lib/bup/hlinkdb.py

   1
   2 from __future__ import absolute_import
   3 import cPickle, errno, os, tempfile
   4
   5 from bup import compat
   6
   7 class Error(Exception):
   8     pass
   9
  10 class HLinkDB:
  11     def __init__(self, filename):
  12         # Map a "dev:ino" node to a list of paths associated with that node.
  13         self._node_paths = {}
  14         # Map a path to a "dev:ino" node.
  15         self._path_node = {}
  16         self._filename = filename
  17         self._save_prepared = None
  18         self._tmpname = None
  19         f = None
  20         try:
  21             f = open(filename, 'r')
  22         except IOError as e:
  23             if e.errno == errno.ENOENT:
  24                 pass
  25             else:
  26                 raise
  27         if f:
  28             try:
  29                 self._node_paths = cPickle.load(f)
  30             finally:
  31                 f.close()
  32                 f = None
  33         # Set up the reverse hard link index.
  34         for node, paths in compat.items(self._node_paths):
  35             for path in paths:
  36                 self._path_node[path] = node
  37
  38     def prepare_save(self):
  39         """ Commit all of the relevant data to disk.  Do as much work
  40         as possible without actually making the changes visible."""
  41         if self._save_prepared:
  42             raise Error('save of %r already in progress' % self._filename)
  43         if self._node_paths:
  44             (dir, name) = os.path.split(self._filename)
  45             (ffd, self._tmpname) = tempfile.mkstemp('.tmp', name, dir)
  46             try:
  47                 try:
  48                     f = os.fdopen(ffd, 'wb', 65536)
  49                 except:
  50                     os.close(ffd)
  51                     raise
  52                 try:
  53                     cPickle.dump(self._node_paths, f, 2)
  54                 finally:
  55                     f.close()
  56                     f = None
  57             except:
  58                 tmpname = self._tmpname
  59                 self._tmpname = None
  60                 os.unlink(tmpname)
  61                 raise
  62         self._save_prepared = True
  63
  64     def commit_save(self):
  65         if not self._save_prepared:
  66             raise Error('cannot commit save of %r; no save prepared'
  67                         % self._filename)
  68         if self._tmpname:
  69             os.rename(self._tmpname, self._filename)
  70             self._tmpname = None
  71         else: # No data -- delete _filename if it exists.
  72             try:
  73                 os.unlink(self._filename)
  74             except OSError as e:
  75                 if e.errno == errno.ENOENT:
  76                     pass
  77                 else:
  78                     raise
  79         self._save_prepared = None
  80
  81     def abort_save(self):
  82         if self._tmpname:
  83             os.unlink(self._tmpname)
  84             self._tmpname = None
  85
  86     def __del__(self):
  87         self.abort_save()
  88
  89     def add_path(self, path, dev, ino):
  90         # Assume path is new.
  91         node = '%s:%s' % (dev, ino)
  92         self._path_node[path] = node
  93         link_paths = self._node_paths.get(node)
  94         if link_paths and path not in link_paths:
  95             link_paths.append(path)
  96         else:
  97             self._node_paths[node] = [path]
  98
  99     def _del_node_path(self, node, path):
 100         link_paths = self._node_paths[node]
 101         link_paths.remove(path)
 102         if not link_paths:
 103             del self._node_paths[node]
 104
 105     def change_path(self, path, new_dev, new_ino):
 106         prev_node = self._path_node.get(path)
 107         if prev_node:
 108             self._del_node_path(prev_node, path)
 109         self.add_path(new_dev, new_ino, path)
 110
 111     def del_path(self, path):
 112         # Path may not be in db (if updating a pre-hardlink support index).
 113         node = self._path_node.get(path)
 114         if node:
 115             self._del_node_path(node, path)
 116             del self._path_node[path]
 117
 118     def node_paths(self, dev, ino):
 119         node = '%s:%s' % (dev, ino)
 120         return self._node_paths[node]