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improve bit slice, take care of edge case, move BitSliceType

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CocoSimone
2022-05-09 10:22:12 +02:00
parent a2a6de65a1
commit 429541ab0c
2 changed files with 23 additions and 14 deletions
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26
src/core/util.hpp
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@@ -1,12 +1,32 @@
#pragma once
#include <common.hpp>
#include <type_traits>
#include <cassert>
namespace natsukashii::util {
template <u8 start, u8 end>
using BitSliceType =
typename std::conditional<(end - start) <= 7, u8,
typename std::conditional<(end - start) <= 15, u16,
typename std::conditional<(end - start) <= 31, u32,
typename std::conditional<(end - start) <= 63, u64,
typename std::conditional<(end - start) <= 127, u128, void>::type
>::type
>::type
>::type
>::type;
template <u8 start, u8 end, typename T>
BitSliceType<start, end> BitSlice(const T& num) {
static_assert(end - start > 127);
static_assert(end - start > sizeof(T));
return (num >> start) & ((1 << end) - 1);
static_assert(end < (sizeof(T) * 8) && start < (sizeof(T) * 8));
constexpr auto correctedEnd = end == (sizeof(T) * 8) - 1 ? end : end + 1;
return (num >> start) & ((1 << correctedEnd) - 1);
}
template <typename T>
T BitSlice(const T& num, int start, int end) {
assert(end < (sizeof(T) * 8) && start < (sizeof(T) * 8));
auto correctedEnd = end == (sizeof(T) * 8) - 1 ? end : end + 1;
return (num >> start) & ((1 << correctedEnd) - 1);
}
}