lib/bup/hlinkdb.py

   1
   2 from __future__ import absolute_import
   3 import errno, os, tempfile
   4
   5 from bup import compat
   6
   7 if compat.py_maj > 2:
   8     import pickle
   9 else:
  10     import cPickle as pickle
  11
  12
  13 class Error(Exception):
  14     pass
  15
  16 class HLinkDB:
  17     def __init__(self, filename):
  18         # Map a "dev:ino" node to a list of paths associated with that node.
  19         self._node_paths = {}
  20         # Map a path to a "dev:ino" node.
  21         self._path_node = {}
  22         self._filename = filename
  23         self._save_prepared = None
  24         self._tmpname = None
  25         f = None
  26         try:
  27             f = open(filename, 'rb')
  28         except IOError as e:
  29             if e.errno == errno.ENOENT:
  30                 pass
  31             else:
  32                 raise
  33         if f:
  34             try:
  35                 self._node_paths = pickle.load(f)
  36             finally:
  37                 f.close()
  38                 f = None
  39         # Set up the reverse hard link index.
  40         for node, paths in compat.items(self._node_paths):
  41             for path in paths:
  42                 self._path_node[path] = node
  43
  44     def prepare_save(self):
  45         """ Commit all of the relevant data to disk.  Do as much work
  46         as possible without actually making the changes visible."""
  47         if self._save_prepared:
  48             raise Error('save of %r already in progress' % self._filename)
  49         if self._node_paths:
  50             (dir, name) = os.path.split(self._filename)
  51             (ffd, self._tmpname) = tempfile.mkstemp(b'.tmp', name, dir)
  52             try:
  53                 try:
  54                     f = os.fdopen(ffd, 'wb', 65536)
  55                 except:
  56                     os.close(ffd)
  57                     raise
  58                 try:
  59                     pickle.dump(self._node_paths, f, 2)
  60                 finally:
  61                     f.close()
  62                     f = None
  63             except:
  64                 tmpname = self._tmpname
  65                 self._tmpname = None
  66                 os.unlink(tmpname)
  67                 raise
  68         self._save_prepared = True
  69
  70     def commit_save(self):
  71         if not self._save_prepared:
  72             raise Error('cannot commit save of %r; no save prepared'
  73                         % self._filename)
  74         if self._tmpname:
  75             os.rename(self._tmpname, self._filename)
  76             self._tmpname = None
  77         else: # No data -- delete _filename if it exists.
  78             try:
  79                 os.unlink(self._filename)
  80             except OSError as e:
  81                 if e.errno == errno.ENOENT:
  82                     pass
  83                 else:
  84                     raise
  85         self._save_prepared = None
  86
  87     def abort_save(self):
  88         if self._tmpname:
  89             os.unlink(self._tmpname)
  90             self._tmpname = None
  91
  92     def __del__(self):
  93         self.abort_save()
  94
  95     def add_path(self, path, dev, ino):
  96         # Assume path is new.
  97         node = '%s:%s' % (dev, ino)
  98         self._path_node[path] = node
  99         link_paths = self._node_paths.get(node)
 100         if link_paths and path not in link_paths:
 101             link_paths.append(path)
 102         else:
 103             self._node_paths[node] = [path]
 104
 105     def _del_node_path(self, node, path):
 106         link_paths = self._node_paths[node]
 107         link_paths.remove(path)
 108         if not link_paths:
 109             del self._node_paths[node]
 110
 111     def change_path(self, path, new_dev, new_ino):
 112         prev_node = self._path_node.get(path)
 113         if prev_node:
 114             self._del_node_path(prev_node, path)
 115         self.add_path(new_dev, new_ino, path)
 116
 117     def del_path(self, path):
 118         # Path may not be in db (if updating a pre-hardlink support index).
 119         node = self._path_node.get(path)
 120         if node:
 121             self._del_node_path(node, path)
 122             del self._path_node[path]
 123
 124     def node_paths(self, dev, ino):
 125         node = '%s:%s' % (dev, ino)
 126         return self._node_paths[node]