elftools/dwarf/abbrevtable.py

   1 #-------------------------------------------------------------------------------
   2 # elftools: dwarf/abbrevtable.py
   3 #
   4 # DWARF abbreviation table
   5 #
   6 # Eli Bendersky (eliben@gmail.com)
   7 # This code is in the public domain
   8 #-------------------------------------------------------------------------------
   9 from ..common.utils import struct_parse, dwarf_assert
  10
  11
  12 class AbbrevTable(object):
  13     """ Represents a DWARF abbreviation table.
  14     """
  15     def __init__(self, structs, stream, offset):
  16         """ Create new abbreviation table. Parses the actual table from the
  17             stream and stores it internally.
  18
  19             structs:
  20                 A DWARFStructs instance for parsing the data
  21
  22             stream, offset:
  23                 The stream and offset into the stream where this abbreviation
  24                 table lives.
  25         """
  26         self.structs = structs
  27         self.stream = stream
  28         self.offset = offset
  29
  30         self._abbrev_map = self._parse_abbrev_table()
  31
  32     def get_abbrev(self, code):
  33         """ Get the AbbrevDecl for a given code. Raise KeyError if no
  34             declaration for this code exists.
  35         """
  36         return AbbrevDecl(code, self._abbrev_map[code])
  37
  38     def _parse_abbrev_table(self):
  39         """ Parse the abbrev table from the stream
  40         """
  41         map = {}
  42         self.stream.seek(self.offset)
  43         while True:
  44             decl_code = struct_parse(
  45                 struct=self.structs.Dwarf_uleb128(''),
  46                 stream=self.stream)
  47             if decl_code == 0:
  48                 break
  49             declaration = struct_parse(
  50                 struct=self.structs.Dwarf_abbrev_declaration,
  51                 stream=self.stream)
  52             map[decl_code] = declaration
  53         return map
  54
  55
  56 class AbbrevDecl(object):
  57     """ Wraps a parsed abbreviation declaration, exposing its fields with
  58         dict-like access, and adding some convenience methods.
  59
  60         The abbreviation declaration represents an "entry" that points to it.
  61     """
  62     def __init__(self, code, decl):
  63         self.code = code
  64         self.decl = decl
  65
  66     def has_children(self):
  67         """ Does the entry have children?
  68         """
  69         return self['children_flag'] == 'DW_CHILDREN_yes'
  70
  71     def iter_attr_specs(self):
  72         """ Iterate over the attribute specifications for the entry. Yield
  73             (name, form) pairs.
  74         """
  75         for attr_spec in self['attr_spec']:
  76             yield attr_spec.name, attr_spec.form
  77
  78     def __getitem__(self, entry):
  79         return self.decl[entry]
  80