/usr/share/pyshared/fs/multifs.py is in python-fs 0.3.0-2.
This file is owned by root:root, with mode 0o644.
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fs.multifs
==========
A MultiFS is a filesytem composed of a sequence of other filesystems, where
the directory structure of each filesystem is overlaid over the previous filesystem.
When you attempt to access a file from the MultiFS it will try each 'child'
FS in order, until it either finds a path that exists or raises a ResourceNotFoundError.
One use for such a filesystem would be to selectively override a set of files,
to customize behaviour. For example, to create a filesystem that could be used
to *theme* a web application. We start with the following directories::
`-- templates
|-- snippets
| `-- panel.html
|-- index.html
|-- profile.html
`-- base.html
`-- theme
|-- snippets
| |-- widget.html
| `-- extra.html
|-- index.html
`-- theme.html
And we want to create a single filesystem that looks for files in `templates` if
they don't exist in `theme`. We can do this with the following code::
from fs.osfs import OSFS
from fs.multifs import MultiFS
themed_template_fs.addfs('templates', OSFS('templates'))
themed_template_fs.addfs('theme', OSFS('themes'))
Now we have a `themed_template_fs` FS object presents a single view of both
directories::
|-- snippets
| |-- panel.html
| |-- widget.html
| `-- extra.html
|-- index.html
|-- profile.html
|-- base.html
`-- theme.html
"""
from fs.base import FS, FSError, synchronize
from fs.path import *
from fs import _thread_synchronize_default
from fs.errors import ResourceNotFoundError
class MultiFS(FS):
"""A MultiFS is a filesystem that delegates to a sequence of other filesystems.
Operations on the MultiFS will try each 'child' filesystem in order, until it
succeeds. In effect, creating a filesystem that combines the files and dirs of
its children.
"""
def __init__(self):
super(MultiFS, self).__init__(thread_synchronize=_thread_synchronize_default)
self.fs_sequence = []
self.fs_lookup = {}
@synchronize
def __str__(self):
return "<MultiFS: %s>" % ", ".join(str(fs) for fs in self.fs_sequence)
__repr__ = __str__
@synchronize
def __unicode__(self):
return u"<MultiFS: %s>" % ", ".join(unicode(fs) for fs in self.fs_sequence)
@synchronize
def addfs(self, name, fs):
"""Adds a filesystem to the MultiFS.
:param name: A unique name to refer to the filesystem being added
:param fs: The filesystem to add
"""
if name in self.fs_lookup:
raise ValueError("Name already exists.")
self.fs_sequence.append(fs)
self.fs_lookup[name] = fs
@synchronize
def removefs(self, name):
"""Removes a filesystem from the sequence.
:param name: The name of the filesystem, as used in addfs
"""
if name not in self.fs_lookup:
raise ValueError("No filesystem called '%s'"%name)
fs = self.fs_lookup[name]
self.fs_sequence.remove(fs)
del self.fs_lookup[name]
@synchronize
def __getitem__(self, name):
return self.fs_lookup[name]
@synchronize
def __iter__(self):
return reversed(self.fs_sequence[:])
def _delegate_search(self, path):
for fs in self:
if fs.exists(path):
return fs
return None
@synchronize
def which(self, path):
"""Retrieves the filesystem that a given path would delegate to.
Returns a tuple of the filesystem's name and the filesystem object itself.
:param path: A path in MultiFS
"""
for fs in self:
if fs.exists(path):
for fs_name, fs_object in self.fs_lookup.iteritems():
if fs is fs_object:
return fs_name, fs
raise ResourceNotFoundError(path, msg="Path does not map to any filesystem: %(path)s")
@synchronize
def getsyspath(self, path, allow_none=False):
fs = self._delegate_search(path)
if fs is not None:
return fs.getsyspath(path, allow_none=allow_none)
raise ResourceNotFoundError(path)
@synchronize
def desc(self, path):
if not self.exists(path):
raise ResourceNotFoundError(path)
name, fs = self.which(path)
if name is None:
return ""
return "%s, on %s (%s)" % (fs.desc(path), name, fs)
@synchronize
def open(self, path, mode="r", **kwargs):
for fs in self:
if fs.exists(path):
fs_file = fs.open(path, mode, **kwargs)
return fs_file
raise ResourceNotFoundError(path)
@synchronize
def exists(self, path):
return self._delegate_search(path) is not None
@synchronize
def isdir(self, path):
fs = self._delegate_search(path)
if fs is not None:
return fs.isdir(path)
return False
@synchronize
def isfile(self, path):
fs = self._delegate_search(path)
if fs is not None:
return fs.isfile(path)
return False
@synchronize
def listdir(self, path="./", *args, **kwargs):
paths = []
for fs in self:
try:
paths += fs.listdir(path, *args, **kwargs)
except FSError, e:
pass
return list(set(paths))
@synchronize
def remove(self, path):
for fs in self:
if fs.exists(path):
fs.remove(path)
return
raise ResourceNotFoundError(path)
@synchronize
def removedir(self, path, recursive=False):
for fs in self:
if fs.isdir(path):
fs.removedir(path, recursive)
return
raise ResourceNotFoundError(path)
@synchronize
def rename(self, src, dst):
for fs in self:
if fs.exists(src):
fs.rename(src, dst)
return
raise ResourceNotFoundError(path)
@synchronize
def settimes(self, path, accessed_time=None, modified_time=None):
for fs in self:
if fs.exists(path):
return fs.settimes(path, accessed_time, modified_time)
raise ResourceNotFoundError(path)
@synchronize
def getinfo(self, path):
for fs in self:
if fs.exists(path):
return fs.getinfo(path)
raise ResourceNotFoundError(path)
|