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#![feature(test)]
#[macro_use]
extern crate lazy_static;
extern crate backtrace;
extern crate test;
use backtrace::Backtrace;
use std::collections::HashMap;
use std::sync::Mutex;
#[derive(Hash, PartialEq, Eq)]
struct Trace(Vec<usize>);
lazy_static! {
static ref BACKTRACES: Mutex<HashMap<Trace, usize>> = Mutex::new(HashMap::new());
}
pub fn at_most(n: usize) {
let hits = {
let mut backtraces = BACKTRACES.lock().unwrap();
let backtrace = Trace(
Backtrace::new_unresolved()
.frames()
.iter()
.map(|f| f.ip() as usize)
.collect(),
);
let hits = backtraces.entry(backtrace).or_insert(0);
*hits += 1;
*hits
};
assert!(hits <= n);
}
#[cfg(test)]
mod tests {
use test::Bencher;
#[test]
fn it_works() {
super::at_most(1);
super::at_most(1);
super::at_most(1);
super::at_most(3);
for _ in 0..5 {
super::at_most(5);
}
}
#[test]
#[should_panic]
fn never_call() {
super::at_most(0);
}
#[test]
#[should_panic]
fn in_loop() {
for _ in 0..5 {
super::at_most(4);
}
}
#[bench]
fn bench(b: &mut Bencher) {
b.iter(|| super::at_most(1000_000_000));
}
}