how to convert bool array in one byte and later convert back in bool array

Question

I would like to pack bool array with max length 8 in one byte, send it over network and then unpack it back to bool array. Tried some solutions here already but it didn't work. I'm using Mono.

I made BitArray and then tried to convert it in byte

public static byte[] BitArrayToByteArray(BitArray bits)
    {
      byte[] ret = new byte[Math.Max(1, bits.Length / 8)];
      bits.CopyTo(ret, 0);
      return ret;
    }

but I'm getting errors telling only int and long type can be used. Tried int instead of byte but same problem. I would like to avoid BitArray and use simple conversion from bool array to byte if possible

Can you specify exactly what you've tried? Show us some code? Can you also show us the input data and the desired output data? Actual code would make all the difference and will prevent downvoting. — Enigmativity, Jun 20 '14 at 07:51

score 26 · Accepted Answer · edited Apr 05 '22 at 07:05

Here's how I would implement this.

To convert the bool[] to a byte:

private static byte ConvertBoolArrayToByte(bool[] source)
{
    byte result = 0;
    // This assumes the array never contains more than 8 elements!
    int index = 8 - source.Length;

    // Loop through the array
    foreach (bool b in source)
    {
        // if the element is 'true' set the bit at that position
        if (b)
            result |= (byte)(1 << (7 - index));

        index++;
    }

    return result;
}

To convert a byte to an array of bools with length 8:

private static bool[] ConvertByteToBoolArray(byte b)
{
    // prepare the return result
    bool[] result = new bool[8];

    // check each bit in the byte. if 1 set to true, if 0 set to false
    for (int i = 0; i < 8; i++)
        result[i] = (b & (1 << i)) != 0;

    // reverse the array
    Array.Reverse(result);

    return result;
}

score 3 · Answer 2 · answered Jul 16 '20 at 10:15

Other static functions version

/// <summary>
/// Convert Byte Array To Bool Array
/// </summary>
/// <param name="bytes"></param>
/// <returns></returns>
public static bool[] ConvertByteArrayToBoolArray(byte[] bytes)
{
    System.Collections.BitArray b = new System.Collections.BitArray(bytes);
    bool[] bitValues = new bool[b.Count];
    b.CopyTo(bitValues, 0);
    Array.Reverse(bitValues);
    return bitValues;
}

/// <summary>
/// Packs a bit array into bytes, most significant bit first
/// </summary>
/// <param name="boolArr"></param>
/// <returns></returns>
public static byte[] ConvertBoolArrayToByteArray(bool[] boolArr)
{
    byte[] byteArr = new byte[(boolArr.Length + 7) / 8];
    for (int i = 0; i < byteArr.Length; i++)
    {
        byteArr[i] = ReadByte(boolArr, 8 * i);
    }
    return byteArr;
}

If I try this in .Net 6.0 I get a [CS0103](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/cs0103?f1url=%3FappId%3Droslyn%26k%3Dk(CS0103)) `The name 'ReadByte' does not exist in the current context`. Did you check the ReadByte? There are ReadByte implementations in C# but they require some kind of Stream. — user2986756, Sep 14 '22 at 09:00

score 1 · Answer 3 · answered Sep 30 '20 at 07:47

Without Array.Reverse version :

public static void Byte2Flags(bool[] flags, byte range)
{
    if (flags == null || flags.Length < 8)
    {
        return;
    }

    for (int i = 0; i < 8; i++)
        flags[i] = (range & (1 << i)) > 0;
}

public static byte Flags2Byte(bool[] flags)
{
    byte range = 0;
    if (flags == null || flags.Length < 8)
    {
        range = 0;
    }

    for (int i = 0; i < 8; i++)
    {
        if (flags[i])
        {
            range |= (byte)(1 << i);
        }
    }

    return range;
}

And How to test:

    bool[] flags = new bool[8];
    byte b;

    for(int i = 0; i < 256; i++)
    {
        b = (byte)i;
        Byte2Flags(flags, b);
        byte back = Flags2Byte(flags);

        if(b != back)
        {
            //Not Match!
        }
    }

score 0 · Answer 4 · answered Aug 26 '20 at 20:58

Here is a series of methods that do just that

using System;
using System.Text;                  
public class Program
{
    public void Main(){     
      byte _num = 1;
        Console.WriteLine(ReadAllBits(WriteBools(new bool[] {true,true,false,false,false,false,false,true})));
    }
    
    public string ReadAllBits(byte _mask){
        string _data = "";
        for(int i = 0; i < 8; i++){
            if((_mask& (1<<i)) !=0){
                _data += "1";
            }else{
                _data+="0";
            }
        }
        return _data;
    }
    
    public bool[] GetBools(byte _mask){
        bool[] _values = new bool[8];
        for(int i = 0; i < 8; i++){
            if((_mask& (1<<i)) !=0){
                _values[i] = true;
            }else{
                _values[i] = false;
            }
        }
        return _values;
    }
    
    public byte WriteBools(bool[] _data){
        byte _byte = 0;
            for(int i = 0; i < 8; i++){
                if(_data[i]){
                    _byte = System.Convert.ToByte(( _byte | (1<<i)));
                }
            }
        return _byte;
    }
}

you can find the full gist here https://gist.github.com/namusanga/abecca458a3a15ca9bfa6fcdd7953e31

how to convert bool array in one byte and later convert back in bool array

4 Answers4

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