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#[cfg(feature = "timer")]
use tokio_timer::{throttle::Throttle, Timeout};
use futures::Stream;
#[cfg(feature = "timer")]
use std::time::Duration;
pub use util::enumerate::Enumerate;
/// An extension trait for `Stream` that provides a variety of convenient
/// combinator functions.
///
/// Currently, there are only [`timeout`] and [`throttle`] functions, but
/// this will increase over time.
///
/// Users are not expected to implement this trait. All types that implement
/// `Stream` already implement `StreamExt`.
///
/// This trait can be imported directly or via the Tokio prelude: `use
/// tokio::prelude::*`.
///
/// [`timeout`]: #method.timeout
pub trait StreamExt: Stream {
/// Throttle down the stream by enforcing a fixed delay between items.
///
/// Errors are also delayed.
#[cfg(feature = "timer")]
fn throttle(self, duration: Duration) -> Throttle<Self>
where
Self: Sized,
{
Throttle::new(self, duration)
}
/// Creates a new stream which gives the current iteration count as well
/// as the next value.
///
/// The stream returned yields pairs `(i, val)`, where `i` is the
/// current index of iteration and `val` is the value returned by the
/// iterator.
///
/// # Overflow Behavior
///
/// The method does no guarding against overflows, so counting elements of
/// an iterator with more than [`std::usize::MAX`] elements either produces the
/// wrong result or panics.
fn enumerate(self) -> Enumerate<Self>
where
Self: Sized,
{
Enumerate::new(self)
}
/// Creates a new stream which allows `self` until `timeout`.
///
/// This combinator creates a new stream which wraps the receiving stream
/// with a timeout. For each item, the returned stream is allowed to execute
/// until it completes or `timeout` has elapsed, whichever happens first.
///
/// If an item completes before `timeout` then the stream will yield
/// with that item. Otherwise the stream will yield to an error.
///
/// # Examples
///
/// ```
/// # extern crate tokio;
/// # extern crate futures;
/// use tokio::prelude::*;
/// use std::time::Duration;
/// # use futures::future::{self, FutureResult};
///
/// # fn long_future() -> FutureResult<(), ()> {
/// # future::ok(())
/// # }
/// #
/// # fn main() {
/// let stream = long_future()
/// .into_stream()
/// .timeout(Duration::from_secs(1))
/// .for_each(|i| future::ok(println!("item = {:?}", i)))
/// .map_err(|e| println!("error = {:?}", e));
///
/// tokio::run(stream);
/// # }
/// ```
#[cfg(feature = "timer")]
fn timeout(self, timeout: Duration) -> Timeout<Self>
where
Self: Sized,
{
Timeout::new(self, timeout)
}
}
impl<T: ?Sized> StreamExt for T where T: Stream {}
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