1 files changed, 53 insertions, 0 deletions
diff --git a/lib/bit.h b/lib/bit.h
new file mode 100644
index 0000000..7f09eb4
--- /dev/null
+++ b/lib/bit.h
@@ -0,0 +1,53 @@
+/*
+ * SPDX-FileCopyrightText:  2022 - 2023, Alejandro Colomar <alx@kernel.org>
+ *
+ * SPDX-License-Identifier:  BSD-3-Clause
+ */
+
+
+#ifndef SHADOW_INCLUDE_LIB_BIT_H_
+#define SHADOW_INCLUDE_LIB_BIT_H_
+
+
+#include <config.h>
+
+#include <limits.h>
+
+
+#ifndef ULONG_WIDTH
+#define ULONG_WIDTH (sizeof(unsigned long) * CHAR_BIT)
+#endif
+
+
+inline unsigned long bit_ceilul(unsigned long x);
+inline unsigned long bit_ceil_wrapul(unsigned long x);
+inline int leading_zerosul(unsigned long x);
+
+
+/* stdc_bit_ceilul(3) */
+inline unsigned long
+bit_ceilul(unsigned long x)
+{
+	return 1 + (ULONG_MAX >> leading_zerosul(x));
+}
+
+
+/* stdc_bit_ceilul(3), but wrap instead of having Undefined Behavior */
+inline unsigned long
+bit_ceil_wrapul(unsigned long x)
+{
+	if (x == 0)
+		return 0;
+
+	return bit_ceilul(x);
+}
+
+/* stdc_leading_zerosul(3) */
+inline int
+leading_zerosul(unsigned long x)
+{
+	return (x == 0) ? ULONG_WIDTH : __builtin_clzl(x);
+}
+
+
+#endif  // include guard