Crate foundation_ur

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ur is a crate to interact with “Uniform Resources (UR)” encodings of binary data.

The encoding scheme is optimized for transport in URIs and QR codes.

The encoder allows a byte payload to be transmitted in multiple stages, respecting maximum size requirements. Under the hood, a fountain encoder is used to create an unbounded stream of URIs, subsets of which can be recombined at the receiving side into the payload.

For example:

const MAX_FRAGMENT_LENGTH: usize = 5;

let data = "Ten chars!".repeat(10);

encoder.start("bytes", data.as_bytes(), MAX_FRAGMENT_LENGTH);
assert_eq!(
    encoder.next_part().to_string(),
    "ur:bytes/1-20/lpadbbcsiecyvdidatkpfeghihjtcxiabdfevlms"
);

while !decoder.is_complete() {
    let sequence = encoder.current_sequence();
    let part = encoder.next_part();
    // Simulate some communication loss
    if sequence & 1 > 0 {
        decoder.receive(part).unwrap();
    }
}
assert_eq!(decoder.message().unwrap().as_deref(), Some(data.as_bytes()));

The following useful building blocks are also part of the public API:

  • The bytewords module contains functionality to encode byte payloads into a suitable alphabet, achieving hexadecimal byte-per-character efficiency.

  • The fountain module provides an implementation of a fountain encoder, which splits up a byte payload into multiple segments and emits an unbounded stream of parts which can be recombined at the receiving decoder side.

Modules§

Structs§

  • BaseDecoder
    A uniform resource decoder able to receive URIs that encode a fountain part.
  • BaseEncoder
    A uniform resource encoder with an underlying fountain encoding.

Enums§

  • ParseURError
    Errors that can happen during parsing of Uniform Resources.
  • UR
    An uniform resource.

Functions§

  • max_fragment_len
    Calculates the maximum fragment length in bytes that can fit in max_characters, for example, it could be the maximum number of alphanumeric characters in a given QR code.
  • to_string
    Encode a single part UR to a string.

Type Aliases§