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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftASN1 open source project
//
// Copyright (c) 2019-2020 Apple Inc. and the SwiftASN1 project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftASN1 project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
/// An ``ASN1Identifier`` is a representation of the abstract notion of an ASN.1 identifier.
public struct ASN1Identifier {
/// The base tag.
public var tagNumber: UInt
/// The class of the tag.
public var tagClass: TagClass
@inlinable
var _shortForm: UInt8? {
// An ASN.1 identifier can be encoded in short form iff the tag number is strictly
// less than 0x1f.
guard self.tagNumber < 0x1f else { return nil }
var baseNumber = UInt8(truncatingIfNeeded: self.tagNumber)
baseNumber |= self.tagClass._topByteFlags
return baseNumber
}
/// The class of an ASN.1 tag.
public enum TagClass: Hashable, Sendable {
case universal
case application
case contextSpecific
case `private`
@inlinable
init(topByteInWireFormat topByte: UInt8) {
switch topByte >> 6 {
case 0x00:
self = .universal
case 0x01:
self = .application
case 0x02:
self = .contextSpecific
case 0x03:
self = .private
default:
fatalError("Unreachable")
}
}
@inlinable
var _topByteFlags: UInt8 {
switch self {
case .universal:
return 0x00
case .application:
return 0x01 << 6
case .contextSpecific:
return 0x02 << 6
case .private:
return 0x03 << 6
}
}
}
@inlinable
init(shortIdentifier: UInt8) {
precondition(shortIdentifier & 0x1F != 0x1F)
self.tagClass = TagClass(topByteInWireFormat: shortIdentifier)
self.tagNumber = UInt(shortIdentifier & 0x1f)
}
/// Produces a tag from components.
///
/// - parameters:
/// - number: The tag number.
/// - tagClass: The class of the ASN.1 tag.
@inlinable
public init(tagWithNumber number: UInt, tagClass: TagClass) {
self.tagNumber = number
self.tagClass = tagClass
}
}
extension ASN1Identifier {
/// This tag represents an OBJECT IDENTIFIER.
public static let objectIdentifier = ASN1Identifier(shortIdentifier: 0x06)
/// This tag represents a BIT STRING.
public static let bitString = ASN1Identifier(shortIdentifier: 0x03)
/// This tag represents an OCTET STRING.
public static let octetString = ASN1Identifier(shortIdentifier: 0x04)
/// This tag represents an INTEGER.
public static let integer = ASN1Identifier(shortIdentifier: 0x02)
/// This tag represents a SEQUENCE or SEQUENCE OF.
public static let sequence = ASN1Identifier(shortIdentifier: 0x30)
/// This tag represents a SET or SET OF.
public static let set = ASN1Identifier(shortIdentifier: 0x31)
/// This tag represents an ASN.1 NULL.
public static let null = ASN1Identifier(shortIdentifier: 0x05)
/// This tag represents a BOOLEAN.
public static let boolean = ASN1Identifier(shortIdentifier: 0x01)
/// This tag represents an ENUMERATED.
public static let enumerated = ASN1Identifier(shortIdentifier: 0x0a)
/// This tag represents a UTF8STRING.
public static let utf8String = ASN1Identifier(shortIdentifier: 0x0c)
/// This tag represents a NumericString.
public static let numericString = ASN1Identifier(shortIdentifier: 0x12)
/// This tag represents a PrintableString.
public static let printableString = ASN1Identifier(shortIdentifier: 0x13)
/// This tag represents a TeletexString.
public static let teletexString = ASN1Identifier(shortIdentifier: 0x14)
/// This tag represents a VideotexString.
public static let videotexString = ASN1Identifier(shortIdentifier: 0x15)
/// This tag represents an IA5String.
public static let ia5String = ASN1Identifier(shortIdentifier: 0x16)
/// This tag represents a GraphicString.
public static let graphicString = ASN1Identifier(shortIdentifier: 0x19)
/// This tag represents a VisibleString.
public static let visibleString = ASN1Identifier(shortIdentifier: 0x1a)
/// This tag represents a GeneralString.
public static let generalString = ASN1Identifier(shortIdentifier: 0x1b)
/// This tag represents a UniversalString.
public static let universalString = ASN1Identifier(shortIdentifier: 0x1c)
/// This tag represents a BMPString.
public static let bmpString = ASN1Identifier(shortIdentifier: 0x1e)
/// This tag represents a GeneralizedTime.
public static let generalizedTime = ASN1Identifier(shortIdentifier: 0x18)
/// This tag represents a UTCTime.
public static let utcTime = ASN1Identifier(shortIdentifier: 0x17)
}
extension ASN1Identifier: Hashable {}
extension ASN1Identifier: Sendable {}
extension ASN1Identifier: CustomStringConvertible {
@inlinable
public var description: String {
return "ASN1Identifier(tagNumber: \(self.tagNumber), tagClass: \(self.tagClass))"
}
}
extension Array where Element == UInt8 {
@inlinable
mutating func writeIdentifier(_ identifier: ASN1Identifier, constructed: Bool) {
if var shortForm = identifier._shortForm {
if constructed {
shortForm |= 0x20
}
self.append(shortForm)
} else {
// Long-form encoded. The top byte is 0x1f plus the various flags.
var topByte = UInt8(0x1f)
if constructed {
topByte |= 0x20
}
topByte |= identifier.tagClass._topByteFlags
self.append(topByte)
// Then we encode this in base128, just like an OID subidentifier.
self.writeUsing7BitBytesASN1Discipline(unsignedInteger: identifier.tagNumber)
}
}
}
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