Is this usage of TBytes as a PAnsiChar "memory manager" correct?

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The Simple MAPI makes memory management pretty hard unless you write a lot of pointer (PAnsiChar) allocation and deallocation code.

I like to use compiler managed data types as much as possible, so I tried to use a TList<TBytes> to store my PAnsiChar data for me:

type
  TMapiEmailSender = class(TEmailSender)
  private
    FRecipDescs   : TList<TMapiRecipDesc>;
    FStrings      : TList<TBytes>;
    procedure AddRecipient(AClass: Cardinal; const ARecipient: string);
    procedure AddRecipients(AClass: Cardinal; ARecipients: TStrings);
    function GetString(const S: string): PAnsiChar;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Run; override;
  end;

procedure TMapiEmailSender.AddRecipient(AClass: Cardinal;
  const ARecipient: string);
var
  D: TMapiRecipDesc;
begin
  FillChar(D, SizeOf(D), 0);
  D.ulRecipClass := AClass;
  D.lpszName     := GetString(ARecipient);
  FRecipDescs.Add(D);
end;

procedure TMapiEmailSender.AddRecipients(AClass: Cardinal;
  ARecipients: TStrings);
var
  Recipient: string;
begin
  for Recipient in ARecipients do begin
    AddRecipient(AClass, Recipient);
  end;
end;

constructor TMapiEmailSender.Create;
begin
  inherited Create;
  FStrings    := TList<TBytes>.Create;
  FRecipDescs := TList<TMapiRecipDesc>.Create;
end;

destructor TMapiEmailSender.Destroy;
begin
  FRecipDescs.Free;
  FStrings.Free;
  inherited;
end;

function TMapiEmailSender.GetString(const S: string): PAnsiChar;
var
  Bytes: TBytes;
begin
  Bytes := TEncoding.Default.GetBytes(S);
  SetLength(Bytes, Length(Bytes) + 1);
  Bytes[High(Bytes)] := 0;
  FStrings.Add(Bytes);
  Result := @Bytes[0];
end;

procedure TMapiEmailSender.Run;
var
  Msg: TMapiMessage;
begin
  try
    AddRecipients(MAPI_TO, FEmail.ToRecipients);
    AddRecipients(MAPI_CC, FEmail.CcRecipients);
    AddRecipients(MAPI_BCC, FEmail.BccRecipients);
    FillChar(Msg, SizeOf(Msg), 0);
    Msg.nRecipCount  := FRecipDescs.Count;
    Msg.lpRecips     := @FRecipDescs.ToArray[0];
    // Code that uses Msg to send a MAPI message here
  finally
    FRecipDescs.Clear;
    FStrings.Clear;
  end;
end;

The code seems to be correct (this is only a fragment of the whole thing). I tried it and FastMM is not reporting any memory leaks.

I don't like that I have to resize the Result from TEncoding.Default.GetBytes() to include a trailing zero byte.

Otherwise I think the code is fine.

So the question is: Is the code correct and is it simple enough? Am I overcomplicating things?

asked 1 min ago

Jens Mühlenhoff

5,453