Struct Length 

pub struct Length {
    inner: u32,
}

ASN.1-encoded length.

Examples

use der::{Decode, Length, SliceReader};

let mut reader = SliceReader::new(&[0x82, 0xAA, 0xBB]).unwrap();
let length = Length::decode(&mut reader).expect("valid length");

assert_eq!(length, Length::new(0xAABB));

5-byte lengths are supported:

use der::{Encode, Length};
let length = Length::new(0x10000000);

assert_eq!(length.encoded_len(), Ok(Length::new(5)));

Invalid lengths produce an error:

use der::{Decode, Length, SliceReader};

let mut reader = SliceReader::new(&[0x81, 0x7F]).unwrap();

Length::decode(&mut reader).expect_err("non-canonical length should be rejected");

Fields

inner: u32

Inner length as a u32. Note that the decoder and encoder also support a maximum length of 32-bits.

Implementations

impl Length

pub const ZERO: Self

Length of 0

pub const ONE: Self

Length of 1

pub const MAX: Self

Maximum length (u32::MAX).

pub const fn new(value: u32) -> Self

Create a new Length for any value which fits inside of a u16.

This function is const-safe and therefore useful for Length constants.

pub(crate) const fn new_usize(len: usize) -> Result<Self>

Create a new Length for any value which fits inside the length type.

This function is const-safe and therefore useful for Length constants.

pub const fn is_zero(self) -> bool

Is this length equal to zero?

pub fn for_tlv(self, tag: Tag) -> Result<Self>

Get the length of DER Tag-Length-Value (TLV) encoded data if self is the length of the inner “value” portion of the message.

Errors

Returns an error if an overflow occurred computing the length.

pub fn saturating_add(self, rhs: Self) -> Self

Perform saturating addition of two lengths.

pub fn saturating_sub(self, rhs: Self) -> Self

Perform saturating subtraction of two lengths.

fn initial_octet(self) -> Option<u8>

Get initial octet of the encoded length (if one is required).

From X.690 Section 8.1.3.5:

In the long form, the length octets shall consist of an initial octet and one or more subsequent octets. The initial octet shall be encoded as follows:

a) bit 8 shall be one; b) bits 7 to 1 shall encode the number of subsequent octets in the length octets, as an unsigned binary integer with bit 7 as the most significant bit; c) the value 11111111₂ shall not be used.

Trait Implementations

impl Add<Length> for Result<Length>

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: Length) -> Self

Performs the + operation.

impl Add<u16> for Length

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: u16) -> Result<Self>

Performs the + operation.

impl Add<u32> for Length

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: u32) -> Result<Self>

Performs the + operation.

impl Add<u8> for Length

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: u8) -> Result<Self>

Performs the + operation.

impl Add<usize> for Length

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: usize) -> Result<Self>

Performs the + operation.

impl Add for Length

type Output = Result<Length, Error>

The resulting type after applying the + operator.

fn add(self, other: Self) -> Result<Self>

Performs the + operation.

impl Clone for Length

fn clone(&self) -> Length

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Length

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

Formats the value using the given formatter.

impl<'a> Decode<'a> for Length

type Error = Error

Type returned in the event of a decoding error.

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

Attempt to decode this TLV message using the provided decoder.

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

Parse Self from the provided DER-encoded byte slice.

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

Parse Self from the provided DER-encoded byte slice.

impl Default for Length

fn default() -> Length

Returns the “default value” for a type.

impl DerOrd for Length

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

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

impl Display for Length

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

Formats the value using the given formatter.

impl Encode for Length

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

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

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

Encode this TLV object as ASN.1 DER using the provided Writer.

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

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

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

Encode this TLV object as ASN.1 DER, returning a byte vector.

impl From<Length> for u32

fn from(length: Length) -> u32

Converts to this type from the input type.

impl From<u16> for Length

fn from(len: u16) -> Length

Converts to this type from the input type.

impl From<u32> for Length

fn from(len: u32) -> Length

Converts to this type from the input type.

impl From<u8> for Length

fn from(len: u8) -> Length

Converts to this type from the input type.

impl Hash for Length

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Length

fn cmp(&self, other: &Length) -> 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 Length

fn eq(&self, other: &Length) -> 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 Length

fn partial_cmp(&self, other: &Length) -> 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 Sub<Length> for Result<Length>

type Output = Result<Length, Error>

The resulting type after applying the - operator.

fn sub(self, other: Length) -> Self

Performs the - operation.

impl Sub for Length

type Output = Result<Length, Error>

The resulting type after applying the - operator.

fn sub(self, other: Length) -> Result<Self>

Performs the - operation.

impl TryFrom<Length> for usize

type Error = Error

The type returned in the event of a conversion error.

fn try_from(len: Length) -> Result<usize>

Performs the conversion.

impl TryFrom<usize> for Length

type Error = Error

The type returned in the event of a conversion error.

fn try_from(len: usize) -> Result<Length>

Performs the conversion.

impl Copy for Length

impl Eq for Length

impl StructuralPartialEq for Length