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Cygwin: lseek: improve seeking posix_getdents descriptors

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Transfer code lseeking on posix_getdents() directory descriptor
into its own static function and rework it so SEEK_END, SEEK_DATA
and SEEK_HOLE work here as expected, too.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2024-03-01 15:16:44 +01:00
parent c77a5689f7
commit 6d93691547
1 changed files with 61 additions and 22 deletions
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83
winsup/cygwin/syscalls.cc
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@ -1596,6 +1596,66 @@ open (const char *unix_path, int flags, ...)
EXPORT_ALIAS (open, _open )
static int
posix_getdents_lseek (cygheap_fdget &cfd, off_t pos, int dir)
{
long cur = cfd->telldir (cfd->getdents_dir ());
long abs_pos;
switch (dir)
{
case SEEK_CUR:
abs_pos = cur + pos;
break;
case SEEK_SET:
case SEEK_DATA:
abs_pos = pos;
break;
case SEEK_END:
case SEEK_HOLE:
/* First read full dir to learn end-of-dir position. */
while (::readdir (cfd->getdents_dir ()))
;
long eod = cfd->telldir (cfd->getdents_dir ());
/* Seek back so it looks like nothing happend in error case */
cfd->seekdir (cfd->getdents_dir (), cur);
if (dir == SEEK_HOLE)
{
if (pos > eod)
{
set_errno (ENXIO);
return -1;
}
abs_pos = eod;
}
else
abs_pos = eod + pos;
break;
}
if (abs_pos < 0)
{
set_errno (EINVAL);
return -1;
}
if (abs_pos != cur)
{
cfd->seekdir (cfd->getdents_dir (), abs_pos);
/* In SEEK_DATA case, check that we didn't seek beyond EOF */
if (dir == SEEK_DATA || dir == SEEK_HOLE)
{
pos = cfd->telldir (cfd->getdents_dir ());
if (pos < abs_pos)
{
/* Seek back so it looks like nothing happend */
cfd->seekdir (cfd->getdents_dir (), cur);
set_errno (ENXIO);
return -1;
}
}
}
return abs_pos;
}
extern "C" off_t
lseek (int fd, off_t pos, int dir)
{
@ -1612,28 +1672,7 @@ lseek (int fd, off_t pos, int dir)
if (cfd < 0)
res = -1;
else if (cfd->getdents_dir ())
{
if (dir != SEEK_SET && dir != SEEK_CUR) /* No SEEK_END */
{
set_errno (EINVAL);
res = -1;
}
else
{
long cur;
cur = cfd->telldir (cfd->getdents_dir ());
if (dir == SEEK_CUR && cur == 0)
res = cur;
else
{
if (dir == SEEK_CUR)
pos = cur + pos;
cfd->seekdir (cfd->getdents_dir (), pos);
res = pos;
}
}
}
res = posix_getdents_lseek (cfd, pos, dir);
else
res = cfd->lseek (pos, dir);
}