Re: [Boost-bugs] [Boost C++ Libraries] #699: Changing size of memory-mapped file on Windows

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #699: Changing size of memory-mapped file on Windows
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2007-08-19 15:55:53

#699: Changing size of memory-mapped file on Windows
---------------------+------------------------------------------------------
  Reporter:  nobody  |       Owner:  turkanis 
      Type:  Bugs    |      Status:  assigned 
 Milestone:          |   Component:  iostreams
   Version:  None    |    Severity:  Problem  
Resolution:  None    |    Keywords:           
---------------------+------------------------------------------------------
Changes (by marshall):

  * component:  None => iostreams
  * severity:  => Problem

Old description:

> {{{
> My email address is barrywhart_at_yahoo.com.
>
> There is a bug in
> mapped_file_source::open_impl(mapped_file_params p)
>
> This function does not correctly check for errors from
> SetFilePointer, as documented in the MSDN page below.
> (See "Case Two: calling the function with
> lpDistanceToMoveHigh != NULL")
>
> http://msdn.microsoft.com/library/default.asp?url=/library/en-

> us/fileio/fs/setfilepointer.asp
>
> Current code:
>
>         ::SetFilePointer(pimpl_->handle_, sizelow,
> &sizehigh, FILE_BEGIN);
>         if (::GetLastError() != NO_ERROR ||
> !::SetEndOfFile(pimpl_->handle_))
>             detail::cleanup_and_throw(*pimpl_, "failed
> setting file size");
>
> Should be:
>
>         DWORD dwResult =
> ::SetFilePointer(pimpl_->handle_, sizelow, &sizehigh,
> FILE_BEGIN);
>         if (dwResult == INVALID_SET_FILE_POINTER
> ::GetLastError() != NO_ERROR ||
> !::SetEndOfFile(pimpl_->handle_))
>             detail::cleanup_and_throw(*pimpl_, "failed
> setting file size");
>
> --
>
> Even after this fix, the ability to resize an existing
> file is not really useful because the file is
> apparently recreated rather than resized. I am working
> around this by resizing the file using system calls,
> but I wonder if this is how the function is supposed to
> work?!
> }}}

New description:

 {{{
 My email address is barrywhart_at_yahoo.com.

 There is a bug in
 mapped_file_source::open_impl(mapped_file_params p)

 This function does not correctly check for errors from
 SetFilePointer, as documented in the MSDN page below.
 (See "Case Two: calling the function with
 lpDistanceToMoveHigh != NULL")

 http://msdn.microsoft.com/library/default.asp?url=/library/en-

 us/fileio/fs/setfilepointer.asp

 Current code:

         ::SetFilePointer(pimpl_->handle_, sizelow,
 &sizehigh, FILE_BEGIN);
         if (::GetLastError() != NO_ERROR ||
 !::SetEndOfFile(pimpl_->handle_))
             detail::cleanup_and_throw(*pimpl_, "failed
 setting file size");

 Should be:

         DWORD dwResult =
 ::SetFilePointer(pimpl_->handle_, sizelow, &sizehigh,
 FILE_BEGIN);
         if (dwResult == INVALID_SET_FILE_POINTER
 ::GetLastError() != NO_ERROR ||
 !::SetEndOfFile(pimpl_->handle_))
             detail::cleanup_and_throw(*pimpl_, "failed
 setting file size");

 --

 Even after this fix, the ability to resize an existing
 file is not really useful because the file is
 apparently recreated rather than resized. I am working
 around this by resizing the file using system calls,
 but I wonder if this is how the function is supposed to
 work?!
 }}}

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/699#comment:1>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.