Struct postcard::accumulator::CobsAccumulator

pub struct CobsAccumulator<const N: usize> { /* private fields */ }

An accumulator used to collect chunked COBS data and deserialize it.

This is often useful when you receive “parts” of the message at a time, for example when draining a serial port buffer that may not contain an entire uninterrupted message.

Examples

Deserialize a struct by reading chunks from a Reader.

use postcard::accumulator::{CobsAccumulator, FeedResult};
use serde::Deserialize;
use std::io::Read;

let input = /* Anything that implements the `Read` trait */

let mut raw_buf = [0u8; 32];
let mut cobs_buf: CobsAccumulator<256> = CobsAccumulator::new();

while let Ok(ct) = input.read(&mut raw_buf) {
    // Finished reading input
    if ct == 0 {
        break;
    }

    let buf = &raw_buf[..ct];
    let mut window = &buf[..];

    'cobs: while !window.is_empty() {
        window = match cobs_buf.feed::<MyData>(&window) {
            FeedResult::Consumed => break 'cobs,
            FeedResult::OverFull(new_wind) => new_wind,
            FeedResult::DeserError(new_wind) => new_wind,
            FeedResult::Success { data, remaining } => {
                // Do something with `data: MyData` here.

                dbg!(data);

                remaining
            }
        };
    }
}

Implementations

impl<const N: usize> CobsAccumulator<N>

pub const fn new() -> Self

Create a new accumulator.

pub fn feed<'a, T>(&mut self, input: &'a [u8]) -> FeedResult<'a, T>

where T: for<'de> Deserialize<'de>,

Appends data to the internal buffer and attempts to deserialize the accumulated data into T.

pub fn feed_ref<'de, 'a, T>(&'de mut self, input: &'a [u8]) -> FeedResult<'a, T>

where T: Deserialize<'de>,

Appends data to the internal buffer and attempts to deserialize the accumulated data into T.

This differs from feed, as it allows the T to reference data within the internal buffer, but mutably borrows the accumulator for the lifetime of the deserialization. If T does not require the reference, the borrow of self ends at the end of the function.