How to search for hex in a stream?

Question

How to search for hex in a stream Effectively and quickly?
if the flow is large, how to quickly search for the flow and reconfigure the position?

function FindInMemStream(Stream: TMemoryStream; What: String):Integer; var bufBuffer, bufBuffer2: array[0..254] of Char; i: Integer; begin Result := 0; i := 0; FillChar(bufBuffer, 255, #0); FillChar(bufBuffer2, 255, #0); StrPCopy(@bufBuffer2, What); Stream.Position:=0; while Stream.Position <> Stream.Size do begin Stream.Read(bufBuffer[0],Length(What)); if CompareMem(@bufBuffer,@bufBuffer2,Length(What)) then begin Result := Stream.Position-Length(What); Exit; end; i := i + 1; Stream.Seek(i,0) end; end; 

I want to change the function in hexadecimal, is this function effective? can you give me an efficient function in hex?

Answer 1

I adapted the code from the POS function available in system.pas :) If you need to find any hex, you can use it like:

 PosHex(#$15#$AA#$04, MyStream); 

 function PosHex(const SubStr: AnsiString; const StrStream: TMemoryStream): Integer; var SubLen, SrcLen, Len, I, J: Integer; C1: AnsiChar; Str: PAnsiChar; begin SrcLen := StrStream.Size; SubLen := Length(SubStr); Result := 0; if (SubLen <= 0) or (SrcLen <= 0) or (SrcLen < SubLen) then Exit; StrStream.Position := 0; Str := StrStream.Memory; Len := SrcLen - SubLen + 1; C1 := SubStr[1]; for I := 1 to Len do begin if Str[I] = C1 then begin Result := I; for J := 1 to SubLen-1 do begin if Str[I+J] <> SubStr[1+J] then begin Result := 0; break; end; end; if Result <> 0 then Exit; end; end; end; Usage: procedure TForm3.FormCreate(Sender: TObject); Var M: TMemoryStream; S: AnsiString; begin S := 'I would like to Find This string!'; M := TMemoryStream.Create; M.WriteBuffer(S[1], Length(S)); Memo1.Lines.Add(IntToStr(PosHex('Find This', M))); M.Free; end;