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# Copyright (C) 2013-2014 Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# =*= License: GPL-2 =*=
import collections
import glob
import json
import os
class SystemMetadataDir(collections.MutableMapping):
'''An abstraction over the /baserock metadata directory.
This allows methods of iterating over it, and accessing it like
a dict.
The /baserock metadata directory contains information about all of
the chunks in a built system. It exists to provide traceability from
the input sources to the output.
If you create the object with smd = SystemMetadataDir('/baserock')
data = smd['key'] will read /baserock/key.meta and return its JSON
encoded contents as native python objects.
smd['key'] = data will write data to /baserock/key.meta as JSON
The key may not have '\0' characters in it since the underlying
system calls don't support embedded NUL bytes.
The key may not have '/' characters in it since we do not support
morphologies with slashes in their names.
'''
def __init__(self, metadata_path):
collections.MutableMapping.__init__(self)
self._metadata_path = metadata_path
def _join_path(self, *args):
return os.path.join(self._metadata_path, *args)
def _raw_path_iter(self):
return glob.iglob(self._join_path('*.meta'))
@staticmethod
def _check_key(key):
if any(c in key for c in "\0/"):
raise KeyError(key)
def __getitem__(self, key):
self._check_key(key)
try:
with open(self._join_path('%s.meta' % key), 'r') as f:
return json.load(f, encoding='unicode-escape')
except IOError:
raise KeyError(key)
def __setitem__(self, key, value):
self._check_key(key)
with open(self._join_path('%s.meta' % key), 'w') as f:
json.dump(value, f, indent=4, sort_keys=True,
encoding='unicode-escape')
def __delitem__(self, key):
self._check_key(key)
os.unlink(self._join_path('%s.meta' % key))
def __iter__(self):
return (os.path.basename(fn)[:-len('.meta')]
for fn in self._raw_path_iter())
def __len__(self):
return len(list(self._raw_path_iter()))
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