Grcov report - rand

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//! Utility to return a random hostname.

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use crate::RngExt as _;

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use rand::{Rng, seq::IndexedRandom as _};

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/// The prefixes we put at the front of every random hostname, with terminating `.`.

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const PREFIXES: &[&str] = &["www."];

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/// The suffixes that we use when picking a random hostname, with preceding `.`.

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const SUFFIXES: &[&str] = &[".com", ".net", ".org"];

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/// The characters that we use for the middle part of a hostname.

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// NOTE: Some characters have restrictions.

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// For example `-` isn't allowed as the first or last character of a subdomain,

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// so we don't include it here (see arti#2597).

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const CHARSET: &[u8] = b"abcdefghijklmnopqrstuvwxyz0123456789";

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/// Lowest permissible hostname length.

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const MIN_LEN: usize = 16;

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/// Highest permissible hostname length.

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const MAX_LEN: usize = 32;

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/// Return a somewhat random-looking hostname.

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///

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/// The specific format of the hostname is not guaranteed.

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pub fn random_hostname<R: Rng>(rng: &mut R) -> String {

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    // TODO: This is, roughly, what C tor does.

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    // But that doesn't mean it's remotely clever.

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    let prefix = PREFIXES.choose(rng).expect("TLDS was empty!?");

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    let suffix = SUFFIXES.choose(rng).expect("TLDS was empty!?");

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    let length: usize = rng

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        .gen_range_checked(MIN_LEN..=MAX_LEN)

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        .expect("Somehow MIN..=MAX wasn't a valid range?");

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    let center_length = length

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        .checked_sub(prefix.len() + suffix.len())

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        .expect("prefix and suffix exceeded MIN_LEN");

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    let mut output = String::from(*prefix);

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    for _ in 0..center_length {

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        output.push(*CHARSET.choose(rng).expect("CHARSET was empty!?") as char);

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    output.push_str(suffix);

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    assert_eq!(length, output.len());

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    output

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#[cfg(test)]

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mod test {

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    // @@ begin test lint list maintained by maint/add_warning @@

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    #![allow(clippy::bool_assert_comparison)]

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    #![allow(clippy::clone_on_copy)]

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    #![allow(clippy::dbg_macro)]

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    #![allow(clippy::mixed_attributes_style)]

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    #![allow(clippy::print_stderr)]

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    #![allow(clippy::print_stdout)]

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    #![allow(clippy::single_char_pattern)]

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    #![allow(clippy::unwrap_used)]

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    #![allow(clippy::unchecked_time_subtraction)]

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    #![allow(clippy::useless_vec)]

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    #![allow(clippy::needless_pass_by_value)]

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    #![allow(clippy::string_slice)] // See arti#2571

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    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

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    use super::*;

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    use crate::test_rng::testing_rng;

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    #[test]

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    fn generate_names() {

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        let mut rng = testing_rng();

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        for _ in 0..100 {

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            let name = random_hostname(&mut rng);

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            assert!(PREFIXES.iter().any(|tld| name.starts_with(tld)));

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            assert!(SUFFIXES.iter().any(|tld| name.ends_with(tld)));

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            assert!(name.len() >= MIN_LEN);

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            assert!(name.len() <= MAX_LEN);

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            for ch in name.chars() {

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                assert!(matches!(ch, '.' | '0'..='9' | 'a'..='z'));

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