rust-bitcoin-unsafe-fast/fuzz/fuzz_targets/bitcoin/script_bytes_to_asm_fmt.rs

use std::fmt;

use honggfuzz::fuzz;

// faster than String, we don't need to actually produce the value, just check absence of panics
struct NullWriter;

impl fmt::Write for NullWriter {
    fn write_str(&mut self, _s: &str) -> fmt::Result { Ok(()) }

    fn write_char(&mut self, _c: char) -> fmt::Result { Ok(()) }
}

fn do_test(data: &[u8]) {
    let mut writer = NullWriter;
    bitcoin::Script::from_bytes(data).fmt_asm(&mut writer).unwrap();
}

fn main() {
    loop {
        fuzz!(|data| {
            do_test(data);
        });
    }
}

#[cfg(all(test, fuzzing))]
mod tests {
    fn extend_vec_from_hex(hex: &str, out: &mut Vec<u8>) {
        let mut b = 0;
        for (idx, c) in hex.as_bytes().iter().enumerate() {
            b <<= 4;
            match *c {
                b'A'..=b'F' => b |= c - b'A' + 10,
                b'a'..=b'f' => b |= c - b'a' + 10,
                b'0'..=b'9' => b |= c - b'0',
                _ => panic!("Bad hex"),
            }
            if (idx & 1) == 1 {
                out.push(b);
                b = 0;
            }
        }
    }

    #[test]
    fn duplicate_crash() {
        let mut a = Vec::new();
        extend_vec_from_hex("00000", &mut a);
        super::do_test(&a);
    }
}