Convert Byte Array to Integer in Delphi

Question

type B02 = array [01..02] of byte ;

...

var b : B02;

...

//here i read from tcp socket

socket.ReadBuffer(b, 2);

The question is: how to convert B02 to an integer?

Answer 1

My integers are often 4 bytes long. Which part do you want to set?

Answer 2

You could declare a Word/Smallint at the same memory location, like this:

var
  b : B02;
  myInt: smallint absolute B02;

Then again, is there any particular reason why you don't just create the smallint and pass it to ReadBuffer instead of an array? I don't know exactly what class you're using, but that looks a lot like the way you read from a TStream, and it'll accept variables of any type, along with a size in bytes. Why not just declare your buffer as the integer type you're looking for and cut out the middleman?

Answer 3

If the data is being transmitted in "network" order (highest byte first) and not in "Intel" order (lowest byte first), you can do some byte shufling yourself.

uses
  SysUtils;

var
  b: B02;
  w: word; //two bytes represent a word, not an integer

socket.ReadBuffer(b, 2);
WordRec(w).Hi := b[1];
WordRec(w).Lo := b[2];

Mghie suggested following approach in comments (and I agree with him):

uses Winsock;

var
  w: word;

socket.ReadBuffer(w, 2);
w := ntohs(w);

Answer 4

You can just cast it:

var
  a: array[01..02] of Byte;
  i: Integer;
begin
  i := PWORD(@a)^;
end;

or if you need to change the byte order:

  i := Swap(PWORD(@a)^);