Convert BitArray to byte[]

Convert BitArray to byte[]

• Laura Cavanagh

  shakalama,

  Thanks for your response, however it appears as if you are still using data types.

  Let me give an example:

  ....

  public void Whole()

  {

  BinaryReader BinIn = new BinaryReader(BaseFile); //Basefile Class Member is a Filestream

  BinaryWriter BinOut = new BinaryWriter(OutputFile); //OutputFile Class Member is
  //a Filestream

  BitArray Extracted;

  Extracted = new BitArray(BinIn.ReadByte());

  //Code here that Process the Individual Binary Bits in this byte using index
  //"Extracted[Index]".

  //Now how can the BitArray "Extracted" be dumped into the OutputFile (BinOut)

  }

  
  

• Ignasio Dondo

  Do you really need to convert the whole byte array into a BitArray You might work more efficiently with the byte array and bitmasks to extract and manipulate information.

  I wrote a sample that convert BitArray to a byte[]. Depending on how large arrays you are working with this can be taking a while.

  byte[] BitArrayToByteArray(BitArray bits)
  {
  // Who knows, might change
  const int BITSPERBYTE = 8;
  
  // Get the size of bytes needed to store all bytes
  int bytesize = bits.Length / BITSPERBYTE;
  // Any bit left over another byte is necessary
  if (bits.Length % BITSPERBYTE > 0)
  {
  bytesize++;
  }
  
  // For the result
  byte[] bytes = new byte[bytesize];
  
  // Must init to good value, all zero bit byte has value zero
  // Lowest significant bit has a place value of 1, each position to
  // to the left doubles the value
  byte value = 0;
  byte significance = 1;
  
  // Remember where in the input/output arrays
  int bytepos = 0;
  int bitpos = 0;
  
  while (bitpos < bits.Length)
  {
  // If the bit is set add its value to the byte
  if (true == bits[bitpos])
  {
  value += significance;
  }
  bitpos++;
  if (0 == bitpos % BITSPERBYTE)
  {
  // A full byte has been processed, store it
  // increase output buffer index and reset work values
  bytes[bytepos] = value;
  bytepos++;
  value = 0;
  significance = 1;
  }
  else
  {
  // Another bit processed, next has doubled value
  significance *= 2;
  }
  }
  return bytes;
  }

  
  
  

• Jelle vd Beek

  Andreas Johansson,

  Fantastic!. However I am very surprised that BitArrays do not already come with this capability!!!

  This makes me think that perhaps I am doing things the hard way.

  If you received data into a computer in Binary (discrete message defined in bits and stored in a file), and you then want to write a program that interrogates the activity (by looking at the binary) and sends back binary instructions, how would you do this

  The program MUST respond in Binary, and store it in a file. Maybe there is a better way

  Please take these restrictions as fore-granted since I cannot go through the problem in detail on a public forum.

  I know you mentioned Bit Masks but I am not exactly sure how you would use them to achieve what I am trying to do.

  Cheers All!.

  
  

• Ragas

  I wrote another two methods, these will let you work with a byte array in a similar way as BitArray does. IsBitSet() will check a bit and SetBit will set/clear it.

  If you want to read some more about bitmasks.
  http://en.wikipedia.org/wiki/Bitmask

  const int BITSPERBYTE = 8;
  // This gives the same result as BitArray[bitpos] on an
  // array that was created with new BitArray(bytes)
  bool IsBitSet(byte[] bytes, int bitpos)
  {
     // Get position in byte array
     int bytepos = bitpos / BITSPERBYTE;
  
     // Create bitmask, the byte array is per byte and the
     // bitmask take this into consideration. Bit 10 in the
     // bit array is bit 2 on the second byte.
     byte mask = 1;
     byte shift = (byte)(bitpos % BITSPERBYTE);
     mask = (byte)(mask << shift);

     // "Bitwise and" with the mask will return the mask
     // if the bit is set or zero if it is not.
     return ((bytes[bytepos] & mask) != 0);
  }

  // Sets the bit if state is true, otherwise clears it
  static void SetBit(byte[] bytes, int bitpos, bool state)
  {
     // Check if there actually is something to do
     if (IsBitSet(bytes, bitpos) == state)
     {
        return;
     }

     // get position in bytearray and bitmask
     int bytepos = bitpos / BITSPERBYTE;
     byte mask = 1;
     byte shift = (byte)(bitpos % BITSPERBYTE);
     mask = (byte)(mask << shift);

     if (true == state)
     {
        // bitwise or with mask
        bytes[bytepos] |= mask;
     }
     else
     {
        // bitwise and with inverted mask
        bytes[bytepos] &= (byte)~mask;
     }
  }

  
  
  

• Drca

  hi,

  you say for comercial i don't see anything comercial in bitarray but if binarywriter just take byte you can convert the bitarray to byte array, but if you iterate through it you will find it has extra elments than you actual data something like this

  int[] n = {1,2,3,4,5,6}; BitArray bt = new BitArray(n); byte[] b = new byte[bt.Count]; bt.CopyTo(b, 0); int i = 0; foreach (byte item in b) { Console.WriteLine("line number {0} : value = {1} ",i,item.ToString()); i++; }

  hope this helps

  
  
  

• Aswani Kumar T

  hi,

  i guess your life will be easier if you used binary for just saving but to manuplate data you data you need datatypes and save it as binary no problem

  did you try to use filestream class and to set it as source for your reader and writer streams something like this

  FileStream fs = new FileStream(@"path.extention", FileMode.OpenOrCreate, FileAccess.ReadWrite); BinaryReader br = new BinaryReader(fs); BinaryWriter bw = new BinaryWriter(fs);

  if the file is embeded resources in you project you can use System.Reflection name space here its a part of code that i have

  System.Reflection.Assembly assmb;  int[, ,] array = new int[4, 5, 3]; assmb = this.GetType().Assembly;//or System.Reflection.Assembly.GetExecutingAssembly() Stream s = assmb.GetManifestResourceStream("MyNamespace.Myfile.bin"); BinaryReader r = new BinaryReader(s); for (int i = 0; i < 4; i++) { for (int j = 0; j < 5; j++) { Array[i, j, 0] = r.ReadByte(); Array[i, j, 1] = r.ReadInt32(); Array[i, j, 2] = r.ReadInt16(); } } r.Close(); s.Close();

  hope this helps

  
  
  
• Convert BitArray to byte[]