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include/intarith: rewrite cbits() in C++20

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rewrite cbits() using concept and std::countl_zero(), for better
readability and maintanability.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>
This commit is contained in:
Kefu Chai 2022-08-22 00:59:01 +08:00
parent 275ec55c95
commit dc92dfc9c3
1 changed files with 5 additions and 30 deletions
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35
src/include/intarith.h
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@ -15,6 +15,8 @@
#ifndef CEPH_INTARITH_H
#define CEPH_INTARITH_H
#include <bit>
#include <concepts>
#include <type_traits>
template<typename T, typename U>
@ -150,36 +152,9 @@ template<class T>
}
// count bits (set + any 0's that follow)
template<class T>
inline typename std::enable_if<
(std::is_integral<T>::value &&
sizeof(T) <= sizeof(unsigned)),
unsigned>::type cbits(T v) {
if (v == 0)
return 0;
return (sizeof(v) * 8) - __builtin_clz(v);
}
template<class T>
inline typename std::enable_if<
(std::is_integral<T>::value &&
sizeof(T) > sizeof(unsigned int) &&
sizeof(T) <= sizeof(unsigned long)),
unsigned>::type cbits(T v) {
if (v == 0)
return 0;
return (sizeof(v) * 8) - __builtin_clzl(v);
}
template<class T>
inline typename std::enable_if<
(std::is_integral<T>::value &&
sizeof(T) > sizeof(unsigned long) &&
sizeof(T) <= sizeof(unsigned long long)),
unsigned>::type cbits(T v) {
if (v == 0)
return 0;
return (sizeof(v) * 8) - __builtin_clzll(v);
template<std::integral T>
unsigned cbits(T v) {
return (sizeof(v) * 8) - std::countl_zero(std::make_unsigned_t<T>(v));
}
// count the bits set to 1, a.k.a. population count