Question

I’m want to convert a string value to a global memory handle and vice versa, using the following functions I’ve just written.

But StrToGlobalHandle() causes my testing program hangs. So GlobalHandleToStr() is untest-able yet and I’m also wondering if my code is logical or not.

function StrToGlobalHandle(const aText: string): HGLOBAL;
var
  ptr: PChar;
begin
  Result := 0;
  if aText <> '' then
  begin
    Result := GlobalAlloc(GMEM_MOVEABLE or GMEM_ZEROINIT, length(aText) + 1);
    if Result <> 0 then
    begin
      ptr := GlobalLock(Result);
      if Assigned(ptr) then
      begin
        StrCopy(ptr, PChar(aText));
        GlobalUnlock(Result);
      end
    end;
  end;
end;

function GlobalHandleToStr(const aHandle: HGLOBAL): string;
var
  ptrSrc: PChar;
begin
  ptrSrc := GlobalLock(aHandle);
  if Assigned(ptrSrc) then
  begin
    SetLength(Result, Length(ptrSrc));
    StrCopy(PChar(Result), ptrSrc);
    GlobalUnlock(aHandle);
  end
end;

Testing code:

procedure TForm3.Button1Click(Sender: TObject);
var
  h: HGLOBAL;
  s: string;
  s2: string;
begin
  s := 'this is a test string';
  h := StrToGlobalHandle(s);
  s2 := GlobalHandleToStr(h);
  ShowMessage(s2);
  GlobalFree(h);
end;

BTW, I want to use these two functions as helpers to send string values between programs – send a global handle from process A to process B, and process B get the string using GlobalHandleToStr().
BTW 2, I know WM_COPY and other IPC methods, those are not suitable in my case.

Answer 1

The strings in Delphi 2010 are unicode, so you are not allocating the proper buffer size.

replace this line

Result := GlobalAlloc(GMEM_MOVEABLE or GMEM_ZEROINIT, length(aText) + 1);

with this

Result := GlobalAlloc(GMEM_MOVEABLE or GMEM_ZEROINIT, (length(aText) + 1)* SizeOf(Char));