WIP: start work on porting udp load test to http

aquatic_http_load_test/src/utils.rs

@@ -0,0 +1,53 @@
+use std::sync::Arc;
+
+use rand_distr::{Standard, Pareto};
+use rand::prelude::*;
+
+use crate::common::*;
+
+
+pub fn select_info_hash_index(
+    config: &Config,
+    state: &LoadTestState,
+    rng: &mut impl Rng,
+) -> usize {
+    pareto_usize(rng, state.pareto, config.handler.number_of_torrents - 1)
+}
+
+
+pub fn pareto_usize(
+    rng: &mut impl Rng,
+    pareto: Arc<Pareto<f64>>,
+    max: usize,
+) -> usize {
+    let p: f64 = pareto.sample(rng);
+    let p = (p.min(101.0f64) - 1.0) / 100.0;
+
+    (p * max as f64) as usize
+}
+
+
+pub fn generate_peer_id() -> PeerId {
+    PeerId(random_20_bytes())
+}
+
+
+pub fn generate_info_hash() -> InfoHash {
+    InfoHash(random_20_bytes())
+}
+
+
+// Don't use SmallRng here for now
+fn random_20_bytes() -> [u8; 20] {
+    let mut bytes = [0; 20];
+
+    for (i, b) in rand::thread_rng()
+        .sample_iter(&Standard)
+        .enumerate()
+        .take(20) {
+
+        bytes[i] = b
+    }
+
+    bytes
+}