Question

I have an array of byte that I wish to convert into a hex string, and then back into an array of byte.

I am using the following to convert into a hex string:

function bintoHex(const bin: array of byte): String;
const HexSymbols = '0123456789ABCDEF';
var i: integer;
begin
  SetLength(Result, 2*Length(bin));
  for i :=  0 to Length(bin)-1 do begin
    Result[1 + 2*i + 0] := HexSymbols[1 + bin[i] shr 4];
    Result[1 + 2*i + 1] := HexSymbols[1 + bin[i] and $0F];
  end;
end;

I am unsure how to convert it back into an array of byte properly. I am shooting for something like the following:

Type TDCArray = Array of Byte;

function xHexToBin(const HexStr: String): TDCArray;
const HexSymbols = '0123456789ABCDEF';
var i: integer;
begin
  SetLength(Result, ???); //Need to now get half of the length, unsure how to go about that
  for i :=  0 to Length(HexStr)-1 do begin
    //Here convert back into an array somehow...
    //Result[i] := ???
  end;
end;

How would I go about doing this?

Also, I am using Delphi XE2.

Answer 1

If you want to do it yourself:

function xHexToBin(const HexStr: String): TBytes;
const HexSymbols = '0123456789ABCDEF';
var i, J: integer;
    B: Byte;
begin
  SetLength(Result, (Length(HexStr) + 1) shr 1);
  B:= 0;
  i :=  0;
  while I < Length(HexStr) do begin
    J:= 0;
    while J < Length(HexSymbols) do begin
      if HexStr[I + 1] = HexSymbols[J + 1] then Break;
      Inc(J);
    end;
    if J = Length(HexSymbols) then ; // error
    if Odd(I) then
      Result[I shr 1]:= B shl 4 + J
    else
      B:= J;
    Inc(I);
  end;
  if Odd(I) then Result[I shr 1]:= B;
end;