AppPkg/Applications/Python/Python-2.7.2/Lib/imputil.py

   1 """
   2 Import utilities
   3
   4 Exported classes:
   5     ImportManager   Manage the import process
   6
   7     Importer        Base class for replacing standard import functions
   8     BuiltinImporter Emulate the import mechanism for builtin and frozen modules
   9
  10     DynLoadSuffixImporter
  11 """
  12 from warnings import warnpy3k
  13 warnpy3k("the imputil module has been removed in Python 3.0", stacklevel=2)
  14 del warnpy3k
  15
  16 # note: avoid importing non-builtin modules
  17 import imp                      ### not available in Jython?
  18 import sys
  19 import __builtin__
  20
  21 # for the DirectoryImporter
  22 import struct
  23 import marshal
  24
  25 __all__ = ["ImportManager","Importer","BuiltinImporter"]
  26
  27 _StringType = type('')
  28 _ModuleType = type(sys)         ### doesn't work in Jython...
  29
  30 class ImportManager:
  31     "Manage the import process."
  32
  33     def install(self, namespace=vars(__builtin__)):
  34         "Install this ImportManager into the specified namespace."
  35
  36         if isinstance(namespace, _ModuleType):
  37             namespace = vars(namespace)
  38
  39         # Note: we have no notion of "chaining"
  40
  41         # Record the previous import hook, then install our own.
  42         self.previous_importer = namespace['__import__']
  43         self.namespace = namespace
  44         namespace['__import__'] = self._import_hook
  45
  46         ### fix this
  47         #namespace['reload'] = self._reload_hook
  48
  49     def uninstall(self):
  50         "Restore the previous import mechanism."
  51         self.namespace['__import__'] = self.previous_importer
  52
  53     def add_suffix(self, suffix, importFunc):
  54         assert hasattr(importFunc, '__call__')
  55         self.fs_imp.add_suffix(suffix, importFunc)
  56
  57     ######################################################################
  58     #
  59     # PRIVATE METHODS
  60     #
  61
  62     clsFilesystemImporter = None
  63
  64     def __init__(self, fs_imp=None):
  65         # we're definitely going to be importing something in the future,
  66         # so let's just load the OS-related facilities.
  67         if not _os_stat:
  68             _os_bootstrap()
  69
  70         # This is the Importer that we use for grabbing stuff from the
  71         # filesystem. It defines one more method (import_from_dir) for our use.
  72         if fs_imp is None:
  73             cls = self.clsFilesystemImporter or _FilesystemImporter
  74             fs_imp = cls()
  75         self.fs_imp = fs_imp
  76
  77         # Initialize the set of suffixes that we recognize and import.
  78         # The default will import dynamic-load modules first, followed by
  79         # .py files (or a .py file's cached bytecode)
  80         for desc in imp.get_suffixes():
  81             if desc[2] == imp.C_EXTENSION:
  82                 self.add_suffix(desc[0],
  83                                 DynLoadSuffixImporter(desc).import_file)
  84         self.add_suffix('.py', py_suffix_importer)
  85
  86     def _import_hook(self, fqname, globals=None, locals=None, fromlist=None):
  87         """Python calls this hook to locate and import a module."""
  88
  89         parts = fqname.split('.')
  90
  91         # determine the context of this import
  92         parent = self._determine_import_context(globals)
  93
  94         # if there is a parent, then its importer should manage this import
  95         if parent:
  96             module = parent.__importer__._do_import(parent, parts, fromlist)
  97             if module:
  98                 return module
  99
 100         # has the top module already been imported?
 101         try:
 102             top_module = sys.modules[parts[0]]
 103         except KeyError:
 104
 105             # look for the topmost module
 106             top_module = self._import_top_module(parts[0])
 107             if not top_module:
 108                 # the topmost module wasn't found at all.
 109                 raise ImportError, 'No module named ' + fqname
 110
 111         # fast-path simple imports
 112         if len(parts) == 1:
 113             if not fromlist:
 114                 return top_module
 115
 116             if not top_module.__dict__.get('__ispkg__'):
 117                 # __ispkg__ isn't defined (the module was not imported by us),
 118                 # or it is zero.
 119                 #
 120                 # In the former case, there is no way that we could import
 121                 # sub-modules that occur in the fromlist (but we can't raise an
 122                 # error because it may just be names) because we don't know how
 123                 # to deal with packages that were imported by other systems.
 124                 #
 125                 # In the latter case (__ispkg__ == 0), there can't be any sub-
 126                 # modules present, so we can just return.
 127                 #
 128                 # In both cases, since len(parts) == 1, the top_module is also
 129                 # the "bottom" which is the defined return when a fromlist
 130                 # exists.
 131                 return top_module
 132
 133         importer = top_module.__dict__.get('__importer__')
 134         if importer:
 135             return importer._finish_import(top_module, parts[1:], fromlist)
 136
 137         # Grrr, some people "import os.path" or do "from os.path import ..."
 138         if len(parts) == 2 and hasattr(top_module, parts[1]):
 139             if fromlist:
 140                 return getattr(top_module, parts[1])
 141             else:
 142                 return top_module
 143
 144         # If the importer does not exist, then we have to bail. A missing
 145         # importer means that something else imported the module, and we have
 146         # no knowledge of how to get sub-modules out of the thing.
 147         raise ImportError, 'No module named ' + fqname
 148
 149     def _determine_import_context(self, globals):
 150         """Returns the context in which a module should be imported.
 151
 152         The context could be a loaded (package) module and the imported module
 153         will be looked for within that package. The context could also be None,
 154         meaning there is no context -- the module should be looked for as a
 155         "top-level" module.
 156         """
 157
 158         if not globals or not globals.get('__importer__'):
 159             # globals does not refer to one of our modules or packages. That
 160             # implies there is no relative import context (as far as we are
 161             # concerned), and it should just pick it off the standard path.
 162             return None
 163
 164         # The globals refer to a module or package of ours. It will define
 165         # the context of the new import. Get the module/package fqname.
 166         parent_fqname = globals['__name__']
 167
 168         # if a package is performing the import, then return itself (imports
 169         # refer to pkg contents)
 170         if globals['__ispkg__']:
 171             parent = sys.modules[parent_fqname]
 172             assert globals is parent.__dict__
 173             return parent
 174
 175         i = parent_fqname.rfind('.')
 176
 177         # a module outside of a package has no particular import context
 178         if i == -1:
 179             return None
 180
 181         # if a module in a package is performing the import, then return the
 182         # package (imports refer to siblings)
 183         parent_fqname = parent_fqname[:i]
 184         parent = sys.modules[parent_fqname]
 185         assert parent.__name__ == parent_fqname
 186         return parent
 187
 188     def _import_top_module(self, name):
 189         # scan sys.path looking for a location in the filesystem that contains
 190         # the module, or an Importer object that can import the module.
 191         for item in sys.path:
 192             if isinstance(item, _StringType):
 193                 module = self.fs_imp.import_from_dir(item, name)
 194             else:
 195                 module = item.import_top(name)
 196             if module:
 197                 return module
 198         return None
 199
 200     def _reload_hook(self, module):
 201         "Python calls this hook to reload a module."
 202
 203         # reloading of a module may or may not be possible (depending on the
 204         # importer), but at least we can validate that it's ours to reload
 205         importer = module.__dict__.get('__importer__')
 206         if not importer:
 207             ### oops. now what...
 208             pass
 209
 210         # okay. it is using the imputil system, and we must delegate it, but
 211         # we don't know what to do (yet)
 212         ### we should blast the module dict and do another get_code(). need to
 213         ### flesh this out and add proper docco...
 214         raise SystemError, "reload not yet implemented"
 215
 216
 217 class Importer:
 218     "Base class for replacing standard import functions."
 219
 220     def import_top(self, name):
 221         "Import a top-level module."
 222         return self._import_one(None, name, name)
 223
 224     ######################################################################
 225     #
 226     # PRIVATE METHODS
 227     #
 228     def _finish_import(self, top, parts, fromlist):
 229         # if "a.b.c" was provided, then load the ".b.c" portion down from
 230         # below the top-level module.
 231         bottom = self._load_tail(top, parts)
 232
 233         # if the form is "import a.b.c", then return "a"
 234         if not fromlist:
 235             # no fromlist: return the top of the import tree
 236             return top
 237
 238         # the top module was imported by self.
 239         #
 240         # this means that the bottom module was also imported by self (just
 241         # now, or in the past and we fetched it from sys.modules).
 242         #
 243         # since we imported/handled the bottom module, this means that we can
 244         # also handle its fromlist (and reliably use __ispkg__).
 245
 246         # if the bottom node is a package, then (potentially) import some
 247         # modules.
 248         #
 249         # note: if it is not a package, then "fromlist" refers to names in
 250         #       the bottom module rather than modules.
 251         # note: for a mix of names and modules in the fromlist, we will
 252         #       import all modules and insert those into the namespace of
 253         #       the package module. Python will pick up all fromlist names
 254         #       from the bottom (package) module; some will be modules that
 255         #       we imported and stored in the namespace, others are expected
 256         #       to be present already.
 257         if bottom.__ispkg__:
 258             self._import_fromlist(bottom, fromlist)
 259
 260         # if the form is "from a.b import c, d" then return "b"
 261         return bottom
 262
 263     def _import_one(self, parent, modname, fqname):
 264         "Import a single module."
 265
 266         # has the module already been imported?
 267         try:
 268             return sys.modules[fqname]
 269         except KeyError:
 270             pass
 271
 272         # load the module's code, or fetch the module itself
 273         result = self.get_code(parent, modname, fqname)
 274         if result is None:
 275             return None
 276
 277         module = self._process_result(result, fqname)
 278
 279         # insert the module into its parent
 280         if parent:
 281             setattr(parent, modname, module)
 282         return module
 283
 284     def _process_result(self, result, fqname):
 285         ispkg, code, values = result
 286         # did get_code() return an actual module? (rather than a code object)
 287         is_module = isinstance(code, _ModuleType)
 288
 289         # use the returned module, or create a new one to exec code into
 290         if is_module:
 291             module = code
 292         else:
 293             module = imp.new_module(fqname)
 294
 295         ### record packages a bit differently??
 296         module.__importer__ = self
 297         module.__ispkg__ = ispkg
 298
 299         # insert additional values into the module (before executing the code)
 300         module.__dict__.update(values)
 301
 302         # the module is almost ready... make it visible
 303         sys.modules[fqname] = module
 304
 305         # execute the code within the module's namespace
 306         if not is_module:
 307             try:
 308                 exec code in module.__dict__
 309             except:
 310                 if fqname in sys.modules:
 311                     del sys.modules[fqname]
 312                 raise
 313
 314         # fetch from sys.modules instead of returning module directly.
 315         # also make module's __name__ agree with fqname, in case
 316         # the "exec code in module.__dict__" played games on us.
 317         module = sys.modules[fqname]
 318         module.__name__ = fqname
 319         return module
 320
 321     def _load_tail(self, m, parts):
 322         """Import the rest of the modules, down from the top-level module.
 323
 324         Returns the last module in the dotted list of modules.
 325         """
 326         for part in parts:
 327             fqname = "%s.%s" % (m.__name__, part)
 328             m = self._import_one(m, part, fqname)
 329             if not m:
 330                 raise ImportError, "No module named " + fqname
 331         return m
 332
 333     def _import_fromlist(self, package, fromlist):
 334         'Import any sub-modules in the "from" list.'
 335
 336         # if '*' is present in the fromlist, then look for the '__all__'
 337         # variable to find additional items (modules) to import.
 338         if '*' in fromlist:
 339             fromlist = list(fromlist) + \
 340                        list(package.__dict__.get('__all__', []))
 341
 342         for sub in fromlist:
 343             # if the name is already present, then don't try to import it (it
 344             # might not be a module!).
 345             if sub != '*' and not hasattr(package, sub):
 346                 subname = "%s.%s" % (package.__name__, sub)
 347                 submod = self._import_one(package, sub, subname)
 348                 if not submod:
 349                     raise ImportError, "cannot import name " + subname
 350
 351     def _do_import(self, parent, parts, fromlist):
 352         """Attempt to import the module relative to parent.
 353
 354         This method is used when the import context specifies that <self>
 355         imported the parent module.
 356         """
 357         top_name = parts[0]
 358         top_fqname = parent.__name__ + '.' + top_name
 359         top_module = self._import_one(parent, top_name, top_fqname)
 360         if not top_module:
 361             # this importer and parent could not find the module (relatively)
 362             return None
 363
 364         return self._finish_import(top_module, parts[1:], fromlist)
 365
 366     ######################################################################
 367     #
 368     # METHODS TO OVERRIDE
 369     #
 370     def get_code(self, parent, modname, fqname):
 371         """Find and retrieve the code for the given module.
 372
 373         parent specifies a parent module to define a context for importing. It
 374         may be None, indicating no particular context for the search.
 375
 376         modname specifies a single module (not dotted) within the parent.
 377
 378         fqname specifies the fully-qualified module name. This is a
 379         (potentially) dotted name from the "root" of the module namespace
 380         down to the modname.
 381         If there is no parent, then modname==fqname.
 382
 383         This method should return None, or a 3-tuple.
 384
 385         * If the module was not found, then None should be returned.
 386
 387         * The first item of the 2- or 3-tuple should be the integer 0 or 1,
 388             specifying whether the module that was found is a package or not.
 389
 390         * The second item is the code object for the module (it will be
 391             executed within the new module's namespace). This item can also
 392             be a fully-loaded module object (e.g. loaded from a shared lib).
 393
 394         * The third item is a dictionary of name/value pairs that will be
 395             inserted into new module before the code object is executed. This
 396             is provided in case the module's code expects certain values (such
 397             as where the module was found). When the second item is a module
 398             object, then these names/values will be inserted *after* the module
 399             has been loaded/initialized.
 400         """
 401         raise RuntimeError, "get_code not implemented"
 402
 403
 404 ######################################################################
 405 #
 406 # Some handy stuff for the Importers
 407 #
 408
 409 # byte-compiled file suffix character
 410 _suffix_char = __debug__ and 'c' or 'o'
 411
 412 # byte-compiled file suffix
 413 _suffix = '.py' + _suffix_char
 414
 415 def _compile(pathname, timestamp):
 416     """Compile (and cache) a Python source file.
 417
 418     The file specified by <pathname> is compiled to a code object and
 419     returned.
 420
 421     Presuming the appropriate privileges exist, the bytecodes will be
 422     saved back to the filesystem for future imports. The source file's
 423     modification timestamp must be provided as a Long value.
 424     """
 425     codestring = open(pathname, 'rU').read()
 426     if codestring and codestring[-1] != '\n':
 427         codestring = codestring + '\n'
 428     code = __builtin__.compile(codestring, pathname, 'exec')
 429
 430     # try to cache the compiled code
 431     try:
 432         f = open(pathname + _suffix_char, 'wb')
 433     except IOError:
 434         pass
 435     else:
 436         f.write('\0\0\0\0')
 437         f.write(struct.pack('<I', timestamp))
 438         marshal.dump(code, f)
 439         f.flush()
 440         f.seek(0, 0)
 441         f.write(imp.get_magic())
 442         f.close()
 443
 444     return code
 445
 446 _os_stat = _os_path_join = None
 447 def _os_bootstrap():
 448     "Set up 'os' module replacement functions for use during import bootstrap."
 449
 450     names = sys.builtin_module_names
 451
 452     join = None
 453     if 'posix' in names:
 454         sep = '/'
 455         from posix import stat
 456     elif 'nt' in names:
 457         sep = '\\'
 458         from nt import stat
 459     elif 'dos' in names:
 460         sep = '\\'
 461         from dos import stat
 462     elif 'os2' in names:
 463         sep = '\\'
 464         from os2 import stat
 465     else:
 466         raise ImportError, 'no os specific module found'
 467
 468     if join is None:
 469         def join(a, b, sep=sep):
 470             if a == '':
 471                 return b
 472             lastchar = a[-1:]
 473             if lastchar == '/' or lastchar == sep:
 474                 return a + b
 475             return a + sep + b
 476
 477     global _os_stat
 478     _os_stat = stat
 479
 480     global _os_path_join
 481     _os_path_join = join
 482
 483 def _os_path_isdir(pathname):
 484     "Local replacement for os.path.isdir()."
 485     try:
 486         s = _os_stat(pathname)
 487     except OSError:
 488         return None
 489     return (s.st_mode & 0170000) == 0040000
 490
 491 def _timestamp(pathname):
 492     "Return the file modification time as a Long."
 493     try:
 494         s = _os_stat(pathname)
 495     except OSError:
 496         return None
 497     return long(s.st_mtime)
 498
 499
 500 ######################################################################
 501 #
 502 # Emulate the import mechanism for builtin and frozen modules
 503 #
 504 class BuiltinImporter(Importer):
 505     def get_code(self, parent, modname, fqname):
 506         if parent:
 507             # these modules definitely do not occur within a package context
 508             return None
 509
 510         # look for the module
 511         if imp.is_builtin(modname):
 512             type = imp.C_BUILTIN
 513         elif imp.is_frozen(modname):
 514             type = imp.PY_FROZEN
 515         else:
 516             # not found
 517             return None
 518
 519         # got it. now load and return it.
 520         module = imp.load_module(modname, None, modname, ('', '', type))
 521         return 0, module, { }
 522
 523
 524 ######################################################################
 525 #
 526 # Internal importer used for importing from the filesystem
 527 #
 528 class _FilesystemImporter(Importer):
 529     def __init__(self):
 530         self.suffixes = [ ]
 531
 532     def add_suffix(self, suffix, importFunc):
 533         assert hasattr(importFunc, '__call__')
 534         self.suffixes.append((suffix, importFunc))
 535
 536     def import_from_dir(self, dir, fqname):
 537         result = self._import_pathname(_os_path_join(dir, fqname), fqname)
 538         if result:
 539             return self._process_result(result, fqname)
 540         return None
 541
 542     def get_code(self, parent, modname, fqname):
 543         # This importer is never used with an empty parent. Its existence is
 544         # private to the ImportManager. The ImportManager uses the
 545         # import_from_dir() method to import top-level modules/packages.
 546         # This method is only used when we look for a module within a package.
 547         assert parent
 548
 549         for submodule_path in parent.__path__:
 550             code = self._import_pathname(_os_path_join(submodule_path, modname), fqname)
 551             if code is not None:
 552                 return code
 553         return self._import_pathname(_os_path_join(parent.__pkgdir__, modname),
 554                                      fqname)
 555
 556     def _import_pathname(self, pathname, fqname):
 557         if _os_path_isdir(pathname):
 558             result = self._import_pathname(_os_path_join(pathname, '__init__'),
 559                                            fqname)
 560             if result:
 561                 values = result[2]
 562                 values['__pkgdir__'] = pathname
 563                 values['__path__'] = [ pathname ]
 564                 return 1, result[1], values
 565             return None
 566
 567         for suffix, importFunc in self.suffixes:
 568             filename = pathname + suffix
 569             try:
 570                 finfo = _os_stat(filename)
 571             except OSError:
 572                 pass
 573             else:
 574                 return importFunc(filename, finfo, fqname)
 575         return None
 576
 577 ######################################################################
 578 #
 579 # SUFFIX-BASED IMPORTERS
 580 #
 581
 582 def py_suffix_importer(filename, finfo, fqname):
 583     file = filename[:-3] + _suffix
 584     t_py = long(finfo[8])
 585     t_pyc = _timestamp(file)
 586
 587     code = None
 588     if t_pyc is not None and t_pyc >= t_py:
 589         f = open(file, 'rb')
 590         if f.read(4) == imp.get_magic():
 591             t = struct.unpack('<I', f.read(4))[0]
 592             if t == t_py:
 593                 code = marshal.load(f)
 594         f.close()
 595     if code is None:
 596         file = filename
 597         code = _compile(file, t_py)
 598
 599     return 0, code, { '__file__' : file }
 600
 601 class DynLoadSuffixImporter:
 602     def __init__(self, desc):
 603         self.desc = desc
 604
 605     def import_file(self, filename, finfo, fqname):
 606         fp = open(filename, self.desc[1])
 607         module = imp.load_module(fqname, fp, filename, self.desc)
 608         module.__file__ = filename
 609         return 0, module, { }
 610
 611
 612 ######################################################################
 613
 614 def _print_importers():
 615     items = sys.modules.items()
 616     items.sort()
 617     for name, module in items:
 618         if module:
 619             print name, module.__dict__.get('__importer__', '-- no importer')
 620         else:
 621             print name, '-- non-existent module'
 622
 623 def _test_revamp():
 624     ImportManager().install()
 625     sys.path.insert(0, BuiltinImporter())
 626
 627 ######################################################################
 628
 629 #
 630 # TODO
 631 #
 632 # from Finn Bock:
 633 #   type(sys) is not a module in Jython. what to use instead?
 634 #   imp.C_EXTENSION is not in Jython. same for get_suffixes and new_module
 635 #
 636 #   given foo.py of:
 637 #      import sys
 638 #      sys.modules['foo'] = sys
 639 #
 640 #   ---- standard import mechanism
 641 #   >>> import foo
 642 #   >>> foo
 643 #   <module 'sys' (built-in)>
 644 #
 645 #   ---- revamped import mechanism
 646 #   >>> import imputil
 647 #   >>> imputil._test_revamp()
 648 #   >>> import foo
 649 #   >>> foo
 650 #   <module 'foo' from 'foo.py'>
 651 #
 652 #
 653 # from MAL:
 654 #   should BuiltinImporter exist in sys.path or hard-wired in ImportManager?
 655 #   need __path__ processing
 656 #   performance
 657 #   move chaining to a subclass [gjs: it's been nuked]
 658 #   deinstall should be possible
 659 #   query mechanism needed: is a specific Importer installed?
 660 #   py/pyc/pyo piping hooks to filter/process these files
 661 #   wish list:
 662 #     distutils importer hooked to list of standard Internet repositories
 663 #     module->file location mapper to speed FS-based imports
 664 #     relative imports
 665 #     keep chaining so that it can play nice with other import hooks
 666 #
 667 # from Gordon:
 668 #   push MAL's mapper into sys.path[0] as a cache (hard-coded for apps)
 669 #
 670 # from Guido:
 671 #   need to change sys.* references for rexec environs
 672 #   need hook for MAL's walk-me-up import strategy, or Tim's absolute strategy
 673 #   watch out for sys.modules[...] is None
 674 #   flag to force absolute imports? (speeds _determine_import_context and
 675 #       checking for a relative module)
 676 #   insert names of archives into sys.path  (see quote below)
 677 #   note: reload does NOT blast module dict
 678 #   shift import mechanisms and policies around; provide for hooks, overrides
 679 #       (see quote below)
 680 #   add get_source stuff
 681 #   get_topcode and get_subcode
 682 #   CRLF handling in _compile
 683 #   race condition in _compile
 684 #   refactoring of os.py to deal with _os_bootstrap problem
 685 #   any special handling to do for importing a module with a SyntaxError?
 686 #       (e.g. clean up the traceback)
 687 #   implement "domain" for path-type functionality using pkg namespace
 688 #       (rather than FS-names like __path__)
 689 #   don't use the word "private"... maybe "internal"
 690 #
 691 #
 692 # Guido's comments on sys.path caching:
 693 #
 694 # We could cache this in a dictionary: the ImportManager can have a
 695 # cache dict mapping pathnames to importer objects, and a separate
 696 # method for coming up with an importer given a pathname that's not yet
 697 # in the cache.  The method should do a stat and/or look at the
 698 # extension to decide which importer class to use; you can register new
 699 # importer classes by registering a suffix or a Boolean function, plus a
 700 # class.  If you register a new importer class, the cache is zapped.
 701 # The cache is independent from sys.path (but maintained per
 702 # ImportManager instance) so that rearrangements of sys.path do the
 703 # right thing.  If a path is dropped from sys.path the corresponding
 704 # cache entry is simply no longer used.
 705 #
 706 # My/Guido's comments on factoring ImportManager and Importer:
 707 #
 708 # > However, we still have a tension occurring here:
 709 # >
 710 # > 1) implementing policy in ImportManager assists in single-point policy
 711 # >    changes for app/rexec situations
 712 # > 2) implementing policy in Importer assists in package-private policy
 713 # >    changes for normal, operating conditions
 714 # >
 715 # > I'll see if I can sort out a way to do this. Maybe the Importer class will
 716 # > implement the methods (which can be overridden to change policy) by
 717 # > delegating to ImportManager.
 718 #
 719 # Maybe also think about what kind of policies an Importer would be
 720 # likely to want to change.  I have a feeling that a lot of the code
 721 # there is actually not so much policy but a *necessity* to get things
 722 # working given the calling conventions for the __import__ hook: whether
 723 # to return the head or tail of a dotted name, or when to do the "finish
 724 # fromlist" stuff.
 725 #