Changeset 8a0c67f for fedd/compose.py

Timestamp:

May 19, 2010 4:16:56 AM (14 years ago)

Author:

Ted Faber <faber@…>

Branches:

axis_example, compt_changes, info-ops, master, version-3.01, version-3.02

Children:

7ee16b3

Parents:

89e2138

Message:

comments

File:

• fedd/compose.py (modified) (6 diffs)

fedd/compose.py

@@ -16 +16 @@
 class constraint:
     """
-    This is just a struct to hold constraint fields, really
+    This is mainly a struct to hold constraint fields and convert to XML output
     """
     def __init__(self, name=None, required=False, accepts=None, provides=None,
@@ -44 +44 @@
 def constraints_from_xml(string=None, file=None, filename=None, 
         top="constraints"):
+    """
+    Pull constraints from an xml file.  Only constraints in the top element are
+    recognized.  A constraint consists of a constraint element with one name,
+    one required, and multiple accepts nd provides elements.  Each contains a
+    string.  A list of constraints is returned.
+    """
     class parser:
+        """
+        A little class to encapsulate some state used to parse the constraints.
+        The methods are all bound to the analogous handlers in an XML parser.
+        It collects the constraints in self.constraint.
+        """
         def __init__(self, top):
             self.top = top
@@ -53 +64 @@
         
         def start_element(self, name, attrs):
+            # Clear any collected strings (from inside elements)
             self.chars = None
             self.key = str(name)
-
+            
+            # See if we've entered the containing context
             if name == self.top:
                 self.in_top = True
 
+            # Entering a constraint, create the object which also acts as a
+            # flag to indicate we're collecting constraint data.
             if self.in_top:
                 if name == 'constraint':
@@ -65 +80 @@
         def end_element(self, name):
             if self.current:
+                # In a constraint and leaving an element.  Clean up any string
+                # we've collected and process elements we know.
                 if self.chars is not None:
                     self.chars = self.chars.strip()
@@ -80 +97 @@
                     self.current.provides.append(self.chars)
                 elif name == 'constraint':
+                    # Leaving this constraint.  Record it and clear the flag
                     self.constraints.append(self.current)
                     self.current = None
@@ -86 +104 @@
                             "Unexpected element in constraint: %s" % name
             elif name == self.top:
+                # We've left the containing context
                 self.in_top = False
 
 
         def char_data(self, data):
+            # Collect strings if we're in the overall context
             if self.in_top:
                 if self.chars is None: self.chars = data
                 else: self.chars += data
 
+    # Beginning of constraints_from_xml.  Connect up the parser and call it
+    # properly for the kind of input supplied.
     p = parser(top=top)
     xp = xml.parsers.expat.ParserCreate()