ctx is safe to use as immutable

[pyderasn.git] / pyderasn.py

diff --git a/pyderasn.py b/pyderasn.py
index aa91b04052c100a8ba6dfc102cd840dcfce64c4a..4142af690d616b316ac46494dfde8857fcb25a02 100755 (executable)
--- a/pyderasn.py
+++ b/pyderasn.py
@@ -539,6 +539,7 @@ from codecs import getdecoder
 from codecs import getencoder
 from collections import namedtuple
 from collections import OrderedDict
+from copy import copy
 from datetime import datetime
 from math import ceil
 from os import environ
@@ -646,6 +647,7 @@ LENINDEF_PP_CHAR = "I" if PY2 else "∞"
 class ASN1Error(ValueError):
     pass
 
+
 class DecodeError(ASN1Error):
     def __init__(self, msg="", klass=None, decode_path=(), offset=0):
         """
@@ -1027,6 +1029,7 @@ class Obj(object):
             decode_path=(),
             ctx=None,
             tag_only=False,
+            _ctx_immutable=True,
     ):
         """Decode the data
 
@@ -1038,10 +1041,13 @@ class Obj(object):
         :param tag_only: decode only the tag, without length and contents
                          (used only in Choice and Set structures, trying to
                          determine if tag satisfies the scheme)
+        :param _ctx_immutable: do we need to copy ``ctx`` before using it
         :returns: (Obj, remaining data)
         """
         if ctx is None:
             ctx = {}
+        elif _ctx_immutable:
+            ctx = copy(ctx)
         tlv = memoryview(data)
         if self._expl is None:
             result = self._decode(
@@ -2387,6 +2393,7 @@ class BitString(Obj):
                         decode_path=sub_decode_path,
                         leavemm=True,
                         ctx=ctx,
+                        _ctx_immutable=False,
                     )
                 except TagMismatch:
                     raise DecodeError(
@@ -2751,6 +2758,7 @@ class OctetString(Obj):
                         decode_path=sub_decode_path,
                         leavemm=True,
                         ctx=ctx,
+                        _ctx_immutable=False,
                     )
                 except TagMismatch:
                     raise DecodeError(
@@ -4007,6 +4015,7 @@ class Choice(Obj):
                     decode_path=sub_decode_path,
                     ctx=ctx,
                     tag_only=True,
+                    _ctx_immutable=False,
                 )
             except TagMismatch:
                 continue
@@ -4025,6 +4034,7 @@ class Choice(Obj):
             leavemm=True,
             decode_path=sub_decode_path,
             ctx=ctx,
+            _ctx_immutable=False,
         )
         obj = self.__class__(
             schema=self.specs,
@@ -4226,6 +4236,7 @@ class Any(Obj):
                     decode_path=decode_path + (str(chunk_i),),
                     leavemm=True,
                     ctx=ctx,
+                    _ctx_immutable=False,
                 )
                 vlen += chunk.tlvlen
                 sub_offset += chunk.tlvlen
@@ -4641,6 +4652,7 @@ class Sequence(Obj):
                     leavemm=True,
                     decode_path=sub_decode_path,
                     ctx=ctx,
+                    _ctx_immutable=False,
                 )
             except TagMismatch:
                 if spec.optional:
@@ -4665,6 +4677,7 @@ class Sequence(Obj):
                             leavemm=True,
                             decode_path=sub_sub_decode_path,
                             ctx=ctx,
+                            _ctx_immutable=False,
                         )
                         if len(defined_tail) > 0:
                             raise DecodeError(
@@ -4684,6 +4697,7 @@ class Sequence(Obj):
                         leavemm=True,
                         decode_path=sub_decode_path + (DecodePathDefBy(defined_by),),
                         ctx=ctx,
+                        _ctx_immutable=False,
                     )
                     if len(defined_tail) > 0:
                         raise DecodeError(
@@ -4885,6 +4899,7 @@ class Set(Sequence):
                         decode_path=sub_decode_path,
                         ctx=ctx,
                         tag_only=True,
+                        _ctx_immutable=False,
                     )
                 except TagMismatch:
                     continue
@@ -4901,6 +4916,7 @@ class Set(Sequence):
                 leavemm=True,
                 decode_path=sub_decode_path,
                 ctx=ctx,
+                _ctx_immutable=False,
             )
             value_len = value.fulllen
             if value_prev.tobytes() > v[:value_len].tobytes():
@@ -5210,6 +5226,7 @@ class SequenceOf(Obj):
                 leavemm=True,
                 decode_path=sub_decode_path,
                 ctx=ctx,
+                _ctx_immutable=False,
             )
             value_len = value.fulllen
             if ordering_check: