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# Copyright (C) 2006 Lars Wirzenius <liw@iki.fi>
#
# 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; either version 2 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 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.
"""Block cache for backup program"""
import os
class Cache:
def __init__(self, config):
self.cachedir = config.get("backup", "cache")
def cache_pathname(self, block_id):
"""Return pathname in local block cache for a given block id"""
return os.path.join(self.cachedir, block_id)
def create_new_cache_file(self, block_id):
"""Create a new file in the local block cache, open for writing"""
pathname = self.cache_pathname(block_id)
dirname = os.path.dirname(pathname)
if not os.path.isdir(dirname):
os.makedirs(dirname, 0700)
return file(pathname + ".new", "w", 0600)
def close_new_cache_file(self, block_id, f):
"""Close a file opened by open_cache_file"""
f.close()
pathname = self.cache_pathname(block_id)
os.rename(pathname + ".new", pathname)
def put_block(self, block_id, block):
"""Put a block into the cache"""
f = self.create_new_cache_file(block_id)
f.write(block)
self.close_new_cache_file(block_id, f)
def get_block(self, block_id):
"""Return the contents of a block in the block cache, or None"""
try:
f = file(self.cache_pathname(block_id), "r")
block = f.read()
f.close()
except IOError, e:
return None
return block
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