From c6bd01b2f2c33d5e752cd207a5b779b818a80aa0 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sun, 5 Dec 2021 17:40:42 +0000
Subject: [PATCH] Add an IsOddParity bitmath function

---
 src/core/bitmath_func.hpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/core/bitmath_func.hpp b/src/core/bitmath_func.hpp
index 18684dc637..c4cc4d6153 100644
--- a/src/core/bitmath_func.hpp
+++ b/src/core/bitmath_func.hpp
@@ -317,6 +317,30 @@ static inline uint CountBits(T value)
 #endif
 }
 
+/**
+ * Return whether the input has odd parity (odd number of bits set).
+ *
+ * @param value the value to return the parity of.
+ * @return true if the parity is odd.
+ */
+template <typename T>
+static inline bool IsOddParity(T value)
+{
+	static_assert(sizeof(T) <= sizeof(unsigned long long));
+#ifdef WITH_BITMATH_BUILTINS
+	typename std::make_unsigned<T>::type unsigned_value = value;
+	if (sizeof(T) <= sizeof(unsigned int)) {
+		return __builtin_parity(unsigned_value);
+	} else if (sizeof(T) == sizeof(unsigned long)) {
+		return __builtin_parityl(unsigned_value);
+	} else {
+		return __builtin_parityll(unsigned_value);
+	}
+#else
+	return CountBits<T>(value) & 1;
+#endif
+}
+
 /**
  * Test whether \a value has exactly 1 bit set
  *