wreq_util/emulation/
rand.rs

1use std::{
2    cell::Cell,
3    collections::hash_map::RandomState,
4    hash::{BuildHasher, Hasher},
5    num::Wrapping,
6};
7
8use strum::VariantArray;
9
10use super::{Emulation, EmulationOS, EmulationOption};
11
12// from: https://github.com/seanmonstar/reqwest/blob/44ac897f1ab35ba24a195927043d185d5cbb6912/src/util.rs#L27
13fn fast_random() -> u64 {
14    thread_local! {
15        static RNG: Cell<Wrapping<u64>> = Cell::new(Wrapping(seed()));
16    }
17
18    #[inline]
19    fn seed() -> u64 {
20        let seed = RandomState::new();
21
22        let mut out = 0;
23        let mut cnt = 0;
24        while out == 0 {
25            cnt += 1;
26            let mut hasher = seed.build_hasher();
27            hasher.write_usize(cnt);
28            out = hasher.finish();
29        }
30        out
31    }
32
33    RNG.with(|rng| {
34        let mut n = rng.get();
35        debug_assert_ne!(n.0, 0);
36        n ^= n >> 12;
37        n ^= n << 25;
38        n ^= n >> 27;
39        rng.set(n);
40        n.0.wrapping_mul(0x2545_f491_4f6c_dd1d)
41    })
42}
43
44impl Emulation {
45    /// Returns a random variant of the `Emulation` enum.
46    ///
47    /// This method uses a fast random number generator to select a random variant
48    /// from the `Emulation::VARIANTS` array. The random number generator is based
49    /// on the XOR-Shift algorithm, which is efficient and suitable for use in
50    /// multi-threaded environments.
51    ///
52    /// # Examples
53    ///
54    /// ```
55    /// use wreq_util::Emulation;
56    ///
57    /// let random_emulation = Emulation::random();
58    /// println!("{:?}", random_emulation);
59    /// ```
60    ///
61    /// # Panics
62    ///
63    /// This method will panic if the `Emulation::VARIANTS` array is empty.
64    #[inline]
65    pub fn random() -> EmulationOption {
66        let emulation = Emulation::VARIANTS;
67        let emulation_os = EmulationOS::VARIANTS;
68        let rand = fast_random() as usize;
69        EmulationOption::builder()
70            .emulation(emulation[rand % emulation.len()])
71            .emulation_os(emulation_os[rand % emulation_os.len()])
72            .build()
73    }
74}
75
76#[cfg(test)]
77mod tests {
78    use std::{
79        sync::{Arc, Mutex},
80        thread,
81    };
82
83    use super::*;
84
85    #[test]
86    fn test_concurrent_get_random_emulation() {
87        const THREAD_COUNT: usize = 10;
88        const ITERATIONS: usize = 100;
89
90        let results = Arc::new(Mutex::new(Vec::new()));
91
92        let mut handles = vec![];
93
94        for _ in 0..THREAD_COUNT {
95            let results = Arc::clone(&results);
96            let handle = thread::spawn(move || {
97                for _ in 0..ITERATIONS {
98                    let emulation = Emulation::random();
99                    let mut results = results.lock().unwrap();
100                    results.push(emulation);
101                }
102            });
103            handles.push(handle);
104        }
105
106        for handle in handles {
107            handle.join().unwrap();
108        }
109
110        let results = results.lock().unwrap();
111        println!("Total results: {}", results.len());
112    }
113}
wreq_util/emulation/rand.rs

wreq_util/emulation/
rand.rs
