git.roojs.org Git - gnome.gobject-introspection/blob - giscanner/cachestore.py

   1 # -*- Mode: Python -*-
   2 # GObject-Introspection - a framework for introspecting GObject libraries
   3 # Copyright (C) 2008  Johan Dahlin
   4 #
   5 # This library is free software; you can redistribute it and/or
   6 # modify it under the terms of the GNU Lesser General Public
   7 # License as published by the Free Software Foundation; either
   8 # version 2 of the License, or (at your option) any later version.
   9 #
  10 # This library is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 # Lesser General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU Lesser General Public
  16 # License along with this library; if not, write to the
  17 # Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 # Boston, MA 02111-1307, USA.
  19 #
  20
  21 import errno
  22 import cPickle
  23 import hashlib
  24 import os
  25 import shutil
  26 import tempfile
  27
  28
  29 def _get_cachedir():
  30     homedir = os.environ.get('HOME')
  31     if homedir is None:
  32         return None
  33     if not os.path.exists(homedir):
  34         return None
  35
  36     cachedir = os.path.join(homedir, '.cache')
  37     if not os.path.exists(cachedir):
  38         try:
  39             os.mkdir(cachedir, 0755)
  40         except OSError:
  41             return None
  42
  43     scannerdir = os.path.join(cachedir, 'g-ir-scanner')
  44     if not os.path.exists(scannerdir):
  45         os.mkdir(scannerdir, 0755)
  46     # If it exists and is a file, don't cache at all
  47     elif not os.path.isdir(scannerdir):
  48         return None
  49     return scannerdir
  50
  51
  52 class CacheStore(object):
  53
  54     def __init__(self):
  55         try:
  56             self._directory = _get_cachedir()
  57         except OSError, e:
  58             if e.errno != errno.EPERM:
  59                 raise
  60             self._directory = None
  61
  62     def _get_filename(self, filename):
  63         # If we couldn't create the directory we're probably
  64         # on a read only home directory where we just disable
  65         # the cache all together.
  66         if self._directory is None:
  67             return
  68         hexdigest = hashlib.sha1(filename).hexdigest()
  69         return os.path.join(self._directory, hexdigest)
  70
  71     def _cache_is_valid(self, store_filename, filename):
  72         return (os.stat(store_filename).st_mtime >=
  73                 os.stat(filename).st_mtime)
  74
  75     def _remove_filename(self, filename):
  76         try:
  77             os.unlink(filename)
  78         except IOError, e:
  79             # Permission denied
  80             if e.errno == errno.EACCES:
  81                 return
  82             else:
  83                 raise
  84         except OSError, e:
  85             # File does not exist
  86             if e.errno == errno.ENOENT:
  87                 return
  88             else:
  89                 raise
  90
  91     def store(self, filename, data):
  92         store_filename = self._get_filename(filename)
  93         if store_filename is None:
  94             return
  95
  96         if (os.path.exists(store_filename) and
  97             self._cache_is_valid(store_filename, filename)):
  98             return None
  99
 100         tmp_fd, tmp_filename = tempfile.mkstemp(prefix='g-ir-scanner-cache-')
 101         try:
 102             cPickle.dump(data, os.fdopen(tmp_fd, 'w'))
 103         except IOError, e:
 104             # No space left on device
 105             if e.errno == errno.ENOSPC:
 106                 self._remove_filename(tmp_filename)
 107                 return
 108             else:
 109                 raise
 110
 111         try:
 112             shutil.move(tmp_filename, store_filename)
 113         except IOError, e:
 114             # Permission denied
 115             if e.errno == errno.EACCES:
 116                 self._remove_filename(tmp_filename)
 117             else:
 118                 raise
 119
 120     def load(self, filename):
 121         store_filename = self._get_filename(filename)
 122         if store_filename is None:
 123             return
 124         try:
 125             fd = open(store_filename)
 126         except IOError, e:
 127             if e.errno == errno.ENOENT:
 128                 return None
 129             else:
 130                 raise
 131         if not self._cache_is_valid(store_filename, filename):
 132             return None
 133         try:
 134             data = cPickle.load(fd)
 135         except (AttributeError, EOFError, ValueError, cPickle.BadPickleGet):
 136             # Broken cache entry, remove it
 137             self._remove_filename(store_filename)
 138             data = None
 139         return data