pub struct Sequence<'a> {
    pub content: Cow<'a, [u8]>,
}
Expand description

The SEQUENCE object is an ordered list of heteregeneous types.

Sequences can usually be of 2 types:

  • a list of different objects (SEQUENCE, usually parsed as a struct)
  • a list of similar objects (SEQUENCE OF, usually parsed as a Vec<T>)

The current object covers the former. For the latter, see the SequenceOf documentation.

The Sequence object contains the (unparsed) encoded representation of its content. It provides methods to parse and iterate contained objects, or convert the sequence to other types.

Building a Sequence

To build a DER sequence:

  • if the sequence is composed of objects of the same type, the Sequence::from_iter_to_der method can be used
  • otherwise, the ToDer trait can be used to create content incrementally
use asn1_rs::{Integer, Sequence, SerializeResult, ToDer};

fn build_seq<'a>() -> SerializeResult<Sequence<'a>> {
    let mut v = Vec::new();
    // add an Integer object (construct type):
    let i = Integer::from_u32(4);
    let _ = i.write_der(&mut v)?;
    // some primitive objects also implement `ToDer`. A string will be mapped as `Utf8String`:
    let _ = "abcd".write_der(&mut v)?;
    // return the sequence built from the DER content
    Ok(Sequence::new(v.into()))
}

let seq = build_seq().unwrap();

Examples

use asn1_rs::{Error, Sequence};

// build sequence
let it = [2, 3, 4].iter();
let seq = Sequence::from_iter_to_der(it).unwrap();

// `seq` now contains the serialized DER representation of the array

// iterate objects
let mut sum = 0;
for item in seq.der_iter::<u32, Error>() {
    // item has type `Result<u32>`, since parsing the serialized bytes could fail
    sum += item.expect("parsing list item failed");
}
assert_eq!(sum, 9);

Note: the above example encodes a SEQUENCE OF INTEGER object, the SequenceOf object could be used to provide a simpler API.

Fields

content: Cow<'a, [u8]>

Serialized DER representation of the sequence content

Implementations

Build a sequence, given the provided content

Consume the sequence and return the content

Apply the parsing function to the sequence content, consuming the sequence

Note: this function expects the caller to take ownership of content. In some cases, handling the lifetime of objects is not easy (when keeping only references on data). Other methods are provided (depending on the use case):

  • Sequence::parse takes a reference on the sequence data, but does not consume it,
  • Sequence::from_der_and_then does the parsing of the sequence and applying the function in one step, ensuring there are only references (and dropping the temporary sequence).

Same as Sequence::from_der_and_then, but using BER encoding (no constraints).

Parse a DER sequence and apply the provided parsing function to content

After parsing, the sequence object and header are discarded.

use asn1_rs::{FromDer, ParseResult, Sequence};

// Parse a SEQUENCE {
//      a INTEGER (0..255),
//      b INTEGER (0..4294967296)
// }
// and return only `(a,b)
fn parser(i: &[u8]) -> ParseResult<(u8, u32)> {
    Sequence::from_der_and_then(i, |i| {
            let (i, a) = u8::from_der(i)?;
            let (i, b) = u32::from_der(i)?;
            Ok((i, (a, b)))
        }
    )
}

Apply the parsing function to the sequence content (non-consuming version)

Apply the parsing function to the sequence content (consuming version)

Note: to parse and apply a parsing function in one step, use the Sequence::from_der_and_then method.

Limitations

This function fails if the sequence contains Owned data, because the parsing function takes a reference on data (which is dropped).

Return an iterator over the sequence content, attempting to decode objects as BER

This method can be used when all objects from the sequence have the same type.

Return an iterator over the sequence content, attempting to decode objects as DER

This method can be used when all objects from the sequence have the same type.

Attempt to parse the sequence as a SEQUENCE OF items (BER), and return the parsed items as a Vec.

Attempt to parse the sequence as a SEQUENCE OF items (DER), and return the parsed items as a Vec.

Attempt to parse the sequence as a SEQUENCE OF items (BER) (consuming input), and return the parsed items as a Vec.

Note: if Self is an Owned object, the data will be duplicated (causing allocations) into separate objects.

Attempt to parse the sequence as a SEQUENCE OF items (DER) (consuming input), and return the parsed items as a Vec.

Note: if Self is an Owned object, the data will be duplicated (causing allocations) into separate objects.

Attempt to create a Sequence from an iterator over serializable objects (to DER)

Examples
use asn1_rs::Sequence;

// build sequence
let it = [2, 3, 4].iter();
let seq = Sequence::from_iter_to_der(it).unwrap();

Trait Implementations

Converts this type into a shared reference of the (usually inferred) input type.

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

Get the length of the object, when encoded Read more

Attempt to write the DER header to this writer.

Attempt to write the DER content (all except header) to this writer.

Write the DER encoded representation to a newly allocated Vec<u8>.

Similar to using to_vec, but uses provided values without changes. This can generate an invalid encoding for a DER object. Read more

Attempt to write the DER encoded representation (header and content) into this writer. Read more

Similar to using to_der, but uses provided values without changes. This can generate an invalid encoding for a DER object. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.