zeroinstall/injector/model.py

   1 """In-memory representation of interfaces and other data structures.
   2
   3 The objects in this module are used to build a representation of an XML interface
   4 file in memory.
   5
   6 @see: L{reader} constructs these data-structures.
   7
   8 @var defaults: Default values for the 'default' attribute for <environment> bindings of
   9 well-known variables.
  10 """
  11
  12 # Copyright (C) 2006, Thomas Leonard
  13 # See the README file for details, or visit http://0install.net.
  14
  15 import os, re
  16 from logging import warn, info, debug
  17 from zeroinstall import SafeException, version
  18 from zeroinstall.injector.namespaces import XMLNS_IFACE
  19
  20 # Element names for bindings in feed files
  21 binding_names = frozenset(['environment'])
  22
  23 network_offline = 'off-line'
  24 network_minimal = 'minimal'
  25 network_full = 'full'
  26 network_levels = (network_offline, network_minimal, network_full)
  27
  28 stability_levels = {}   # Name -> Stability
  29
  30 defaults = {
  31         'PATH': '/bin:/usr/bin',
  32         'XDG_CONFIG_DIRS': '/etc/xdg',
  33         'XDG_DATA_DIRS': '/usr/local/share:/usr/share',
  34 }
  35
  36 class InvalidInterface(SafeException):
  37         """Raised when parsing an invalid feed."""
  38         def __init__(self, message, ex = None):
  39                 if ex:
  40                         message += "\n\n(exact error: %s)" % ex
  41                 SafeException.__init__(self, message)
  42
  43 def _split_arch(arch):
  44         """Split an arch into an (os, machine) tuple. Either or both parts may be None."""
  45         if not arch:
  46                 return None, None
  47         elif '-' not in arch:
  48                 raise SafeException("Malformed arch '%s'" % arch)
  49         else:
  50                 os, machine = arch.split('-', 1)
  51                 if os == '*': os = None
  52                 if machine == '*': machine = None
  53                 return os, machine
  54
  55 def _join_arch(os, machine):
  56         if os == machine == None: return None
  57         return "%s-%s" % (os or '*', machine or '*')
  58
  59 class Stability(object):
  60         """A stability rating. Each implementation has an upstream stability rating and,
  61         optionally, a user-set rating."""
  62         __slots__ = ['level', 'name', 'description']
  63         def __init__(self, level, name, description):
  64                 self.level = level
  65                 self.name = name
  66                 self.description = description
  67                 assert name not in stability_levels
  68                 stability_levels[name] = self
  69
  70         def __cmp__(self, other):
  71                 return cmp(self.level, other.level)
  72
  73         def __str__(self):
  74                 return self.name
  75
  76         def __repr__(self):
  77                 return "<Stability: " + self.description + ">"
  78
  79 def process_binding(e):
  80         """Internal"""
  81         if e.name == 'environment':
  82                 mode = {
  83                         None: EnvironmentBinding.PREPEND,
  84                         'prepend': EnvironmentBinding.PREPEND,
  85                         'append': EnvironmentBinding.APPEND,
  86                         'replace': EnvironmentBinding.REPLACE,
  87                 }[e.getAttribute('mode')]
  88
  89                 binding = EnvironmentBinding(e.getAttribute('name'),
  90                                              insert = e.getAttribute('insert'),
  91                                              default = e.getAttribute('default'),
  92                                              mode = mode)
  93                 if not binding.name: raise InvalidInterface("Missing 'name' in binding")
  94                 if binding.insert is None: raise InvalidInterface("Missing 'insert' in binding")
  95                 return binding
  96         else:
  97                 raise Exception("Unknown binding type '%s'" % e.name)
  98
  99 def process_depends(item):
 100         """Internal"""
 101         # Note: also called from selections
 102         dep_iface = item.getAttribute('interface')
 103         if not dep_iface:
 104                 raise InvalidInterface("Missing 'interface' on <requires>")
 105         dependency = InterfaceDependency(dep_iface, metadata = item.attrs)
 106
 107         for e in item.childNodes:
 108                 if e.uri != XMLNS_IFACE: continue
 109                 if e.name in binding_names:
 110                         dependency.bindings.append(process_binding(e))
 111                 elif e.name == 'version':
 112                         dependency.restrictions.append(
 113                                 Restriction(not_before = parse_version(e.getAttribute('not-before')),
 114                                             before = parse_version(e.getAttribute('before'))))
 115         return dependency
 116
 117
 118 insecure = Stability(0, 'insecure', 'This is a security risk')
 119 buggy = Stability(5, 'buggy', 'Known to have serious bugs')
 120 developer = Stability(10, 'developer', 'Work-in-progress - bugs likely')
 121 testing = Stability(20, 'testing', 'Stability unknown - please test!')
 122 stable = Stability(30, 'stable', 'Tested - no serious problems found')
 123 packaged = Stability(35, 'packaged', 'Supplied by the local package manager')
 124 preferred = Stability(40, 'preferred', 'Best of all - must be set manually')
 125
 126 class Restriction(object):
 127         """A Restriction limits the allowed implementations of an Interface."""
 128         __slots__ = ['before', 'not_before']
 129         def __init__(self, before, not_before):
 130                 self.before = before
 131                 self.not_before = not_before
 132
 133         def meets_restriction(self, impl):
 134                 if self.not_before and impl.version < self.not_before:
 135                         return False
 136                 if self.before and impl.version >= self.before:
 137                         return False
 138                 return True
 139
 140         def __str__(self):
 141                 if self.not_before is not None or self.before is not None:
 142                         range = ''
 143                         if self.not_before is not None:
 144                                 range += format_version(self.not_before) + ' <= '
 145                         range += 'version'
 146                         if self.before is not None:
 147                                 range += ' < ' + format_version(self.before)
 148                 else:
 149                         range = 'none'
 150                 return "(restriction: %s)" % range
 151
 152 class Binding(object):
 153         """Information about how the choice of a Dependency is made known
 154         to the application being run."""
 155
 156 class EnvironmentBinding(Binding):
 157         """Indicate the chosen implementation using an environment variable."""
 158         __slots__ = ['name', 'insert', 'default', 'mode']
 159
 160         PREPEND = 'prepend'
 161         APPEND = 'append'
 162         REPLACE = 'replace'
 163
 164         def __init__(self, name, insert, default = None, mode = PREPEND):
 165                 """mode argument added in version 0.28"""
 166                 self.name = name
 167                 self.insert = insert
 168                 self.default = default
 169                 self.mode = mode
 170
 171         def __str__(self):
 172                 return "<environ %s %s %s>" % (self.name, self.mode, self.insert)
 173
 174         __repr__ = __str__
 175
 176         def get_value(self, path, old_value):
 177                 """Calculate the new value of the environment variable after applying this binding.
 178                 @param path: the path to the selected implementation
 179                 @param old_value: the current value of the environment variable
 180                 @return: the new value for the environment variable"""
 181                 extra = os.path.join(path, self.insert)
 182
 183                 if self.mode == EnvironmentBinding.REPLACE:
 184                         return extra
 185
 186                 if old_value is None:
 187                         old_value = self.default or defaults.get(self.name, None)
 188                 if old_value is None:
 189                         return extra
 190                 if self.mode == EnvironmentBinding.PREPEND:
 191                         return extra + ':' + old_value
 192                 else:
 193                         return old_value + ':' + extra
 194
 195         def _toxml(self, doc):
 196                 """Create a DOM element for this binding.
 197                 @param doc: document to use to create the element
 198                 @return: the new element
 199                 """
 200                 env_elem = doc.createElementNS(XMLNS_IFACE, 'environment')
 201                 env_elem.setAttributeNS(None, 'name', self.name)
 202                 env_elem.setAttributeNS(None, 'insert', self.insert)
 203                 if self.default:
 204                         env_elem.setAttributeNS(None, 'default', self.default)
 205                 return env_elem
 206
 207 class Feed(object):
 208         """An interface's feeds are other interfaces whose implementations can also be
 209         used as implementations of this interface."""
 210         __slots__ = ['uri', 'os', 'machine', 'user_override', 'langs']
 211         def __init__(self, uri, arch, user_override, langs = None):
 212                 self.uri = uri
 213                 # This indicates whether the feed comes from the user's overrides
 214                 # file. If true, writer.py will write it when saving.
 215                 self.user_override = user_override
 216                 self.os, self.machine = _split_arch(arch)
 217                 self.langs = langs
 218
 219         def __str__(self):
 220                 return "<Feed from %s>" % self.uri
 221         __repr__ = __str__
 222
 223         arch = property(lambda self: _join_arch(self.os, self.machine))
 224
 225 class Dependency(object):
 226         """A Dependency indicates that an Implementation requires some additional
 227         code to function. This is an abstract base class.
 228         @ivar metadata: any extra attributes from the XML element
 229         @type metadata: {str: str}
 230         """
 231         __slots__ = ['metadata']
 232
 233         def __init__(self, metadata):
 234                 if metadata is None:
 235                         metadata = {}
 236                 else:
 237                         assert not isinstance(metadata, basestring)     # Use InterfaceDependency instead!
 238                 self.metadata = metadata
 239
 240 class InterfaceDependency(Dependency):
 241         """A Dependency on a Zero Install interface.
 242         @ivar interface: the interface required by this dependency
 243         @type interface: str
 244         @ivar restrictions: a list of constraints on acceptable implementations
 245         @type restrictions: [L{Restriction}]
 246         @ivar bindings: how to make the choice of implementation known
 247         @type bindings: [L{Binding}]
 248         @since: 0.28
 249         """
 250         __slots__ = ['interface', 'restrictions', 'bindings', 'metadata']
 251
 252         def __init__(self, interface, restrictions = None, metadata = None):
 253                 Dependency.__init__(self, metadata)
 254                 assert isinstance(interface, (str, unicode))
 255                 assert interface
 256                 self.interface = interface
 257                 if restrictions is None:
 258                         self.restrictions = []
 259                 else:
 260                         self.restrictions = restrictions
 261                 self.bindings = []
 262
 263         def __str__(self):
 264                 return "<Dependency on %s; bindings: %s%s>" % (self.interface, self.bindings, self.restrictions)
 265
 266 class RetrievalMethod(object):
 267         """A RetrievalMethod provides a way to fetch an implementation."""
 268         __slots__ = []
 269
 270 class DownloadSource(RetrievalMethod):
 271         """A DownloadSource provides a way to fetch an implementation."""
 272         __slots__ = ['implementation', 'url', 'size', 'extract', 'start_offset', 'type']
 273
 274         def __init__(self, implementation, url, size, extract, start_offset = 0, type = None):
 275                 assert url.startswith('http:') or url.startswith('ftp:') or url.startswith('/')
 276                 self.implementation = implementation
 277                 self.url = url
 278                 self.size = size
 279                 self.extract = extract
 280                 self.start_offset = start_offset
 281                 self.type = type                # MIME type - see unpack.py
 282
 283 class Recipe(RetrievalMethod):
 284         """Get an implementation by following a series of steps.
 285         @ivar size: the combined download sizes from all the steps
 286         @type size: int
 287         @ivar steps: the sequence of steps which must be performed
 288         @type steps: [L{RetrievalMethod}]"""
 289         __slots__ = ['steps']
 290
 291         def __init__(self):
 292                 self.steps = []
 293
 294         size = property(lambda self: sum([x.size for x in self.steps]))
 295
 296 class Implementation(object):
 297         """An Implementation is a package which implements an Interface.
 298         @ivar download_sources: list of methods of getting this implementation
 299         @type download_sources: [L{RetrievalMethod}]
 300         @ivar feed: the feed owning this implementation (since 0.32)
 301         @type feed: [L{ZeroInstallFeed}]
 302         @ivar bindings: how to tell this component where it itself is located (since 0.31)
 303         @type bindings: [Binding]
 304         """
 305
 306         # Note: user_stability shouldn't really be here
 307
 308         __slots__ = ['upstream_stability', 'user_stability', 'langs',
 309                      'requires', 'main', 'metadata', 'download_sources',
 310                      'id', 'feed', 'version', 'released', 'bindings']
 311
 312         def __init__(self, feed, id):
 313                 assert id
 314                 self.feed = feed
 315                 self.id = id
 316                 self.main = None
 317                 self.user_stability = None
 318                 self.upstream_stability = None
 319                 self.metadata = {}      # [URI + " "] + localName -> value
 320                 self.requires = []
 321                 self.version = None
 322                 self.released = None
 323                 self.download_sources = []
 324                 self.langs = None
 325                 self.bindings = []
 326
 327         def get_stability(self):
 328                 return self.user_stability or self.upstream_stability or testing
 329
 330         def __str__(self):
 331                 return self.id
 332
 333         def __cmp__(self, other):
 334                 """Newer versions come first"""
 335                 return cmp(other.version, self.version)
 336
 337         def get_version(self):
 338                 """Return the version as a string.
 339                 @see: L{format_version}
 340                 """
 341                 return format_version(self.version)
 342
 343         arch = property(lambda self: _join_arch(self.os, self.machine))
 344
 345         os = machine = None
 346
 347 class DistributionImplementation(Implementation):
 348         """An implementation provided by the distribution. Information such as the version
 349         comes from the package manager.
 350         @since: 0.28"""
 351         __slots__ = ['installed']
 352
 353         def __init__(self, feed, id):
 354                 assert id.startswith('package:')
 355                 Implementation.__init__(self, feed, id)
 356                 self.installed = True
 357
 358 class ZeroInstallImplementation(Implementation):
 359         """An implementation where all the information comes from Zero Install.
 360         @since: 0.28"""
 361         __slots__ = ['os', 'machine', 'upstream_stability', 'user_stability',
 362                      'size', 'requires', 'main', 'id']
 363
 364         def __init__(self, feed, id):
 365                 """id can be a local path (string starting with /) or a manifest hash (eg "sha1=XXX")"""
 366                 Implementation.__init__(self, feed, id)
 367                 self.size = None
 368                 self.os = None
 369                 self.machine = None
 370
 371         # Deprecated
 372         dependencies = property(lambda self: dict([(x.interface, x) for x in self.requires
 373                                                    if isinstance(x, InterfaceDependency)]))
 374
 375         def add_download_source(self, url, size, extract, start_offset = 0, type = None):
 376                 """Add a download source."""
 377                 self.download_sources.append(DownloadSource(self, url, size, extract, start_offset, type))
 378
 379         def set_arch(self, arch):
 380                 self.os, self.machine = _split_arch(arch)
 381         arch = property(lambda self: _join_arch(self.os, self.machine), set_arch)
 382
 383 class Interface(object):
 384         """An Interface represents some contract of behaviour.
 385         @ivar uri: the URI for this interface.
 386         @ivar stability_policy: user's configured policy.
 387         Implementations at this level or higher are preferred.
 388         Lower levels are used only if there is no other choice.
 389         """
 390         __slots__ = ['uri', 'stability_policy', '_main_feed', 'extra_feeds']
 391
 392         implementations = property(lambda self: self._main_feed.implementations)
 393         name = property(lambda self: self._main_feed.name)
 394         description = property(lambda self: self._main_feed.description)
 395         summary = property(lambda self: self._main_feed.summary)
 396         last_modified = property(lambda self: self._main_feed.last_modified)
 397         feeds = property(lambda self: self.extra_feeds + self._main_feed.feeds)
 398         metadata = property(lambda self: self._main_feed.metadata)
 399
 400         last_checked = property(lambda self: self._main_feed.last_checked)
 401
 402         def __init__(self, uri):
 403                 assert uri
 404                 if uri.startswith('http:') or uri.startswith('/'):
 405                         self.uri = uri
 406                 else:
 407                         raise SafeException("Interface name '%s' doesn't start "
 408                                             "with 'http:'" % uri)
 409                 self.reset()
 410
 411         def _get_feed_for(self):
 412                 retval = {}
 413                 for key in self._main_feed.feed_for:
 414                         retval[key] = True
 415                 return retval
 416         feed_for = property(_get_feed_for)      # Deprecated (used by 0publish)
 417
 418         def reset(self):
 419                 self.extra_feeds = []
 420                 self._main_feed = _dummy_feed
 421                 self.stability_policy = None
 422
 423         def get_name(self):
 424                 if self._main_feed is not _dummy_feed:
 425                         return self._main_feed.get_name()
 426                 return '(' + os.path.basename(self.uri) + ')'
 427
 428         def __repr__(self):
 429                 return "<Interface %s>" % self.uri
 430
 431         def set_stability_policy(self, new):
 432                 assert new is None or isinstance(new, Stability)
 433                 self.stability_policy = new
 434
 435         def get_feed(self, url):
 436                 for x in self.extra_feeds:
 437                         if x.uri == url:
 438                                 return x
 439                 return self._main_feed.get_feed(url)
 440
 441         def get_metadata(self, uri, name):
 442                 return self._main_feed.get_metadata(uri, name)
 443
 444 def _merge_attrs(attrs, item):
 445         """Add each attribute of item to a copy of attrs and return the copy.
 446         @type attrs: {str: str}
 447         @type item: L{qdom.Element}
 448         @rtype: {str: str}
 449         """
 450         new = attrs.copy()
 451         for a in item.attrs:
 452                 new[str(a)] = item.attrs[a]
 453         return new
 454
 455 def _get_long(elem, attr_name):
 456         val = elem.getAttribute(attr_name)
 457         if val is not None:
 458                 try:
 459                         val = long(val)
 460                 except ValueError, ex:
 461                         raise SafeException("Invalid value for integer attribute '%s': %s" % (attr_name, val))
 462         return val
 463
 464 class ZeroInstallFeed(object):
 465         """A feed lists available implementations of an interface.
 466         @ivar url: the URL for this feed
 467         @ivar implementations: Implementations in this feed, indexed by ID
 468         @type implementations: {str: L{Implementation}}
 469         @ivar name: human-friendly name
 470         @ivar summary: short textual description
 471         @ivar description: long textual description
 472         @ivar last_modified: timestamp on signature
 473         @ivar last_checked: time feed was last successfully downloaded and updated
 474         @ivar feeds: list of <feed> elements in this feed
 475         @type feeds: [L{Feed}]
 476         @ivar feed_for: interfaces for which this could be a feed
 477         @type feed_for: set(str)
 478         @ivar metadata: extra elements we didn't understand
 479         """
 480         # _main is deprecated
 481         __slots__ = ['url', 'implementations', 'name', 'description', 'summary',
 482                      'last_checked', 'last_modified', 'feeds', 'feed_for', 'metadata']
 483
 484         def __init__(self, feed_element, local_path = None, distro = None):
 485                 """Create a feed object from a DOM.
 486                 @param feed_element: the root element of a feed file
 487                 @type feed_element: L{qdom.Element}
 488                 @param interface: temporary hack for restructuring. will go away.
 489                 @param local_name: the pathname of this local feed, or None for remote feeds
 490                 @param distro: used to resolve distribution package references
 491                 @type distro: L{distro.Distribution} or None"""
 492                 assert feed_element
 493                 self.implementations = {}
 494                 self.name = None
 495                 self.summary = None
 496                 self.description = ""
 497                 self.last_modified = None
 498                 self.feeds = []
 499                 self.feed_for = set()
 500                 self.metadata = []
 501                 self.last_checked = None
 502
 503                 assert feed_element.name in ('interface', 'feed'), "Root element should be <interface>, not %s" % feed_element
 504                 assert feed_element.uri == XMLNS_IFACE, "Wrong namespace on root element: %s" % feed_element.uri
 505
 506                 main = feed_element.getAttribute('main')
 507                 #if main: warn("Setting 'main' on the root element is deprecated. Put it on a <group> instead")
 508
 509                 if local_path:
 510                         self.url = local_path
 511                         local_dir = os.path.dirname(local_path)
 512                 else:
 513                         self.url = feed_element.getAttribute('uri')
 514                         if not self.url:
 515                                 raise InvalidInterface("<interface> uri attribute missing")
 516                         local_dir = None        # Can't have relative paths
 517
 518                 min_injector_version = feed_element.getAttribute('min-injector-version')
 519                 if min_injector_version:
 520                         if parse_version(min_injector_version) > parse_version(version):
 521                                 raise InvalidInterface("This feed requires version %s or later of "
 522                                                         "Zero Install, but I am only version %s. "
 523                                                         "You can get a newer version from http://0install.net" %
 524                                                         (min_injector_version, version))
 525
 526                 for x in feed_element.childNodes:
 527                         if x.uri != XMLNS_IFACE:
 528                                 self.metadata.append(x)
 529                                 continue
 530                         if x.name == 'name':
 531                                 self.name = x.content
 532                         elif x.name == 'description':
 533                                 self.description = x.content
 534                         elif x.name == 'summary':
 535                                 self.summary = x.content
 536                         elif x.name == 'feed-for':
 537                                 feed_iface = x.getAttribute('interface')
 538                                 if not feed_iface:
 539                                         raise InvalidInterface('Missing "interface" attribute in <feed-for>')
 540                                 self.feed_for.add(feed_iface)
 541                                 # Bug report from a Debian/stable user that --feed gets the wrong value.
 542                                 # Can't reproduce (even in a Debian/stable chroot), but add some logging here
 543                                 # in case it happens again.
 544                                 debug("Is feed-for %s", feed_iface)
 545                         elif x.name == 'feed':
 546                                 feed_src = x.getAttribute('src')
 547                                 if not feed_src:
 548                                         raise InvalidInterface('Missing "src" attribute in <feed>')
 549                                 if feed_src.startswith('http:') or local_path:
 550                                         self.feeds.append(Feed(feed_src, x.getAttribute('arch'), False, langs = x.getAttribute('langs')))
 551                                 else:
 552                                         raise InvalidInterface("Invalid feed URL '%s'" % feed_src)
 553                         else:
 554                                 self.metadata.append(x)
 555
 556                 if not self.name:
 557                         raise InvalidInterface("Missing <name> in feed")
 558                 if not self.summary:
 559                         raise InvalidInterface("Missing <summary> in feed")
 560
 561                 def process_group(group, group_attrs, base_depends, base_bindings):
 562                         for item in group.childNodes:
 563                                 if item.uri != XMLNS_IFACE: continue
 564
 565                                 if item.name not in ('group', 'implementation', 'package-implementation'):
 566                                         continue
 567
 568                                 depends = base_depends[:]
 569                                 bindings = base_bindings[:]
 570
 571                                 item_attrs = _merge_attrs(group_attrs, item)
 572
 573                                 # We've found a group or implementation. Scan for dependencies
 574                                 # and bindings. Doing this here means that:
 575                                 # - We can share the code for groups and implementations here.
 576                                 # - The order doesn't matter, because these get processed first.
 577                                 # A side-effect is that the document root cannot contain
 578                                 # these.
 579                                 for child in item.childNodes:
 580                                         if child.uri != XMLNS_IFACE: continue
 581                                         if child.name == 'requires':
 582                                                 dep = process_depends(child)
 583                                                 depends.append(dep)
 584                                         elif child.name in binding_names:
 585                                                 bindings.append(process_binding(child))
 586
 587                                 if item.name == 'group':
 588                                         process_group(item, item_attrs, depends, bindings)
 589                                 elif item.name == 'implementation':
 590                                         process_impl(item, item_attrs, depends, bindings)
 591                                 elif item.name == 'package-implementation':
 592                                         process_native_impl(item, item_attrs, depends)
 593                                 else:
 594                                         assert 0
 595
 596                 def process_impl(item, item_attrs, depends, bindings):
 597                         id = item.getAttribute('id')
 598                         if id is None:
 599                                 raise InvalidInterface("Missing 'id' attribute on %s" % item)
 600                         if local_dir and (id.startswith('/') or id.startswith('.')):
 601                                 impl = self._get_impl(os.path.abspath(os.path.join(local_dir, id)))
 602                         else:
 603                                 if '=' not in id:
 604                                         raise InvalidInterface('Invalid "id"; form is "alg=value" (got "%s")' % id)
 605                                 alg, sha1 = id.split('=')
 606                                 try:
 607                                         long(sha1, 16)
 608                                 except Exception, ex:
 609                                         raise InvalidInterface('Bad SHA1 attribute: %s' % ex)
 610                                 impl = self._get_impl(id)
 611
 612                         impl.metadata = item_attrs
 613                         try:
 614                                 version = item_attrs['version']
 615                                 version_mod = item_attrs.get('version-modifier', None)
 616                                 if version_mod: version += version_mod
 617                         except KeyError:
 618                                 raise InvalidInterface("Missing version attribute")
 619                         impl.version = parse_version(version)
 620
 621                         item_main = item_attrs.get('main', None)
 622                         if item_main and item_main.startswith('/'):
 623                                 raise InvalidInterface("'main' attribute must be relative, but '%s' starts with '/'!" %
 624                                                         item_main)
 625                         impl.main = item_main
 626
 627                         impl.released = item_attrs.get('released', None)
 628                         impl.langs = item_attrs.get('langs', None)
 629
 630                         size = item.getAttribute('size')
 631                         if size:
 632                                 impl.size = long(size)
 633                         impl.arch = item_attrs.get('arch', None)
 634                         try:
 635                                 stability = stability_levels[str(item_attrs['stability'])]
 636                         except KeyError:
 637                                 stab = str(item_attrs['stability'])
 638                                 if stab != stab.lower():
 639                                         raise InvalidInterface('Stability "%s" invalid - use lower case!' % item_attrs.stability)
 640                                 raise InvalidInterface('Stability "%s" invalid' % item_attrs['stability'])
 641                         if stability >= preferred:
 642                                 raise InvalidInterface("Upstream can't set stability to preferred!")
 643                         impl.upstream_stability = stability
 644
 645                         impl.bindings = bindings
 646                         impl.requires = depends
 647
 648                         for elem in item.childNodes:
 649                                 if elem.uri != XMLNS_IFACE: continue
 650                                 if elem.name == 'archive':
 651                                         url = elem.getAttribute('href')
 652                                         if not url:
 653                                                 raise InvalidInterface("Missing href attribute on <archive>")
 654                                         size = elem.getAttribute('size')
 655                                         if not size:
 656                                                 raise InvalidInterface("Missing size attribute on <archive>")
 657                                         impl.add_download_source(url = url, size = long(size),
 658                                                         extract = elem.getAttribute('extract'),
 659                                                         start_offset = _get_long(elem, 'start-offset'),
 660                                                         type = elem.getAttribute('type'))
 661                                 elif elem.name == 'recipe':
 662                                         recipe = Recipe()
 663                                         for recipe_step in elem.childNodes:
 664                                                 if recipe_step.uri == XMLNS_IFACE and recipe_step.name == 'archive':
 665                                                         url = recipe_step.getAttribute('href')
 666                                                         if not url:
 667                                                                 raise InvalidInterface("Missing href attribute on <archive>")
 668                                                         size = recipe_step.getAttribute('size')
 669                                                         if not size:
 670                                                                 raise InvalidInterface("Missing size attribute on <archive>")
 671                                                         recipe.steps.append(DownloadSource(None, url = url, size = long(size),
 672                                                                         extract = recipe_step.getAttribute('extract'),
 673                                                                         start_offset = _get_long(recipe_step, 'start-offset'),
 674                                                                         type = recipe_step.getAttribute('type')))
 675                                                 else:
 676                                                         info("Unknown step '%s' in recipe; skipping recipe", recipe_step.name)
 677                                                         break
 678                                         else:
 679                                                 impl.download_sources.append(recipe)
 680
 681                 def process_native_impl(item, item_attrs, depends):
 682                         package = item_attrs.get('package', None)
 683                         if package is None:
 684                                 raise InvalidInterface("Missing 'package' attribute on %s" % item)
 685
 686                         def factory(id):
 687                                 assert id.startswith('package:')
 688                                 impl = self._get_impl(id)
 689
 690                                 impl.metadata = item_attrs
 691
 692                                 item_main = item_attrs.get('main', None)
 693                                 if item_main and not item_main.startswith('/'):
 694                                         raise InvalidInterface("'main' attribute must be absolute, but '%s' doesn't start with '/'!" %
 695                                                                 item_main)
 696                                 impl.main = item_main
 697                                 impl.upstream_stability = packaged
 698                                 impl.requires = depends
 699
 700                                 return impl
 701
 702                         distro.get_package_info(package, factory)
 703
 704                 process_group(feed_element,
 705                         {'stability': 'testing',
 706                          'main' : main,
 707                         },
 708                         [], [])
 709
 710         def get_name(self):
 711                 return self.name or '(' + os.path.basename(self.url) + ')'
 712
 713         def __repr__(self):
 714                 return "<Feed %s>" % self.url
 715
 716         def _get_impl(self, id):
 717                 if id not in self.implementations:
 718                         if id.startswith('package:'):
 719                                 impl = DistributionImplementation(self, id)
 720                         else:
 721                                 impl = ZeroInstallImplementation(self, id)
 722                         self.implementations[id] = impl
 723                 return self.implementations[id]
 724
 725         def set_stability_policy(self, new):
 726                 assert new is None or isinstance(new, Stability)
 727                 self.stability_policy = new
 728
 729         def get_feed(self, url):
 730                 for x in self.feeds:
 731                         if x.uri == url:
 732                                 return x
 733                 return None
 734
 735         def add_metadata(self, elem):
 736                 self.metadata.append(elem)
 737
 738         def get_metadata(self, uri, name):
 739                 """Return a list of interface metadata elements with this name and namespace URI."""
 740                 return [m for m in self.metadata if m.name == name and m.uri == uri]
 741
 742 class DummyFeed(object):
 743         last_modified = None
 744         name = '-'
 745         last_checked = property(lambda self: None)
 746         implementations = property(lambda self: {})
 747         feeds = property(lambda self: [])
 748         summary = property(lambda self: '-')
 749         description = property(lambda self: '')
 750         def get_name(self): return self.name
 751         def get_feed(self, url): return None
 752         def get_metadata(self, uri, name): return []
 753 _dummy_feed = DummyFeed()
 754
 755 def unescape(uri):
 756         """Convert each %20 to a space, etc.
 757         @rtype: str"""
 758         uri = uri.replace('#', '/')
 759         if '%' not in uri: return uri
 760         return re.sub('%[0-9a-fA-F][0-9a-fA-F]',
 761                 lambda match: chr(int(match.group(0)[1:], 16)),
 762                 uri).decode('utf-8')
 763
 764 def escape(uri):
 765         """Convert each space to %20, etc
 766         @rtype: str"""
 767         return re.sub('[^-_.a-zA-Z0-9]',
 768                 lambda match: '%%%02x' % ord(match.group(0)),
 769                 uri.encode('utf-8'))
 770
 771 def _pretty_escape(uri):
 772         """Convert each space to %20, etc
 773         : is preserved and / becomes #. This makes for nicer strings,
 774         and may replace L{escape} everywhere in future.
 775         @rtype: str"""
 776         return re.sub('[^-_.a-zA-Z0-9:/]',
 777                 lambda match: '%%%02x' % ord(match.group(0)),
 778                 uri.encode('utf-8')).replace('/', '#')
 779
 780 def canonical_iface_uri(uri):
 781         """If uri is a relative path, convert to an absolute one.
 782         Otherwise, return it unmodified.
 783         @rtype: str
 784         @raise SafeException: if uri isn't valid
 785         """
 786         if uri.startswith('http:'):
 787                 return uri
 788         else:
 789                 iface_uri = os.path.realpath(uri)
 790                 if os.path.isfile(iface_uri):
 791                         return iface_uri
 792         raise SafeException("Bad interface name '%s'.\n"
 793                         "(doesn't start with 'http:', and "
 794                         "doesn't exist as a local file '%s' either)" %
 795                         (uri, iface_uri))
 796
 797 _version_mod_to_value = {
 798         'pre': -2,
 799         'rc': -1,
 800         '': 0,
 801         'post': 1,
 802 }
 803
 804 # Reverse mapping
 805 _version_value_to_mod = {}
 806 for x in _version_mod_to_value: _version_value_to_mod[_version_mod_to_value[x]] = x
 807 del x
 808
 809 _version_re = re.compile('-([a-z]*)')
 810
 811 def parse_version(version_string):
 812         """Convert a version string to an internal representation.
 813         The parsed format can be compared quickly using the standard Python functions.
 814          - Version := DottedList ("-" Mod DottedList?)*
 815          - DottedList := (Integer ("." Integer)*)
 816         @rtype: tuple (opaque)
 817         @raise SafeException: if the string isn't a valid version
 818         @since: 0.24 (moved from L{reader}, from where it is still available):"""
 819         if version_string is None: return None
 820         parts = _version_re.split(version_string)
 821         if parts[-1] == '':
 822                 del parts[-1]   # Ends with a modifier
 823         else:
 824                 parts.append('')
 825         if not parts:
 826                 raise SafeException("Empty version string!")
 827         l = len(parts)
 828         try:
 829                 for x in range(0, l, 2):
 830                         part = parts[x]
 831                         if part:
 832                                 parts[x] = map(int, parts[x].split('.'))
 833                         else:
 834                                 parts[x] = []   # (because ''.split('.') == [''], not [])
 835                 for x in range(1, l, 2):
 836                         parts[x] = _version_mod_to_value[parts[x]]
 837                 return parts
 838         except ValueError, ex:
 839                 raise SafeException("Invalid version format in '%s': %s" % (version_string, ex))
 840         except KeyError, ex:
 841                 raise SafeException("Invalid version modifier in '%s': %s" % (version_string, ex))
 842
 843 def format_version(version):
 844         """Format a parsed version for display. Undoes the effect of L{parse_version}.
 845         @see: L{Implementation.get_version}
 846         @rtype: str
 847         @since: 0.24"""
 848         version = version[:]
 849         l = len(version)
 850         for x in range(0, l, 2):
 851                 version[x] = '.'.join(map(str, version[x]))
 852         for x in range(1, l, 2):
 853                 version[x] = '-' + _version_value_to_mod[version[x]]
 854         if version[-1] == '-': del version[-1]
 855         return ''.join(version)
 856