On Fri, Jan 25, 2008 at 05:12:39PM -0800, Andreas Raab wrote:
> Colin Putney wrote:
> >
> >On 25-Jan-08, at 10:38 AM, Andreas Raab wrote:
> >
> >>etc. Is there an easy way to patch the Unix file code to avoid this,
> >>e.g., behave like Windows in such that it would disallow opening the
> >>same file for multiple writes?
> >
> >I've been bitten by this as well, but in reverse. Code that works great
> >on Unix is totally broken on Windows because you can't open the same
> >file for writing twice.
>
> Easy to change. In sqWin32FilePrims.c function sqFileOpen() modify:
>
> h = CreateFileW(win32Path,
> writeFlag ? (GENERIC_READ | GENERIC_WRITE) : GENERIC_READ,
> writeFlag ? FILE_SHARE_READ : (FILE_SHARE_READ | FILE_SHARE_WRITE),
> "... etc ..."
>
> to read:
>
> h = CreateFileW(win32Path,
> writeFlag ? (GENERIC_READ | GENERIC_WRITE) : GENERIC_READ,
> FILE_SHARE_READ | FILE_SHARE_WRITE,
> "... etc ..."
>
> So what's the equivalent change for Unix?
The Unix VM is opening the file with fopen(), which does not provide
such a control. However, you could use open() to open a file descriptor
with the O_EXCL and O_CREAT flags, then pass that file descriptor to
fdopen() to get the (FILE *) handle. I have not tested this, but I
think it would do what you are looking for here.
Dave
p.s. The Windows VM uses lower level HANDLE rather than the (FILE *)
used on other VMs. It would be interesting to know which approach
produces the best overall Squeak performance for applications that
do significant file I/O.
Locked
