Struct Resource 

pub struct Resource { /* private fields */ }

A cloneable handle to a capacity-limited resource pool.

Units are acquired by calling request and awaiting the returned future. If no unit is available the calling process is suspended and woken in FIFO order when one becomes free.

Resource wraps an Rc<RefCell<>> internally, so cloning is cheap and all clones share the same pool. It is !Send + !Sync — consistent with SimEnv.

Two processes sharing a single-unit pump — the second queues until the first one’s guard drops:

use simu::{SimEnv, Resource};

let mut env = SimEnv::with_seed(0);
let pump = Resource::new(1);

for _ in 0..2 {
    let h = env.handle();
    let p = pump.clone(); // same pool — share by cloning, never Arc
    env.spawn(async move {
        let _guard = p.request().await; // second process suspends here
        h.timeout(3.0).await;           // use the pump for 3 time units
    }); // guard drops → pump handed to the next waiter
}

env.run();
assert_eq!(env.now(), 6.0); // servings ran back-to-back, not in parallel

FIFO ordering is the degenerate WaitQueue<()> case: every waiter shares the same (unit) key, so they are served purely in insertion order.

Implementations

impl Resource

pub fn new(capacity: usize) -> Self

Create a new resource pool with the given capacity.

Panics

Panics if capacity is zero.

pub fn request(&self) -> ResourceRequest

Request one unit. Resolves immediately if a unit is available, otherwise suspends the calling process until one is released.

The returned ResourceGuard releases the unit when dropped.

pub fn in_use(&self) -> usize

Number of units currently in use.

pub fn capacity(&self) -> usize

Total capacity of this resource pool.

pub fn queue_len(&self) -> usize

Number of processes currently queued waiting for a unit (SimPy’s len(resource.queue)). Excludes abandoned (canceled) requests.

Trait Implementations

impl Clone for Resource

fn clone(&self) -> Resource

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Resource

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.