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 _, logger
  14 import sys, os
  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 = b''
  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         logger.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 (os.getcwd() + os.path.sep).startswith(root + os.path.sep):
  79                 import warnings
  80                 warnings.warn("Removing tree ({tree}) containing the current directory ({cwd}) - this will not work on Windows".format(cwd = os.getcwd(), tree = root), stacklevel = 2)
  81
  82         if platform.system() == 'Windows':
  83                 for main, dirs, files in os.walk(root):
  84                         for i in files + dirs:
  85                                 os.chmod(os.path.join(main, i), 0o700)
  86                 os.chmod(root, 0o700)
  87         else:
  88                 for main, dirs, files in os.walk(root):
  89                         os.chmod(main, 0o700)
  90         shutil.rmtree(root)
  91
  92 def raise_with_traceback(ex, tb):
  93         """Raise an exception in a way that works on Python 2 and Python 3"""
  94         if hasattr(ex, 'with_traceback'):
  95                 raise ex                                        # Python 3
  96         exec("raise ex, None, tb", {'ex': ex, 'tb': tb})        # Python 2
  97         assert 0
  98
  99 def portable_rename(src, dst):
 100         """Rename 'src' to 'dst', which must be on the same filesystem.
 101         On POSIX systems, this operation is atomic.
 102         On Windows, do the best we can by deleting dst and then renaming.
 103         @since: 1.9"""
 104         if os.name == "nt" and os.path.exists(dst):
 105                 os.unlink(dst)
 106         os.rename(src, dst)
 107
 108 def windows_args_escape(args):
 109         """Combines multiple strings into one for use as a Windows command-line argument.
 110         This coressponds to Windows' handling of command-line arguments as specified in: http://msdn.microsoft.com/library/17w5ykft.
 111         @since: 1.11"""
 112         def _escape(arg):
 113                 # Add leading quotation mark if there are whitespaces
 114                 import string
 115                 contains_whitespace = any(whitespace in arg for whitespace in string.whitespace)
 116                 result = '"' if contains_whitespace else ''
 117
 118                 # Split by quotation marks
 119                 parts = arg.split('"')
 120                 for i, part in enumerate(parts):
 121                         # Count slashes preceeding the quotation mark
 122                         slashes_count = len(part) - len(part.rstrip('\\'))
 123
 124                         result = result + part
 125                         if i < len(parts) - 1:
 126                                 # Not last part
 127                                 result = result + ("\\" * slashes_count) # Double number of slashes
 128                                 result = result + "\\" + '"' # Escaped quotation mark
 129                         elif contains_whitespace:
 130                                 # Last part if there are whitespaces
 131                                 result = result + ("\\" * slashes_count) # Double number of slashes
 132                                 result = result + '"' # Non-escaped quotation mark
 133
 134                 return result
 135
 136         return ' '.join(map(_escape, args))
 137
 138 if sys.version_info[0] > 2:
 139         # Python 3
 140         unicode = str
 141         basestring = str
 142         intern = sys.intern
 143         raw_input = input
 144
 145         def urlparse(url):
 146                 from urllib import parse
 147                 return parse.urlparse(url)
 148 else:
 149         # Python 2
 150         unicode = unicode               # (otherwise it can't be imported)
 151         basestring = basestring
 152         intern = intern
 153         raw_input = raw_input
 154
 155         def urlparse(url):
 156                 import urlparse
 157                 return urlparse.urlparse(url)