src/third_party/pyelftools/elftools/common/construct_utils.py

   1 #-------------------------------------------------------------------------------
   2 # elftools: common/construct_utils.py
   3 #
   4 # Some complementary construct utilities
   5 #
   6 # Eli Bendersky (eliben@gmail.com)
   7 # This code is in the public domain
   8 #-------------------------------------------------------------------------------
   9 from ..construct import Subconstruct, ConstructError, ArrayError
  10
  11
  12 class RepeatUntilExcluding(Subconstruct):
  13     """ A version of construct's RepeatUntil that doesn't include the last
  14         element (which casued the repeat to exit) in the return value.
  15
  16         Only parsing is currently implemented.
  17
  18         P.S. removed some code duplication
  19     """
  20     __slots__ = ["predicate"]
  21     def __init__(self, predicate, subcon):
  22         Subconstruct.__init__(self, subcon)
  23         self.predicate = predicate
  24         self._clear_flag(self.FLAG_COPY_CONTEXT)
  25         self._set_flag(self.FLAG_DYNAMIC)
  26     def _parse(self, stream, context):
  27         obj = []
  28         try:
  29             context_for_subcon = context
  30             if self.subcon.conflags & self.FLAG_COPY_CONTEXT:
  31                 context_for_subcon = context.__copy__()
  32
  33             while True:
  34                 subobj = self.subcon._parse(stream, context_for_subcon)
  35                 if self.predicate(subobj, context):
  36                     break
  37                 obj.append(subobj)
  38         except ConstructError as ex:
  39             raise ArrayError("missing terminator", ex)
  40         return obj
  41     def _build(self, obj, stream, context):
  42         raise NotImplementedError('no building')
  43     def _sizeof(self, context):
  44         raise SizeofError("can't calculate size")
  45