From 48c106429a197d9c35c30523d3f5c711f3137333 Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Wed, 27 Jul 2022 23:51:17 +0300 Subject: libcamera: base: utils: Provide defopt to simplify std::optional::value_or() usage The std::optional::value_or(U &&default_value) function returns the contained value if available, or default_value if the std::optional has no value. If the desired default value is a default-constructed T, the obvious option is to call std::optional::value_or(T{}). This approach has two drawbacks: - The \a default_value T{} is constructed even if the std::optional instance has a value, which impacts efficiency. - The T{} default constructor needs to be spelled out explicitly in the value_or() call, leading to long lines if the type is complex. Introduce a defopt variable that solves these issues by providing a value that can be passed to std::optional::value_or() and get implicitly converted to a default-constructed T. Signed-off-by: Laurent Pinchart Reviewed-by: Umang Jain Reviewed-by: Jacopo Mondi --- include/libcamera/base/utils.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include') diff --git a/include/libcamera/base/utils.h b/include/libcamera/base/utils.h index cfff0583..889bb4a2 100644 --- a/include/libcamera/base/utils.h +++ b/include/libcamera/base/utils.h @@ -361,6 +361,20 @@ decltype(auto) abs_diff(const T &a, const T &b) return a - b; } +namespace details { + +struct defopt_t { + template + operator T() const + { + return T{}; + } +}; + +} /* namespace details */ + +constexpr details::defopt_t defopt; + } /* namespace utils */ #ifndef __DOXYGEN__ -- cgit v1.2.1