leftover

leftover provides a BufRead adapter for processing data, such as records, that spans buffer boundaries. It lets you save a partial record before reading the next chunk and then work with both parts together.

LeftoverReader gives you a view of the current chunk and any bytes saved from earlier chunks. When a record spans chunks, accumulate() saves the current chunk so the next view can include it:

use std::io::BufReader;

use leftover::LeftoverReader;

let input = BufReader::with_capacity(3, b"abcdef".as_slice());
let mut reader = LeftoverReader::new(input);
reader.fill_view().unwrap().accumulate();

let view = reader.fill_view().unwrap();
assert_eq!(view.leftover(), b"abc");
assert_eq!(view.buffer(), b"def");
assert_eq!(view.take_view(2), b"abcde");

accumulate() copies the current chunk. take_view() borrows directly when there is no leftover; otherwise it copies the selected bytes into the leftover. Use take_owned() to copy the result into a new vector that can outlive the next read. Its end argument, like take_view()'s, counts bytes in the current chunk only.

The adapter does not implement BufRead. To append through a delimiter into a reusable vector, use read_until() with any BufRead reader instead.