Byte array to a number

Byte array to a number

• Fradam

  Well, it was just an arbitrary example.  I'm basically asking how I can take the bytes from a 4-byte array and put them together in the same order they occur in. I figured something like shifting would help, but I've never been able to wrap my head around shifting bits for whatever reason.
  

• World

  One obvious way would be to use shift operators, as in

  long myNum = someArray[0] << 24 + someArray[1] << 16 + someArray[2] << 8 + someArray[3];

  You could also write a loop to do this. Where is the data coming from Are you sure the bytes are in that order

  
  
  

• Aqib

  Check out the BitConverter class http://msdn2.microsoft.com/en-us/library/system.bitconverter.aspx

  In your particular case you'd call BitConverter.ToInt32 or BitConverter.ToUInt32. 

  i = BitConverter.ToInt32(someArray, 0);

  Note however that i will most likely have the value 0x21C24AFF because Intel processors are little-endian and BitConveter (on Intel at least) takes array[0] to be the least significant byte. 

  You can use BitConverter.IsLittleEndian to discover whether the platform you are running on is little-endian or big-endian.  If the contents of the byte array don't match BitConverter's expectations the easiest way to swap the bytes is to use Array.Reverse

  Array.Reverse(someArray);

  I have no actual experience with BitConverter on a big-endian processor but this blog indicates that it puts the most significant byte in array [0].  http://blogs.msdn.com/robunoki/archive/2006/04/05/568737.aspx

  
  

• skilled_desinger

  This is exactly what I was looking for. :) Thanks a lot!
  
• Byte array to a number