[RFC PATCH v1 05/23] libcamera: base: cxx20: Add `has_single_bit()`

[Barnabás Pőcze]

`has_single_bit()` checks if the given unsigned integer has a single
bit set, that is, whether the number is a power of two or not.

Not all requirements of the C++20 standard are implemented.

See https://en.cppreference.com/w/cpp/numeric/has_single_bit

Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
---
 include/libcamera/base/details/cxx20.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/libcamera/base/details/cxx20.h b/include/libcamera/base/details/cxx20.h
index 2d26db53e..8bf45ff11 100644
--- a/include/libcamera/base/details/cxx20.h
+++ b/include/libcamera/base/details/cxx20.h
@@ -7,9 +7,19 @@
 
 #pragma once
 
+#include <type_traits>
+
 namespace libcamera::details::cxx20 {
 
 template<typename T> struct type_identity { using type = T; };
 template<typename T> using type_identity_t = typename type_identity<T>::type;
 
+template<typename T>
+constexpr bool has_single_bit(T x) noexcept
+{
+	static_assert(std::is_unsigned_v<T>);
+
+	return x != 0 && (x & (x - 1)) == 0;
+}
+
 } /* namespace libcamera::details::cxx20 */
-- 
2.49.0