http://d.puremagic.com/issues/show_bug.cgi?id=3409

           Summary: stdio.File.seek() doesn't work for files >2GB
           Product: D
           Version: 2.035
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: patch
          Severity: major
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: dsimcha@yahoo.com


--- Comment #0 from David Simcha <dsimcha@yahoo.com> 2009-10-16 23:01:40 PDT ---
stdio.File.seek() doesn't work for large files.  This is because fseek() is using an int to represent the offset because it's crufty old C code from the Stone Age.  Instead, it throws a ConvOverflowError exception on trying to seek a long distance (> int.max).  The proper fix would be to use the C function that takes a long instead, but this is apparently not available on all platforms and not part of the C standard.

I've attached a file with an implementation of a kludge to work around this issue by seeking incrementally.  It's ugly but it works.  It's implemented in terms of the current seek() implementation, and I haven't integrated it into the File struct, but the basic code is there.

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--- Comment #1 from David Simcha <dsimcha@yahoo.com> 2009-10-16 23:18:26 PDT ---
Oops, looks like I forgot to attach the attachment.  That's ok, on further testing, it only solved the problem up to 4GB anyhow.  I guess what *really* needs to happen is LFS support.

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David Simcha <dsimcha@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|patch                       |


--- Comment #2 from David Simcha <dsimcha@yahoo.com> 2009-10-17 08:45:01 PDT ---
Note that std.stream gets this right on Win32 but not Linux by using the Win32 API directly.

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Andrei Alexandrescu <andrei@metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |andrei@metalanguage.com
         AssignedTo|nobody@puremagic.com        |andrei@metalanguage.com


--- Comment #3 from Andrei Alexandrescu <andrei@metalanguage.com> 2009-10-17 09:00:27 PDT ---
The bug is in druntime. It defines fseek and ftell in core.stdc.stdio like this:

int    fseek(FILE* stream, long offset, int whence);
c_long ftell(FILE* stream);

And it defines c_long in core.stdc.config like this:


version( Windows )
{
    alias int   c_long;
    alias uint  c_ulong;
}
else
{
  static if( (void*).sizeof > int.sizeof )
  {
    alias long  c_long;
    alias ulong c_ulong;
  }
  else
  {
    alias int   c_long;
    alias uint  c_ulong;
  }
}

I don't know why under Windows c_long is actually 32 bit.

Then, in my code I had this note:

    void seek(long offset, int origin = SEEK_SET)
    {
        enforce(p && p.handle,
                "Attempting to seek() in an unopened file");
        // @@@ Dubious: why is fseek in std.c.stdio taking an int???
        errnoEnforce(core.stdc.stdio.fseek(
                    p.handle, to!int(offset), origin) == 0,
                "Could not seek in file `"~p.name~"'");
    }

So it seeme like there was something fishy going on.

I emailed Sean about the problem. He needs to fix druntime, then I will fix stdio, and then we can close this.

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--- Comment #4 from David Simcha <dsimcha@yahoo.com> 2009-10-17 09:41:44 PDT ---
Could be wrong, but I think the way druntime defines these functions is because that's the way they're defined in the C std lib API.  I think to do better you need to use OS-specific APIs directly.

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--- Comment #5 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2009-10-19 02:08:08 PDT ---
> I don't know why under Windows c_long is actually 32 bit.
because msvc compiler is LLP64.

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--- Comment #6 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2009-10-19 02:13:29 PDT ---
(In reply to comment #4)
> Could be wrong, but I think the way druntime defines these functions is because that's the way they're defined in the C std lib API.
Yes, but that's *C* API, so the type should be c_long.

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Sobirari Muhomori <dfj1esp02@sneakemail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |regression


--- Comment #7 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2009-10-19 02:20:19 PDT ---
Strange, in 2.020 it was

int    fseek(FILE* stream, c_long offset, int whence);

so this is regression.

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Sobirari Muhomori <dfj1esp02@sneakemail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|regression                  |major


--- Comment #8 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2009-10-19 02:25:26 PDT ---
No, headers are correct, see http://www.dsource.org/projects/druntime/browser/trunk/import/core/stdc/stdio.d http://www.kernel.org/doc/man-pages/online/pages/man3/fseek.3.html

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Andrei Alexandrescu <andrei@metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|andrei@metalanguage.com     |nobody@puremagic.com


--- Comment #9 from Andrei Alexandrescu <andrei@metalanguage.com> 2011-06-05 08:13:04 PDT ---
David or Sobirari, any chance you could take a second look at this? I'd appreciate it - thanks!

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