Enum Tag

#[non_exhaustive]
pub enum Tag {
    Boolean,
    Integer,
    BitString,
    OctetString,
    Null,
    ObjectIdentifier,
    Real,
    Enumerated,
    Utf8String,
    Sequence,
    Set,
    NumericString,
    PrintableString,
    TeletexString,
    VideotexString,
    Ia5String,
    UtcTime,
    GeneralizedTime,
    VisibleString,
    BmpString,
    Application {
        constructed: bool,
        number: TagNumber,
    },
    ContextSpecific {
        constructed: bool,
        number: TagNumber,
    },
    Private {
        constructed: bool,
        number: TagNumber,
    },
}

ASN.1 tags.

Tags are the leading identifier octet of the Tag-Length-Value encoding used by ASN.1 DER and identify the type of the subsequent value.

They are described in X.690 Section 8.1.2: Identifier octets, and structured as follows:

| Class | P/C | Tag Number |

• Bits 8/7: Class
• Bit 6: primitive (0) or constructed (1)
• Bits 5-1: tag number

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Boolean

BOOLEAN tag: 1.

Integer

INTEGER tag: 2.

BitString

BIT STRING tag: 3.

OctetString

OCTET STRING tag: 4.

Null

NULL tag: 5.

ObjectIdentifier

OBJECT IDENTIFIER tag: 6.

Real

REAL tag: 9.

Enumerated

ENUMERATED tag: 10.

Utf8String

UTF8String tag: 12.

Sequence

SEQUENCE tag: 16.

Set

SET and SET OF tag: 17.

NumericString

NumericString tag: 18.

PrintableString

PrintableString tag: 19.

TeletexString

TeletexString tag: 20.

VideotexString

VideotexString tag: 21.

Ia5String

IA5String tag: 22.

UtcTime

UTCTime tag: 23.

GeneralizedTime

GeneralizedTime tag: 24.

VisibleString

VisibleString tag: 26.

BmpString

BMPString tag: 30.

Application

Application tag.

Fields

constructed: bool

Is this tag constructed? (vs primitive).

number: TagNumber

Tag number.

ContextSpecific

Context-specific tag.

Fields

constructed: bool

Is this tag constructed? (vs primitive).

number: TagNumber

Tag number.

Private

Private tag number.

Fields

constructed: bool

Is this tag constructed? (vs primitive).

number: TagNumber

Tag number.

Implementations

impl Tag

pub fn assert_eq(self, expected: Tag) -> Result<Tag>

Assert that this Tag matches the provided expected tag.

On mismatch, returns an Error with ErrorKind::TagUnexpected.

pub fn class(self) -> Class

Get the Class that corresponds to this Tag.

pub fn number(self) -> TagNumber

Get the TagNumber (lower 6-bits) for this tag.

pub fn is_constructed(self) -> bool

Does this tag represent a constructed (as opposed to primitive) field?

pub fn is_application(self) -> bool

Is this an application tag?

pub fn is_context_specific(self) -> bool

Is this a context-specific tag?

pub fn is_private(self) -> bool

Is this a private tag?

pub fn is_universal(self) -> bool

Is this a universal tag?

pub fn octet(self) -> u8

Get the octet encoding for this Tag.

pub fn length_error(self) -> Error

Create an Error for an invalid Length.

pub fn non_canonical_error(self) -> Error

Create an Error for an non-canonical value with the ASN.1 type identified by this tag.

pub fn unexpected_error(self, expected: Option<Self>) -> Error

Create an Error because the current tag was unexpected, with an optional expected tag.

pub fn value_error(self) -> Error

Create an Error for an invalid value with the ASN.1 type identified by this tag.

Trait Implementations

impl Clone for Tag

fn clone(&self) -> Tag

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Tag

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Decode<'a> for Tag

fn decode<R: Reader<'a>>(reader: &mut R) -> Result<Self>

Attempt to decode this message using the provided decoder.

fn from_der(bytes: &'a [u8]) -> Result<Self>

Parse Self from the provided DER-encoded byte slice.

impl DerOrd for Tag

fn der_cmp(&self, other: &Self) -> Result<Ordering>

Return an Ordering between self and other when serialized as ASN.1 DER.

impl Display for Tag

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Encode for Tag

fn encoded_len(&self) -> Result<Length>

Compute the length of this value in bytes when encoded as ASN.1 DER.

fn encode(&self, writer: &mut impl Writer) -> Result<()>

Encode this value as ASN.1 DER using the provided Writer.

fn encode_to_slice<'a>(&self, buf: &'a mut [u8]) -> Result<&'a [u8]>

Encode this value to the provided byte slice, returning a sub-slice containing the encoded message.

fn encode_to_vec(&self, buf: &mut Vec<u8>) -> Result<Length>

Encode this message as ASN.1 DER, appending it to the provided byte vector.

fn to_der(&self) -> Result<Vec<u8>>

Encode this type as DER, returning a byte vector.

impl From<&Tag> for u8

fn from(tag: &Tag) -> u8

Converts to this type from the input type.

impl From<Tag> for u8

fn from(tag: Tag) -> u8

Converts to this type from the input type.

impl Ord for Tag

fn cmp(&self, other: &Tag) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Tag

fn eq(&self, other: &Tag) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Tag

fn partial_cmp(&self, other: &Tag) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl TryFrom<u8> for Tag

type Error = Error

The type returned in the event of a conversion error.

fn try_from(byte: u8) -> Result<Tag>

Performs the conversion.

impl Copy for Tag

impl Eq for Tag

impl StructuralPartialEq for Tag