Merge pull request #525 from beached/v2

Added digit counting of unsigned integers
beached · Aug 10, 2024 · e9e9f87 · e9e9f87
2 parents fcd352a + c765c92
commit e9e9f87
Show file tree

Hide file tree

Showing 2 changed files with 30 additions and 1 deletion.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -9,7 +9,7 @@
 cmake_minimum_required( VERSION 3.14 )
 
 project( "daw-header-libraries"
-         VERSION "2.106.2"
+         VERSION "2.107.0"
          DESCRIPTION "Various headers"
          HOMEPAGE_URL "https://github.com/beached/header_libraries"
          LANGUAGES C CXX

diff --git a/include/daw/daw_cxmath.h b/include/daw/daw_cxmath.h
@@ -1340,4 +1340,33 @@ namespace daw::cxmath {
 	DAW_ATTRIB_INLINE constexpr auto to_signed( Integer value ) {
 		return static_cast<daw::make_signed_t<Integer>>( value );
 	}
+
+	inline constexpr std::uint64_t powers_of_ten[19] = {
+	  10ull,
+	  100ull,
+	  1'000ull,
+	  10'000ull,
+	  100'000ull,
+	  1'000'000ull,
+	  10'000'000ull,
+	  100'000'000ull,
+	  1'000'000'000ull,
+	  10'000'000'000ull,
+	  100'000'000'000ull,
+	  1'000'000'000'000ull,
+	  10'000'000'000'000ull,
+	  100'000'000'000'000ull,
+	  1'000'000'000'000'000ull,
+	  10'000'000'000'000'000ull,
+	  100'000'000'000'000'000ull,
+	  1'000'000'000'000'000'000ull,
+	  10'000'000'000'000'000'000ull };
+
+	constexpr int count_digits( std::uint64_t value ) {
+		auto b = -( value > 0 ) & ( 63 - count_leading_zeroes( value ) );
+		auto a = ( b * 77 ) / 256;
+		return static_cast<int>( 1 + a + ( value >= powers_of_ten[a] ) );
+	}
+	static_assert( count_digits( 1'000'000ULL ) == 7 );
 } // namespace daw::cxmath
+