Refactor codec classes linkage

Make it looking more uniform and easier to override if needed.

9 files changed, 34 insertions, 22 deletions

diff --git a/pyasn1/codec/ber/decoder.py b/pyasn1/codec/ber/decoder.py
index af9d89e..6dc8866 100644
--- a/pyasn1/codec/ber/decoder.py
+++ b/pyasn1/codec/ber/decoder.py
@@ -1899,16 +1899,17 @@ class StreamingDecoder(object):
          1 2 3
     """
 
-    SINGLE_ITEM_DECODER = SingleItemDecoder()
+    SINGLE_ITEM_DECODER = SingleItemDecoder
 
-    def __init__(self, substrate, asn1Spec=None, **kwargs):
+    def __init__(self, substrate, asn1Spec=None, **options):
+        self._singleItemDecoder = self.SINGLE_ITEM_DECODER()
         self._substrate = asSeekableStream(substrate)
         self._asn1Spec = asn1Spec
-        self._options = kwargs
+        self._options = options
 
     def __iter__(self):
         while True:
-            for asn1Object in self.SINGLE_ITEM_DECODER(
+            for asn1Object in self._singleItemDecoder(
                     self._substrate, self._asn1Spec, **self._options):
                 yield asn1Object
 
@@ -1990,7 +1991,10 @@ class Decoder(object):
         """
         substrate = asSeekableStream(substrate)
 
-        for asn1Object in cls.STREAMING_DECODER(substrate, asn1Spec, **kwargs):
+        streamingDecoder = cls.STREAMING_DECODER(
+            substrate, asn1Spec, **kwargs)
+
+        for asn1Object in streamingDecoder:
             if isinstance(asn1Object, SubstrateUnderrunError):
                 raise error.SubstrateUnderrunError('Short substrate on input')
 
diff --git a/pyasn1/codec/ber/encoder.py b/pyasn1/codec/ber/encoder.py
index e80a007..7ee9b47 100644
--- a/pyasn1/codec/ber/encoder.py
+++ b/pyasn1/codec/ber/encoder.py
@@ -846,11 +846,14 @@ class SingleItemEncoder(object):
 
 
 class Encoder(object):
-    SINGLE_ITEM_ENCODER = SingleItemEncoder()
+    SINGLE_ITEM_ENCODER = SingleItemEncoder
 
-    @classmethod
-    def __call__(cls, pyObject, asn1Spec=None, **options):
-        return cls.SINGLE_ITEM_ENCODER(pyObject, asn1Spec=asn1Spec, **options)
+    def __init__(self, **options):
+        self._singleItemEncoder = self.SINGLE_ITEM_ENCODER()
+
+    def __call__(self, pyObject, asn1Spec=None, **options):
+        return self._singleItemEncoder(
+            pyObject, asn1Spec=asn1Spec, **options)
 
 
 #: Turns ASN.1 object into BER octet stream.
diff --git a/pyasn1/codec/cer/decoder.py b/pyasn1/codec/cer/decoder.py
index 852415a..0a92b26 100644
--- a/pyasn1/codec/cer/decoder.py
+++ b/pyasn1/codec/cer/decoder.py
@@ -80,7 +80,7 @@ class SingleItemDecoder(decoder.SingleItemDecoder):
 class StreamingDecoder(decoder.StreamingDecoder):
     __doc__ = decoder.StreamingDecoder.__doc__
 
-    SINGLE_ITEM_DECODER = SingleItemDecoder()
+    SINGLE_ITEM_DECODER = SingleItemDecoder
 
 
 class Decoder(decoder.Decoder):
diff --git a/pyasn1/codec/cer/encoder.py b/pyasn1/codec/cer/encoder.py
index b11c7ff..9e6cdac 100644
--- a/pyasn1/codec/cer/encoder.py
+++ b/pyasn1/codec/cer/encoder.py
@@ -270,7 +270,7 @@ class SingleItemEncoder(encoder.SingleItemEncoder):
 
 
 class Encoder(encoder.Encoder):
-    SINGLE_ITEM_ENCODER = SingleItemEncoder()
+    SINGLE_ITEM_ENCODER = SingleItemEncoder
 
 
 #: Turns ASN.1 object into CER octet stream.
diff --git a/pyasn1/codec/der/decoder.py b/pyasn1/codec/der/decoder.py
index ff3f004..b9526c3 100644
--- a/pyasn1/codec/der/decoder.py
+++ b/pyasn1/codec/der/decoder.py
@@ -50,7 +50,7 @@ class SingleItemDecoder(decoder.SingleItemDecoder):
 class StreamingDecoder(decoder.StreamingDecoder):
     __doc__ = decoder.StreamingDecoder.__doc__
 
-    SINGLE_ITEM_DECODER = SingleItemDecoder()
+    SINGLE_ITEM_DECODER = SingleItemDecoder
 
 
 class Decoder(decoder.Decoder):
diff --git a/pyasn1/codec/der/encoder.py b/pyasn1/codec/der/encoder.py
index 21102b8..1a6af82 100644
--- a/pyasn1/codec/der/encoder.py
+++ b/pyasn1/codec/der/encoder.py
@@ -67,7 +67,7 @@ class SingleItemEncoder(encoder.SingleItemEncoder):
 
 
 class Encoder(encoder.Encoder):
-    SINGLE_ITEM_ENCODER = SingleItemEncoder()
+    SINGLE_ITEM_ENCODER = SingleItemEncoder
 
 
 #: Turns ASN.1 object into DER octet stream.
diff --git a/pyasn1/codec/native/decoder.py b/pyasn1/codec/native/decoder.py
index 04ae129..db30c71 100644
--- a/pyasn1/codec/native/decoder.py
+++ b/pyasn1/codec/native/decoder.py
@@ -181,11 +181,13 @@ class SingleItemDecoder(object):
 
 
 class Decoder(object):
-    SINGLE_ITEM_DECODER = SingleItemDecoder()
+    SINGLE_ITEM_DECODER = SingleItemDecoder
 
-    @classmethod
-    def __call__(cls, pyObject, asn1Spec=None, **kwargs):
-        return cls.SINGLE_ITEM_DECODER(pyObject, asn1Spec=asn1Spec, **kwargs)
+    def __init__(self, **options):
+        self._singleItemDecoder = self.SINGLE_ITEM_DECODER()
+
+    def __call__(self, pyObject, asn1Spec=None, **kwargs):
+        return self._singleItemDecoder(pyObject, asn1Spec=asn1Spec, **kwargs)
 
 
 #: Turns Python objects of built-in types into ASN.1 objects.
diff --git a/pyasn1/codec/native/encoder.py b/pyasn1/codec/native/encoder.py
index 0001916..d0d65ec 100644
--- a/pyasn1/codec/native/encoder.py
+++ b/pyasn1/codec/native/encoder.py
@@ -225,11 +225,14 @@ class SingleItemEncoder(object):
 
 
 class Encoder(object):
-    SINGLE_ITEM_ENCODER = SingleItemEncoder()
+    SINGLE_ITEM_ENCODER = SingleItemEncoder
 
-    @classmethod
-    def __call__(cls, pyObject, asn1Spec=None, **kwargs):
-        return cls.SINGLE_ITEM_ENCODER(pyObject, asn1Spec=asn1Spec, **kwargs)
+    def __init__(self, **kwargs):
+        self._singleItemEncoder = self.SINGLE_ITEM_ENCODER()
+
+    def __call__(self, pyObject, asn1Spec=None, **options):
+        return self._singleItemEncoder(
+            pyObject, asn1Spec=asn1Spec, **options)
 
 
 #: Turns ASN.1 object into a Python built-in type object(s).
diff --git a/tests/codec/ber/test_decoder.py b/tests/codec/ber/test_decoder.py
index 4b73f6a..a559209 100644
--- a/tests/codec/ber/test_decoder.py
+++ b/tests/codec/ber/test_decoder.py
@@ -1615,7 +1615,7 @@ class ErrorOnDecodingTestCase(BaseTestCase):
             defaultErrorState = decoder.stDumpRawValue
 
         class StreamingDecoder(decoder.StreamingDecoder):
-            SINGLE_ITEM_DECODER = SingleItemEncoder()
+            SINGLE_ITEM_DECODER = SingleItemEncoder
 
         class OneShotDecoder(decoder.Decoder):
             STREAMING_DECODER = StreamingDecoder