unit ObexParserUnit;

interface

uses
  System.SysUtils, System.Classes, System.Generics.Collections,
  Winapi.WinSock2; // ntohs, ntohl ÇÔ¼ö »ç¿ë

    // OBEX Çì´õ ID »ó¼ö
const
    OBEX_HID_NAME   = $01;
    OBEX_HID_BODY   = $48;
    OBEX_HID_BODY_FINAL = $49;
    OBEX_HID_LENGTH = $C3;

type


  { TObexHeader: ÆÄ½ÌµÈ °³º° Çì´õ (ID, Value)¸¦ ÀúÀå }
  TObexHeader = class
  public
    HeaderID: Byte;
    Value: TBytes;
  end;

  { TObexPacket: OBEX ÆÐŶ Àüü¸¦ ÆĽÌÇÏ°í µ¥ÀÌÅ͸¦ º¸°ü }
  TObexPacket = class
  private
    FHeaders: TList<TObexHeader>;
    FOpcode: Byte;
    FPacketLength: Word;

    function GetHeader(HeaderID: Byte): TObexHeader;
    function GetBody: TBytes;
    function GetName: string;
    function GetTotalLength: Cardinal;
  public
    constructor Create;
    destructor Destroy; override;

    // ÀÌ ÇÔ¼ö°¡ »ç¿ëÀÚ°¡ ¿äûÇÑ "ij½ºÆà ÇÔ¼ö"ÀÔ´Ï´Ù.
    procedure Parse(Buffer: PByte; Size: Integer);

    // ÁÖ¿ä ¼Ó¼º
    property Opcode: Byte read FOpcode;
    property PacketLength: Word read FPacketLength;
    property Name: string read GetName;         // 0x01 Çì´õ
    property TotalLength: Cardinal read GetTotalLength; // 0xC3 Çì´õ
    property Body: TBytes read GetBody;         // 0x48 ¶Ç´Â 0x49 Çì´õ
  end;

implementation

{ TObexPacket }

constructor TObexPacket.Create;
begin
  inherited;
  FHeaders := TList<TObexHeader>.Create;
end;

destructor TObexPacket.Destroy;
var
  Header: TObexHeader;
begin
  for Header in FHeaders do
    Header.Free;
  FHeaders.Free;
  inherited;
end;

function TObexPacket.GetHeader(HeaderID: Byte): TObexHeader;
var
  Header: TObexHeader;
begin
  Result := nil;
  for Header in FHeaders do
  begin
    if Header.HeaderID = HeaderID then
      Exit(Header);
  end;
end;

function TObexPacket.GetBody: TBytes;
var
  Header: TObexHeader;
begin
  // Body-Final (0x49)À» ¸ÕÀú ã°í, ¾øÀ¸¸é Body (0x48)¸¦ ãÀ½
  Header := GetHeader(OBEX_HID_BODY_FINAL);
  if Header = nil then
    Header := GetHeader(OBEX_HID_BODY);

  if Header <> nil then
    Result := Header.Value
  else
    Result := nil;
end;

function TObexPacket.GetName: string;
var
  Header: TObexHeader;
begin
  Result := '';
  Header := GetHeader(OBEX_HID_NAME);
  if (Header <> nil) and (Length(Header.Value) > 0) then
  begin
    // OBEX À̸§Àº UTF-16 Big Endian, ¸¶Áö¸· 2¹ÙÀÌÆ®´Â ³Î Á¾°á
    Result := TEncoding.BigEndianUnicode.GetString(Header.Value, 0, Length(Header.Value) - 2);
  end;
end;

function TObexPacket.GetTotalLength: Cardinal;
var
  Header: TObexHeader;
begin
  Result := 0;
  Header := GetHeader(OBEX_HID_LENGTH);
  if (Header <> nil) and (Length(Header.Value) = 4) then
  begin
    // 32ºñÆ® Big Endian (Network) °ªÀ» Host (Little Endian)·Î º¯È¯
    Result := ntohl(PCardinal(Header.Value)^);
  end;
end;

procedure TObexPacket.Parse(Buffer: PByte; Size: Integer);
var
  CurrentOffset: Integer;
  Header: TObexHeader;
  HeaderID: Byte;
  HeaderLen: Word;
  ValueLen: Integer;
begin
  // ±âÁ¸ Çì´õ Ŭ¸®¾î
  for Header in FHeaders do
    Header.Free;
  FHeaders.Clear;

  if (Buffer = nil) or (Size < 3) then
    Exit; // ÃÖ¼Ò 3¹ÙÀÌÆ® (Opcode + PacketLength)

  FOpcode := Buffer[0];
  // 16ºñÆ® Big Endian (Network) °ªÀ» Host (Little Endian)·Î º¯È¯
  FPacketLength := ntohs(PWord(@Buffer[1])^);

  // ÆÐŶ Å©±â °ËÁõ
  if FPacketLength > Size then
    Exit; // ½ÇÁ¦ ¹öÆÛ Å©±âº¸´Ù ÆÐŶ ±æÀÌ°¡ ´õ Å­ (À߸øµÈ µ¥ÀÌÅÍ)

  CurrentOffset := 3; // Çì´õ ½ÃÀÛ À§Ä¡

  // Çì´õ ÆÄ½Ì ·çÇÁ
  while CurrentOffset < FPacketLength do
  begin
    Header := TObexHeader.Create;
    HeaderID := Buffer[CurrentOffset];
    Header.HeaderID := HeaderID;
    Inc(CurrentOffset);

    // Çì´õ IDÀÇ »óÀ§ 2ºñÆ®·Î ŸÀÔÀ» ±¸ºÐ (01=À¯´ÏÄÚµå, 10=¹ÙÀÌÆ®½ÃÄö½º, 11=4¹ÙÀÌÆ®Á¤¼ö)
    case (HeaderID and $C0) of
      $00, // Name (0x01)
      $40: // Body (0x48, 0x49)
      begin
        // Çì´õ ±æÀÌ (2¹ÙÀÌÆ® Big Endian)
        if (CurrentOffset + 2) > FPacketLength then
        begin
          Header.Free;
          Break;
        end;

        HeaderLen := ntohs(PWord(@Buffer[CurrentOffset])^);
        Inc(CurrentOffset, 2);

        // [¼öÁ¤] Çì´õ ±æÀÌ°¡ ÃÖ¼Ò 3¹ÙÀÌÆ®ÀÎÁö È®ÀÎ
        if HeaderLen < 3 then
        begin
          Header.Free;
          Break;
        end;

        // ½ÇÁ¦ °ª ±æÀÌ (Àüü Çì´õ ±æÀÌ - ID(1) - Length(2))
        ValueLen := HeaderLen - 3;
        if (CurrentOffset + ValueLen) > FPacketLength then
        begin
          Header.Free;
          Break; // ÆÐŶÀÌ °ÅÁþ¸»À» ÇÏ°í ÀÖÀ½
        end;

        SetLength(Header.Value, ValueLen);
        Move(Buffer[CurrentOffset], Header.Value[0], ValueLen);
        Inc(CurrentOffset, ValueLen);
      end;

      $C0: // Length (0xC3)
      begin
        // 4¹ÙÀÌÆ® Á¤¼ö (°ª ÀÚü°¡ 4¹ÙÀÌÆ®)
        ValueLen := 4;
        SetLength(Header.Value, ValueLen);
        Move(Buffer[CurrentOffset], Header.Value[0], ValueLen);
        Inc(CurrentOffset, ValueLen);
      end
    else
      // ¾Ë ¼ö ¾ø´Â Çì´õ ŸÀÔ
      Break;
    end;

    FHeaders.Add(Header);
  end;
end;


end.