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795 lines
19 KiB
HTML
795 lines
19 KiB
HTML
<html>
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<title>
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PyASN1 data model and scalar types
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</title>
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<head>
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</head>
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<body>
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<center>
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<table width=60%>
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<tr>
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<td>
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<h3>
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1. Data model for ASN.1 types
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</h3>
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<p>
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All ASN.1 types could be categorized into two groups: scalar (also called
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simple or primitive) and constructed. The first group is populated by
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well-known types like Integer or String. Members of constructed group
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hold other types (simple or constructed) as their inner components, thus
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they are semantically close to a programming language records or lists.
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</p>
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<p>
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In pyasn1, all ASN.1 types and values are implemented as Python objects.
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The same pyasn1 object can represent either ASN.1 type and/or value
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depending of the presense of value initializer on object instantiation.
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We will further refer to these as <i>pyasn1 type object</i> versus <i>pyasn1
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value object</i>.
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</p>
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<p>
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Primitive ASN.1 types are implemented as immutable scalar objects. There values
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could be used just like corresponding native Python values (integers,
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strings/bytes etc) and freely mixed with them in expressions.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> asn1IntegerValue = univ.Integer(12)
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>>> asn1IntegerValue - 2
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10
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>>> univ.OctetString('abc') == 'abc'
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True # Python 2
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>>> univ.OctetString(b'abc') == b'abc'
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True # Python 3
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</pre>
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</td></tr></table>
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<p>
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It would be an error to perform an operation on a pyasn1 type object
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as it holds no value to deal with:
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> asn1IntegerType = univ.Integer()
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>>> asn1IntegerType - 2
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...
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pyasn1.error.PyAsn1Error: No value for __coerce__()
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</pre>
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</td></tr></table>
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<a name="1.1"></a>
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<h4>
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1.1 Scalar types
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</h4>
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<p>
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In the sub-sections that follow we will explain pyasn1 mapping to those
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primitive ASN.1 types. Both, ASN.1 notation and corresponding pyasn1
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syntax will be given in each case.
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</p>
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<a name="1.1.1"></a>
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<h4>
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1.1.1 Boolean type
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</h4>
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<p>
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This is the simplest type those values could be either True or False.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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;; type specification
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FunFactorPresent ::= BOOLEAN
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;; values declaration and assignment
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pythonFunFactor FunFactorPresent ::= TRUE
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cobolFunFactor FunFactorPresent :: FALSE
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</pre>
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</td></tr></table>
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<p>
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And here's pyasn1 version of it:
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> class FunFactorPresent(univ.Boolean): pass
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...
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>>> pythonFunFactor = FunFactorPresent(True)
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>>> cobolFunFactor = FunFactorPresent(False)
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>>> pythonFunFactor
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FunFactorPresent('True(1)')
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>>> cobolFunFactor
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FunFactorPresent('False(0)')
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>>> pythonFunFactor == cobolFunFactor
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False
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>>>
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</pre>
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</td></tr></table>
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<a name="1.1.2"></a>
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<h4>
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1.1.2 Null type
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</h4>
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<p>
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The NULL type is sometimes used to express the absense of any information.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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;; type specification
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Vote ::= CHOICE {
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agreed BOOLEAN,
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skip NULL
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}
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</td></tr></table>
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;; value declaration and assignment
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myVote Vote ::= skip:NULL
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</pre>
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<p>
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We will explain the CHOICE type later in this paper, meanwhile the NULL
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type:
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> skip = univ.Null()
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>>> skip
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Null('')
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>>>
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</pre>
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</td></tr></table>
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<a name="1.1.3"></a>
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<h4>
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1.1.3 Integer type
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</h4>
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<p>
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ASN.1 defines the values of Integer type as negative or positive of whatever
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length. This definition plays nicely with Python as the latter places no
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limit on Integers. However, some ASN.1 implementations may impose certain
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limits of integer value ranges. Keep that in mind when designing new
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data structures.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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;; values specification
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age-of-universe INTEGER ::= 13750000000
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mean-martian-surface-temperature INTEGER ::= -63
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</pre>
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</td></tr></table>
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<p>
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A rather strigntforward mapping into pyasn1:
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> ageOfUniverse = univ.Integer(13750000000)
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>>> ageOfUniverse
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Integer(13750000000)
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>>>
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>>> meanMartianSurfaceTemperature = univ.Integer(-63)
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>>> meanMartianSurfaceTemperature
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Integer(-63)
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>>>
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</pre>
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</td></tr></table>
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<p>
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ASN.1 allows to assign human-friendly names to particular values of
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an INTEGER type.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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Temperature ::= INTEGER {
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freezing(0),
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boiling(100)
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}
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</pre>
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</td></tr></table>
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<p>
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The Temperature type expressed in pyasn1:
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ, namedval
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>>> class Temperature(univ.Integer):
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... namedValues = namedval.NamedValues(('freezing', 0), ('boiling', 100))
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...
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>>> t = Temperature(0)
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>>> t
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Temperature('freezing(0)')
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>>> t + 1
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Temperature(1)
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>>> t + 100
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Temperature('boiling(100)')
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>>> t = Temperature('boiling')
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>>> t
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Temperature('boiling(100)')
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>>> Temperature('boiling') / 2
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Temperature(50)
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>>> -1 < Temperature('freezing')
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True
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>>> 47 > Temperature('boiling')
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False
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>>>
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</pre>
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</td></tr></table>
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<p>
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These values labels have no effect on Integer type operations, any value
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still could be assigned to a type (information on value constraints will
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follow further in this paper).
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</p>
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<a name="1.1.4"></a>
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<h4>
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1.1.4 Enumerated type
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</h4>
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<p>
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ASN.1 Enumerated type differs from an Integer type in a number of ways.
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Most important is that its instance can only hold a value that belongs
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to a set of values specified on type declaration.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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error-status ::= ENUMERATED {
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no-error(0),
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authentication-error(10),
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authorization-error(20),
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general-failure(51)
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}
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</pre>
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</td></tr></table>
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<p>
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When constructing Enumerated type we will use two pyasn1 features: values
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labels (as mentioned above) and value constraint (will be described in
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more details later on).
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ, namedval, constraint
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>>> class ErrorStatus(univ.Enumerated):
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... namedValues = namedval.NamedValues(
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... ('no-error', 0),
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... ('authentication-error', 10),
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... ('authorization-error', 20),
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... ('general-failure', 51)
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... )
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... subtypeSpec = univ.Enumerated.subtypeSpec + \
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... constraint.SingleValueConstraint(0, 10, 20, 51)
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...
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>>> errorStatus = univ.ErrorStatus('no-error')
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>>> errorStatus
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ErrorStatus('no-error(0)')
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>>> errorStatus == univ.ErrorStatus('general-failure')
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False
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>>> univ.ErrorStatus('non-existing-state')
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Traceback (most recent call last):
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...
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pyasn1.error.PyAsn1Error: Can't coerce non-existing-state into integer
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>>>
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</pre>
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</td></tr></table>
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<p>
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Particular integer values associated with Enumerated value states
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have no meaning. They should not be used as such or in any kind of
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math operation. Those integer values are only used by codecs to
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transfer state from one entity to another.
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</p>
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<a name="1.1.5"></a>
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<h4>
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1.1.5 Real type
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</h4>
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<p>
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Values of the Real type are a three-component tuple of mantissa, base and
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exponent. All three are integers.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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pi ::= REAL { mantissa 314159, base 10, exponent -5 }
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</pre>
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</td></tr></table>
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<p>
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Corresponding pyasn1 objects can be initialized with either a three-component
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tuple or a Python float. Infinite values could be expressed in a way,
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compatible with Python float type.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> pi = univ.Real((314159, 10, -5))
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>>> pi
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Real((314159, 10,-5))
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>>> float(pi)
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3.14159
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>>> pi == univ.Real(3.14159)
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True
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>>> univ.Real('inf')
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Real('inf')
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>>> univ.Real('-inf') == float('-inf')
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True
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>>>
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</pre>
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</td></tr></table>
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<p>
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If a Real object is initialized from a Python float or yielded by a math
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operation, the base is set to decimal 10 (what affects encoding).
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</p>
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<a name="1.1.6"></a>
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<h4>
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1.1.6 Bit string type
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</h4>
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<p>
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ASN.1 BIT STRING type holds opaque binary data of an arbitrarily length.
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A BIT STRING value could be initialized by either a binary (base 2) or
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hex (base 16) value.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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public-key BIT STRING ::= '1010111011110001010110101101101
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1011000101010000010110101100010
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0110101010000111101010111111110'B
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signature BIT STRING ::= 'AF01330CD932093392100B39FF00DE0'H
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</pre>
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</td></tr></table>
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<p>
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The pyasn1 BitString objects can initialize from native ASN.1 notation
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(base 2 or base 16 strings) or from a Python tuple of binary components.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ
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>>> publicKey = univ.BitString(
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... "'1010111011110001010110101101101"
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... "1011000101010000010110101100010"
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... "0110101010000111101010111111110'B"
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)
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>>> publicKey
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BitString("'10101110111100010101101011011011011000101010000010110101100010\
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0110101010000111101010111111110'B")
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>>> signature = univ.BitString(
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... "'AF01330CD932093392100B39FF00DE0'H"
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... )
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>>> signature
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BitString("'101011110000000100110011000011001101100100110010000010010011001\
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1100100100001000000001011001110011111111100000000110111100000'B")
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>>> fingerprint = univ.BitString(
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... (1, 0, 1, 1 ,0, 1, 1, 1, 0, 1, 0, 1)
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... )
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>>> fingerprint
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BitString("'101101110101'B")
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>>>
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</pre>
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</td></tr></table>
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<p>
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Another BIT STRING initialization method supported by ASN.1 notation
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is to specify only 1-th bits along with their human-friendly label
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and bit offset relative to the beginning of the bit string. With this
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method, all not explicitly mentioned bits are doomed to be zeros.
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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bit-mask BIT STRING ::= {
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read-flag(0),
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write-flag(2),
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run-flag(4)
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}
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</pre>
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</td></tr></table>
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<p>
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To express this in pyasn1, we will employ the named values feature (as with
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Enumeration type).
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</p>
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<table bgcolor="lightgray" border=0 width=100%><TR><TD>
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<pre>
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>>> from pyasn1.type import univ, namedval
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>>> class BitMask(univ.BitString):
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... namedValues = namedval.NamedValues(
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... ('read-flag', 0),
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... ('write-flag', 2),
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... ('run-flag', 4)
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... )
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>>> bitMask = BitMask('read-flag,run-flag')
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>>> bitMask
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BitMask("'10001'B")
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>>> tuple(bitMask)
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(1, 0, 0, 0, 1)
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>>> bitMask[4]
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1
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>>>
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</pre>
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</td></tr></table>
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|
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<p>
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The BitString objects mimic the properties of Python tuple type in part
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of immutable sequence object protocol support.
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</p>
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<a name="1.1.7"></a>
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<h4>
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1.1.7 OctetString type
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</h4>
|
||
|
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<p>
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The OCTET STRING type is a confusing subject. According to ASN.1
|
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specification, this type is similar to BIT STRING, the major difference
|
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is that the former operates in 8-bit chunks of data. What is important
|
||
to note, is that OCTET STRING was NOT designed to handle text strings - the
|
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standard provides many other types specialized for text content. For that
|
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reason, ASN.1 forbids to initialize OCTET STRING values with "quoted text
|
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strings", only binary or hex initializers, similar to BIT STRING ones,
|
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are allowed.
|
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</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
thumbnail OCTET STRING ::= '1000010111101110101111000000111011'B
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thumbnail OCTET STRING ::= 'FA9823C43E43510DE3422'H
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
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However, ASN.1 users (e.g. protocols designers) seem to ignore the original
|
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purpose of the OCTET STRING type - they used it for handling all kinds of
|
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data, including text strings.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
welcome-message OCTET STRING ::= "Welcome to ASN.1 wilderness!"
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
In pyasn1, we have taken a liberal approach and allowed both BIT STRING
|
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style and quoted text initializers for the OctetString objects. To avoid
|
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possible collisions, quoted text is the default initialization syntax.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import univ
|
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>>> thumbnail = univ.OctetString(
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... binValue='1000010111101110101111000000111011'
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... )
|
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>>> thumbnail
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||
OctetString(hexValue='85eebcec0')
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>>> thumbnail = univ.OctetString(
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... hexValue='FA9823C43E43510DE3422'
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... )
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>>> thumbnail
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OctetString(hexValue='fa9823c43e4351de34220')
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>>>
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||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
Most frequent usage of the OctetString class is to instantiate it with
|
||
a text string.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import univ
|
||
>>> welcomeMessage = univ.OctetString('Welcome to ASN.1 wilderness!')
|
||
>>> welcomeMessage
|
||
OctetString(b'Welcome to ASN.1 wilderness!')
|
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>>> print('%s' % welcomeMessage)
|
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Welcome to ASN.1 wilderness!
|
||
>>> welcomeMessage[11:16]
|
||
OctetString(b'ASN.1')
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>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
OctetString objects support the immutable sequence object protocol.
|
||
In other words, they behave like Python 3 bytes (or Python 2 strings).
|
||
</p>
|
||
|
||
<p>
|
||
When running pyasn1 on Python 3, it's better to use the bytes objects for
|
||
OctetString instantiation, as it's more reliable and efficient.
|
||
</p>
|
||
|
||
<p>
|
||
Additionally, OctetString's can also be instantiated with a sequence of
|
||
8-bit integers (ASCII codes).
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> univ.OctetString((77, 101, 101, 103, 111))
|
||
OctetString(b'Meego')
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
It is sometimes convenient to express OctetString instances as 8-bit
|
||
characters (Python 3 bytes or Python 2 strings) or 8-bit integers.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> octetString = univ.OctetString('ABCDEF')
|
||
>>> octetString.asNumbers()
|
||
(65, 66, 67, 68, 69, 70)
|
||
>>> octetString.asOctets()
|
||
b'ABCDEF'
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<a name="1.1.8"></a>
|
||
<h4>
|
||
1.1.8 ObjectIdentifier type
|
||
</h4>
|
||
|
||
<p>
|
||
Values of the OBJECT IDENTIFIER type are sequences of integers that could
|
||
be used to identify virtually anything in the world. Various ASN.1-based
|
||
protocols employ OBJECT IDENTIFIERs for their own identification needs.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
internet-id OBJECT IDENTIFIER ::= {
|
||
iso(1) identified-organization(3) dod(6) internet(1)
|
||
}
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
One of the natural ways to map OBJECT IDENTIFIER type into a Python
|
||
one is to use Python tuples of integers. So this approach is taken by
|
||
pyasn1.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import univ
|
||
>>> internetId = univ.ObjectIdentifier((1, 3, 6, 1))
|
||
>>> internetId
|
||
ObjectIdentifier('1.3.6.1')
|
||
>>> internetId[2]
|
||
6
|
||
>>> internetId[1:3]
|
||
ObjectIdentifier('3.6')
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
A more human-friendly "dotted" notation is also supported.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import univ
|
||
>>> univ.ObjectIdentifier('1.3.6.1')
|
||
ObjectIdentifier('1.3.6.1')
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
Symbolic names of the arcs of object identifier, sometimes present in
|
||
ASN.1 specifications, are not preserved and used in pyasn1 objects.
|
||
</p>
|
||
|
||
<p>
|
||
The ObjectIdentifier objects mimic the properties of Python tuple type in
|
||
part of immutable sequence object protocol support.
|
||
</p>
|
||
|
||
<a name="1.1.9"></a>
|
||
<h4>
|
||
1.1.9 Character string types
|
||
</h4>
|
||
|
||
<p>
|
||
ASN.1 standard introduces a diverse set of text-specific types. All of them
|
||
were designed to handle various types of characters. Some of these types seem
|
||
be obsolete nowdays, as their target technologies are gone. Another issue
|
||
to be aware of is that raw OCTET STRING type is sometimes used in practice
|
||
by ASN.1 users instead of specialized character string types, despite
|
||
explicit prohibition imposed by ASN.1 specification.
|
||
</p>
|
||
|
||
<p>
|
||
The two types are specific to ASN.1 are NumericString and PrintableString.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
welcome-message ::= PrintableString {
|
||
"Welcome to ASN.1 text types"
|
||
}
|
||
|
||
dial-pad-numbers ::= NumericString {
|
||
"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
|
||
}
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
Their pyasn1 implementations are:
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import char
|
||
>>> '%s' % char.PrintableString("Welcome to ASN.1 text types")
|
||
'Welcome to ASN.1 text types'
|
||
>>> dialPadNumbers = char.NumericString(
|
||
"0" "1" "2" "3" "4" "5" "6" "7" "8" "9"
|
||
)
|
||
>>> dialPadNumbers
|
||
NumericString(b'0123456789')
|
||
>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
The following types came to ASN.1 from ISO standards on character sets.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import char
|
||
>>> char.VisibleString("abc")
|
||
VisibleString(b'abc')
|
||
>>> char.IA5String('abc')
|
||
IA5String(b'abc')
|
||
>>> char.TeletexString('abc')
|
||
TeletexString(b'abc')
|
||
>>> char.VideotexString('abc')
|
||
VideotexString(b'abc')
|
||
>>> char.GraphicString('abc')
|
||
GraphicString(b'abc')
|
||
>>> char.GeneralString('abc')
|
||
GeneralString(b'abc')
|
||
>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
The last three types are relatively recent addition to the family of
|
||
character string types: UniversalString, BMPString, UTF8String.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import char
|
||
>>> char.UniversalString("abc")
|
||
UniversalString(b'abc')
|
||
>>> char.BMPString('abc')
|
||
BMPString(b'abc')
|
||
>>> char.UTF8String('abc')
|
||
UTF8String(b'abc')
|
||
>>> utf8String = char.UTF8String('У попа была собака')
|
||
>>> utf8String
|
||
UTF8String(b'\xd0\xa3 \xd0\xbf\xd0\xbe\xd0\xbf\xd0\xb0 \xd0\xb1\xd1\x8b\xd0\xbb\xd0\xb0 \
|
||
\xd1\x81\xd0\xbe\xd0\xb1\xd0\xb0\xd0\xba\xd0\xb0')
|
||
>>> print(utf8String)
|
||
У попа была собака
|
||
>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
In pyasn1, all character type objects behave like Python strings. None of
|
||
them is currently constrained in terms of valid alphabet so it's up to
|
||
the data source to keep an eye on data validation for these types.
|
||
</p>
|
||
|
||
<a name="1.1.10"></a>
|
||
<h4>
|
||
1.1.10 Useful types
|
||
</h4>
|
||
|
||
<p>
|
||
There are three so-called useful types defined in the standard:
|
||
ObjectDescriptor, GeneralizedTime, UTCTime. They all are subtypes
|
||
of GraphicString or VisibleString types therefore useful types are
|
||
character string types.
|
||
</p>
|
||
|
||
<p>
|
||
It's advised by the ASN.1 standard to have an instance of ObjectDescriptor
|
||
type holding a human-readable description of corresponding instance of
|
||
OBJECT IDENTIFIER type. There are no formal linkage between these instances
|
||
and provision for ObjectDescriptor uniqueness in the standard.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import useful
|
||
>>> descrBER = useful.ObjectDescriptor(
|
||
"Basic encoding of a single ASN.1 type"
|
||
)
|
||
>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
GeneralizedTime and UTCTime types are designed to hold a human-readable
|
||
timestamp in a universal and unambiguous form. The former provides
|
||
more flexibility in notation while the latter is more strict but has
|
||
Y2K issues.
|
||
</p>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
;; Mar 8 2010 12:00:00 MSK
|
||
moscow-time GeneralizedTime ::= "20110308120000.0"
|
||
;; Mar 8 2010 12:00:00 UTC
|
||
utc-time GeneralizedTime ::= "201103081200Z"
|
||
;; Mar 8 1999 12:00:00 UTC
|
||
utc-time UTCTime ::= "9803081200Z"
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<table bgcolor="lightgray" border=0 width=100%><TR><TD>
|
||
<pre>
|
||
>>> from pyasn1.type import useful
|
||
>>> moscowTime = useful.GeneralizedTime("20110308120000.0")
|
||
>>> utcTime = useful.UTCTime("9803081200Z")
|
||
>>>
|
||
</pre>
|
||
</td></tr></table>
|
||
|
||
<p>
|
||
Despite their intended use, these types possess no special, time-related,
|
||
handling in pyasn1. They are just printable strings.
|
||
</p>
|
||
|
||
<hr>
|
||
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</center>
|
||
</body>
|
||
</html>
|