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Re: Problems with lcc-win32 (trimmed)

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jacobnavia <jacob@jacob.remcomp.fr> writes:

> Le 08/03/2017 à 02:06, Ben Bacarisse a écrit :
>> jacobnavia <jacob@jacob.remcomp.fr> writes:
>> <snip>
>>> Here is the code for fseeki64. Could you please compile that and see if it works?
>>>
>>> Thanks
>>> ------------------------------------------------------fseeki64.c
>>> #include <windows.h>
>>> #include <errno.h>
>>> #include <stdio.h>
>>> long long fseeki64(FILE *f,long long offset,int origin)
>>> {
>>>     if (f == NULL)
>>>         return -1;
>>>     fflush(f);
>>>     void *handle = (HANDLE)_get_osfhandle(_fileno(f));
>>>     long result;
>>>     long long r;
>>>     LARGE_INTEGER Offset;
>>>
>>>     if (handle == (HANDLE)-1) {
>>>         errno = EBADF;
>>>         return -1;
>>>     }
>>>     if (origin != 0 && origin != 1 && origin != 2) {
>>>         errno = EINVAL;
>>>         return -1;
>>>     }
>>>     memcpy(&Offset,&offset,sizeof(long long));
>>>     SetLastError(0);
>>>     result = SetFilePointerEx(handle,Offset,(PLARGE_INTEGER)&r,origin);
>>>     if (result == 0) {
>>>         errno = GetLastError();
>>>     }
>>>     return !result;
>>> }
>>> ----------------------------------------------------------------------
>>
>> That's a strange bit of code.  The strangest thing is the memcpy.  I
>> can't see why you'd do that rather than write
>>
>>   long result = SetFilePointerEx(handle, offset, NULL, origin);
>>
>> Presumably there is a prototype in scope so offset will be converted to
>> LARGE_INTEGER as if by assignment.  If there is no prototype then
>>
>>   long result = SetFilePointerEx(handle, (LARGE_INTEGER)offset, NULL, origin);
>>
>> would do, I think.  Am I missing something?
>
> Look, I wrote that function under 32 bits windows, some 15 years ago
> at least. What I remember is that LARGE_INTEGER was a STRUCTURE of two
> fields: high and low, of 32 bits each. You can't assign a structure to
> an integer even if they are the same length.

Ah, right, that's exactly the kind of thing I thought I might be
missing.  It did not seem likely that on a system with long long ints
you'd have LARGE_INTEGER be anything else (because it sounds like an
integer type), but the interface presumably dates from a time when MS C
did not have 64-bit integers.

It seems that nowadays it's a union so C99 provides a neat way to use
the interface:

  SetFilePointerEx(handle, (LARGE_INTEGER){.QuadPart = offset}, NULL, origin);

It's a shame that MS chose a name that suggests an integer type, but
that can't be helped.

-- 
Ben.

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Problems with lcc-win32 mertesthomas@gmail.com - 2017-03-05 14:12 -0800
  Re: Problems with lcc-win32 luser droog <luser.droog@gmail.com> - 2017-03-05 14:46 -0800
    Re: Problems with lcc-win32 gazelle@shell.xmission.com (Kenny McCormack) - 2017-03-05 22:57 +0000
    Re: Problems with lcc-win32 jacob navia <jacob@jacob.remcomp.fr> - 2017-03-06 00:49 +0100
      Re: Problems with lcc-win32 luser droog <luser.droog@gmail.com> - 2017-03-05 22:10 -0800
  Re: Problems with lcc-win32 BartC <bc@freeuk.com> - 2017-03-05 23:32 +0000
    Re: Problems with lcc-win32 jacob navia <jacob@jacob.remcomp.fr> - 2017-03-06 00:48 +0100
  Re: Problems with lcc-win32 jacob navia <jacob@jacob.remcomp.fr> - 2017-03-06 00:44 +0100
    Re: Problems with lcc-win32 BartC <bc@freeuk.com> - 2017-03-06 00:13 +0000
    Re: Problems with lcc-win32 Keith Thompson <kst-u@mib.org> - 2017-03-05 19:35 -0800
      Re: Problems with lcc-win32 David Brown <david.brown@hesbynett.no> - 2017-03-06 10:26 +0100
        Re: Problems with lcc-win32 James Kuyper <jameskuyper@verizon.net> - 2017-03-06 07:08 -0500
        Re: Problems with lcc-win32 Keith Thompson <kst-u@mib.org> - 2017-03-06 08:37 -0800
          Re: Problems with lcc-win32 David Brown <david.brown@hesbynett.no> - 2017-03-06 21:16 +0100
      Re: Problems with lcc-win32 jm.bourguet@gmail.com - 2017-03-06 06:54 -0800
        Re: Problems with lcc-win32 David Brown <david.brown@hesbynett.no> - 2017-03-06 17:18 +0100
          Re: Problems with lcc-win32 Keith Thompson <kst-u@mib.org> - 2017-03-06 08:42 -0800
            Re: Problems with lcc-win32 David Brown <david.brown@hesbynett.no> - 2017-03-06 21:19 +0100
          Re: Problems with lcc-win32 jm.bourguet@gmail.com - 2017-03-06 08:44 -0800
            Re: Problems with lcc-win32 David Brown <david.brown@hesbynett.no> - 2017-03-06 21:20 +0100
    Re: Problems with lcc-win32 mertesthomas@gmail.com - 2017-03-06 00:24 -0800
  Re: Problems with lcc-win32 jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-06 18:15 +0100
    Re: Problems with lcc-win32 (trimmed) jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-06 18:50 +0100
      Re: Problems with lcc-win32 (trimmed) mertesthomas@gmail.com - 2017-03-07 04:50 -0800
        Re: Problems with lcc-win32 (trimmed) jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-07 14:54 +0100
          Re: Problems with lcc-win32 (trimmed) mertesthomas@gmail.com - 2017-03-07 06:20 -0800
            Re: Problems with lcc-win32 (trimmed) scott@slp53.sl.home (Scott Lurndal) - 2017-03-07 15:02 +0000
              Re: Problems with lcc-win32 (trimmed) mertesthomas@gmail.com - 2017-03-07 08:00 -0800
                Re: Problems with lcc-win32 (trimmed) jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-07 20:30 +0100
                Re: Problems with lcc-win32 (trimmed) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-08 01:06 +0000
                Re: Problems with lcc-win32 (trimmed) jacobnavia <jacob@jacob.remcomp.fr> - 2017-03-08 12:17 +0100
                Assigning a struct to an integer (Was: Problems with lcc-win32 (trimmed)) gazelle@shell.xmission.com (Kenny McCormack) - 2017-03-08 11:40 +0000
                Re: Problems with lcc-win32 (trimmed) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-08 11:51 +0000
              Re: Problems with lcc-win32 (trimmed) Robert Wessel <robertwessel2@yahoo.com> - 2017-03-07 15:27 -0600
                Re: Problems with lcc-win32 (trimmed) scott@slp53.sl.home (Scott Lurndal) - 2017-03-08 13:50 +0000
                Re: Problems with lcc-win32 (trimmed) scott@slp53.sl.home (Scott Lurndal) - 2017-03-08 13:51 +0000

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