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# Copyright (C) 2011-2012 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.
import hashlib
import os
import morphlib
class CacheDir(object):
'''Manage Baserock cached binaries.'''
def __init__(self, dirname):
self.dirname = os.path.abspath(dirname)
def key(self, dict_key):
'''Create a string key from a dictionary key.
The string key can be used as a filename, or as part of one.
The dictionary key is a dict that maps any set of strings to
another set of strings.
The same string key is guaranteed to be returned for a given
dictionary key. It is highly unlikely that two different dictionary
keys result in the same string key.
'''
data = ''.join(key + value for key, value in dict_key.iteritems())
return hashlib.sha256(data).hexdigest()
def name(self, dict_key):
'''Return a filename for an object described by dictionary key.
It is the caller's responsibility to set the fields in the
dictionary key suitably. For example, if there is a field
specifying a commit id, it should be the full git SHA-1
identifier, not something ephemeral like HEAD.
If the field 'kind' has a value, it is used as a suffix for
the filename.
'''
key = self.key(dict_key)
if 'kind' in dict_key and dict_key['kind']:
suffix = '.%s' % dict_key['kind']
else:
suffix = ''
return os.path.join(self.dirname, key + suffix)
def open(self, relative_name_or_cache_key, suffix='', **kwargs):
'''Open a file for writing in the cache.
The file will be written with a temporary name, and renamed to
the final name when the file is closed. Additionally, if the
caller decides, mid-writing, that they don't want to write the
file after all (e.g., a log file), then the ``abort`` method
in the returned file handle can be called to remove the
temporary file.
'''
if type(relative_name_or_cache_key) is dict:
path = self.name(relative_name_or_cache_key)
else:
path = os.path.join(self.dirname, relative_name_or_cache_key)
path += suffix
if 'mode' not in kwargs:
kwargs['mode'] = 'w'
return morphlib.savefile.SaveFile(path, **kwargs)
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