src/python/importer.py

   1 # Copyright (c) 2008 The Hewlett-Packard Development Company
   2 # All rights reserved.
   3 #
   4 # Redistribution and use in source and binary forms, with or without
   5 # modification, are permitted provided that the following conditions are
   6 # met: redistributions of source code must retain the above copyright
   7 # notice, this list of conditions and the following disclaimer;
   8 # redistributions in binary form must reproduce the above copyright
   9 # notice, this list of conditions and the following disclaimer in the
  10 # documentation and/or other materials provided with the distribution;
  11 # neither the name of the copyright holders nor the names of its
  12 # contributors may be used to endorse or promote products derived from
  13 # this software without specific prior written permission.
  14 #
  15 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  16 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  17 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  18 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  19 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  20 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  21 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  25 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26
  27 # Simple importer that allows python to import data from a dict of
  28 # code objects.  The keys are the module path, and the items are the
  29 # filename and bytecode of the file.
  30 class CodeImporter(object):
  31     def __init__(self):
  32         self.modules = {}
  33
  34     def add_module(self, filename, abspath, modpath, code):
  35         if modpath in self.modules:
  36             raise AttributeError("%s already found in importer" % modpath)
  37
  38         self.modules[modpath] = (filename, abspath, code)
  39
  40     def find_module(self, fullname, path):
  41         if fullname in self.modules:
  42             return self
  43
  44         return None
  45
  46     def load_module(self, fullname):
  47         # Because the importer is created and initialized in its own
  48         # little sandbox (in init.cc), the globals that were available
  49         # when the importer module was loaded and CodeImporter was
  50         # defined are not available when load_module is actually
  51         # called. Soooo, the imports must live here.
  52         import imp
  53         import os
  54         import sys
  55
  56         try:
  57             mod = sys.modules[fullname]
  58         except KeyError:
  59             mod = imp.new_module(fullname)
  60             sys.modules[fullname] = mod
  61
  62         try:
  63             mod.__loader__ = self
  64             srcfile,abspath,code = self.modules[fullname]
  65
  66             override = os.environ.get('M5_OVERRIDE_PY_SOURCE', 'false').lower()
  67             if override in ('true', 'yes') and  os.path.exists(abspath):
  68                 src = open(abspath, 'r').read()
  69                 code = compile(src, abspath, 'exec')
  70
  71             if os.path.basename(srcfile) == '__init__.py':
  72                 mod.__path__ = fullname.split('.')
  73                 mod.__package__ = fullname
  74             else:
  75                 mod.__package__ = fullname.rpartition('.')[0]
  76             mod.__file__ = srcfile
  77
  78             exec(code, mod.__dict__)
  79         except Exception:
  80             del sys.modules[fullname]
  81             raise
  82
  83         return mod
  84
  85 # Create an importer and add it to the meta_path so future imports can
  86 # use it.  There's currently nothing in the importer, but calls to
  87 # add_module can be used to add code.
  88 import sys
  89 importer = CodeImporter()
  90 add_module = importer.add_module
  91 sys.meta_path.append(importer)