lldb/examples/synthetic/recognizer_function/example.py

   1 # Formatters for classes that derive from Message.
   2 #
   3 # Usage:
   4 #   command script import ./example.py
   5 #   type summary add --expand --recognizer-function --python-function example.message_summary example.is_message_type
   6 #   type synth add --recognizer-function --python-class example.MessageChildProvider example.is_message_type
   7
   8 import sys
   9
  10
  11 def is_message_type(t, internal_dict):
  12     for base in t.get_bases_array():
  13         if base.GetName() == "Message":
  14             return True
  15     return False
  16
  17
  18 def message_summary(value, internal_dict):
  19     # Could have used a summary string as well. All the work is done by the child
  20     # provider.
  21     return "Message"
  22
  23
  24 class MessageChildProvider:
  25     def __init__(self, value, internal_dict):
  26         self.value = value
  27         self.synthetic_children = self._analyze_children(value)
  28
  29     def has_children(self):
  30         return self.num_children() > 0
  31
  32     def num_children(self):
  33         return len(self.synthetic_children)
  34
  35     def get_child_index(self, name):
  36         for index, child in enumerate(self.synthetic_children):
  37             if child.GetName() == name:
  38                 return index
  39         return None
  40
  41     def get_child_at_index(self, index):
  42         return self.synthetic_children[index]
  43
  44     def _rename_sbvalue(self, value):
  45         # We want to display the field with its original name without a trailing
  46         # underscore. So we create a new SBValue with the same type and address but
  47         # a different name.
  48         name = value.GetName()
  49         assert name.endswith("_")
  50         new_name = name[:-1]
  51         return value.CreateValueFromAddress(
  52             new_name, value.GetLoadAddress(), value.GetType()
  53         )
  54
  55     def _analyze_children(self, value):
  56         result = []
  57         for i in range(value.GetNumChildren()):
  58             child = value.GetChildAtIndex(i)
  59             child_name = child.GetName()
  60             if child_name.startswith("_"):
  61                 continue  # Internal field, skip
  62             # Normal field. Check presence bit.
  63             presence_bit = value.GetChildMemberWithName("_has_" + child_name)
  64             if presence_bit.GetValueAsUnsigned() != 0:
  65                 result.append(self._rename_sbvalue(child))
  66         return result