Base 2 byte array to string

Question

I have a byte array (byte[16]) with one byte in each cell:

0000000000010010 -> [0][0] ..... [1][0][0][1][0].

How do I get the result with base 2 logic?

I want to get the result : 18. I use C#.

Like [this](http://stackoverflow.com/questions/11654562/how-convert-byte-array-to-string)? — Brian, Nov 22 '13 at 21:43
Does your array represent a 16-bit binary number with each byte representing a single bit (0 or 1)? — Alex, Nov 22 '13 at 21:45
Perhaps something like this? `if (BitConverter.IsLittleEndian) Array.Reverse(bytes); int i = BitConverter.ToInt32(bytes, 0);` — Kemo Sabe, Nov 22 '13 at 21:47
@KemoSabe Your comment assumes that the byte array is the 4 byte representation of a 32bit integer, which doesn't appear to be the case here - each byte in the array appears to represent a single *bit*. — Iridium, Nov 22 '13 at 21:51
Depending on how you got that array in the first place, you might want to use the [`BitArray`](http://msdn.microsoft.com/en-us/library/system.collections.bitarray(v=vs.110).aspx) class instead. — Tim S., Nov 22 '13 at 21:52
@Iridium agreed, I wasn't sure at first. I very much like your solution. — Kemo Sabe, Nov 22 '13 at 21:53

Iridium · Accepted Answer · 2013-11-22T21:57:52.443

4

Should be able to use the following, on the assumption that your byte array is purely 0s and 1s), (although if this is the case, a bool[] would probably be a better choice), and that the most significant bit is the 0th element.

private int BytesToInt(byte[] byteArray)
{
    // Start with zero
    int result = 0;
    foreach (var b in byteArray)
    {
        // For each item in the array, first left-shift the result one bit
        result <<= 1;
        // If the byte is non-zero, set the lowest bit in the result
        if (b != 0) result |= 1;
    }
    return result;
}

edited Nov 22 '13 at 21:57

answered Nov 22 '13 at 21:46

Iridium

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1

Could you explain what result <<= 1; and result |= 1; mean? I've never seen those before. – Kemo Sabe Nov 22 '13 at 21:52
3

`<<=` is the left-shift assignment operator (equivalent here to: `result = result << 1`, and `|=` is the or assignment operator (equivalent to `result = result | 1`). – Iridium Nov 22 '13 at 21:54
My math lacks the skills to understand left-shift, but thanks for the explanation. – Kemo Sabe Nov 22 '13 at 21:58
1

@KemoSabe left-shift by 1 is just the same as multiplying by 2. More generally, left-shift by n is the same as multiplying by 2^n. Similarly, right-shift is division by a power of 2 (and dropping any fractions). – Iridium Nov 22 '13 at 22:01

score -1 · Answer 2 · edited May 25 '15 at 06:25

A little bit-twiddling should do you. A LINQ one-liner:

public static ushort ToUShort( this byte[] buffer )
{
  const int ushort_bits = sizeof(ushort) * 8 ;
  int bits = ushort_bits - 1 ;
  return (ushort) buffer
                  .Take( ushort_bits ) 
                  .Select( b => b != 0 ? 1 : 0 )
                  .Aggregate(0 , (acc,b) => acc | (b<<(bits--)))
                  ;
}

or the equally succinct (and probably faster):

public static ushort ToUShort( this byte[] buffer )
{
  uint acc = 0 ;
  int bits = sizeof(ushort) * 8 - 1 ;
  int max  = sizeof(ushort) * 8     ;
  for ( int i = 0 ; i < max  ; ++i )
  {
    acc |= (buffer[i]==0?0u:1u)<<(bits--) ;
  }
  return (ushort) acc ;
}

Thanks, it is more faster than the previous ! :) – Michael Nov 23 '13 at 06:37 — Michael, Nov 23 '13 at 06:37

Base 2 byte array to string

2 Answers2