[PATCH 1/2] libcamera: utils: Add to_underlying() helper function

[Laurent Pinchart]

C++23 has a std::to_underlying() helper function that converts an
enumeration value to its underlying type. Add a compatible
implementation to the libcamera::utils namespace.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/base/utils.h |  6 ++++++
 src/libcamera/base/utils.cpp   | 10 ++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/libcamera/base/utils.h b/include/libcamera/base/utils.h
index 37d9af609ec7..922e4dfaf9fa 100644
--- a/include/libcamera/base/utils.h
+++ b/include/libcamera/base/utils.h
@@ -369,6 +369,12 @@ decltype(auto) abs_diff(const T &a, const T &b)
 
 double strtod(const char *__restrict nptr, char **__restrict endptr);
 
+template<class Enum>
+constexpr std::underlying_type_t<Enum> to_underlying(Enum e) noexcept
+{
+	return static_cast<std::underlying_type_t<Enum>>(e);
+}
+
 } /* namespace utils */
 
 #ifndef __DOXYGEN__
diff --git a/src/libcamera/base/utils.cpp b/src/libcamera/base/utils.cpp
index 3b73b442260a..2f4c3177ac13 100644
--- a/src/libcamera/base/utils.cpp
+++ b/src/libcamera/base/utils.cpp
@@ -521,6 +521,16 @@ double strtod(const char *__restrict nptr, char **__restrict endptr)
 #endif
 }
 
+/**
+ * \fn to_underlying(Enum e)
+ * \brief Convert an enumeration to its underlygin type
+ * \param[in] e Enumeration value to convert
+ *
+ * This function is equivalent to the C++23 std::to_underlying().
+ *
+ * \return The value of e converted to its underlying type
+ */
+
 } /* namespace utils */
 
 #ifndef __DOXYGEN__
-- 
Regards,

Laurent Pinchart