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#
# Based on standard python library functions but avoid
# repeated stat calls. Its assumed the files will not change from under us
# so we can cache stat calls.
#
import os
import errno
import stat as statmod
class CachedPath(object):
def __init__(self):
self.statcache = {}
self.lstatcache = {}
self.normpathcache = {}
return
def updatecache(self, x):
x = self.normpath(x)
if x in self.statcache:
del self.statcache[x]
if x in self.lstatcache:
del self.lstatcache[x]
def normpath(self, path):
if path in self.normpathcache:
return self.normpathcache[path]
newpath = os.path.normpath(path)
self.normpathcache[path] = newpath
return newpath
def _callstat(self, path):
if path in self.statcache:
return self.statcache[path]
try:
st = os.stat(path)
self.statcache[path] = st
return st
except os.error:
self.statcache[path] = False
return False
# We might as well call lstat and then only
# call stat as well in the symbolic link case
# since this turns out to be much more optimal
# in real world usage of this cache
def callstat(self, path):
path = self.normpath(path)
self.calllstat(path)
return self.statcache[path]
def calllstat(self, path):
path = self.normpath(path)
if path in self.lstatcache:
return self.lstatcache[path]
#bb.error("LStatpath:" + path)
try:
lst = os.lstat(path)
self.lstatcache[path] = lst
if not statmod.S_ISLNK(lst.st_mode):
self.statcache[path] = lst
else:
self._callstat(path)
return lst
except (os.error, AttributeError):
self.lstatcache[path] = False
self.statcache[path] = False
return False
# This follows symbolic links, so both islink() and isdir() can be true
# for the same path ono systems that support symlinks
def isfile(self, path):
"""Test whether a path is a regular file"""
st = self.callstat(path)
if not st:
return False
return statmod.S_ISREG(st.st_mode)
# Is a path a directory?
# This follows symbolic links, so both islink() and isdir()
# can be true for the same path on systems that support symlinks
def isdir(self, s):
"""Return true if the pathname refers to an existing directory."""
st = self.callstat(s)
if not st:
return False
return statmod.S_ISDIR(st.st_mode)
def islink(self, path):
"""Test whether a path is a symbolic link"""
st = self.calllstat(path)
if not st:
return False
return statmod.S_ISLNK(st.st_mode)
# Does a path exist?
# This is false for dangling symbolic links on systems that support them.
def exists(self, path):
"""Test whether a path exists. Returns False for broken symbolic links"""
if self.callstat(path):
return True
return False
def lexists(self, path):
"""Test whether a path exists. Returns True for broken symbolic links"""
if self.calllstat(path):
return True
return False
def stat(self, path):
return self.callstat(path)
def lstat(self, path):
return self.calllstat(path)
def walk(self, top, topdown=True, onerror=None, followlinks=False):
# Matches os.walk, not os.path.walk()
# We may not have read permission for top, in which case we can't
# get a list of the files the directory contains. os.path.walk
# always suppressed the exception then, rather than blow up for a
# minor reason when (say) a thousand readable directories are still
# left to visit. That logic is copied here.
try:
names = os.listdir(top)
except os.error as err:
if onerror is not None:
onerror(err)
return
dirs, nondirs = [], []
for name in names:
if self.isdir(os.path.join(top, name)):
dirs.append(name)
else:
nondirs.append(name)
if topdown:
yield top, dirs, nondirs
for name in dirs:
new_path = os.path.join(top, name)
if followlinks or not self.islink(new_path):
for x in self.walk(new_path, topdown, onerror, followlinks):
yield x
if not topdown:
yield top, dirs, nondirs
## realpath() related functions
def __is_path_below(self, file, root):
return (file + os.path.sep).startswith(root)
def __realpath_rel(self, start, rel_path, root, loop_cnt, assume_dir):
"""Calculates real path of symlink 'start' + 'rel_path' below
'root'; no part of 'start' below 'root' must contain symlinks. """
have_dir = True
for d in rel_path.split(os.path.sep):
if not have_dir and not assume_dir:
raise OSError(errno.ENOENT, "no such directory %s" % start)
if d == os.path.pardir: # '..'
if len(start) >= len(root):
# do not follow '..' before root
start = os.path.dirname(start)
else:
# emit warning?
pass
else:
(start, have_dir) = self.__realpath(os.path.join(start, d),
root, loop_cnt, assume_dir)
assert(self.__is_path_below(start, root))
return start
def __realpath(self, file, root, loop_cnt, assume_dir):
while self.islink(file) and len(file) >= len(root):
if loop_cnt == 0:
raise OSError(errno.ELOOP, file)
loop_cnt -= 1
target = os.path.normpath(os.readlink(file))
if not os.path.isabs(target):
tdir = os.path.dirname(file)
assert(self.__is_path_below(tdir, root))
else:
tdir = root
file = self.__realpath_rel(tdir, target, root, loop_cnt, assume_dir)
try:
is_dir = self.isdir(file)
except:
is_dir = False
return (file, is_dir)
def realpath(self, file, root, use_physdir = True, loop_cnt = 100, assume_dir = False):
""" Returns the canonical path of 'file' with assuming a
toplevel 'root' directory. When 'use_physdir' is set, all
preceding path components of 'file' will be resolved first;
this flag should be set unless it is guaranteed that there is
no symlink in the path. When 'assume_dir' is not set, missing
path components will raise an ENOENT error"""
root = os.path.normpath(root)
file = os.path.normpath(file)
if not root.endswith(os.path.sep):
# letting root end with '/' makes some things easier
root = root + os.path.sep
if not self.__is_path_below(file, root):
raise OSError(errno.EINVAL, "file '%s' is not below root" % file)
try:
if use_physdir:
file = self.__realpath_rel(root, file[(len(root) - 1):], root, loop_cnt, assume_dir)
else:
file = self.__realpath(file, root, loop_cnt, assume_dir)[0]
except OSError as e:
if e.errno == errno.ELOOP:
# make ELOOP more readable; without catching it, there will
# be printed a backtrace with 100s of OSError exceptions
# else
raise OSError(errno.ELOOP,
"too much recursions while resolving '%s'; loop in '%s'" %
(file, e.strerror))
raise
return file
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