bits.h

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#pragma once
 
#include <cstdint>
 
namespace ktl::detail
{
    constexpr inline uintmax_t log2(uintmax_t n) noexcept
    {
        uintmax_t r = 0;
 
        if (n >> 32) { r += 32U; n >>= 32U; }
        if (n >> 16) { r += 16U; n >>= 16U; }
        if (n >> 8) { r += 8U; n >>= 8U; }
        if (n >> 4) { r += 4U; n >>= 4U; }
        if (n >> 2) { r += 2U; n >>= 2U; }
        if (n >> 1) { r += 1U; n >>= 1U; }
 
        return r;
    }
 
    constexpr inline uintmax_t bits_to_represent(uintmax_t n) noexcept
    {
        uintmax_t r = 0;
 
        if (n >> 32) { r += 32U; n >>= 32U; }
        if (n >> 16) { r += 16U; n >>= 16U; }
        if (n >> 8) { r += 8U; n >>= 8U; }
        if (n >> 4) { r += 4U; n >>= 4U; }
        if (n >> 2) { r += 2U; n >>= 2U; }
        if (n >> 1) { r += 1U; n >>= 1U; }
 
        return r + static_cast<uintmax_t>(n);
    }
 
    constexpr inline uintmax_t bits_in_range(intmax_t min, intmax_t max) noexcept
    {
        return bits_to_represent(static_cast<uintmax_t>(max - min));
    }
}