libcruft-util/bitwise.hpp

93 lines
2.6 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2011 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_BITWISE_HPP
#define __UTIL_BITWISE_HPP
#include <type_traits>
#include <cstdint>
namespace util {
const uint8_t BITMASK_1BITS = 0x01;
const uint8_t BITMASK_2BITS = 0x03;
const uint8_t BITMASK_3BITS = 0x07;
const uint8_t BITMASK_4BITS = 0x0F;
const uint8_t BITMASK_5BITS = 0x1F;
const uint8_t BITMASK_6BITS = 0x3F;
const uint8_t BITMASK_7BITS = 0x7F;
const uint8_t BITMASK_8BITS = 0xFF;
///////////////////////////////////////////////////////////////////////////
template <typename T>
constexpr T
rotatel [[gnu::pure]] (const T value, std::size_t magnitude)
{
return (value << magnitude) | (value >> sizeof (value) * 8 - magnitude);
}
template <typename T>
constexpr T
rotater [[gnu::pure]] (const T value, std::size_t magnitude)
{
return (value >> magnitude) | (value << sizeof (value) * 8 - magnitude);
}
///////////////////////////////////////////////////////////////////////////
// adapted from 'bit twiddling hacks'
template <typename T>
constexpr
std::enable_if_t<std::is_integral<T>::value, T>
reverse (T src)
{
T dst = src; // dst will be reversed bits of v; first get LSB of v
int bits = sizeof (src) * 8 - 1; // extra shift needed at end
for (src >>= 1; src; src >>= 1) {
dst <<= 1;
dst |= src & 1;
bits--;
}
dst <<= bits; // shift when src's highest bits are zero
return dst;
}
///////////////////////////////////////////////////////////////////////////
// adapted from 'bit twiddling hacks'
template <>
constexpr
uint8_t
reverse (uint8_t val)
{
return ((val * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;
}
///////////////////////////////////////////////////////////////////////////
template <typename T>
constexpr T
popcount (std::enable_if_t<std::is_integral<T>::value,T> t)
{
return __builtin_popcount (t);
}
}
#endif