using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics.X86;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Columns;
using BenchmarkDotNet.Configs;
using BenchmarkDotNet.Jobs;
using BenchmarkDotNet.Reports;
using BenchmarkDotNet.Running;

class Program
{
	public static void Main()
	{
		BenchmarkRunner.Run<CountDigitsBenchmark>(new LocalCoreClrConfig());
	}
}


public class CountDigitsBenchmark
{
	[Params(0ul, 0xAul, 0x42ul, 0x123ul, 0xDEADF00ul, 0xDEADF00D12345ul)]
	public ulong Number { get; set; }
	
	[Benchmark] 
	public int CountHexDigits_original() => CountHexDigits_original(Number);

	[Benchmark(Baseline = true)]
	public int CountHexDigits_Lzcnt_shifts() => CountHexDigits_Lzcnt_shifts(Number);


	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public static int CountHexDigits_Lzcnt_shifts(ulong value)
	{
		if (Lzcnt.IsSupported)
		{
			var right = 64 - (int)Lzcnt.LeadingZeroCount(value | 1); 
			return (right + 3) >> 2;
		}

		int digits = 1;

		if (value > 0xFFFFFFFF)
		{
			digits += 8;
			value >>= 0x20;
		}
		if (value > 0xFFFF)
		{
			digits += 4;
			value >>= 0x10;
		}
		if (value > 0xFF)
		{
			digits += 2;
			value >>= 0x8;
		}
		if (value > 0xF)
			digits++;

		return digits;
	}

	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	public static int CountHexDigits_original(ulong value)
	{
		int digits = 1;

		if (value > 0xFFFFFFFF)
		{
			digits += 8;
			value >>= 0x20;
		}
		if (value > 0xFFFF)
		{
			digits += 4;
			value >>= 0x10;
		}
		if (value > 0xFF)
		{
			digits += 2;
			value >>= 0x8;
		}
		if (value > 0xF)
			digits++;

		return digits;
	}
}