diff --git a/Lib/pkgutil.py b/Lib/pkgutil.py
index fbd708a..7316892 100644
--- a/Lib/pkgutil.py
+++ b/Lib/pkgutil.py
@@ -1,7 +1,432 @@
 """Utilities to support packages."""
 
+# NOTE: This module must remain compatible with Python 2.3, as it is shared
+# by setuptools for distribution with Python 2.3 and up.
+
 import os
 import sys
+import imp
+import os.path
+from types import ModuleType
+
+__all__ = [
+    'get_importer', 'iter_importers', 'get_loader', 'find_loader',
+    'walk_packages', 'iter_modules',
+    'ImpImporter', 'ImpLoader', 'read_code', 'extend_path',
+]
+
+def read_code(stream):
+    # This helper is needed in order for the PEP 302 emulation to
+    # correctly handle compiled files
+    import marshal
+
+    magic = stream.read(4)
+    if magic != imp.get_magic():
+        return None
+
+    stream.read(4) # Skip timestamp
+    return marshal.load(stream)
+
+
+def simplegeneric(func):
+    """Make a trivial single-dispatch generic function"""
+    registry = {}
+    def wrapper(*args,**kw):
+        ob = args[0]
+        try:
+            cls = ob.__class__
+        except AttributeError:
+            cls = type(ob)
+        try:
+            mro = cls.__mro__
+        except AttributeError:
+            try:
+                class cls(cls,object): pass
+                mro = cls.__mro__[1:]
+            except TypeError:
+                mro = object,   # must be an ExtensionClass or some such  :(
+        for t in mro:
+            if t in registry:
+                return registry[t](*args,**kw)
+        else:
+            return func(*args,**kw)
+    try:
+        wrapper.__name__ = func.__name__
+    except (TypeError,AttributeError):
+        pass    # Python 2.3 doesn't allow functions to be renamed
+
+    def register(typ, func=None):
+        if func is None:
+            return lambda f: register(typ, f)
+        registry[typ] = func
+        return func
+
+    wrapper.__dict__ = func.__dict__
+    wrapper.__doc__ = func.__doc__
+    wrapper.register = register
+    return wrapper
+
+
+def walk_packages(path=None, prefix='', onerror=None):
+    """Yield submodule names+loaders recursively, for path or sys.path"""
+
+    def seen(p,m={}):
+        if p in m: return True
+        m[p] = True
+
+    for importer, name, ispkg in iter_modules(path, prefix):
+        yield importer, name, ispkg
+
+        if ispkg:
+            try:
+                __import__(name)
+            except ImportError:
+                if onerror is not None:
+                    onerror()
+            else:
+                path = getattr(sys.modules[name], '__path__', None) or []
+
+                # don't traverse path items we've seen before
+                path = [p for p in path if not seen(p)]
+
+                for item in walk_packages(path, name+'.'):
+                    yield item
+
+
+def iter_modules(path=None, prefix=''):
+    """Yield submodule names+loaders for path or sys.path"""
+    if path is None:
+        importers = iter_importers()
+    else:
+        importers = map(get_importer, path)
+
+    yielded = {}
+    for i in importers:
+        for name, ispkg in iter_importer_modules(i, prefix):
+            if name not in yielded:
+                yielded[name] = 1
+                yield i, name, ispkg
+
+
+#@simplegeneric
+def iter_importer_modules(importer, prefix=''):
+    if not hasattr(importer,'iter_modules'):
+        return []
+    return importer.iter_modules(prefix)
+
+iter_importer_modules = simplegeneric(iter_importer_modules)
+
+
+class ImpImporter:
+    """PEP 302 Importer that wraps Python's "classic" import algorithm
+
+    ImpImporter(dirname) produces a PEP 302 importer that searches that
+    directory.  ImpImporter(None) produces a PEP 302 importer that searches
+    the current sys.path, plus any modules that are frozen or built-in.
+
+    Note that ImpImporter does not currently support being used by placement
+    on sys.meta_path.
+    """
+
+    def __init__(self, path=None):
+        self.path = path
+
+    def find_module(self, fullname, path=None):
+        # Note: we ignore 'path' argument since it is only used via meta_path
+        subname = fullname.split(".")[-1]
+        if subname != fullname and self.path is None:
+            return None
+        if self.path is None:
+            path = None
+        else:
+            path = [os.path.realpath(self.path)]
+        try:
+            file, filename, etc = imp.find_module(subname, path)
+        except ImportError:
+            return None
+        return ImpLoader(fullname, file, filename, etc)
+
+    def iter_modules(self, prefix=''):
+        if self.path is None or not os.path.isdir(self.path):
+            return
+
+        yielded = {}
+        import inspect
+
+        filenames = os.listdir(self.path)
+        filenames.sort()  # handle packages before same-named modules
+
+        for fn in filenames:
+            modname = inspect.getmodulename(fn)
+            if modname=='__init__' or modname in yielded:
+                continue
+
+            path = os.path.join(self.path, fn)
+            ispkg = False
+
+            if not modname and os.path.isdir(path) and '.' not in fn:
+                modname = fn
+                for fn in os.listdir(path):
+                    subname = inspect.getmodulename(fn)
+                    if subname=='__init__':
+                        ispkg = True
+                        break
+                else:
+                    continue    # not a package
+
+            if modname and '.' not in modname:
+                yielded[modname] = 1
+                yield prefix + modname, ispkg
+
+
+class ImpLoader:
+    """PEP 302 Loader that wraps Python's "classic" import algorithm
+    """
+    code = source = None
+
+    def __init__(self, fullname, file, filename, etc):
+        self.file = file
+        self.filename = filename
+        self.fullname = fullname
+        self.etc = etc
+
+    def load_module(self, fullname):
+        self._reopen()
+        try:
+            mod = imp.load_module(fullname, self.file, self.filename, self.etc)
+        finally:
+            if self.file:
+                self.file.close()
+        # Note: we don't set __loader__ because we want the module to look
+        # normal; i.e. this is just a wrapper for standard import machinery
+        return mod
+
+    def get_data(self, pathname):
+        return open(pathname, "rb").read()
+
+    def _reopen(self):
+        if self.file and self.file.closed:
+            if mod_type==imp.PY_SOURCE:
+                self.file = open(self.filename, 'rU')
+            elif mod_type in (imp.PY_COMPILED, imp.C_EXTENSION):
+                self.file = open(self.filename, 'rb')
+
+    def _fix_name(self, fullname):
+        if fullname is None:
+            fullname = self.fullname
+        elif fullname != self.fullname:
+            raise ImportError("Loader for module %s cannot handle "
+                              "module %s" % (self.fullname, fullname))
+        return fullname
+
+    def is_package(self, fullname):
+        fullname = self._fix_name(fullname)
+        return self.etc[2]==imp.PKG_DIRECTORY
+
+    def get_code(self, fullname=None):
+        fullname = self._fix_name(fullname)
+        if self.code is None:
+            mod_type = self.etc[2]
+            if mod_type==imp.PY_SOURCE:
+                source = self.get_source(fullname)
+                self.code = compile(source, self.filename, 'exec')
+            elif mod_type==imp.PY_COMPILED:
+                self._reopen()
+                try:
+                    self.code = read_code(self.file)
+                finally:
+                    self.file.close()
+            elif mod_type==imp.PKG_DIRECTORY:
+                self.code = self._get_delegate().get_code()
+        return self.code
+
+    def get_source(self, fullname=None):
+        fullname = self._fix_name(fullname)
+        if self.source is None:
+            mod_type = self.etc[2]
+            if mod_type==imp.PY_SOURCE:
+                self._reopen()
+                try:
+                    self.source = self.file.read()
+                finally:
+                    self.file.close()
+            elif mod_type==imp.PY_COMPILED:
+                if os.path.exists(self.filename[:-1]):
+                    f = open(self.filename[:-1], 'rU')
+                    self.source = f.read()
+                    f.close()
+            elif mod_type==imp.PKG_DIRECTORY:
+                self.source = self._get_delegate().get_source()
+        return self.source
+
+
+    def _get_delegate(self):
+        return ImpImporter(self.filename).find_module('__init__')
+
+    def get_filename(self, fullname=None):
+        fullname = self._fix_name(fullname)
+        mod_type = self.etc[2]
+        if self.etc[2]==imp.PKG_DIRECTORY:
+            return self._get_delegate().get_filename()
+        elif self.etc[2] in (imp.PY_SOURCE, imp.PY_COMPILED, imp.C_EXTENSION):
+            return self.filename
+        return None
+
+
+try:
+    import zipimport
+    from zipimport import zipimporter
+
+    def iter_zipimport_modules(importer, prefix=''):
+        dirlist = zipimport._zip_directory_cache[importer.archive].keys()
+        dirlist.sort()
+        _prefix = importer.prefix
+        plen = len(_prefix)
+        yielded = {}
+        import inspect
+        for fn in dirlist:
+            if not fn.startswith(_prefix):
+                continue
+
+            fn = fn[plen:].split(os.sep)
+
+            if len(fn)==2 and fn[1].startswith('__init__.py'):
+                if fn[0] not in yielded:
+                    yielded[fn[0]] = 1
+                    yield fn[0], True
+
+            if len(fn)!=1:
+                continue
+
+            modname = inspect.getmodulename(fn[0])
+            if modname=='__init__':
+                continue
+
+            if modname and '.' not in modname and modname not in yielded:
+                yielded[modname] = 1
+                yield prefix + modname, False
+
+    iter_importer_modules.register(zipimporter, iter_zipimport_modules)
+
+except ImportError:
+    pass
+
+
+def get_importer(path_item):
+    """Retrieve a PEP 302 importer for the given path item
+
+    The returned importer is cached in sys.path_importer_cache
+    if it was newly created by a path hook.
+
+    If there is no importer, a wrapper around the basic import
+    machinery is returned. This wrapper is never inserted into
+    the importer cache (None is inserted instead).
+
+    The cache (or part of it) can be cleared manually if a
+    rescan of sys.path_hooks is necessary.
+    """
+    try:
+        importer = sys.path_importer_cache[path_item]
+    except KeyError:
+        for path_hook in sys.path_hooks:
+            try:
+                importer = path_hook(path_item)
+                break
+            except ImportError:
+                pass
+        else:
+            importer = None
+        sys.path_importer_cache.setdefault(path_item,importer)
+
+    if importer is None:
+        try:
+            importer = ImpImporter(path_item)
+        except ImportError:
+            pass
+    return importer
+
+
+def iter_importers(fullname=""):
+    """Yield PEP 302 importers for the given module name
+
+    If fullname contains a '.', the importers will be for the package
+    containing fullname, otherwise they will be importers for sys.meta_path,
+    sys.path, and Python's "classic" import machinery, in that order.  If
+    the named module is in a package, that package is imported as a side
+    effect of invoking this function.
+
+    Non PEP 302 mechanisms (e.g. the Windows registry) used by the
+    standard import machinery to find files in alternative locations
+    are partially supported, but are searched AFTER sys.path. Normally,
+    these locations are searched BEFORE sys.path, preventing sys.path
+    entries from shadowing them.
+
+    For this to cause a visible difference in behaviour, there must
+    be a module or package name that is accessible via both sys.path
+    and one of the non PEP 302 file system mechanisms. In this case,
+    the emulation will find the former version, while the builtin
+    import mechanism will find the latter.
+
+    Items of the following types can be affected by this discrepancy:
+        imp.C_EXTENSION, imp.PY_SOURCE, imp.PY_COMPILED, imp.PKG_DIRECTORY
+    """
+    if fullname.startswith('.'):
+        raise ImportError("Relative module names not supported")
+    if '.' in fullname:
+        # Get the containing package's __path__
+        pkg = '.'.join(fullname.split('.')[:-1])
+        if pkg not in sys.modules:
+            __import__(pkg)
+        path = getattr(sys.modules[pkg],'__path__',None) or []
+    else:
+        for importer in sys.meta_path:
+            yield importer
+        path = sys.path
+    for item in path:
+        yield get_importer(item)
+    if '.' not in fullname:
+        yield ImpImporter()
+
+def get_loader(module_or_name):
+    """Get a PEP 302 "loader" object for module_or_name
+
+    If the module or package is accessible via the normal import
+    mechanism, a wrapper around the relevant part of that machinery
+    is returned.  Returns None if the module cannot be found or imported.
+    If the named module is not already imported, its containing package
+    (if any) is imported, in order to establish the package __path__.
+
+    This function uses iter_importers(), and is thus subject to the same
+    limitations regarding platform-specific special import locations such
+    as the Windows registry.
+    """
+    if module_or_name in sys.modules:
+        module_or_name = sys.modules[module_or_name]
+    if isinstance(module_or_name, ModuleType):
+        module = module_or_name
+        loader = getattr(module,'__loader__',None)
+        if loader is not None:
+            return loader
+        fullname = module.__name__
+    else:
+        fullname = module_or_name
+    return find_loader(fullname)
+
+def find_loader(fullname):
+    """Find a PEP 302 "loader" object for fullname
+
+    If fullname contains dots, path must be the containing package's __path__.
+    Returns None if the module cannot be found or imported. This function uses
+    iter_importers(), and is thus subject to the same limitations regarding
+    platform-specific special import locations such as the Windows registry.
+    """
+    for importer in iter_importers(fullname):
+        loader = importer.find_module(fullname)
+        if loader is not None:
+            return loader
+
+    return None
+
 
 def extend_path(path, name):
     """Extend a package's path.