zeroinstall/support/__init__.py

   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: %s") % repr(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)