NextPowerOfTwo, ClosestPowerOfTwo, IsPowerOfTwo

PowerOfTwo.cs

// https://github.com/Unity-Technologies/UnityCsReference/blob/master/Runtime/Export/Math/Mathf.cs
public static int NextPowerOfTwo(int value)
{
    value -= 1;
    value |= value >> 16;
    value |= value >> 8;
    value |= value >> 4;
    value |= value >> 2;
    value |= value >> 1;
    return value + 1;
}

public static int ClosestPowerOfTwo(int value)
{
    int nextPower = NextPowerOfTwo(value);
    int prevPower = nextPower >> 1;
    if (value - prevPower < nextPower - value)

        return prevPower;
    else
        return nextPower;
}

public static bool IsPowerOfTwo(int value)
{
    return (value & (value - 1)) == 0;
}