GetMinBitSize.h

// Copyright 2019, Jonas Reich. All Rights Reserved.

// This file was created for an Unreal Engine project. Feel free to change uint32 to a custom unsigned integer type.

#include "CoreMinimal.h"
#pragma once

/**
 * Get the number of bits required to display a given number.
 * #TODO: Should be extended with static asserts to ensure it only compiles with unsigned integer types
 * or modified to also work with signed ints.
 */
template<typename T>
constexpr uint32 GetMinBitSize(T value)
{
	static_assert(sizeof(T) < sizeof(uint32), "GetMinBitSize can only be used with types smaller or equal to uint32");

	uint32 Size = 0;
	uint32 ValueAsInt = static_cast<uint32>(value);
	// continue unsetting bits until ValueAsInt is 0
	while (ValueAsInt)
	{
		// unset Size'th bit
		ValueAsInt &= ~(1 << Size);
		Size += 1;
	}

	return Size;
}

static_assert(GetMinBitSize(5) == 3, "GetMinSize(5) returns wrong value! (should be 3)");
static_assert(GetMinBitSize(0) == 1, "GetMinSize(0) returns wrong value! (should be 1)");