Added boto/ to depot_tools/third_party

third_party/boto/plugin.py

+# Copyright 2010 Google Inc.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish, dis-
+# tribute, sublicense, and/or sell copies of the Software, and to permit
+# persons to whom the Software is furnished to do so, subject to the fol-
+# lowing conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
+# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
+# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+# IN THE SOFTWARE.
+
+
+"""
+Implements plugin related api.
+
+To define a new plugin just subclass Plugin, like this.
+
+class AuthPlugin(Plugin):
+  pass
+
+Then start creating subclasses of your new plugin.
+
+class MyFancyAuth(AuthPlugin):
+  capability = ['sign', 'vmac'] 
+
+The actual interface is duck typed.
+ 
+"""
+
+import glob
+import imp, os.path
+
+class Plugin(object):
+    """Base class for all plugins."""
+
+    capability = []
+
+    @classmethod
+    def is_capable(cls, requested_capability):
+        """Returns true if the requested capability is supported by this plugin
+        """
+        for c in requested_capability:
+            if not c in cls.capability:
+                return False
+        return True
+
+def get_plugin(cls, requested_capability=None):
+    if not requested_capability:
+        requested_capability = []
+    result = []
+    for handler in cls.__subclasses__():
+        if handler.is_capable(requested_capability):
+            result.append(handler)
+    return result
+
+def _import_module(filename):
+    (path, name) = os.path.split(filename)
+    (name, ext) = os.path.splitext(name)
+
+    (file, filename, data) = imp.find_module(name, [path])
+    try:
+      return imp.load_module(name, file, filename, data)
+    finally:
+      if file:
+        file.close()
+
+_plugin_loaded = False 
+
+def load_plugins(config):
+    global _plugin_loaded
+    if _plugin_loaded:
+        return
+    _plugin_loaded = True
+
+    if not config.has_option('Plugin', 'plugin_directory'):
+        return
+    directory = config.get('Plugin', 'plugin_directory')
+    for file in glob.glob(os.path.join(directory, '*.py')):
+        _import_module(file)
+