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         for d in os.environ.get('PATH', '/bin:/usr/bin').split(':'):
  25                 path = os.path.join(d, prog)
  26                 if os.path.isfile(path):
  27                         return path
  28         return None
  29
  30 def read_bytes(fd, nbytes, null_ok = False):
  31         """Read exactly nbytes from fd.
  32         @param fd: file descriptor to read from
  33         @param nbytes: number of bytes to read
  34         @param null_ok: if True, it's OK to receive EOF immediately (we then return None)
  35         @return: the bytes read
  36         @raise Exception: if we received less than nbytes of data
  37         """
  38         data = ''
  39         while nbytes:
  40                 got = os.read(fd, nbytes)
  41                 if not got:
  42                         if null_ok and not data:
  43                                 return None
  44                         raise Exception(_("Unexpected end-of-stream. Data so far %(data)s; expecting %(bytes)d bytes more.")
  45                                         % {'data': repr(data), 'bytes': nbytes})
  46                 data += got
  47                 nbytes -= len(got)
  48         logging.debug(_("Message received: %s") % repr(data))
  49         return data
  50
  51 def pretty_size(size):
  52         """Format a size for printing.
  53         @param size: the size in bytes
  54         @type size: int (or None)
  55         @return: the formatted size
  56         @rtype: str
  57         @since: 0.27"""
  58         if size is None:
  59                 return '?'
  60         if size < 2048:
  61                 return _('%d bytes') % size
  62         size = float(size)
  63         for unit in (_('KB'), _('MB'), _('GB'), _('TB')):
  64                 size /= 1024
  65                 if size < 2048:
  66                         break
  67         return _('%(size).1f %(unit)s') % {'size': size, 'unit': unit}
  68
  69 def ro_rmtree(root):
  70         """Like shutil.rmtree, except that we also delete read-only items.
  71         @param root: the root of the subtree to remove
  72         @type root: str
  73         @since: 0.28"""
  74         import shutil
  75         for main, dirs, files in os.walk(root):
  76                 os.chmod(main, 0700)
  77         shutil.rmtree(root)