1 // Copyright 2017 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 // Package asn1 contains supporting types for parsing and building ASN.1
6 // messages with the cryptobyte package.
7 package asn1
8 9 // Tag represents an ASN.1 identifier octet, consisting of a tag number
10 // (indicating a type) and class (such as context-specific or constructed).
11 //
12 // Methods in the cryptobyte package only support the low-tag-number form, i.e.
13 // a single identifier octet with bits 7-8 encoding the class and bits 1-6
14 // encoding the tag number.
15 type Tag uint8
16 17 const (
18 classConstructed = 0x20
19 classContextSpecific = 0x80
20 )
21 22 // Constructed returns t with the constructed class bit set.
23 func (t Tag) Constructed() Tag { return t | classConstructed }
24 25 // ContextSpecific returns t with the context-specific class bit set.
26 func (t Tag) ContextSpecific() Tag { return t | classContextSpecific }
27 28 // The following is a list of standard tag and class combinations.
29 const (
30 BOOLEAN = Tag(1)
31 INTEGER = Tag(2)
32 BIT_STRING = Tag(3)
33 OCTET_STRING = Tag(4)
34 NULL = Tag(5)
35 OBJECT_IDENTIFIER = Tag(6)
36 ENUM = Tag(10)
37 UTF8String = Tag(12)
38 SEQUENCE = Tag(16 | classConstructed)
39 SET = Tag(17 | classConstructed)
40 PrintableString = Tag(19)
41 T61String = Tag(20)
42 IA5String = Tag(22)
43 UTCTime = Tag(23)
44 GeneralizedTime = Tag(24)
45 GeneralString = Tag(27)
46 )
47