diff options
| author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2022-07-27 23:51:17 +0300 |
|---|---|---|
| committer | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2022-07-28 14:54:41 +0300 |
| commit | 48c106429a197d9c35c30523d3f5c711f3137333 (patch) | |
| tree | d188e436875e54b1764eb79babdc7c2dc36f632c /src | |
| parent | f6d6181d3c91efa526b5027319331db9ac75f65b (diff) | |
libcamera: base: utils: Provide defopt to simplify std::optional::value_or() usage
The std::optional<T>::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<T>::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<T>::value_or() and get
implicitly converted to a default-constructed T.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Diffstat (limited to 'src')
| -rw-r--r-- | src/libcamera/base/utils.cpp | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/libcamera/base/utils.cpp b/src/libcamera/base/utils.cpp index 6a307940..9cd6cb19 100644 --- a/src/libcamera/base/utils.cpp +++ b/src/libcamera/base/utils.cpp @@ -463,6 +463,27 @@ std::string toAscii(const std::string &str) * \a b */ +/** + * \var defopt + * \brief Constant used with std::optional::value_or() to create a + * default-constructed object + * + * The std::optional<T>::value_or(U &&default_value) function returns the + * contained value if available, or \a 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<T>::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. + * + * The defopt variable solves these issues by providing a value that can be + * passed to std::optional<T>::value_or() and get implicitly converted to a + * default-constructed T. + */ + } /* namespace utils */ #ifndef __DOXYGEN__ |