Delphi - BinToHex and HexToBin : Reversal - arrays

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

Why not just use the BinToHex and HexToBin RTL functions?
{$APPTYPE CONSOLE}
uses
System.Classes,
System.SysUtils;
var
LArray : array[1..6] of Byte = (10, 11, 12, 13, 14, 15);
LText: string;
I : integer;
begin
try
SetLength(LText, Length(LArray)*2);
BinToHex(#LArray, PChar(LText), SizeOf(LArray));
//show the hex string
Writeln(LText);
//fill the array with 0
FillChar(LArray, SizeOf(LArray), #0);
//get the values from the hex string
HexToBin(PChar(LText), #LArray, Length(LArray));
//show the array values
for i := 1 to Length(LArray) do
Write(LArray[i]);
Readln;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end.

Answer 2

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;

Answer 3

2 hex chars represent 1 byte
The code i wrote earlier was pseudocode I wanted you to get the ideea. But if you need some code to paste here is the actual implementation:
program project1;
uses SysUtils,classes;
type
TByteArray = array of byte;
function StrToArray(const Hexstr: String): TByteArray ;
var
i: Integer;
begin
SetLength(Result, Length(Hexstr) div 2);
for i:=0 to (Length(Hexstr) div 2 - 1) do
Result[i]:= StrToInt('$' + Copy(Hexstr, (i * 2) + 1, 2));
end;
var
arr : TByteArray;
i : Integer;
begin
arr := StrToArray('0A0B0C0D');
for i:=0 to High(arr) do
WriteLn(arr[i]);
Readln;
end.
Btw coding is not about cuting and pasting ;)

Answer 4

unit Unit1;
{$mode objfpc}{$H+}
interface
uses
SysUtils, Forms, StdCtrls, ExtCtrls, Classes;
type
{ TTextToHex_HexToBin }
TTextToHex_HexToBin = class(TForm)
Button1: TButton;
Edit1: TEdit;
Edit2: TEdit;
CheckTime: TImage;
Label1: TLabel;
Label2: TLabel;
Label3: TLabel;
Label4: TLabel;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
procedure CheckTimeClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
end;
var
TextToHex_HexToBin: TTextToHex_HexToBin;
implementation
{$R *.lfm}
{ TTextToHex_HexToBin }
//hex to binary
function HextoBinary(const AHexStr: string):string;
var
i, j: Integer;
const
HexParts: array[0..$F] of string =
(
{0} '0000',{1} '0001',{2} '0010',{3} '0011',{4} '0100',{5} '0101',{6} '0110',{7} '0111',
{8} '1000',{9} '1001',{A} '1010',{B} '1011',{C} '1100',{D} '1101',{E} '1110',{F} '1111'
);
begin
SetLength(Result, 4 * AHexStr.Length);
j := 1;
for i := 1 to AHexStr.Length do
begin
case AHexStr[i] of
'0'..'9':
Move(HexParts[Ord(AHexStr[i]) - Ord('0')][1], Result[j], sizeof(char) * 4);
'A'..'F':
Move(HexParts[$A + Ord(AHexStr[i]) - Ord('A')][1], Result[j], sizeof(char) * 4);
'a'..'f':
Move(HexParts[$A + Ord(AHexStr[i]) - Ord('a')][1], Result[j], sizeof(char) * 4);
else
raise EConvertError.CreateFmt('Invalid hexadecimal string "%s".', [AHexStr]);
end;
Inc(j, 4);
end;
end;
procedure TTextToHex_HexToBin.Button1Click(Sender: TObject);
var
TB: TBytes;
WS: WideString;
S: string;
i: Integer;
begin
WS := Trim(Edit1.Caption);
TB := WideBytesOf(WS);
// WideString to Hexadecimal
S := '';
for i := Low(TB) to High(TB) do
S := S + IntToHex(TB[i], -1);
Edit2.Caption :=Trim(S);
// Hex to Binary
Memo1.Caption:= HextoBinary(Trim(S));
end;
procedure TTextToHex_HexToBin.CheckTimeClick(Sender: TObject);
begin
end;
procedure TTextToHex_HexToBin.FormCreate(Sender: TObject);
begin
end;
end.
[Result Show as Below]