🚀 go-pugleaf

>i have assurances that this code should work. i've tried it on 3 computers 
>here, it fails every time


It fails for me on the Assert line.  If I commented out that line, I get 
"Could not open temporary file..."

-- 
David Cornelius
CorneliusConcepts.com 

Ian Boyd wrote:

> i have assurances that this code should work. i've tried it on 3
> computers here, it fails every time
> 
> 
> procedure TForm1.Button4Click(Sender: TObject);
> var
>    dwSharingMode: DWORD;
>    hCreatedFile: THandle;
>    hFile: THandle;
> begin
>    //Sharing mode when we create the file
>    dwSharingMode :=
>            FILE_SHARE_READ or
>            FILE_SHARE_WRITE;
> 
>    hFile := CreateFile(
>            'c:\tempFile.dat',
>            GENERIC_WRITE,
>            dwSharingMode,
>            nil,
>            CREATE_ALWAYS,
>            FILE_FLAG_DELETE_ON_CLOSE,
>            0);
>    Assert(hFile <> INVALID_HANDLE_VALUE,
>                SysErrorMessage(GetLastError));
>    hFile := 0; //Leave the handle open
> 
>    hFile := CreateFile(
>            'c:\tempFile.dat',
>            GENERIC_READ,
>            FILE_SHARE_READ or FILE_SHARE_WRITE,
>            nil,
>            OPEN_EXISTING,
>            0,
>            0);
>    if hFile <> INVALID_HANDLE_VALUE then
>    begin
>        CloseHandle(hFile);
>        MessageDlg('Sucessfully opened temporary file.',
>                    mtInformation, [mbOk], 0)
>    end
>    else
>        MessageDlg('Could not open temporary file: '+
>                SysErrorMessage(GetLastError), mtError, [mbOk], 0);
> end;


It fails the second call needs to specify FILE_SHARE_DELETE...

   hFile := CreateFile(
           'c:\tempFile.dat',
           GENERIC_READ,
           FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE,
           nil,
           OPEN_EXISTING,
           0,
           0);


From the MSDN docs 
(http://msdn.microsoft.com/en-us/library/aa363858.aspx):

<quote>
FILE_FLAG_DELETE_ON_CLOSE
0x04000000
 The file is to be deleted immediately after all of its handles are
closed, which includes the specified handle and any other open or
duplicated handles.

If there are existing open handles to a file, the call fails unless
they were all opened with the FILE_SHARE_DELETE share mode.

Subsequent open requests for the file fail, unless the
FILE_SHARE_DELETE share mode is specified.
</quote>
 

-- 
Pieter

Ian Boyd wrote:
> i have assurances that this code should work. i've tried it on 3 computers 
> here, it fails every time

On the first click, the if on line 57 fails ("file already in use by
another process"). On subsequent clicks, the assert on line 46 fails 
(same error).

Delphi 5 - XP Pro SP2

-- 
Rgds,
Ronaldo

Ronaldo Souza wrote:
> Ian Boyd wrote:
>> i have assurances that this code should work. i've tried it on 3 
>> computers here, it fails every time
> 
> On the first click, the if on line 57 fails ("file already in use by
> another process"). On subsequent clicks, the assert on line 46 fails 
> (same error).
> 
> Delphi 5 - XP Pro SP2
> 


With Pieter's suggestion, it works on the first click and the assert 
fails on subsequent clicks.

-- 
Rgds,
Ronaldo

Ronaldo Souza wrote:

> Ronaldo Souza wrote:
> > Ian Boyd wrote:
> > > i have assurances that this code should work. i've tried it on 3
> > > computers here, it fails every time
> > 
> > On the first click, the if on line 57 fails ("file already in use by
> > another process"). On subsequent clicks, the assert on line 46
> > fails  (same error).
> > 
> > Delphi 5 - XP Pro SP2
> 
> 
> With Pieter's suggestion, it works on the first click and the assert
> fails on subsequent clicks.

Of course ;-) In that case the first call to CreateFile also needs to
specify FILE_SHARE_DELETE in the sharing mode (dwSharingMode).

-- 
Pieter

 > Pieter Zijlstra wrote:
> >Ronaldo Souza wrote:
> >
> > With Pieter's suggestion, it works on the first click and the assert
> > fails on subsequent clicks.
> 
> Of course ;-) In that case the first call to CreateFile also needs to
> specify FILE_SHARE_DELETE in the sharing mode (dwSharingMode).


<g>

-- 
Rgds,
Ronaldo

> It fails for me on the Assert line.  If I commented out that line, I get 
> "Could not open temporary file..."

That assert should only fail if you can't write to c:\. Which i know is the 
case if you login as a standard user.

i didn't want to include the GetTemporaryPath api call to confuse the 
example. 

> It fails the second call needs to specify FILE_SHARE_DELETE...
>
>   hFile := CreateFile(
>           'c:\tempFile.dat',
>           GENERIC_READ,
>           FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE,
>           nil,
>           OPEN_EXISTING,
>           0,
>           0);
>

Well, the goal was to try to create a "temporary file", spawn the associated 
application (e.g. Excel, Word, Notepad), and have the temporary file clean 
itself up when the last handle closes.

i can't control how these other programs decide to open files, but all of 
them do FILE_SHARE_READ|FILE_SHARE_WRITE. 

"Ronaldo Souza" <nospam@nospam.org> wrote in message 
news:4887b891@newsgroups.borland.com...
> Ian Boyd wrote:
>> i have assurances that this code should work. i've tried it on 3 
>> computers here, it fails every time
>
> On the first click, the if on line 57 fails ("file already in use by
> another process"). On subsequent clicks, the assert on line 46 fails (same 
> error).

You get the same error i do.

i would expect it to fail if it were clicked more than once - you'd have to 
close the app to have the file delete. 

Thank you, all.

You confirmed what i already knew: it can't work.


Although someone here swears it can be made to work.

try this:

procedure TForm1.Button1Click(Sender: TObject);
var b: Cardinal;
    hFile: THandle;
    Buffer,ReturnBuffer: Array[0..5] of Char;
begin
    Buffer:='teste'#0;
    hFile := CreateFile(
            'c:\tempFile.dat',
            GENERIC_READ or GENERIC_WRITE,
            FILE_SHARE_READ or FILE_SHARE_WRITE,
            nil,
            CREATE_ALWAYS,
            FILE_FLAG_DELETE_ON_CLOSE,
            0);
    WriteFile(hFile,Buffer,5,b,nil);   //write some text
    SetFilePointer(hFile,0,nil,file_begin);
    ReadFile(hFile,ReturnBuffer,5,b,nil);  //read back
    ShowMessage(string(ReturnBuffer));
    CloseHandle(hFile);
end;




"Ian Boyd" <ian.borlandnews008@zunblvlda1.dyndns.org.spamsucks> escreveu na
mensagem news:4887d966$1@newsgroups.borland.com...
> Thank you, all.
>
> You confirmed what i already knew: it can't work.
>
>
> Although someone here swears it can be made to work.

Here is what do you want:

procedure TForm1.Button1Click(Sender: TObject);
var b: Cardinal;
    hFile,hFile2: THandle;
    Buffer,ReturnBuffer: Array[0..5] of Char;
begin
    Buffer:='teste'#0;
    hFile := CreateFile(
            'c:\tempFile.dat',
            GENERIC_READ or GENERIC_WRITE,
            FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE,
            nil,
            CREATE_ALWAYS,
            FILE_FLAG_DELETE_ON_CLOSE,
            0);
    WriteFile(hFile,Buffer,5,b,nil);   //write some text
    SetFilePointer(hFile,0,nil,file_begin);
    ReadFile(hFile,ReturnBuffer,5,b,nil);  //read back
    ShowMessage(string(ReturnBuffer));

    hFile2:= CreateFile(
            'c:\tempFile.dat',
            GENERIC_READ,
            FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE,
            nil,
            OPEN_EXISTING,
            0,
            0);
    if hFile2 <> INVALID_HANDLE_VALUE then
    begin
        CloseHandle(hFile2);
        MessageDlg('Sucessfully opened temporary file.',
                    mtInformation, [mbOk], 0)
    end;
    CloseHandle(hFile);

"Ian Boyd" <ian.borlandnews008@zunblvlda1.dyndns.org.spamsucks> escreveu na
mensagem news:4887d966$1@newsgroups.borland.com...
> Thank you, all.
>
> You confirmed what i already knew: it can't work.
>
>
> Although someone here swears it can be made to work.

>    hFile2:= CreateFile(
>            'c:\tempFile.dat',
>            GENERIC_READ,
>            FILE_SHARE_READ or FILE_SHARE_WRITE or FILE_SHARE_DELETE,
>            nil,
>            OPEN_EXISTING,
>            0,
>            0);

Although, once again, i can't control the 2nd call to CreateFile, it's what 
Excel, Word, Notepad, would do.

i'm trying to make my initial CreateFile compatible with someone who calls 
CreateFile with READ|WRITE.


Which cannot be done, since i also want the DELETE_ON_CLOSE feature, which 
would require Excel to be re-written.  In other words, i'm want to achieve 
something which cannot be done.