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_file_cache.py
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102 lines (86 loc) · 3.26 KB
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#!/usr/bin/env python
import errno
import os
import tempfile
from hashlib import md5
class _FileCacheError(Exception):
"""Base exception class for FileCache related errors"""
class _FileCache(object):
DEPTH = 3
def __init__(self, root_directory=None):
self._InitializeRootDirectory(root_directory)
def Get(self, key):
path = self._GetPath(key)
if os.path.exists(path):
with open(path) as f:
return f.read()
else:
return None
def Set(self, key, data):
path = self._GetPath(key)
directory = os.path.dirname(path)
if not os.path.exists(directory):
os.makedirs(directory)
if not os.path.isdir(directory):
raise _FileCacheError('%s exists but is not a directory' % directory)
temp_fd, temp_path = tempfile.mkstemp()
temp_fp = os.fdopen(temp_fd, 'w')
temp_fp.write(data)
temp_fp.close()
if not path.startswith(self._root_directory):
raise _FileCacheError('%s does not appear to live under %s' %
(path, self._root_directory))
if os.path.exists(path):
os.remove(path)
os.rename(temp_path, path)
def Remove(self, key):
path = self._GetPath(key)
if not path.startswith(self._root_directory):
raise _FileCacheError('%s does not appear to live under %s' %
(path, self._root_directory))
if os.path.exists(path):
os.remove(path)
def GetCachedTime(self, key):
path = self._GetPath(key)
if os.path.exists(path):
return os.path.getmtime(path)
else:
return None
def _GetUsername(self):
"""Attempt to find the username in a cross-platform fashion."""
try:
return os.getenv('USER') or \
os.getenv('LOGNAME') or \
os.getenv('USERNAME') or \
os.getlogin() or \
'nobody'
except (AttributeError, IOError, OSError):
return 'nobody'
def _GetTmpCachePath(self):
username = self._GetUsername()
cache_directory = 'python.cache_' + username
return os.path.join(tempfile.gettempdir(), cache_directory)
def _InitializeRootDirectory(self, root_directory):
if not root_directory:
root_directory = self._GetTmpCachePath()
root_directory = os.path.abspath(root_directory)
try:
os.mkdir(root_directory)
except OSError as e:
if e.errno == errno.EEXIST and os.path.isdir(root_directory):
# directory already exists
pass
else:
# exists but is a file, or no permissions, or...
raise
self._root_directory = root_directory
def _GetPath(self, key):
try:
hashed_key = md5(key.encode('utf-8')).hexdigest()
except TypeError:
hashed_key = md5.new(key).hexdigest()
return os.path.join(self._root_directory,
self._GetPrefix(hashed_key),
hashed_key)
def _GetPrefix(self, hashed_key):
return os.path.sep.join(hashed_key[0:_FileCache.DEPTH])