Source Code for Module lastfm.filecache

  1  #!/usr/bin/env python 
  2   
  3  __author__ = "Abhinav Sarkar <abhinav@abhinavsarkar.net>" 
  4  __version__ = "0.2" 
  5  __license__ = "GNU Lesser General Public License" 
  6   
  7  import sys 
  8  if sys.version < '2.6': 
  9      import md5 
 10 -    def md5hash(string): 
 11          return md5.new(string).hexdigest() 
 12  else: 
 13      from hashlib import md5 
 14 -    def md5hash(string): 
 15          return md5(string).hexdigest() 
 16       
 17  import os 
 18  import tempfile 
 19   
 20 -class _FileCacheError(Exception): 
 21          '''Base exception class for FileCache related errors''' 
 22   
 23 -class FileCache(object): 
 24   
 25          DEPTH = 3 
 26   
 27 -        def __init__(self,root_directory=None): 
 28                  self._InitializeRootDirectory(root_directory) 
 29   
 30 -        def Get(self,key): 
 31                  path = self._GetPath(key) 
 32                  if os.path.exists(path): 
 33                          return open(path).read() 
 34                  else: 
 35                          return None 
 36   
 37 -        def Set(self,key,data): 
 38                  path = self._GetPath(key) 
 39                  directory = os.path.dirname(path) 
 40                  if not os.path.exists(directory): 
 41                          os.makedirs(directory) 
 42                  if not os.path.isdir(directory): 
 43                          raise _FileCacheError('%s exists but is not a directory' % directory) 
 44                  temp_fd, temp_path = tempfile.mkstemp() 
 45                  temp_fp = os.fdopen(temp_fd, 'w') 
 46                  temp_fp.write(data) 
 47                  temp_fp.close() 
 48                  if not path.startswith(self._root_directory): 
 49                          raise _FileCacheError('%s does not appear to live under %s' % 
 50                                                                    (path, self._root_directory)) 
 51                  if os.path.exists(path): 
 52                          os.remove(path) 
 53                  os.rename(temp_path, path) 
 54   
 55 -        def Remove(self,key): 
 56                  path = self._GetPath(key) 
 57                  if not path.startswith(self._root_directory): 
 58                          raise _FileCacheError('%s does not appear to live under %s' % 
 59                                                                    (path, self._root_directory )) 
 60                  if os.path.exists(path): 
 61                          os.remove(path) 
 62   
 63 -        def GetCachedTime(self,key): 
 64                  path = self._GetPath(key) 
 65                  if os.path.exists(path): 
 66                          return os.path.getmtime(path) 
 67                  else: 
 68                          return None 
 69   
 70 -        def _GetUsername(self): 
 71                  '''Attempt to find the username in a cross-platform fashion.''' 
 72                  return os.getenv('USER') or \ 
 73                          os.getenv('LOGNAME') or \ 
 74                          os.getenv('USERNAME') or \ 
 75                          os.getlogin() or \ 
 76                          'nobody' 
 77   
 78 -        def _GetTmpCachePath(self): 
 79                  username = self._GetUsername() 
 80                  cache_directory = 'python.cache_' + username 
 81                  return os.path.join(tempfile.gettempdir(), cache_directory) 
 82   
 83 -        def _InitializeRootDirectory(self, root_directory): 
 84                  if not root_directory: 
 85                          root_directory = self._GetTmpCachePath() 
 86                  root_directory = os.path.abspath(root_directory) 
 87                  if not os.path.exists(root_directory): 
 88                          os.mkdir(root_directory) 
 89                  if not os.path.isdir(root_directory): 
 90                          raise _FileCacheError('%s exists but is not a directory' % 
 91                                                                    root_directory) 
 92                  self._root_directory = root_directory 
 93   
 94 -        def _GetPath(self,key): 
 95                  hashed_key = md5hash(key) 
 96                  return os.path.join(self._root_directory, 
 97                                                          self._GetPrefix(hashed_key), 
 98                                                          hashed_key) 
 99   
100 -        def _GetPrefix(self,hashed_key): 
101                  return os.path.sep.join(hashed_key[0:FileCache.DEPTH]) 
102