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Fix our Windows stat() emulation to handle file sizes > 4GB.

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Hack things so that our idea of "struct stat" is equivalent to Windows'
struct __stat64, allowing it to have a wide enough st_size field.

Instead of relying on native stat(), use GetFileInformationByHandle().
This avoids a number of issues with Microsoft's multiple and rather
slipshod emulations of stat().  We still need to jump through hoops
to deal with ERROR_DELETE_PENDING, though :-(

Pull the relevant support code out of dirmod.c and put it into
its own file, win32stat.c.

Still TODO: do we need to do something different with lstat(),
rather than treating it identically to stat()?

Juan José Santamaría Flecha, reviewed by Emil Iggland;
based on prior work by Michael Paquier, Sergey Zubkovsky, and others

Discussion: https://postgr.es/m/1803D792815FC24D871C00D17AE95905CF5099@g01jpexmbkw24
Discussion: https://postgr.es/m/15858-9572469fd3b73263@postgresql.org
This commit is contained in:
Tom Lane
2020-10-09 16:20:12 -04:00
parent f13f2e4841
commit bed90759fc
6 changed files with 340 additions and 66 deletions
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52
src/port/dirmod.c
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@ -353,55 +353,3 @@ pgwin32_is_junction(const char *path)
return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
}
#endif /* defined(WIN32) && !defined(__CYGWIN__) */
#if defined(WIN32) && !defined(__CYGWIN__)
#undef stat
/*
* The stat() function in win32 is not guaranteed to update the st_size
* field when run. So we define our own version that uses the Win32 API
* to update this field.
*/
int
pgwin32_safestat(const char *path, struct stat *buf)
{
int r;
WIN32_FILE_ATTRIBUTE_DATA attr;
r = stat(path, buf);
if (r < 0)
{
if (GetLastError() == ERROR_DELETE_PENDING)
{
/*
* File has been deleted, but is not gone from the filesystem yet.
* This can happen when some process with FILE_SHARE_DELETE has it
* open and it will be fully removed once that handle is closed.
* Meanwhile, we can't open it, so indicate that the file just
* doesn't exist.
*/
errno = ENOENT;
return -1;
}
return r;
}
if (!GetFileAttributesEx(path, GetFileExInfoStandard, &attr))
{
_dosmaperr(GetLastError());
return -1;
}
/*
* XXX no support for large files here, but we don't do that in general on
* Win32 yet.
*/
buf->st_size = attr.nFileSizeLow;
return 0;
}
#endif