ASN.1 types __init__(), .clone()/.subtype() refactored into kwargs

7 files changed, 191 insertions, 334 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index fafd7a2..94926e9 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,6 +2,8 @@
 Revision 0.3.1, released XX-07-2017
 -----------------------------------
 
+- ASN.1 types __init__(), .clone() and .subtype() signatures
+  refactored into keyword arguments to simplify their signatures.
 - ASN.1 types initialization refactored to minimize the use of
   relatively expensive isNoValue() call
 - Lazily pre-populate list of values of Sequence/Set/Choice types
diff --git a/pyasn1/codec/ber/decoder.py b/pyasn1/codec/ber/decoder.py
index fc51c85..ede16a7 100644
--- a/pyasn1/codec/ber/decoder.py
+++ b/pyasn1/codec/ber/decoder.py
@@ -32,11 +32,11 @@ class AbstractSimpleDecoder(AbstractDecoder):
     def substrateCollector(asn1Object, substrate, length):
             return substrate[:length], substrate[length:]
 
-    def _createComponent(self, asn1Spec, tagSet, value=None):
+    def _createComponent(self, asn1Spec, tagSet, value=base.noValue):
         if tagSet[0].tagFormat not in self.tagFormats:
             raise error.PyAsn1Error('Invalid tag format %s for %s' % (tagSet[0], self.protoComponent.prettyPrintType()))
         if asn1Spec is None:
-            return self.protoComponent.clone(value, tagSet)
+            return self.protoComponent.clone(value, tagSet=tagSet)
         elif value is None:
             return asn1Spec
         else:
@@ -47,11 +47,11 @@ class AbstractConstructedDecoder(AbstractDecoder):
     tagFormats = (tag.tagFormatConstructed,)
 
     # noinspection PyUnusedLocal
-    def _createComponent(self, asn1Spec, tagSet, value=None):
+    def _createComponent(self, asn1Spec, tagSet, value=base.noValue):
         if tagSet[0].tagFormat not in self.tagFormats:
             raise error.PyAsn1Error('Invalid tag format %s for %s' % (tagSet[0], self.protoComponent.prettyPrintType()))
         if asn1Spec is None:
-            return self.protoComponent.clone(tagSet)
+            return self.protoComponent.clone(tagSet=tagSet)
         else:
             return asn1Spec.clone()
 
@@ -107,7 +107,7 @@ class IntegerDecoder(AbstractSimpleDecoder):
 class BooleanDecoder(IntegerDecoder):
     protoComponent = univ.Boolean(0)
 
-    def _createComponent(self, asn1Spec, tagSet, value=None):
+    def _createComponent(self, asn1Spec, tagSet, value=base.noValue):
         return IntegerDecoder._createComponent(self, asn1Spec, tagSet, value and 1 or 0)
 
 
diff --git a/pyasn1/codec/ber/encoder.py b/pyasn1/codec/ber/encoder.py
index 14bd609..dfef38f 100644
--- a/pyasn1/codec/ber/encoder.py
+++ b/pyasn1/codec/ber/encoder.py
@@ -88,7 +88,7 @@ class EndOfOctetsEncoder(AbstractItemEncoder):
 class ExplicitlyTaggedItemEncoder(AbstractItemEncoder):
     def encodeValue(self, encodeFun, value, defMode, maxChunkSize):
         if isinstance(value, base.AbstractConstructedAsn1Item):
-            value = value.clone(tagSet=value.tagSet[:-1], cloneValueFlag=1)
+            value = value.clone(tagSet=value.tagSet[:-1], cloneValueFlag=True)
         else:
             value = value.clone(tagSet=value.tagSet[:-1])
         return encodeFun(value, defMode, maxChunkSize), True, True
diff --git a/pyasn1/codec/ber/eoo.py b/pyasn1/codec/ber/eoo.py
index b02f5cc..28e33c5 100644
--- a/pyasn1/codec/ber/eoo.py
+++ b/pyasn1/codec/ber/eoo.py
@@ -15,9 +15,9 @@ class EndOfOctets(base.AbstractSimpleAsn1Item):
 
     _instance = None
 
-    def __new__(cls, *args):
+    def __new__(cls, *args, **kwargs):
         if cls._instance is None:
-            cls._instance = object.__new__(cls, *args)
+            cls._instance = object.__new__(cls, *args, **kwargs)
 
         return cls._instance
 
diff --git a/pyasn1/type/base.py b/pyasn1/type/base.py
index 4ee5c21..0f088c6 100644
--- a/pyasn1/type/base.py
+++ b/pyasn1/type/base.py
@@ -34,13 +34,14 @@ class Asn1ItemBase(Asn1Item):
     # Disambiguation ASN.1 types identification
     typeId = None
 
-    def __init__(self, tagSet=None, subtypeSpec=None):
-        if tagSet is not None:
-            self.tagSet = tagSet
-        if subtypeSpec is not None:
-            self.subtypeSpec = subtypeSpec
-        self.readOnly = 'subtypeSpec'
-        self.readOnly = 'tagSet'
+    def __init__(self, **kwargs):
+        for key in ('tagSet', 'subtypeSpec'):
+            if key not in kwargs:
+                kwargs[key] = getattr(self, key)
+
+        for key, value in kwargs.items():
+            setattr(self, key, value)
+            self.readOnly = key
 
     def __setattr__(self, name, value):
         if not name.startswith('_'):
@@ -220,8 +221,8 @@ class AbstractSimpleAsn1Item(Asn1ItemBase):
     #: Default payload value
     defaultValue = noValue
 
-    def __init__(self, value=noValue, tagSet=None, subtypeSpec=None):
-        Asn1ItemBase.__init__(self, tagSet, subtypeSpec)
+    def __init__(self, value=noValue, **kwargs):
+        Asn1ItemBase.__init__(self, **kwargs)
         if value is None or value is noValue:
             value = self.defaultValue
         else:
@@ -300,7 +301,7 @@ class AbstractSimpleAsn1Item(Asn1ItemBase):
         """
         return self._value is not noValue
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None):
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
           Any parameters to the *clone()* method will replace corresponding
@@ -323,28 +324,19 @@ class AbstractSimpleAsn1Item(Asn1ItemBase):
           :
               new instance of |ASN.1| type/value
         """
-        isModified = False
-
         if value is None or value is noValue:
+            if not kwargs:
+                return self
+
             value = self._value
-        else:
-            isModified = True
-        if tagSet is None or tagSet is noValue:
-            tagSet = self.tagSet
-        else:
-            isModified = True
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            isModified = True
 
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec)
-        else:
-            return self
+        for arg in self.readOnly:
+            if arg not in kwargs:
+                kwargs[arg] = getattr(self, arg)
+
+        return self.__class__(value, **kwargs)
 
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
          Any parameters to the *subtype()* method will be added to the corresponding
@@ -374,31 +366,32 @@ class AbstractSimpleAsn1Item(Asn1ItemBase):
          -------
          :
              new instance of |ASN.1| type/value
-         """
-        isModified = False
-
+        """
         if value is None or value is noValue:
+            if not kwargs:
+                return self
+
             value = self._value
-        else:
-            isModified = True
-        if implicitTag is not None and implicitTag is not noValue:
-            tagSet = self.tagSet.tagImplicitly(implicitTag)
-            isModified = True
-        elif explicitTag is not None and explicitTag is not noValue:
-            tagSet = self.tagSet.tagExplicitly(explicitTag)
-            isModified = True
-        else:
-            tagSet = self.tagSet
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            subtypeSpec += self.subtypeSpec
-            isModified = True
 
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec)
-        else:
-            return self
+        for arg in self.readOnly:
+            if arg in kwargs:
+                kwargs[arg] += getattr(self, arg)
+            else:
+                kwargs[arg] = getattr(self, arg)
+
+        try:
+            kwargs['tagSet'] = self.tagSet.tagImplicitly(kwargs['implicitTag'])
+
+        except KeyError:
+            pass
+
+        try:
+            kwargs['tagSet'] = self.tagSet.tagExplicitly(kwargs['explicitTag'])
+
+        except KeyError:
+            pass
+
+        return self.__class__(value, **kwargs)
 
     def prettyIn(self, value):
         return value
@@ -472,16 +465,14 @@ class AbstractConstructedAsn1Item(Asn1ItemBase):
     componentType = None
     sizeSpec = None
 
-    def __init__(self, componentType=None, tagSet=None,
-                 subtypeSpec=None, sizeSpec=None):
-        Asn1ItemBase.__init__(self, tagSet, subtypeSpec)
-        if componentType is not None:
-            self.componentType = componentType
-        if sizeSpec is not None:
-            self.sizeSpec = sizeSpec
+    def __init__(self, **kwargs):
+        for key in ('componentType', 'sizeSpec'):
+            if key not in kwargs:
+                kwargs[key] = getattr(self, key)
+
+        Asn1ItemBase.__init__(self, **kwargs)
+
         self._componentValues = []
-        self.readOnly = 'componentType'
-        self.readOnly = 'sizeSpec'
 
     def __repr__(self):
         representation = []
@@ -527,7 +518,7 @@ class AbstractConstructedAsn1Item(Asn1ItemBase):
     def _cloneComponentValues(self, myClone, cloneValueFlag):
         pass
 
-    def clone(self, tagSet=None, subtypeSpec=None, sizeSpec=None, cloneValueFlag=None):
+    def clone(self, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -550,19 +541,20 @@ class AbstractConstructedAsn1Item(Asn1ItemBase):
             new instance of |ASN.1| type/value
 
         """
-        if tagSet is None:
-            tagSet = self.tagSet
-        if subtypeSpec is None:
-            subtypeSpec = self.subtypeSpec
-        if sizeSpec is None:
-            sizeSpec = self.sizeSpec
-        clone = self.__class__(self.componentType, tagSet, subtypeSpec, sizeSpec)
+        cloneValueFlag = kwargs.pop('cloneValueFlag', False)
+
+        for arg in self.readOnly:
+            if arg not in kwargs:
+                kwargs[arg] = getattr(self, arg)
+
+        clone = self.__class__(**kwargs)
+
         if cloneValueFlag:
             self._cloneComponentValues(clone, cloneValueFlag)
+
         return clone
 
-    def subtype(self, implicitTag=None, explicitTag=None, subtypeSpec=None,
-                sizeSpec=None, cloneValueFlag=None):
+    def subtype(self, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -585,23 +577,31 @@ class AbstractConstructedAsn1Item(Asn1ItemBase):
             new instance of |ASN.1| type/value
 
         """
-        if implicitTag is not None and implicitTag is not noValue:
-            tagSet = self.tagSet.tagImplicitly(implicitTag)
-        elif explicitTag is not None and explicitTag is not noValue:
-            tagSet = self.tagSet.tagExplicitly(explicitTag)
-        else:
-            tagSet = self.tagSet
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            subtypeSpec += self.subtypeSpec
-        if sizeSpec is None or sizeSpec is noValue:
-            sizeSpec = self.sizeSpec
-        else:
-            sizeSpec += self.sizeSpec
-        clone = self.__class__(self.componentType, tagSet, subtypeSpec, sizeSpec)
+        cloneValueFlag = kwargs.pop('cloneValueFlag', False)
+
+        for arg in self.readOnly:
+            if arg in kwargs:
+                kwargs[arg] += getattr(self, arg)
+            else:
+                kwargs[arg] = getattr(self, arg)
+
+        try:
+            kwargs['tagSet'] = self.tagSet.tagImplicitly(kwargs['implicitTag'])
+
+        except KeyError:
+            pass
+
+        try:
+            kwargs['tagSet'] = self.tagSet.tagExplicitly(kwargs['explicitTag'])
+
+        except KeyError:
+            pass
+
+        clone = self.__class__(**kwargs)
+
         if cloneValueFlag:
             self._cloneComponentValues(clone, cloneValueFlag)
+
         return clone
 
     def verifySizeSpec(self):
diff --git a/pyasn1/type/char.py b/pyasn1/type/char.py
index 039e536..4bb46aa 100644
--- a/pyasn1/type/char.py
+++ b/pyasn1/type/char.py
@@ -50,10 +50,10 @@ class AbstractCharacterString(univ.OctetString):
     if sys.version_info[0] <= 2:
         def __str__(self):
             try:
-                return self._value.encode(self._encoding)
+                return self._value.encode(self.encoding)
             except UnicodeEncodeError:
                 raise error.PyAsn1Error(
-                    'Can\'t encode string \'%s\' with \'%s\' codec' % (self._value, self._encoding)
+                    'Can\'t encode string \'%s\' with \'%s\' codec' % (self._value, self.encoding)
                 )
 
         def __unicode__(self):
@@ -64,10 +64,10 @@ class AbstractCharacterString(univ.OctetString):
                 return value
             elif isinstance(value, str):
                 try:
-                    return value.decode(self._encoding)
+                    return value.decode(self.encoding)
                 except (LookupError, UnicodeDecodeError):
                     raise error.PyAsn1Error(
-                        'Can\'t decode string \'%s\' with \'%s\' codec' % (value, self._encoding)
+                        'Can\'t decode string \'%s\' with \'%s\' codec' % (value, self.encoding)
                     )
             elif isinstance(value, (tuple, list)):
                 try:
@@ -96,10 +96,10 @@ class AbstractCharacterString(univ.OctetString):
 
         def __bytes__(self):
             try:
-                return self._value.encode(self._encoding)
+                return self._value.encode(self.encoding)
             except UnicodeEncodeError:
                 raise error.PyAsn1Error(
-                    'Can\'t encode string \'%s\' with \'%s\' codec' % (self._value, self._encoding)
+                    'Can\'t encode string \'%s\' with \'%s\' codec' % (self._value, self.encoding)
                 )
 
         def prettyIn(self, value):
@@ -107,10 +107,10 @@ class AbstractCharacterString(univ.OctetString):
                 return value
             elif isinstance(value, bytes):
                 try:
-                    return value.decode(self._encoding)
+                    return value.decode(self.encoding)
                 except UnicodeDecodeError:
                     raise error.PyAsn1Error(
-                        'Can\'t decode string \'%s\' with \'%s\' codec' % (value, self._encoding)
+                        'Can\'t decode string \'%s\' with \'%s\' codec' % (value, self.encoding)
                     )
             elif isinstance(value, (tuple, list)):
                 return self.prettyIn(bytes(value))
@@ -134,8 +134,7 @@ class AbstractCharacterString(univ.OctetString):
     def __reversed__(self):
         return reversed(self._value)
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None,
-              encoding=None, binValue=noValue, hexValue=noValue):
+    def clone(self, value=noValue, **kwargs):
         """Creates a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -165,10 +164,9 @@ class AbstractCharacterString(univ.OctetString):
             new instance of |ASN.1| type/value
 
         """
-        return univ.OctetString.clone(self, value, tagSet, subtypeSpec, encoding, binValue, hexValue)
+        return univ.OctetString.clone(self, value, **kwargs)
 
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None, encoding=None, binValue=noValue, hexValue=noValue):
+    def subtype(self, value=noValue, **kwargs):
         """Creates a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -205,8 +203,7 @@ class AbstractCharacterString(univ.OctetString):
             new instance of |ASN.1| type/value
 
         """
-        return univ.OctetString.subtype(self, value, implicitTag, explicitTag, subtypeSpec, encoding, binValue, hexValue)
-
+        return univ.OctetString.subtype(self, value, **kwargs)
 
 class NumericString(AbstractCharacterString):
     __doc__ = AbstractCharacterString.__doc__
diff --git a/pyasn1/type/univ.py b/pyasn1/type/univ.py
index 298869b..038744e 100644
--- a/pyasn1/type/univ.py
+++ b/pyasn1/type/univ.py
@@ -64,14 +64,11 @@ class Integer(base.AbstractSimpleAsn1Item):
     # Optimization for faster codec lookup
     typeId = base.AbstractSimpleAsn1Item.getTypeId()
 
-    def __init__(self, value=noValue, tagSet=None, subtypeSpec=None,
-                 namedValues=None):
-        if namedValues is not None:
-            self.namedValues = namedValues
-        base.AbstractSimpleAsn1Item.__init__(
-            self, value, tagSet, subtypeSpec
-        )
-        self.readOnly = 'namedValues'
+    def __init__(self, value=noValue, **kwargs):
+        if 'namedValues' not in kwargs:
+            kwargs['namedValues'] = self.namedValues
+
+        base.AbstractSimpleAsn1Item.__init__(self, value, **kwargs)
 
     def __repr__(self):
         if self.namedValues is not self.__class__.namedValues:
@@ -245,7 +242,7 @@ class Integer(base.AbstractSimpleAsn1Item):
         except KeyError:
             return str(value)
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None, namedValues=None):
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -271,32 +268,9 @@ class Integer(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        isModified = False
-
-        if value is None or value is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if tagSet is None or tagSet is noValue:
-            tagSet = self.tagSet
-        else:
-            isModified = True
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            isModified = True
-        if namedValues is None or namedValues is noValue:
-            namedValues = self.namedValues
-        else:
-            isModified = True
-
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, namedValues)
-        else:
-            return self
+        return base.AbstractSimpleAsn1Item.clone(self, value, **kwargs)
 
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None, namedValues=None):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -332,35 +306,7 @@ class Integer(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        isModified = False
-
-        if value is None or value is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if implicitTag is not None and implicitTag is not noValue:
-            tagSet = self.tagSet.tagImplicitly(implicitTag)
-            isModified = True
-        elif explicitTag is not None and explicitTag is not noValue:
-            tagSet = self.tagSet.tagExplicitly(explicitTag)
-            isModified = True
-        else:
-            tagSet = self.tagSet
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            subtypeSpec += self.subtypeSpec
-            isModified = True
-        if namedValues is None or namedValues is noValue:
-            namedValues = self.namedValues
-        else:
-            namedValues += self.namedValues
-            isModified = True
-
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, namedValues)
-        else:
-            return self
+        return base.AbstractSimpleAsn1Item.subtype(self, value, **kwargs)
 
     # backward compatibility
 
@@ -465,24 +411,34 @@ class BitString(base.AbstractSimpleAsn1Item):
 
             return self.bitLength
 
-    def __init__(self, value=noValue, tagSet=None, subtypeSpec=None,
-                 namedValues=None, binValue=noValue, hexValue=noValue):
-        if namedValues is not None:
-            self.namedValues = namedValues
-        if binValue is not noValue:
-            value = self.fromBinaryString(binValue)
-        elif hexValue is not noValue:
-            value = self.fromHexString(hexValue)
-        elif value is None or value is noValue:
+    def __init__(self, value=noValue, **kwargs):
+        if value is noValue or value is None:
+            if kwargs:
+                try:
+                    value = self.fromBinaryString(kwargs.pop('binValue'))
+
+                except KeyError:
+                    pass
+
+                try:
+                    value = self.fromHexString(kwargs.pop('hexValue'))
+
+                except KeyError:
+                    pass
+
+        if value is noValue or value is None:
             if self.defaultBinValue is not noValue:
                 value = self.fromBinaryString(self.defaultBinValue)
+
             elif self.defaultHexValue is not noValue:
                 value = self.fromHexString(self.defaultHexValue)
-        base.AbstractSimpleAsn1Item.__init__(self, value, tagSet, subtypeSpec)
-        self._readOnly.add('namedValues')
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None,
-              namedValues=None, binValue=noValue, hexValue=noValue):
+        if 'namedValues' not in kwargs:
+            kwargs['namedValues'] = self.namedValues
+
+        base.AbstractSimpleAsn1Item.__init__(self, value, **kwargs)
+
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -516,32 +472,9 @@ class BitString(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        isModified = False
-
-        if (value is None or value is noValue) and binValue is noValue and hexValue is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if tagSet is None or tagSet is noValue:
-            tagSet = self.tagSet
-        else:
-            isModified = True
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            isModified = True
-        if namedValues is None or namedValues is noValue:
-            namedValues = self.namedValues
-        else:
-            isModified = True
+        return base.AbstractSimpleAsn1Item.clone(self, value, **kwargs)
 
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, namedValues, binValue, hexValue)
-        else:
-            return self
-
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None, namedValues=None, binValue=noValue, hexValue=noValue):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -585,35 +518,7 @@ class BitString(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        isModified = False
-
-        if (value is None or value is noValue) and binValue is noValue and hexValue is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if implicitTag is not None and implicitTag is not noValue:
-            tagSet = self.tagSet.tagImplicitly(implicitTag)
-            isModified = True
-        elif explicitTag is not None and explicitTag is not noValue:
-            tagSet = self.tagSet.tagExplicitly(explicitTag)
-            isModified = True
-        else:
-            tagSet = self.tagSet
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            subtypeSpec += self.subtypeSpec
-            isModified = True
-        if namedValues is None or namedValues is noValue:
-            namedValues = self.namedValues
-        else:
-            namedValues += self.namedValues
-            isModified = True
-
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, namedValues, binValue, hexValue)
-        else:
-            return self
+        return base.AbstractSimpleAsn1Item.subtype(self, value, **kwargs)
 
     def __str__(self):
         return self.asBinary()
@@ -877,26 +782,36 @@ class OctetString(base.AbstractSimpleAsn1Item):
     defaultBinValue = defaultHexValue = noValue
     encoding = 'iso-8859-1'
 
-    def __init__(self, value=noValue, tagSet=None, subtypeSpec=None,
-                 encoding=None, binValue=noValue, hexValue=noValue):
-        if encoding is None:
-            self._encoding = self.encoding
-        else:
-            self._encoding = encoding
-        if binValue is not noValue:
-            value = self.fromBinaryString(binValue)
-        elif hexValue is not noValue:
-            value = self.fromHexString(hexValue)
-        elif value is None or value is noValue:
+    def __init__(self, value=noValue, **kwargs):
+        if kwargs:
+            if value is noValue or value is None:
+                try:
+                    value = self.fromBinaryString(kwargs.pop('binValue'))
+
+                except KeyError:
+                    pass
+
+                try:
+                    value = self.fromHexString(kwargs.pop('hexValue'))
+
+                except KeyError:
+                    pass
+
+        if value is noValue or value is None:
             if self.defaultBinValue is not noValue:
                 value = self.fromBinaryString(self.defaultBinValue)
+
             elif self.defaultHexValue is not noValue:
                 value = self.fromHexString(self.defaultHexValue)
+
+        if 'encoding' not in kwargs:
+            kwargs['encoding'] = self.encoding
+
         self.__asNumbersCache = None
-        base.AbstractSimpleAsn1Item.__init__(self, value, tagSet, subtypeSpec)
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None,
-              encoding=None, binValue=noValue, hexValue=noValue):
+        base.AbstractSimpleAsn1Item.__init__(self, value, **kwargs)
+
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -930,33 +845,9 @@ class OctetString(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        isModified = False
+        return base.AbstractSimpleAsn1Item.clone(self, value, **kwargs)
 
-        if (value is None or value is noValue) and binValue is noValue and hexValue is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if tagSet is None or tagSet is noValue:
-            tagSet = self.tagSet
-        else:
-            isModified = True
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            isModified = True
-        if encoding is None or encoding is noValue:
-            encoding = self._encoding
-        else:
-            isModified = True
-
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, encoding, binValue, hexValue)
-        else:
-            return self
-
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None, encoding=None, binValue=noValue,
-                hexValue=noValue):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -998,34 +889,7 @@ class OctetString(base.AbstractSimpleAsn1Item):
         :
              new instance of |ASN.1| type/value
         """
-        isModified = False
-
-        if (value is None or value is noValue) and binValue is noValue and hexValue is noValue:
-            value = self._value
-        else:
-            isModified = True
-        if implicitTag is not None and implicitTag is not noValue:
-            tagSet = self.tagSet.tagImplicitly(implicitTag)
-            isModified = True
-        elif explicitTag is not None and explicitTag is not noValue:
-            tagSet = self.tagSet.tagExplicitly(explicitTag)
-            isModified = True
-        else:
-            tagSet = self.tagSet
-        if subtypeSpec is None or subtypeSpec is noValue:
-            subtypeSpec = self.subtypeSpec
-        else:
-            subtypeSpec += self.subtypeSpec
-            isModified = True
-        if encoding is None or encoding is noValue:
-            encoding = self._encoding
-        else:
-            isModified = True
-
-        if isModified:
-            return self.__class__(value, tagSet, subtypeSpec, encoding, binValue, hexValue)
-        else:
-            return self
+        return base.AbstractSimpleAsn1Item.subtype(self, value, **kwargs)
 
     if sys.version_info[0] <= 2:
         def prettyIn(self, value):
@@ -1033,10 +897,10 @@ class OctetString(base.AbstractSimpleAsn1Item):
                 return value
             elif isinstance(value, unicode):
                 try:
-                    return value.encode(self._encoding)
+                    return value.encode(self.encoding)
                 except (LookupError, UnicodeEncodeError):
                     raise error.PyAsn1Error(
-                        'Can\'t encode string \'%s\' with \'%s\' codec' % (value, self._encoding)
+                        'Can\'t encode string \'%s\' with \'%s\' codec' % (value, self.encoding)
                     )
             elif isinstance(value, (tuple, list)):
                 try:
@@ -1053,11 +917,11 @@ class OctetString(base.AbstractSimpleAsn1Item):
 
         def __unicode__(self):
             try:
-                return self._value.decode(self._encoding)
+                return self._value.decode(self.encoding)
 
             except UnicodeDecodeError:
                 raise error.PyAsn1Error(
-                    'Can\'t decode string \'%s\' with \'%s\' codec' % (self._value, self._encoding)
+                    'Can\'t decode string \'%s\' with \'%s\' codec' % (self._value, self.encoding)
                 )
 
         def asOctets(self):
@@ -1074,10 +938,10 @@ class OctetString(base.AbstractSimpleAsn1Item):
                 return value
             elif isinstance(value, str):
                 try:
-                    return value.encode(self._encoding)
+                    return value.encode(self.encoding)
                 except UnicodeEncodeError:
                     raise error.PyAsn1Error(
-                        'Can\'t encode string \'%s\' with \'%s\' codec' % (value, self._encoding)
+                        'Can\'t encode string \'%s\' with \'%s\' codec' % (value, self.encoding)
                     )
             elif isinstance(value, OctetString):  # a shortcut, bytes() would work the same way
                 return value.asOctets()
@@ -1090,11 +954,11 @@ class OctetString(base.AbstractSimpleAsn1Item):
 
         def __str__(self):
             try:
-                return self._value.decode(self._encoding)
+                return self._value.decode(self.encoding)
 
             except UnicodeDecodeError:
                 raise error.PyAsn1Error(
-                    'Can\'t decode string \'%s\' with \'%s\' codec at \'%s\'' % (self._value, self._encoding, self.__class__.__name__)
+                    'Can\'t decode string \'%s\' with \'%s\' codec at \'%s\'' % (self._value, self.encoding, self.__class__.__name__)
                 )
 
         def __bytes__(self):
@@ -1118,12 +982,12 @@ class OctetString(base.AbstractSimpleAsn1Item):
                 return octets.octs2str('0x') + ''.join(('%.2x' % x for x in numbers))
         else:
             try:
-                return value.decode(self._encoding)
+                return value.decode(self.encoding)
 
             except UnicodeDecodeError:
                 raise error.PyAsn1Error(
                     'Can\'t decode string \'%s\' with \'%s\' codec at \'%s\'' % (
-                    value, self._encoding, self.__class__.__name__)
+                    value, self.encoding, self.__class__.__name__)
                 )
 
     @staticmethod
@@ -1179,8 +1043,8 @@ class OctetString(base.AbstractSimpleAsn1Item):
             r.append('tagSet=%r' % (self.tagSet,))
         if self.subtypeSpec is not self.__class__.subtypeSpec:
             r.append('subtypeSpec=%r' % (self.subtypeSpec,))
-        if self.encoding is not self._encoding:
-            r.append('encoding=%r' % (self._encoding,))
+        if self.encoding is not self.__class__.encoding:
+            r.append('encoding=%r' % (self.encoding,))
         if doHex:
             r.append('hexValue=%r' % ''.join(['%.2x' % x for x in self.asNumbers()]))
         return '%s(%s)' % (self.__class__.__name__, ', '.join(r))
@@ -1257,7 +1121,7 @@ class Null(OctetString):
     # Optimization for faster codec lookup
     typeId = OctetString.getTypeId()
 
-    def clone(self, value=noValue, tagSet=None):
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -1277,9 +1141,9 @@ class Null(OctetString):
         : :py:class:`~pyasn1.type.univ.Null`
             new instance of NULL type/value
         """
-        return OctetString.clone(self, value, tagSet)
+        return OctetString.clone(self, value, **kwargs)
 
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -1306,7 +1170,7 @@ class Null(OctetString):
         : :py:class:`~pyasn1.type.univ.Null`
             new instance of NULL type/value
         """
-        return OctetString.subtype(self, value, implicitTag, explicitTag)
+        return OctetString.subtype(self, value, **kwargs)
 
 
 if sys.version_info[0] <= 2:
@@ -1493,7 +1357,7 @@ class Real(base.AbstractSimpleAsn1Item):
     # Optimization for faster codec lookup
     typeId = base.AbstractSimpleAsn1Item.getTypeId()
 
-    def clone(self, value=noValue, tagSet=None, subtypeSpec=None):
+    def clone(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *clone()* method will replace corresponding
@@ -1516,10 +1380,9 @@ class Real(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        return base.AbstractSimpleAsn1Item.clone(self, value, tagSet, subtypeSpec)
+        return base.AbstractSimpleAsn1Item.clone(self, value, **kwargs)
 
-    def subtype(self, value=noValue, implicitTag=None, explicitTag=None,
-                subtypeSpec=None):
+    def subtype(self, value=noValue, **kwargs):
         """Create a copy of a |ASN.1| type or object.
 
         Any parameters to the *subtype()* method will be added to the corresponding
@@ -1549,7 +1412,7 @@ class Real(base.AbstractSimpleAsn1Item):
         :
             new instance of |ASN.1| type/value
         """
-        return base.AbstractSimpleAsn1Item.subtype(self, value, implicitTag, explicitTag)
+        return base.AbstractSimpleAsn1Item.subtype(self, value, **kwargs)
 
     @staticmethod
     def __normalizeBase10(value):
@@ -1821,8 +1684,6 @@ class SequenceOfAndSetOfBase(base.AbstractConstructedAsn1Item):
         Object representing collection size constraint
      """
 
-    componentType = None
-
     # Python list protocol
 
     def clear(self):
@@ -1935,7 +1796,7 @@ class SequenceOfAndSetOfBase(base.AbstractConstructedAsn1Item):
             if len(self._componentValues) < idx:
                 raise error.PyAsn1Error('Component index out of range')
 
-        if value is None or value is noValue:
+        if value is noValue or value is None:
             if componentType is not None:
                 value = componentType.clone()
             elif currentValue is None:
@@ -2099,11 +1960,8 @@ class SequenceAndSetBase(base.AbstractConstructedAsn1Item):
     #: object representing named ASN.1 types allowed within |ASN.1| type
     componentType = namedtype.NamedTypes()
 
-    def __init__(self, componentType=None, tagSet=None,
-                 subtypeSpec=None, sizeSpec=None):
-        base.AbstractConstructedAsn1Item.__init__(
-            self, componentType, tagSet, subtypeSpec, sizeSpec
-        )
+    def __init__(self, **kwargs):
+        base.AbstractConstructedAsn1Item.__init__(self, **kwargs)
         self._componentTypeLen = len(self.componentType)
 
     def __getitem__(self, idx):