emoji-friendly iterator over chars

main.rs

/// https://stackoverflow.com/a/50396438
/// https://stackoverflow.com/questions/47193584/is-there-an-owned-version-of-stringchars

use std::io::{BufRead, BufReader, Read};
use std::vec::IntoIter;

struct Chunks {
    remaining: IntoIter<char>,
}

impl Chunks {
    fn new(s: String) -> Self {
        Chunks {
            remaining: s.chars().collect::<Vec<_>>().into_iter(),
        }
    }
}

fn reader_chars<R: Read>(rdr: R) -> impl Iterator<Item = char> {
    // We use 6 bytes here to force emoji to be segmented for demo purposes
    // Pick more appropriate size for your case
    let reader = BufReader::with_capacity(6, rdr);

    reader
        .lines()
        .flat_map(|l| l) // Ignoring any errors
        .flat_map(|s| Chunks::new(s).remaining) // from https://stackoverflow.com/q/47193584/155423
}

fn main() {
    // emoji are 4 bytes each
    let data = "😻🧐🐪💩a1.💐\nf😃";
    let data = data.as_bytes();

    for c in reader_chars(data) {
        println!(">{}<", c);
    }
}