tools/telemetry/third_party/gsutil/third_party/pyasn1/doc/tagging.html - Issue 1260493004: Revert "Add gsutil 4.13 to telemetry/third_party"

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Issue 1260493004: Revert "Add gsutil 4.13 to telemetry/third_party" (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master

Patch Set: Created 5 years, 5 months ago

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Index: tools/telemetry/third_party/gsutil/third_party/pyasn1/doc/tagging.html

diff --git a/tools/telemetry/third_party/gsutil/third_party/pyasn1/doc/tagging.html b/tools/telemetry/third_party/gsutil/third_party/pyasn1/doc/tagging.html

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--- a/tools/telemetry/third_party/gsutil/third_party/pyasn1/doc/tagging.html

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@@ -1,233 +0,0 @@

-<html>

-<title>

-Tagging in PyASN1

-</title>

-<head>

-</head>

-<body>

-<center>

-<table width=60%>

-<tr>

-<td>

-<a name="1.2"></a>

-<h4>

-1.2 Tagging in PyASN1

-</h4>

-<p>

-In order to continue with the Constructed ASN.1 types, we will first have

-to introduce the concept of tagging (and its pyasn1 implementation), as

-some of the Constructed types rely upon the tagging feature.

-</p>

-<p>

-When a value is coming into an ASN.1-based system (received from a network

-or read from some storage), the receiving entity has to determine the

-type of the value to interpret and verify it accordingly.

-</p>

-<p>

-Historically, the first data serialization protocol introduced in

-ASN.1 was BER (Basic Encoding Rules). According to BER, any serialized

-value is packed into a triplet of (Type, Length, Value) where Type is a

-code that identifies the value (which is called <i>tag</i> in ASN.1),

-length is the number of bytes occupied by the value in its serialized form

-and value is ASN.1 value in a form suitable for serial transmission or storage.

-</p>

-<p>

-For that reason almost every ASN.1 type has a tag (which is actually a

-BER type) associated with it by default.

-</p>

-<p>

-An ASN.1 tag could be viewed as a tuple of three numbers:

-(Class, Format, Number). While Number identifies a tag, Class component

-is used to create scopes for Numbers. Four scopes are currently defined:

-UNIVERSAL, context-specific, APPLICATION and PRIVATE. The Format component

-is actually a one-bit flag - zero for tags associated with scalar types,

-and one for constructed types (will be discussed later on).

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

-MyIntegerType ::= [12] INTEGER

-MyOctetString ::= [APPLICATION 0] OCTET STRING

-</pre>

-</td></tr></table>

-<p>

-In pyasn1, tags are implemented as immutable, tuple-like objects:

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

->>> from pyasn1.type import tag

->>> myTag = tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 10)

->>> myTag

-Tag(tagClass=128, tagFormat=0, tagId=10)

->>> tuple(myTag)

-(128, 0, 10)

->>> myTag[2]

-10

->>> myTag == tag.Tag(tag.tagClassApplication, tag.tagFormatSimple, 10)

-False

->>>

-</pre>

-</td></tr></table>

-<p>

-Default tag, associated with any ASN.1 type, could be extended or replaced

-to make new type distinguishable from its ancestor. The standard provides

-two modes of tag mangling - IMPLICIT and EXPLICIT.

-</p>

-<p>

-EXPLICIT mode works by appending new tag to the existing ones thus creating

-an ordered set of tags. This set will be considered as a whole for type

-identification and encoding purposes. Important property of EXPLICIT tagging

-mode is that it preserves base type information in encoding what makes it

-possible to completely recover type information from encoding.

-</p>

-<p>

-When tagging in IMPLICIT mode, the outermost existing tag is dropped and

-replaced with a new one.

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

-MyIntegerType ::= [12] IMPLICIT INTEGER

-MyOctetString ::= [APPLICATION 0] EXPLICIT OCTET STRING

-</pre>

-</td></tr></table>

-<p>

-To model both modes of tagging, a specialized container TagSet object (holding

-zero, one or more Tag objects) is used in pyasn1.

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

->>> from pyasn1.type import tag

->>> tagSet = tag.TagSet(

-... # base tag

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 10),

-... # effective tag

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 10)

-... )

->>> tagSet

-TagSet(Tag(tagClass=128, tagFormat=0, tagId=10))

->>> tagSet.getBaseTag()

-Tag(tagClass=128, tagFormat=0, tagId=10)

->>> tagSet = tagSet.tagExplicitly(

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 20)

-... )

->>> tagSet

-TagSet(Tag(tagClass=128, tagFormat=0, tagId=10),

- Tag(tagClass=128, tagFormat=32, tagId=20))

->>> tagSet = tagSet.tagExplicitly(

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 30)

-... )

->>> tagSet

-TagSet(Tag(tagClass=128, tagFormat=0, tagId=10),

- Tag(tagClass=128, tagFormat=32, tagId=20),

- Tag(tagClass=128, tagFormat=32, tagId=30))

->>> tagSet = tagSet.tagImplicitly(

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 40)

-... )

->>> tagSet

-TagSet(Tag(tagClass=128, tagFormat=0, tagId=10),

- Tag(tagClass=128, tagFormat=32, tagId=20),

- Tag(tagClass=128, tagFormat=32, tagId=40))

->>>

-</pre>

-</td></tr></table>

-<p>

-As a side note: the "base tag" concept (accessible through the getBaseTag()

-method) is specific to pyasn1 -- the base tag is used to identify the original

-ASN.1 type of an object in question. Base tag is never occurs in encoding

-and is mostly used internally by pyasn1 for choosing type-specific data

-processing algorithms. The "effective tag" is the one that always appears in

-encoding and is used on tagSets comparation.

-</p>

-<p>

-Any two TagSet objects could be compared to see if one is a derivative

-of the other. Figuring this out is also useful in cases when a type-specific

-data processing algorithms are to be chosen.

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

->>> from pyasn1.type import tag

->>> tagSet1 = tag.TagSet(

-... # base tag

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 10)

-... # effective tag

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 10)

-... )

->>> tagSet2 = tagSet1.tagExplicitly(

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 20)

-... )

->>> tagSet1.isSuperTagSetOf(tagSet2)

-True

->>> tagSet2.isSuperTagSetOf(tagSet1)

-False

->>>

-</pre>

-</td></tr></table>

-<p>

-We will complete this discussion on tagging with a real-world example. The

-following ASN.1 tagged type:

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

-MyIntegerType ::= [12] EXPLICIT INTEGER

-</pre>

-</td></tr></table>

-<p>

-could be expressed in pyasn1 like this:

-</p>

-<table bgcolor="lightgray" border=0 width=100%><TR><TD>

-<pre>

->>> from pyasn1.type import univ, tag

->>> class MyIntegerType(univ.Integer):

-... tagSet = univ.Integer.tagSet.tagExplicitly(

-... tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 12)

-... )

->>> myInteger = MyIntegerType(12345)

->>> myInteger.getTagSet()

-TagSet(Tag(tagClass=0, tagFormat=0, tagId=2),

- Tag(tagClass=128, tagFormat=32, tagId=12))

->>>

-</pre>

-</td></tr></table>

-<p>

-Referring to the above code, the tagSet class attribute is a property of any

-pyasn1 type object that assigns default tagSet to a pyasn1 value object. This

-default tagSet specification can be ignored and effectively replaced by some

-other tagSet value passed on object instantiation.

-</p>

-<p>

-It's important to understand that the tag set property of pyasn1 type/value

-object can never be modifed in place. In other words, a pyasn1 type/value

-object can never change its tags. The only way is to create a new pyasn1

-type/value object and associate different tag set with it.

-</p>

-<hr>

-</td>

-</tr>

-</table>

-</center>

-</body>

-</html>