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# GNU MediaGoblin -- federated, autonomous media hosting
# Copyright (C) 2011, 2012 MediaGoblin contributors. See AUTHORS.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from mediagoblin.storage import StorageInterface, clean_listy_filepath
class MountError(Exception):
pass
class MountStorage(StorageInterface):
"""
Experimental "Mount" virtual Storage Interface
This isn't an interface to some real storage, instead it's a
redirecting interface, that redirects requests to other
"StorageInterface"s.
For example, say you have the paths:
1. ['user_data', 'cwebber', 'avatar.jpg']
2. ['user_data', 'elrond', 'avatar.jpg']
3. ['media_entries', '34352f304c3f4d0ad8ad0f043522b6f2', 'thumb.jpg']
You could mount media_entries under CloudFileStorage and user_data
under BasicFileStorage. Then 1 would be passed to
BasicFileStorage under the path ['cwebber', 'avatar.jpg'] and 3
would be passed to CloudFileStorage under
['34352f304c3f4d0ad8ad0f043522b6f2', 'thumb.jpg'].
In other words, this is kind of like mounting /home/ and /etc/
under different filesystems on your operating system... but with
mediagoblin filestorages :)
To set this up, you currently need to call the mount() method with
the target path and a backend, that shall be available under that
target path. You have to mount things in a sensible order,
especially you can't mount ["a", "b"] before ["a"].
"""
def __init__(self, **kwargs):
self.mounttab = {}
def mount(self, dirpath, backend):
"""
Mount a new backend under dirpath
"""
new_ent = clean_listy_filepath(dirpath)
print("Mounting:", repr(new_ent))
already, rem_1, table, rem_2 = self._resolve_to_backend(new_ent, True)
print("===", repr(already), repr(rem_1), repr(rem_2), len(table))
assert (len(rem_2) > 0) or (None not in table), \
"That path is already mounted"
assert (len(rem_2) > 0) or (len(table) == 0), \
"A longer path is already mounted here"
for part in rem_2:
table[part] = {}
table = table[part]
table[None] = backend
def _resolve_to_backend(self, filepath, extra_info=False):
"""
extra_info = True is for internal use!
Normally, returns the backend and the filepath inside that backend.
With extra_info = True it returns the last directory node and the
remaining filepath from there in addition.
"""
table = self.mounttab
filepath = filepath[:]
res_fp = None
while True:
new_be = table.get(None)
if (new_be is not None) or res_fp is None:
res_be = new_be
res_fp = filepath[:]
res_extra = (table, filepath[:])
# print "... New res: %r, %r, %r" % (res_be, res_fp, res_extra)
if len(filepath) == 0:
break
query = filepath.pop(0)
entry = table.get(query)
if entry is not None:
table = entry
res_extra = (table, filepath[:])
else:
break
if extra_info:
return (res_be, res_fp) + res_extra
else:
return (res_be, res_fp)
def resolve_to_backend(self, filepath):
backend, filepath = self._resolve_to_backend(filepath)
if backend is None:
raise MountError("Path not mounted")
return backend, filepath
def __repr__(self, table=None, indent=[]):
res = []
if table is None:
res.append("MountStorage<")
table = self.mounttab
v = table.get(None)
if v:
res.append(" " * len(indent) + repr(indent) + ": " + repr(v))
for k, v in table.items():
if k == None:
continue
res.append(" " * len(indent) + repr(k) + ":")
res += self.__repr__(v, indent + [k])
if table is self.mounttab:
res.append(">")
return "\n".join(res)
else:
return res
def file_exists(self, filepath):
backend, filepath = self.resolve_to_backend(filepath)
return backend.file_exists(filepath)
def get_file(self, filepath, mode='r'):
backend, filepath = self.resolve_to_backend(filepath)
return backend.get_file(filepath, mode)
def delete_file(self, filepath):
backend, filepath = self.resolve_to_backend(filepath)
return backend.delete_file(filepath)
def file_url(self, filepath):
backend, filepath = self.resolve_to_backend(filepath)
return backend.file_url(filepath)
def get_local_path(self, filepath):
backend, filepath = self.resolve_to_backend(filepath)
return backend.get_local_path(filepath)
def copy_locally(self, filepath, dest_path):
"""
Need to override copy_locally, because the local_storage
attribute is not correct.
"""
backend, filepath = self.resolve_to_backend(filepath)
backend.copy_locally(filepath, dest_path)
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