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> > Reviewed-by: Umang Jain <umang.jain@ideasonboard.com> > Reviewed-by: Hirokazu Honda <hiroh@chromium.org> > --- > include/libcamera/base/class.h | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/libcamera/base/class.h b/include/libcamera/base/class.h > index a07dac057331..8212c3d4a5ae 100644 > --- a/include/libcamera/base/class.h > +++ b/include/libcamera/base/class.h > @@ -33,14 +33,24 @@ namespace libcamera { > #define LIBCAMERA_DECLARE_PRIVATE() \ > public: \ > class Private; \ > - friend class Private; > + friend class Private; \ > + template <bool B = true> \ > + const Private *_d() const \ > + { \ > + return Extensible::_d<Private>(); \ > + } \ > + template <bool B = true> \ > + Private *_d() \ > + { \ > + return Extensible::_d<Private>(); \ > + } > > #define LIBCAMERA_DECLARE_PUBLIC(klass) \ > friend class klass; \ > using Public = klass; > > #define LIBCAMERA_D_PTR() \ > - _d<Private>(); > + _d(); > > #define LIBCAMERA_O_PTR() \ > _o<Public>();
Hi Laurent, On 11/07/2021 22:06, Laurent Pinchart wrote: > On Sun, Jul 11, 2021 at 08:03:57PM +0300, Laurent Pinchart wrote: >> Despite sharing the same name, the private data class created by the >> Extensible design pattern and the C++ private access specifier have >> different goals. The latter specifies class members private to the >> class, while the former stores data not visible to the application. >> >> There are use cases for accessing the private data class from other >> classes inside libcamera. Make this possible by exposing public _d() >> functions in the class deriving from Extensible. This won't allow access >> to the private data by applications as the definition of the Private >> class isn't visible outside of libcamera. >> >> The _d() functions need to be defined as template functions to delay >> their evaluation, as the static_cast() operator in the Extensible::_d() >> functions needs the Private class to be fully defined. > > This should read > > The _d() functions need to be defined as template functions to delay > their evaluation, as the static_cast() operator in the Extensible::_d() > functions needs the Private class to be fully defined. The template > argument is defaulted an ignored, as only its presence is required to s/an/and/ > delay evaluation. > >> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> >> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org> >> Reviewed-by: Umang Jain <umang.jain@ideasonboard.com> >> Reviewed-by: Hirokazu Honda <hiroh@chromium.org> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> >> --- >> include/libcamera/base/class.h | 14 ++++++++++++-- >> 1 file changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/include/libcamera/base/class.h b/include/libcamera/base/class.h >> index a07dac057331..8212c3d4a5ae 100644 >> --- a/include/libcamera/base/class.h >> +++ b/include/libcamera/base/class.h >> @@ -33,14 +33,24 @@ namespace libcamera { >> #define LIBCAMERA_DECLARE_PRIVATE() \ >> public: \ >> class Private; \ >> - friend class Private; >> + friend class Private; \ >> + template <bool B = true> \ >> + const Private *_d() const \ >> + { \ >> + return Extensible::_d<Private>(); \ >> + } \ >> + template <bool B = true> \>> + Private *_d() \ >> + { \ >> + return Extensible::_d<Private>(); \ >> + } >> >> #define LIBCAMERA_DECLARE_PUBLIC(klass) \ >> friend class klass; \ >> using Public = klass; >> >> #define LIBCAMERA_D_PTR() \ >> - _d<Private>(); >> + _d(); >> >> #define LIBCAMERA_O_PTR() \ >> _o<Public>(); >
diff --git a/include/libcamera/base/class.h b/include/libcamera/base/class.h index a07dac057331..8212c3d4a5ae 100644 --- a/include/libcamera/base/class.h +++ b/include/libcamera/base/class.h @@ -33,14 +33,24 @@ namespace libcamera { #define LIBCAMERA_DECLARE_PRIVATE() \ public: \ class Private; \ - friend class Private; + friend class Private; \ + template <bool B = true> \ + const Private *_d() const \ + { \ + return Extensible::_d<Private>(); \ + } \ + template <bool B = true> \ + Private *_d() \ + { \ + return Extensible::_d<Private>(); \ + } #define LIBCAMERA_DECLARE_PUBLIC(klass) \ friend class klass; \ using Public = klass; #define LIBCAMERA_D_PTR() \ - _d<Private>(); + _d(); #define LIBCAMERA_O_PTR() \ _o<Public>();