[vlc-devel] [PATCH] include: Add C++ memory management helpers

[Hugo Beauzée-Luyssen]

On Fri, Jul 13, 2018, at 3:16 PM, Hugo Beauzée-Luyssen wrote:
> ---
>  include/vlc_cxx_helpers.hpp | 122 ++++++++++++++++++++++++++++++++++++
>  src/Makefile.am             |   1 +
>  2 files changed, 123 insertions(+)
>  create mode 100644 include/vlc_cxx_helpers.hpp
> 
> diff --git a/include/vlc_cxx_helpers.hpp b/include/vlc_cxx_helpers.hpp
> new file mode 100644
> index 0000000000..130b5dcf0c
> --- /dev/null
> +++ b/include/vlc_cxx_helpers.hpp
> @@ -0,0 +1,122 @@
> +/
> *****************************************************************************
> + * vlc_cxx_helpers.hpp: C++ helpers
> + 
> *****************************************************************************
> + * Copyright (C) 1998-2018 VLC authors and VideoLAN
> + *
> + * Authors: Hugo Beauzée-Luyssen <hugo at beauzee.fr>
> + *
> + * This program is free software; you can redistribute it and/or modify 
> it
> + * under the terms of the GNU Lesser General Public License as 
> published by
> + * the Free Software Foundation; either version 2.1 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public 
> License
> + * along with this program; if not, write to the Free Software 
> Foundation,
> + * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
> + 
> *****************************************************************************/
> +
> +#ifndef VLC_CXX_HELPERS_HPP
> +#define VLC_CXX_HELPERS_HPP
> +
> +/
> ******************************************************************************
> + * C++ memory management helpers
> + 
> ******************************************************************************/
> +
> +#ifdef __cplusplus
> +
> +#include <memory>
> +#include <utility>
> +#include <type_traits>
> +
> +namespace vlc
> +{
> +
> +namespace
> +{
> +// This helpers need static linkage to avoid their signature to change 
> when
> +// building as C++17 (noexcept becomes part of the function signature 
> stating there)
> +
> +// Wraps a pointer with a custom releaser
> +// ex: auto ptr = vlc_wrap_cptr( input_item, &input_item_Release );
> +
> +///
> +/// Wraps a C pointer into a std::unique_ptr
> +///
> +/// This will convert a C pointer of type T to a std::unique_ptr<T, R> 
> where
> +/// T is the pointee type, and R is an arbitrary releaser type.
> +///
> +/// ptr will be automatically released by calling r( ptr ) when falling 
> out of
> +/// scope (whether by returning of by throwing an exception
> +///
> +/// @param ptr a C pointer
> +/// @param r An instance of a Callable type, that will be invoked with 
> ptr
> +///          as its first and only parameter.
> +template <typename T, typename Releaser>
> +static inline auto wrap_cptr( T* ptr, Releaser&& r ) noexcept
> +    -> std::unique_ptr<T, typename std::decay<decltype( r )>::type>
> +{
> +    return std::unique_ptr<T, typename 
> std::decay<decltype( r )>::type>{
> +                ptr, std::forward<Releaser>( r )
> +    };
> +}
> +
> +///
> +/// Wraps a C pointer into a std::unique_ptr
> +///
> +/// This will convert a C pointer to an array of type T to a
> +/// std::unique_ptr<T[], R> where T is the pointee type, and R is an 
> arbitrary
> +/// releaser type.
> +///
> +/// ptr will be automatically released by calling r( ptr ) when falling 
> out of
> +/// scope (whether by returning of by throwing an exception
> +///
> +/// This function is equivalent to wrap_cptr, except that the returned
> +/// unique_ptr provides an operator[] for array access instead of 
> operator* and
> +/// operator->
> +///
> +/// @param ptr a C pointer
> +/// @param r An instance of a Callable type, that will be invoked with 
> ptr
> +///          as its first and only parameter.
> +template <typename T, typename Releaser>
> +static inline auto wrap_carray( T* ptr, Releaser&& r ) noexcept
> +    -> std::unique_ptr<T[], typename std::decay<decltype( r )>::type>
> +{
> +    return std::unique_ptr<T[], typename 
> std::decay<decltype( r )>::type>{
> +        ptr, std::forward<Releaser>( r )
> +    };
> +}
> +
> +///
> +/// Wraps a C pointer into a std::unique_ptr
> +///
> +/// This is a convenience wrapper that will use free() as its releaser
> +///
> +template <typename T>
> +static inline std::unique_ptr<T, void (*)(void*)> wrap_cptr( T* ptr ) 
> noexcept
> +{
> +    return wrap_cptr( ptr, &free );
> +}
> +
> +///
> +/// Wraps a C pointer into a std::unique_ptr
> +///
> +/// This is a convenience wrapper that will use free() as its releaser
> +///
> +template <typename T>
> +static inline std::unique_ptr<T[], void (*)(void*)> wrap_carray( T* 
> ptr ) noexcept
> +{
> +    return wrap_carray( ptr, &free );
> +}
> +
> +} // anonymous namespace
> +
> +} // namespace vlc
> +
> +#endif
> +
> +#endif // VLC_CXX_HELPERS_HPP
> diff --git a/src/Makefile.am b/src/Makefile.am
> index f9106a17c5..49ac01b26f 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -41,6 +41,7 @@ pluginsinclude_HEADERS = \
>  	../include/vlc_config_cat.h \
>  	../include/vlc_configuration.h \
>  	../include/vlc_cpu.h \
> +	../include/vlc_cxx_helpers.hpp \
>  	../include/vlc_dialog.h \
>  	../include/vlc_demux.h \
>  	../include/vlc_epg.h \

Oops, I forgot to remove the static qualifiers, fixed locally.

-- 
  Hugo Beauzée-Luyssen
  hugo at beauzee.fr