Source Code for Package zeroinstall.support

 1  """ 
 2  Useful support routines (for internal use). 
 3   
 4  These functions aren't really Zero Install specific; they're things we might 
 5  wish were in the standard library. 
 6   
 7  @since: 0.27 
 8  """ 
 9   
10  # Copyright (C) 2009, Thomas Leonard 
11  # See the README file for details, or visit http://0install.net. 
12   
13  from zeroinstall import _ 
14  import os, logging 
15   
16 -def find_in_path(prog): 
17          """Search $PATH for prog. 
18          If prog is an absolute path, return it unmodified. 
19          @param prog: name of executable to find 
20          @return: the full path of prog, or None if not found 
21          @since: 0.27 
22          """ 
23          if os.path.isabs(prog): return prog 
24          if os.name == "nt": 
25                  prog += '.exe' 
26          for d in os.environ.get('PATH', '/bin:/usr/bin').split(os.pathsep): 
27                  path = os.path.join(d, prog) 
28                  if os.path.isfile(path): 
29                          return path 
30          return None 
31   
32 -def read_bytes(fd, nbytes, null_ok = False): 
33          """Read exactly nbytes from fd. 
34          @param fd: file descriptor to read from 
35          @param nbytes: number of bytes to read 
36          @param null_ok: if True, it's OK to receive EOF immediately (we then return None) 
37          @return: the bytes read 
38          @raise Exception: if we received less than nbytes of data 
39          """ 
40          data = '' 
41          while nbytes: 
42                  got = os.read(fd, nbytes) 
43                  if not got: 
44                          if null_ok and not data: 
45                                  return None 
46                          raise Exception(_("Unexpected end-of-stream. Data so far %(data)s; expecting %(bytes)d bytes more.") 
47                                          % {'data': repr(data), 'bytes': nbytes}) 
48                  data += got 
49                  nbytes -= len(got) 
50          logging.debug(_("Message received: %r"), data) 
51          return data 
52   
53 -def pretty_size(size): 
54          """Format a size for printing. 
55          @param size: the size in bytes 
56          @type size: int (or None) 
57          @return: the formatted size 
58          @rtype: str 
59          @since: 0.27""" 
60          if size is None: 
61                  return '?' 
62          if size < 2048: 
63                  return _('%d bytes') % size 
64          size = float(size) 
65          for unit in (_('KB'), _('MB'), _('GB'), _('TB')): 
66                  size /= 1024 
67                  if size < 2048: 
68                          break 
69          return _('%(size).1f %(unit)s') % {'size': size, 'unit': unit} 
70   
71 -def ro_rmtree(root): 
72          """Like shutil.rmtree, except that we also delete read-only items. 
73          @param root: the root of the subtree to remove 
74          @type root: str 
75          @since: 0.28""" 
76          import shutil 
77          import platform 
78          if platform.system() == 'Windows': 
79                  for main, dirs, files in os.walk(root): 
80                          for i in files + dirs: 
81                                  os.chmod(os.path.join(main, i), 0o700) 
82                  os.chmod(root, 0o700) 
83          else: 
84                  for main, dirs, files in os.walk(root): 
85                          os.chmod(main, 0o700) 
86          shutil.rmtree(root) 
87   
88 -def raise_with_traceback(ex, tb): 
89          """Raise an exception in a way that works on Python 2 and Python 3""" 
90          if hasattr(ex, 'with_traceback'): 
91                  raise ex.with_traceback(tb)                     # Python 3 
92          exec("raise ex, None, tb", {'ex': ex, 'tb': tb})        # Python 2 
93          assert 0 
94