diff options
| -rw-r--r-- | include/libcamera/extensible.h | 87 | ||||
| -rw-r--r-- | include/libcamera/meson.build | 1 | ||||
| -rw-r--r-- | src/libcamera/extensible.cpp | 134 | ||||
| -rw-r--r-- | src/libcamera/meson.build | 1 |
4 files changed, 223 insertions, 0 deletions
diff --git a/include/libcamera/extensible.h b/include/libcamera/extensible.h new file mode 100644 index 00000000..3f25a47c --- /dev/null +++ b/include/libcamera/extensible.h @@ -0,0 +1,87 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2020, Google Inc. + * + * extensible.h - Utilities to create extensible public classes with stable ABIs + */ +#ifndef __LIBCAMERA_EXTENSIBLE_H__ +#define __LIBCAMERA_EXTENSIBLE_H__ + +#include <memory> + +namespace libcamera { + +#ifndef __DOXYGEN__ +#define LIBCAMERA_DECLARE_PRIVATE(klass) \ +public: \ + class Private; \ + friend class Private; + +#define LIBCAMERA_DECLARE_PUBLIC(klass) \ + friend class klass; \ + using Public = klass; + +#define LIBCAMERA_D_PTR() \ + _d<Private>(); + +#define LIBCAMERA_O_PTR() \ + _o<Public>(); + +#else +#define LIBCAMERA_DECLARE_PRIVATE(klass) +#define LIBCAMERA_DECLARE_PUBLIC(klass) +#define LIBCAMERA_D_PTR(klass) +#define LIBCAMERA_O_PTR(klass) +#endif + +class Extensible +{ +public: + class Private + { + public: + Private(Extensible *o); + virtual ~Private(); + +#ifndef __DOXYGEN__ + template<typename T> + const T *_o() const + { + return static_cast<const T *>(o_); + } + + template<typename T> + T *_o() + { + return static_cast<T *>(o_); + } +#endif + + private: + Extensible *const o_; + }; + + Extensible(Private *d); + +protected: +#ifndef __DOXYGEN__ + template<typename T> + const T *_d() const + { + return static_cast<const T *>(d_.get()); + } + + template<typename T> + T *_d() + { + return static_cast<T *>(d_.get()); + } +#endif + +private: + const std::unique_ptr<Private> d_; +}; + +} /* namespace libcamera */ + +#endif /* __LIBCAMERA_EXTENSIBLE_H__ */ diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build index 3d5fc701..0b891a8f 100644 --- a/include/libcamera/meson.build +++ b/include/libcamera/meson.build @@ -8,6 +8,7 @@ libcamera_public_headers = files([ 'controls.h', 'event_dispatcher.h', 'event_notifier.h', + 'extensible.h', 'file_descriptor.h', 'framebuffer_allocator.h', 'geometry.h', diff --git a/src/libcamera/extensible.cpp b/src/libcamera/extensible.cpp new file mode 100644 index 00000000..1dcb0bf1 --- /dev/null +++ b/src/libcamera/extensible.cpp @@ -0,0 +1,134 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2020, Google Inc. + * + * extensible.cpp - Utilities to create extensible public classes with stable ABIs + */ + +#include <libcamera/extensible.h> + +/** + * \file extensible.h + * \brief Utilities to create extensible public classes with stable ABIs + */ + +namespace libcamera { + +/** + * \def LIBCAMERA_DECLARE_PRIVATE + * \brief Declare private data for a public class + * \param klass The public class name + * + * The LIBCAMERA_DECLARE_PRIVATE() macro plumbs the infrastructure necessary to + * make a class manage its private data through a d-pointer. It shall be used at + * the very top of the class definition, with the public class name passed as + * the \a klass parameter. + */ + +/** + * \def LIBCAMERA_DECLARE_PUBLIC + * \brief Declare public data for a private class + * \param klass The public class name + * + * The LIBCAMERA_DECLARE_PUBLIC() macro is the counterpart of + * LIBCAMERA_DECLARE_PRIVATE() to be used in the private data class. It shall be + * used at the very top of the private class definition, with the public class + * name passed as the \a klass parameter. + */ + +/** + * \def LIBCAMERA_D_PTR(klass) + * \brief Retrieve the private data pointer + * \param[in] klass The public class name + * + * This macro can be used in any member function of a class that inherits, + * directly or indirectly, from the Extensible class, to create a local + * variable named 'd' that points to the class' private data instance. + */ + +/** + * \def LIBCAMERA_O_PTR(klass) + * \brief Retrieve the public instance corresponding to the private data + * \param[in] klass The public class name + * + * This macro is the counterpart of LIBCAMERA_D_PTR() for private data classes. + * It can be used in any member function of the private data class to create a + * local variable named 'o' that points to the public class instance + * corresponding to the private data. + */ + +/** + * \class Extensible + * \brief Base class to manage private data through a d-pointer + * + * The Extensible class provides a base class to implement the + * <a href="https://wiki.qt.io/D-Pointer">d-pointer</a> design pattern (also + * known as <a href="https://en.wikipedia.org/wiki/Opaque_pointer">opaque pointer</a> + * or <a href="https://en.cppreference.com/w/cpp/language/pimpl">pImpl idiom</a>). + * It helps creating public classes that can be extended without breaking their + * ABI. Such classes store their private data in a separate private data object, + * referenced by a pointer in the public class (hence the name d-pointer). + * + * Classes that follow this design pattern are referred herein as extensible + * classes. To be extensible, a class PublicClass shall: + * + * - inherit from the Extensible class or from another extensible class + * - invoke the LIBCAMERA_DECLARE_PRIVATE() macro at the very top of the class + * definition + * - define a private data class named PublicClass::Private that inherits from + * the Private data class of the base class + * - invoke the LIBCAMERA_DECLARE_PUBLIC() macro at the very top of the Private + * data class definition + * - pass a pointer to a newly allocated Private data object to the constructor + * of the base class + * + * Additionally, if the PublicClass is not final, it shall expose one or more + * constructors that takes a pointer to a Private data instance, to be used by + * derived classes. + * + * The Private class is fully opaque to users of the libcamera public API. + * Internally, it can be kept private to the implementation of PublicClass, or + * be exposed to other classes. In the latter case, the members of the Private + * class need to be qualified with appropriate access specifiers. The + * PublicClass and Private classes always have full access to each other's + * protected and private members. + */ + +/** + * \brief Construct an instance of an Extensible class + * \param[in] d Pointer to the private data instance + */ +Extensible::Extensible(Extensible::Private *d) + : d_(d) +{ +} + +/** + * \var Extensible::d_ + * \brief Pointer to the private data instance + */ + +/** + * \class Extensible::Private + * \brief Base class for private data managed through a d-pointer + */ + +/** + * \brief Construct an instance of an Extensible class private data + * \param[in] o Pointer to the public class object + */ +Extensible::Private::Private(Extensible *o) + : o_(o) +{ +} + +Extensible::Private::~Private() +{ +} + +/** + * \var Extensible::Private::o_ + * \brief Pointer to the public class object + */ + +} /* namespace libcamera */ diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build index 99b27e66..387d5d88 100644 --- a/src/libcamera/meson.build +++ b/src/libcamera/meson.build @@ -17,6 +17,7 @@ libcamera_sources = files([ 'event_dispatcher.cpp', 'event_dispatcher_poll.cpp', 'event_notifier.cpp', + 'extensible.cpp', 'file.cpp', 'file_descriptor.cpp', 'formats.cpp', |