libcamera: utils: Add map_keys() function

Add a map_keys() function to the utils namespace to extract keys from a
map.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[Niklas: change return type to std::vector instead of std::set]
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/utils.cpp

@@ -127,6 +127,13 @@ std::string dirname(const std::string &path)
 	return path.substr(0, pos + 1);
 }
 
+/**
+ * \fn std::vector<typename T::key_type> map_keys(const T &map)
+ * \brief Retrieve the keys of a std::map<>
+ * \param[in] map The map whose keys to retrieve
+ * \return A std::vector<> containing the keys of \a map
+ */
+
 /**
  * \fn libcamera::utils::set_overlap(InputIt1 first1, InputIt1 last1,
  *				     InputIt2 first2, InputIt2 last2)