how to convert byte array to its hex representation in Delphi - delphi

Question

I have TBytes variable with a value [0,0,15,15]. How can I convert it to "00FF" ?
I dont want to use loops, bcoz this logic to be used in time intensive function.
(I tried using BinToHex, but I could not get it working with string variable.)
Thanks & Regards,
Pavan.

Answer 1

// Swapping is necessary because x86 is little-endian.
function Swap32(value: Integer): Integer;
asm
bswap eax
end;
function FourBytesToHex(const bytes: TBytes): string;
var
IntBytes: PInteger;
FullResult: string;
begin
Assert(Length(bytes) = SizeOf(IntBytes^));
IntBytes := PInteger(bytes);
FullResult := IntToHex(Swap32(IntBytes^), 8);
Result := FullResult[2] + FullResult[4] + FullResult[6] + FullResult[8];
end;
If that last line looks a little strange, it's because you requested a four-byte array be turned into a four-character string, whereas in the general case, eight hexadecimal digits are required to represent a four-byte value. I'm simply assumed that your byte values are all below 16, so only one hexadecimal digit is needed. If your example was a typo, then simply replace the last two lines with this one:
Result := IntToHex(Swap32(IntBytes^), 8);
By the way, your requirement forbidding loops will not be met. IntToHex uses a loop internally.

Answer 2

function ByteToHex(InByte:byte):shortstring;
const Digits:array[0..15] of char='0123456789ABCDEF';
begin
result:=digits[InByte shr 4]+digits[InByte and $0F];
end;
Example :
MyHex := ByteTohex($FF);
the result
MyHex is "FF".
MyHex := ByteTohex(255);
the result
MyHex is "FF".
MyHex := ByteTohex($55);
the result
MyHex is "55".

Answer 3

This one is quite fast and works with any array size.. It's like BinToHex, but instead of expecting 0..255 byte values, it only uses the low nibble.
procedure BinToSingleHex(Buffer, Text: PAnsiChar; BufSize: Integer);
const
Convert: array[0..15] of AnsiChar = '0123456789ABCDEF';
var
I: Integer;
begin
for I := 0 to BufSize - 1 do
begin
Text[0] := Convert[Byte(Buffer[I]) and $F];
Inc(Text);
end;
end;
Assembler that does the same:
procedure BinToSingleHex(Buffer, Text: PAnsiChar; BufSize: Integer);assembler;
asm
PUSH ESI
PUSH EDI
MOV ESI,EAX
MOV EDI,EDX
MOV EDX,0
JMP ##1
##0: DB '0123456789ABCDEF'
##1: LODSB
AND DL,AL
AND DL,0FH
MOV AL,##0.Byte[EDX]
STOSB
DEC ECX
JNE ##1
POP EDI
POP ESI
end;
usage:
type THexDigit=0..15;
const ArSize=16;
var Ar:array[0..Pred(ArSize)] of THexDigit=(0,1,2,3,4,5,6,7,8,9,8,7,6,5,4,3);
S:Array[0..Pred(ArSize)] of AnsiChar;
BinToSingleHex(#Ar,S,Length(Ar));
WriteLn(S);

Answer 4

Bit late to the party but why not a simple lookup table?
const
HexChars : Array[0..15] of Char = ('0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F');
Assuming TBytes values of 0..15
Function (ABytea: TBytes): string
begin
Result := HexChars[ABytea[0]];
Result := Result + HexChars[ABytea[1]];
Result := Result + HexChars[ABytea[2]];
Result := Result + HexChars[ABytea[3]];
end;
of course neater with a loop :) and needs modifying for byte values above 15:
begin
Result := HexChars[ABytea[0] shr 4];
Result := Result + HexChars[ABytea[0] and $0F];
Result := Result + HexChars[ABytea[1] shr 4];
Result := Result + HexChars[ABytea[1] and $0F];
Result := Result + HexChars[ABytea[2] shr 4];
Result := Result + HexChars[ABytea[2] and $0F];
Result := Result + HexChars[ABytea[3] shr 4];
Result := Result + HexChars[ABytea[3] and $0F];
end;
Still neater with a loop especially if TBytes gets larger

Answer 5

I had the same problem. My solution using System.SysUtils.TByteHelper.ToHexString (with loop)
function ToHexString(const MinDigits: Integer): string; overload; inline;
Example code:
procedure TForm1.Button2Click(Sender: TObject);
begin
var text:string;
var w:integer:=0;
var bytearray: Tarray<byte>:= [$DE, $AD, $BE, $EF];
repeat
text:= text+ pbyte(#bytearray[w])^.ToHexString(2);
inc(w);
until w >= high(bytearray);
end;
bytearray := $DE $AD $BE $EF
text := DEADBEEF