Oh, since I'm proposing to add a new stat() method to DirEntry, we can
optimize it. stat() can reuse lstat() result if the file is not a
symlink. It simplifies is_dir().
New pseudo-code:
---
class DirEntry:
def __init__(self, path, name, lstat=None, d_type=None):
self.name = name
self.full_name = os.path.join(path, name)
# lstat is known on Windows
self._lstat = lstat
if lstat is not None and not stat.S_ISLNK(lstat.st_mode):
# On Windows, stat() only calls os.stat() for symlinks
self._stat = lstat
else:
self._stat = None
# d_type is known on UNIX
if d_type != DT_UNKNOWN:
self._d_type = d_type
else:
# DT_UNKNOWN is not a very useful information :-p
self._d_type = None
def stat(self):
if self._stat is None:
self._stat = os.stat(self.full_name)
return self._stat
def lstat(self):
if self._lstat is None:
self._lstat = os.lstat(self.full_name)
if self._stat is None and not stat.S_ISLNK(self._lstat.st_mode):
self._stat = lstat
return self._lstat
def is_dir(self):
if self._d_type is not None:
if self._d_type == DT_DIR:
return True
if self._d_type != DT_LNK:
return False
else:
lstat = self.lstat()
if stat.S_ISDIR(lstat.st_mode):
return True
stat = self.stat() # if lstat() was already called, stat()
will only call os.stat() for symlink
return stat.S_ISDIR(stat.st_mode)
---
The extra caching rules are complex, that's why I suggest to not document them.
In short: is_dir() only needs an extra syscall for symlinks, for other
file types it does not need any syscall.
Victor
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