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</pre><pre class="rust ">
<span class="doccomment">//! Futures</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This module contains the `Future` trait and a number of adaptors for this</span>
<span class="doccomment">//! trait. See the crate docs, and the docs for `Future`, for full detail.</span>
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">result</span>;
<span class="comment">// Primitive futures</span>
<span class="kw">mod</span> <span class="ident">empty</span>;
<span class="kw">mod</span> <span class="ident">lazy</span>;
<span class="kw">mod</span> <span class="ident">poll_fn</span>;
<span class="attribute">#[<span class="ident">path</span> <span class="op">=</span> <span class="string">"result.rs"</span>]</span>
<span class="kw">mod</span> <span class="ident">result_</span>;
<span class="kw">mod</span> <span class="ident">loop_fn</span>;
<span class="kw">mod</span> <span class="ident">option</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">empty</span>::{<span class="ident">empty</span>, <span class="ident">Empty</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">lazy</span>::{<span class="ident">lazy</span>, <span class="ident">Lazy</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">poll_fn</span>::{<span class="ident">poll_fn</span>, <span class="ident">PollFn</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">result_</span>::{<span class="ident">result</span>, <span class="ident">ok</span>, <span class="ident">err</span>, <span class="ident">FutureResult</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">loop_fn</span>::{<span class="ident">loop_fn</span>, <span class="ident">Loop</span>, <span class="ident">LoopFn</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.4"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use `ok` instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::{<span class="ident">ok</span> <span class="kw">as</span> <span class="ident">finished</span>, <span class="prelude-val">Ok</span> <span class="kw">as</span> <span class="ident">Finished</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.4"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use `err` instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::{<span class="ident">err</span> <span class="kw">as</span> <span class="ident">failed</span>, <span class="prelude-val">Err</span> <span class="kw">as</span> <span class="ident">Failed</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.4"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use `result` instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::{<span class="ident">result</span> <span class="kw">as</span> <span class="ident">done</span>, <span class="ident">FutureResult</span> <span class="kw">as</span> <span class="ident">Done</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.7"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use `FutureResult` instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::{<span class="ident">FutureResult</span> <span class="kw">as</span> <span class="prelude-val">Ok</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.7"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use `FutureResult` instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::{<span class="ident">FutureResult</span> <span class="kw">as</span> <span class="prelude-val">Err</span>};
<span class="comment">// combinators</span>
<span class="kw">mod</span> <span class="ident">and_then</span>;
<span class="kw">mod</span> <span class="ident">flatten</span>;
<span class="kw">mod</span> <span class="ident">flatten_stream</span>;
<span class="kw">mod</span> <span class="ident">fuse</span>;
<span class="kw">mod</span> <span class="ident">into_stream</span>;
<span class="kw">mod</span> <span class="ident">join</span>;
<span class="kw">mod</span> <span class="ident">map</span>;
<span class="kw">mod</span> <span class="ident">map_err</span>;
<span class="kw">mod</span> <span class="ident">from_err</span>;
<span class="kw">mod</span> <span class="ident">or_else</span>;
<span class="kw">mod</span> <span class="ident">select</span>;
<span class="kw">mod</span> <span class="ident">select2</span>;
<span class="kw">mod</span> <span class="ident">then</span>;
<span class="kw">mod</span> <span class="ident">either</span>;
<span class="kw">mod</span> <span class="ident">inspect</span>;
<span class="comment">// impl details</span>
<span class="kw">mod</span> <span class="ident">chain</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">and_then</span>::<span class="ident">AndThen</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">flatten</span>::<span class="ident">Flatten</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">flatten_stream</span>::<span class="ident">FlattenStream</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">fuse</span>::<span class="ident">Fuse</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">into_stream</span>::<span class="ident">IntoStream</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">join</span>::{<span class="ident">Join</span>, <span class="ident">Join3</span>, <span class="ident">Join4</span>, <span class="ident">Join5</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">map</span>::<span class="ident">Map</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">map_err</span>::<span class="ident">MapErr</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">from_err</span>::<span class="ident">FromErr</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">or_else</span>::<span class="ident">OrElse</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">select</span>::{<span class="ident">Select</span>, <span class="ident">SelectNext</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">select2</span>::<span class="ident">Select2</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">then</span>::<span class="ident">Then</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">either</span>::<span class="ident">Either</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">inspect</span>::<span class="ident">Inspect</span>;
<span class="macro">if_std</span><span class="macro">!</span> {
<span class="kw">mod</span> <span class="ident">catch_unwind</span>;
<span class="kw">mod</span> <span class="ident">join_all</span>;
<span class="kw">mod</span> <span class="ident">select_all</span>;
<span class="kw">mod</span> <span class="ident">select_ok</span>;
<span class="kw">mod</span> <span class="ident">shared</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">catch_unwind</span>::<span class="ident">CatchUnwind</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">join_all</span>::{<span class="ident">join_all</span>, <span class="ident">JoinAll</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">select_all</span>::{<span class="ident">SelectAll</span>, <span class="ident">SelectAllNext</span>, <span class="ident">select_all</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">select_ok</span>::{<span class="ident">SelectOk</span>, <span class="ident">select_ok</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">shared</span>::{<span class="ident">Shared</span>, <span class="ident">SharedItem</span>, <span class="ident">SharedError</span>};
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.4"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use join_all instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">join_all</span>::<span class="ident">join_all</span> <span class="kw">as</span> <span class="ident">collect</span>;
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"0.1.4"</span>, <span class="ident">note</span> <span class="op">=</span> <span class="string">"use JoinAll instead"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"with-deprecated"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">join_all</span>::<span class="ident">JoinAll</span> <span class="kw">as</span> <span class="ident">Collect</span>;
<span class="doccomment">/// A type alias for `Box<Future + Send>`</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">note</span> <span class="op">=</span> <span class="string">"removed without replacement, recommended to use a \
local extension trait or function if needed, more \
details in https://github.com/rust-lang-nursery/futures-rs/issues/228"</span>)]</span>
<span class="kw">pub</span> <span class="kw">type</span> <span class="ident">BoxFuture</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="op">=</span> ::<span class="ident">std</span>::<span class="ident">boxed</span>::<span class="ident">Box</span><span class="op"><</span><span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>, <span class="ident">Error</span> <span class="op">=</span> <span class="ident">E</span><span class="op">></span> <span class="op">+</span> <span class="ident">Send</span><span class="op">></span>;
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Future</span><span class="op">></span> <span class="ident">Future</span> <span class="kw">for</span> ::<span class="ident">std</span>::<span class="ident">boxed</span>::<span class="ident">Box</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Item</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Error</span>;
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
(<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">poll</span>()
}
}
}
<span class="kw">use</span> {<span class="ident">Poll</span>, <span class="ident">stream</span>};
<span class="doccomment">/// Trait for types which are a placeholder of a value that may become</span>
<span class="doccomment">/// available at some later point in time.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In addition to the documentation here you can also find more information</span>
<span class="doccomment">/// about futures [online] at [https://tokio.rs](https://tokio.rs)</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [online]: https://tokio.rs/docs/getting-started/futures/</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Futures are used to provide a sentinel through which a value can be</span>
<span class="doccomment">/// referenced. They crucially allow chaining and composing operations through</span>
<span class="doccomment">/// consumption which allows expressing entire trees of computation as one</span>
<span class="doccomment">/// sentinel value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The ergonomics and implementation of the `Future` trait are very similar to</span>
<span class="doccomment">/// the `Iterator` trait in that there is just one methods you need</span>
<span class="doccomment">/// to implement, but you get a whole lot of others for free as a result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # The `poll` method</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The core method of future, `poll`, is used to attempt to generate the value</span>
<span class="doccomment">/// of a `Future`. This method *does not block* but is allowed to inform the</span>
<span class="doccomment">/// caller that the value is not ready yet. Implementations of `poll` may</span>
<span class="doccomment">/// themselves do work to generate the value, but it's guaranteed that this will</span>
<span class="doccomment">/// never block the calling thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A key aspect of this method is that if the value is not yet available the</span>
<span class="doccomment">/// current task is scheduled to receive a notification when it's later ready to</span>
<span class="doccomment">/// be made available. This follows what's typically known as a "readiness" or</span>
<span class="doccomment">/// "pull" model where values are pulled out of futures on demand, and</span>
<span class="doccomment">/// otherwise a task is notified when a value might be ready to get pulled out.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The `poll` method is not intended to be called in general, but rather is</span>
<span class="doccomment">/// typically called in the context of a "task" which drives a future to</span>
<span class="doccomment">/// completion. For more information on this see the `task` module.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// More information about the details of `poll` and the nitty-gritty of tasks</span>
<span class="doccomment">/// can be [found online at tokio.rs][poll-dox].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [poll-dox]: https://tokio.rs/docs/going-deeper-futures/futures-model/</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Combinators</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Like iterators, futures provide a large number of combinators to work with</span>
<span class="doccomment">/// futures to express computations in a much more natural method than</span>
<span class="doccomment">/// scheduling a number of callbacks. For example the `map` method can change</span>
<span class="doccomment">/// a `Future<Item=T>` to a `Future<Item=U>` or an `and_then` combinator could</span>
<span class="doccomment">/// create a future after the first one is done and only be resolved when the</span>
<span class="doccomment">/// second is done.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Combinators act very similarly to the methods on the `Iterator` trait itself</span>
<span class="doccomment">/// or those on `Option` and `Result`. Like with iterators, the combinators are</span>
<span class="doccomment">/// zero-cost and don't impose any extra layers of indirection you wouldn't</span>
<span class="doccomment">/// otherwise have to write down.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// More information about combinators can be found [on tokio.rs].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [on tokio.rs]: https://tokio.rs/docs/going-deeper-futures/futures-mechanics/</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Future</span> {
<span class="doccomment">/// The type of value that this future will resolved with if it is</span>
<span class="doccomment">/// successful.</span>
<span class="kw">type</span> <span class="ident">Item</span>;
<span class="doccomment">/// The type of error that this future will resolve with if it fails in a</span>
<span class="doccomment">/// normal fashion.</span>
<span class="kw">type</span> <span class="ident">Error</span>;
<span class="doccomment">/// Query this future to see if its value has become available, registering</span>
<span class="doccomment">/// interest if it is not.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will check the internal state of the future and assess</span>
<span class="doccomment">/// whether the value is ready to be produced. Implementers of this function</span>
<span class="doccomment">/// should ensure that a call to this **never blocks** as event loops may</span>
<span class="doccomment">/// not work properly otherwise.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// When a future is not ready yet, the `Async::NotReady` value will be</span>
<span class="doccomment">/// returned. In this situation the future will *also* register interest of</span>
<span class="doccomment">/// the current task in the value being produced. This is done by calling</span>
<span class="doccomment">/// `task::park` to retrieve a handle to the current `Task`. When the future</span>
<span class="doccomment">/// is then ready to make progress (e.g. it should be `poll`ed again) the</span>
<span class="doccomment">/// `unpark` method is called on the `Task`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// More information about the details of `poll` and the nitty-gritty of</span>
<span class="doccomment">/// tasks can be [found online at tokio.rs][poll-dox].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [poll-dox]: https://tokio.rs/docs/going-deeper-futures/futures-model/</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Runtime characteristics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function, `poll`, is the primary method for 'making progress'</span>
<span class="doccomment">/// within a tree of futures. For example this method will be called</span>
<span class="doccomment">/// repeatedly as the internal state machine makes its various transitions.</span>
<span class="doccomment">/// Executors are responsible for ensuring that this function is called in</span>
<span class="doccomment">/// the right location (e.g. always on an I/O thread or not). Unless it is</span>
<span class="doccomment">/// otherwise arranged to be so, it should be ensured that **implementations</span>
<span class="doccomment">/// of this function finish very quickly**.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returning quickly prevents unnecessarily clogging up threads and/or</span>
<span class="doccomment">/// event loops while a `poll` function call, for example, takes up compute</span>
<span class="doccomment">/// resources to perform some expensive computation. If it is known ahead</span>
<span class="doccomment">/// of time that a call to `poll` may end up taking awhile, the work should</span>
<span class="doccomment">/// be offloaded to a thread pool (or something similar) to ensure that</span>
<span class="doccomment">/// `poll` can return quickly.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that the `poll` function is not called repeatedly in a loop for</span>
<span class="doccomment">/// futures typically, but only whenever the future itself is ready. If</span>
<span class="doccomment">/// you're familiar with the `poll(2)` or `select(2)` syscalls on Unix</span>
<span class="doccomment">/// it's worth noting that futures typically do *not* suffer the same</span>
<span class="doccomment">/// problems of "all wakeups must poll all events". Futures have enough</span>
<span class="doccomment">/// support for only polling futures which cause a wakeup.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Return value</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function returns `Async::NotReady` if the future is not ready yet,</span>
<span class="doccomment">/// `Err` if the future is finished but resolved to an error, or</span>
<span class="doccomment">/// `Async::Ready` with the result of this future if it's finished</span>
<span class="doccomment">/// successfully. Once a future has finished it is considered a contract</span>
<span class="doccomment">/// error to continue polling the future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If `NotReady` is returned, then the future will internally register</span>
<span class="doccomment">/// interest in the value being produced for the current task (through</span>
<span class="doccomment">/// `task::park`). In other words, the current task will receive a</span>
<span class="doccomment">/// notification (through the `unpark` method) once the value is ready to be</span>
<span class="doccomment">/// produced or the future can make progress.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that if `NotReady` is returned it only means that *this* task will</span>
<span class="doccomment">/// receive a notification. Historical calls to `poll` with different tasks</span>
<span class="doccomment">/// will not receive notifications. In other words, implementers of the</span>
<span class="doccomment">/// `Future` trait need not store a queue of tasks to notify, but only the</span>
<span class="doccomment">/// last task that called this method. Alternatively callers of this method</span>
<span class="doccomment">/// can only rely on the most recent task which call `poll` being notified</span>
<span class="doccomment">/// when a future is ready.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Once a future has completed (returned `Ready` or `Err` from `poll`),</span>
<span class="doccomment">/// then any future calls to `poll` may panic, block forever, or otherwise</span>
<span class="doccomment">/// cause wrong behavior. The `Future` trait itself provides no guarantees</span>
<span class="doccomment">/// about the behavior of `poll` after a future has completed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Callers who may call `poll` too many times may want to consider using</span>
<span class="doccomment">/// the `fuse` adaptor which defines the behavior of `poll`, but comes with</span>
<span class="doccomment">/// a little bit of extra cost.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Additionally, calls to `poll` must always be made from within the</span>
<span class="doccomment">/// context of a task. If a current task is not set then this method will</span>
<span class="doccomment">/// likely panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Errors</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This future may have failed to finish the computation, in which case</span>
<span class="doccomment">/// the `Err` variant will be returned with an appropriate payload of an</span>
<span class="doccomment">/// error.</span>
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>;
<span class="doccomment">/// Block the current thread until this future is resolved.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method will consume ownership of this future, driving it to</span>
<span class="doccomment">/// completion via `poll` and blocking the current thread while it's waiting</span>
<span class="doccomment">/// for the value to become available. Once the future is resolved the</span>
<span class="doccomment">/// result of this future is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// > **Note:** This method is not appropriate to call on event loops or</span>
<span class="doccomment">/// > similar I/O situations because it will prevent the event</span>
<span class="doccomment">/// > loop from making progress (this blocks the thread). This</span>
<span class="doccomment">/// > method should only be called when it's guaranteed that the</span>
<span class="doccomment">/// > blocking work associated with this future will be completed</span>
<span class="doccomment">/// > by another thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is only available when the `use_std` feature of this</span>
<span class="doccomment">/// library is activated, and it is activated by default.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function does not attempt to catch panics. If the `poll` function</span>
<span class="doccomment">/// of this future panics, panics will be propagated to the caller.</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"use_std"</span>)]</span>
<span class="kw">fn</span> <span class="ident">wait</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">result</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span>
{
::<span class="ident">executor</span>::<span class="ident">spawn</span>(<span class="self">self</span>).<span class="ident">wait_future</span>()
}
<span class="doccomment">/// Convenience function for turning this future into a trait object which</span>
<span class="doccomment">/// is also `Send`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This simply avoids the need to write `Box::new` and can often help with</span>
<span class="doccomment">/// type inference as well by always returning a trait object. Note that</span>
<span class="doccomment">/// this method requires the `Send` bound and returns a `BoxFuture`, which</span>
<span class="doccomment">/// also encodes this. If you'd like to create a `Box<Future>` without the</span>
<span class="doccomment">/// `Send` bound, then the `Box::new` function can be used instead.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is only available when the `use_std` feature of this</span>
<span class="doccomment">/// library is activated, and it is activated by default.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future::{BoxFuture, result};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let a: BoxFuture<i32, i32> = result(Ok(1)).boxed();</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"use_std"</span>)]</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="attribute">#[<span class="ident">deprecated</span>(<span class="ident">note</span> <span class="op">=</span> <span class="string">"removed without replacement, recommended to use a \
local extension trait or function if needed, more \
details in https://github.com/rust-lang-nursery/futures-rs/issues/228"</span>)]</span>
<span class="attribute">#[<span class="ident">allow</span>(<span class="ident">deprecated</span>)]</span>
<span class="kw">fn</span> <span class="ident">boxed</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">BoxFuture</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'static</span>
{
::<span class="ident">std</span>::<span class="ident">boxed</span>::<span class="ident">Box</span>::<span class="ident">new</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Map this future's result to a different type, returning a new future of</span>
<span class="doccomment">/// the resulting type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is similar to the `Option::map` or `Iterator::map` where</span>
<span class="doccomment">/// it will change the type of the underlying future. This is useful to</span>
<span class="doccomment">/// chain along a computation once a future has been resolved.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The closure provided will only be called if this future is resolved</span>
<span class="doccomment">/// successfully. If this future returns an error, panics, or is dropped,</span>
<span class="doccomment">/// then the closure provided will never be invoked.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it, similar to the existing `map` methods in the</span>
<span class="doccomment">/// standard library.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let new_future = future.map(|x| x + 3);</span>
<span class="doccomment">/// assert_eq!(new_future.wait(), Ok(4));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Calling `map` on an errored `Future` has no effect:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::err::<u32, u32>(1);</span>
<span class="doccomment">/// let new_future = future.map(|x| x + 3);</span>
<span class="doccomment">/// assert_eq!(new_future.wait(), Err(1));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">map</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">Map</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="self">Self</span>::<span class="ident">Item</span>) <span class="op">-></span> <span class="ident">U</span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="ident">U</span>, <span class="self">Self</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">map</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Map this future's error to a different error, returning a new future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is similar to the `Result::map_err` where it will change</span>
<span class="doccomment">/// the error type of the underlying future. This is useful for example to</span>
<span class="doccomment">/// ensure that futures have the same error type when used with combinators</span>
<span class="doccomment">/// like `select` and `join`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The closure provided will only be called if this future is resolved</span>
<span class="doccomment">/// with an error. If this future returns a success, panics, or is</span>
<span class="doccomment">/// dropped, then the closure provided will never be invoked.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::future::*;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = err::<u32, u32>(1);</span>
<span class="doccomment">/// let new_future = future.map_err(|x| x + 3);</span>
<span class="doccomment">/// assert_eq!(new_future.wait(), Err(4));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Calling `map_err` on a successful `Future` has no effect:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::future::*;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = ok::<u32, u32>(1);</span>
<span class="doccomment">/// let new_future = future.map_err(|x| x + 3);</span>
<span class="doccomment">/// assert_eq!(new_future.wait(), Ok(1));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">map_err</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">E</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">MapErr</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="self">Self</span>::<span class="ident">Error</span>) <span class="op">-></span> <span class="ident">E</span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">E</span>, _<span class="op">></span>(<span class="ident">map_err</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Map this future's error to any error implementing `From` for</span>
<span class="doccomment">/// this future's `Error`, returning a new future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function does for futures what `try!` does for `Result`,</span>
<span class="doccomment">/// by letting the compiler infer the type of the resulting error.</span>
<span class="doccomment">/// Just as `map_err` above, this is useful for example to ensure</span>
<span class="doccomment">/// that futures have the same error type when used with</span>
<span class="doccomment">/// combinators like `select` and `join`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_with_err_u8 = future::err::<(), u8>(1);</span>
<span class="doccomment">/// let future_with_err_u32 = future_with_err_u8.from_err::<u32>();</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">from_err</span><span class="op"><</span><span class="ident">E</span>:<span class="ident">From</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">>></span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">FromErr</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">E</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">E</span>, _<span class="op">></span>(<span class="ident">from_err</span>::<span class="ident">new</span>(<span class="self">self</span>))
}
<span class="doccomment">/// Chain on a computation for when a future finished, passing the result of</span>
<span class="doccomment">/// the future to the provided closure `f`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used to ensure a computation runs regardless of</span>
<span class="doccomment">/// the conclusion of the future. The closure provided will be yielded a</span>
<span class="doccomment">/// `Result` once the future is complete.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The returned value of the closure must implement the `IntoFuture` trait</span>
<span class="doccomment">/// and can represent some more work to be done before the composed future</span>
<span class="doccomment">/// is finished. Note that the `Result` type implements the `IntoFuture`</span>
<span class="doccomment">/// trait so it is possible to simply alter the `Result` yielded to the</span>
<span class="doccomment">/// closure and return it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If this future is dropped or panics then the closure `f` will not be</span>
<span class="doccomment">/// run.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_1 = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let future_of_4 = future_of_1.then(|x| {</span>
<span class="doccomment">/// x.map(|y| y + 3)</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_err_1 = future::err::<u32, u32>(1);</span>
<span class="doccomment">/// let future_of_4 = future_of_err_1.then(|x| {</span>
<span class="doccomment">/// match x {</span>
<span class="doccomment">/// Ok(_) => panic!("expected an error"),</span>
<span class="doccomment">/// Err(y) => future::ok::<u32, u32>(y + 3),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">then</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">Then</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">result</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>) <span class="op">-></span> <span class="ident">B</span>,
<span class="ident">B</span>: <span class="ident">IntoFuture</span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="ident">B</span>::<span class="ident">Item</span>, <span class="ident">B</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">then</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Execute another future after this one has resolved successfully.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can be used to chain two futures together and ensure that</span>
<span class="doccomment">/// the final future isn't resolved until both have finished. The closure</span>
<span class="doccomment">/// provided is yielded the successful result of this future and returns</span>
<span class="doccomment">/// another value which can be converted into a future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that because `Result` implements the `IntoFuture` trait this method</span>
<span class="doccomment">/// can also be useful for chaining fallible and serial computations onto</span>
<span class="doccomment">/// the end of one future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If this future is dropped, panics, or completes with an error then the</span>
<span class="doccomment">/// provided closure `f` is never called.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future::{self, FutureResult};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_1 = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let future_of_4 = future_of_1.and_then(|x| {</span>
<span class="doccomment">/// Ok(x + 3)</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_err_1 = future::err::<u32, u32>(1);</span>
<span class="doccomment">/// future_of_err_1.and_then(|_| -> FutureResult<u32, u32> {</span>
<span class="doccomment">/// panic!("should not be called in case of an error");</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">and_then</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">AndThen</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="self">Self</span>::<span class="ident">Item</span>) <span class="op">-></span> <span class="ident">B</span>,
<span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="ident">B</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">and_then</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Execute another future if this one resolves with an error.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Return a future that passes along this future's value if it succeeds,</span>
<span class="doccomment">/// and otherwise passes the error to the closure `f` and waits for the</span>
<span class="doccomment">/// future it returns. The closure may also simply return a value that can</span>
<span class="doccomment">/// be converted into a future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that because `Result` implements the `IntoFuture` trait this method</span>
<span class="doccomment">/// can also be useful for chaining together fallback computations, where</span>
<span class="doccomment">/// when one fails, the next is attempted.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If this future is dropped, panics, or completes successfully then the</span>
<span class="doccomment">/// provided closure `f` is never called.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future::{self, FutureResult};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_err_1 = future::err::<u32, u32>(1);</span>
<span class="doccomment">/// let future_of_4 = future_of_err_1.or_else(|x| -> Result<u32, u32> {</span>
<span class="doccomment">/// Ok(x + 3)</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future_of_1 = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// future_of_1.or_else(|_| -> FutureResult<u32, u32> {</span>
<span class="doccomment">/// panic!("should not be called in case of success");</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">or_else</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">OrElse</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="self">Self</span>::<span class="ident">Error</span>) <span class="op">-></span> <span class="ident">B</span>,
<span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Item</span> <span class="op">=</span> <span class="self">Self</span>::<span class="ident">Item</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">B</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">or_else</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Waits for either one of two futures to complete.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will return a new future which awaits for either this or</span>
<span class="doccomment">/// the `other` future to complete. The returned future will finish with</span>
<span class="doccomment">/// both the value resolved and a future representing the completion of the</span>
<span class="doccomment">/// other work. Both futures must have the same item and error type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving futures and returns a</span>
<span class="doccomment">/// wrapped version of them.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```no_run</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use std::time;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future1 = future::lazy(|| {</span>
<span class="doccomment">/// thread::sleep(time::Duration::from_secs(5));</span>
<span class="doccomment">/// future::ok::<char, ()>('a')</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future2 = future::lazy(|| {</span>
<span class="doccomment">/// thread::sleep(time::Duration::from_secs(3));</span>
<span class="doccomment">/// future::ok::<char, ()>('b')</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let (value, last_future) = future1.select(future2).wait().ok().unwrap();</span>
<span class="doccomment">/// assert_eq!(value, 'a');</span>
<span class="doccomment">/// assert_eq!(last_future.wait().unwrap(), 'b');</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A poor-man's `join` implemented on top of `select`:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn join<A>(a: A, b: A) -> Box<Future<Item=(u32, u32), Error=u32>></span>
<span class="doccomment">/// where A: Future<Item = u32, Error = u32> + 'static,</span>
<span class="doccomment">/// {</span>
<span class="doccomment">/// Box::new(a.select(b).then(|res| -> Box<Future<Item=_, Error=_>> {</span>
<span class="doccomment">/// match res {</span>
<span class="doccomment">/// Ok((a, b)) => Box::new(b.map(move |b| (a, b))),</span>
<span class="doccomment">/// Err((a, _)) => Box::new(future::err(a)),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }))</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">select</span><span class="op"><</span><span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">other</span>: <span class="ident">B</span>) <span class="op">-></span> <span class="ident">Select</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="kw">let</span> <span class="ident">f</span> <span class="op">=</span> <span class="ident">select</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">other</span>.<span class="ident">into_future</span>());
<span class="ident">assert_future</span>::<span class="op"><</span>(<span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">SelectNext</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span><span class="op">></span>),
(<span class="self">Self</span>::<span class="ident">Error</span>, <span class="ident">SelectNext</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span><span class="op">></span>), _<span class="op">></span>(<span class="ident">f</span>)
}
<span class="doccomment">/// Waits for either one of two differently-typed futures to complete.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will return a new future which awaits for either this or</span>
<span class="doccomment">/// the `other` future to complete. The returned future will finish with</span>
<span class="doccomment">/// both the value resolved and a future representing the completion of the</span>
<span class="doccomment">/// other work.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving futures and returns a</span>
<span class="doccomment">/// wrapped version of them.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Also note that if both this and the second future have the same</span>
<span class="doccomment">/// success/error type you can use the `Either::split` method to</span>
<span class="doccomment">/// conveniently extract out the value at the end.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future::{self, Either};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // A poor-man's join implemented on top of select2</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn join<A, B, E>(a: A, b: B) -> Box<Future<Item=(A::Item, B::Item), Error=E>></span>
<span class="doccomment">/// where A: Future<Error = E> + 'static,</span>
<span class="doccomment">/// B: Future<Error = E> + 'static,</span>
<span class="doccomment">/// E: 'static,</span>
<span class="doccomment">/// {</span>
<span class="doccomment">/// Box::new(a.select2(b).then(|res| -> Box<Future<Item=_, Error=_>> {</span>
<span class="doccomment">/// match res {</span>
<span class="doccomment">/// Ok(Either::A((x, b))) => Box::new(b.map(move |y| (x, y))),</span>
<span class="doccomment">/// Ok(Either::B((y, a))) => Box::new(a.map(move |x| (x, y))),</span>
<span class="doccomment">/// Err(Either::A((e, _))) => Box::new(future::err(e)),</span>
<span class="doccomment">/// Err(Either::B((e, _))) => Box::new(future::err(e)),</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }))</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">select2</span><span class="op"><</span><span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">other</span>: <span class="ident">B</span>) <span class="op">-></span> <span class="ident">Select2</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span>, <span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="ident">select2</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">other</span>.<span class="ident">into_future</span>())
}
<span class="doccomment">/// Joins the result of two futures, waiting for them both to complete.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will return a new future which awaits both this and the</span>
<span class="doccomment">/// `other` future to complete. The returned future will finish with a tuple</span>
<span class="doccomment">/// of both results.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Both futures must have the same error type, and if either finishes with</span>
<span class="doccomment">/// an error then the other will be dropped and that error will be</span>
<span class="doccomment">/// returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let a = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let b = future::ok::<u32, u32>(2);</span>
<span class="doccomment">/// let pair = a.join(b);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(pair.wait(), Ok((1, 2)));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If one or both of the joined `Future`s is errored, the resulting</span>
<span class="doccomment">/// `Future` will be errored:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let a = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let b = future::err::<u32, u32>(2);</span>
<span class="doccomment">/// let pair = a.join(b);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(pair.wait(), Err(2));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">join</span><span class="op"><</span><span class="ident">B</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">other</span>: <span class="ident">B</span>) <span class="op">-></span> <span class="ident">Join</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="kw">let</span> <span class="ident">f</span> <span class="op">=</span> <span class="ident">join</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">other</span>.<span class="ident">into_future</span>());
<span class="ident">assert_future</span>::<span class="op"><</span>(<span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">B</span>::<span class="ident">Item</span>), <span class="self">Self</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">f</span>)
}
<span class="doccomment">/// Same as `join`, but with more futures.</span>
<span class="kw">fn</span> <span class="ident">join3</span><span class="op"><</span><span class="ident">B</span>, <span class="ident">C</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">b</span>: <span class="ident">B</span>, <span class="ident">c</span>: <span class="ident">C</span>) <span class="op">-></span> <span class="ident">Join3</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span>, <span class="ident">C</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">C</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">join</span>::<span class="ident">new3</span>(<span class="self">self</span>, <span class="ident">b</span>.<span class="ident">into_future</span>(), <span class="ident">c</span>.<span class="ident">into_future</span>())
}
<span class="doccomment">/// Same as `join`, but with more futures.</span>
<span class="kw">fn</span> <span class="ident">join4</span><span class="op"><</span><span class="ident">B</span>, <span class="ident">C</span>, <span class="ident">D</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">b</span>: <span class="ident">B</span>, <span class="ident">c</span>: <span class="ident">C</span>, <span class="ident">d</span>: <span class="ident">D</span>)
<span class="op">-></span> <span class="ident">Join4</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span>, <span class="ident">C</span>::<span class="ident">Future</span>, <span class="ident">D</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">C</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">D</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">join</span>::<span class="ident">new4</span>(<span class="self">self</span>, <span class="ident">b</span>.<span class="ident">into_future</span>(), <span class="ident">c</span>.<span class="ident">into_future</span>(), <span class="ident">d</span>.<span class="ident">into_future</span>())
}
<span class="doccomment">/// Same as `join`, but with more futures.</span>
<span class="kw">fn</span> <span class="ident">join5</span><span class="op"><</span><span class="ident">B</span>, <span class="ident">C</span>, <span class="ident">D</span>, <span class="ident">E</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">b</span>: <span class="ident">B</span>, <span class="ident">c</span>: <span class="ident">C</span>, <span class="ident">d</span>: <span class="ident">D</span>, <span class="ident">e</span>: <span class="ident">E</span>)
<span class="op">-></span> <span class="ident">Join5</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">B</span>::<span class="ident">Future</span>, <span class="ident">C</span>::<span class="ident">Future</span>, <span class="ident">D</span>::<span class="ident">Future</span>, <span class="ident">E</span>::<span class="ident">Future</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">B</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">C</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">D</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="ident">E</span>: <span class="ident">IntoFuture</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">join</span>::<span class="ident">new5</span>(<span class="self">self</span>, <span class="ident">b</span>.<span class="ident">into_future</span>(), <span class="ident">c</span>.<span class="ident">into_future</span>(), <span class="ident">d</span>.<span class="ident">into_future</span>(),
<span class="ident">e</span>.<span class="ident">into_future</span>())
}
<span class="doccomment">/// Convert this future into a single element stream.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The returned stream contains single success if this future resolves to</span>
<span class="doccomment">/// success or single error if this future resolves into error.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::ok::<_, bool>(17);</span>
<span class="doccomment">/// let mut stream = future.into_stream();</span>
<span class="doccomment">/// assert_eq!(Ok(Async::Ready(Some(17))), stream.poll());</span>
<span class="doccomment">/// assert_eq!(Ok(Async::Ready(None)), stream.poll());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::err::<bool, _>(19);</span>
<span class="doccomment">/// let mut stream = future.into_stream();</span>
<span class="doccomment">/// assert_eq!(Err(19), stream.poll());</span>
<span class="doccomment">/// assert_eq!(Ok(Async::Ready(None)), stream.poll());</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">into_stream</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">IntoStream</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="ident">into_stream</span>::<span class="ident">new</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Flatten the execution of this future when the successful result of this</span>
<span class="doccomment">/// future is itself another future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This can be useful when combining futures together to flatten the</span>
<span class="doccomment">/// computation out the final result. This method can only be called</span>
<span class="doccomment">/// when the successful result of this future itself implements the</span>
<span class="doccomment">/// `IntoFuture` trait and the error can be created from this future's error</span>
<span class="doccomment">/// type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is roughly equivalent to `self.and_then(|x| x)`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes the receiving future and returns a</span>
<span class="doccomment">/// wrapped version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let nested_future = future::ok::<_, u32>(future::ok::<u32, u32>(1));</span>
<span class="doccomment">/// let future = nested_future.flatten();</span>
<span class="doccomment">/// assert_eq!(future.wait(), Ok(1));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Calling `flatten` on an errored `Future`, or if the inner `Future` is</span>
<span class="doccomment">/// errored, will result in an errored `Future`:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let nested_future = future::ok::<_, u32>(future::err::<u32, u32>(1));</span>
<span class="doccomment">/// let future = nested_future.flatten();</span>
<span class="doccomment">/// assert_eq!(future.wait(), Err(1));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">flatten</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Flatten</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>::<span class="ident">Item</span>: <span class="ident">IntoFuture</span>,
<span class="op"><<</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">Item</span> <span class="kw">as</span> <span class="ident">IntoFuture</span><span class="op">></span>::<span class="ident">Error</span>:
<span class="ident">From</span><span class="op"><<</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="kw">let</span> <span class="ident">f</span> <span class="op">=</span> <span class="ident">flatten</span>::<span class="ident">new</span>(<span class="self">self</span>);
<span class="ident">assert_future</span>::<span class="op"><<</span><span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">Item</span> <span class="kw">as</span> <span class="ident">IntoFuture</span><span class="op">></span>::<span class="ident">Item</span>,
<span class="op"><<</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">Item</span> <span class="kw">as</span> <span class="ident">IntoFuture</span><span class="op">></span>::<span class="ident">Error</span>,
_<span class="op">></span>(<span class="ident">f</span>)
}
<span class="doccomment">/// Flatten the execution of this future when the successful result of this</span>
<span class="doccomment">/// future is a stream.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This can be useful when stream initialization is deferred, and it is</span>
<span class="doccomment">/// convenient to work with that stream as if stream was available at the</span>
<span class="doccomment">/// call site.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this function consumes this future and returns a wrapped</span>
<span class="doccomment">/// version of it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">/// use futures::stream;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let stream_items = vec![17, 18, 19];</span>
<span class="doccomment">/// let future_of_a_stream = future::ok::<_, bool>(stream::iter_ok(stream_items));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let stream = future_of_a_stream.flatten_stream();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut iter = stream.wait();</span>
<span class="doccomment">/// assert_eq!(Ok(17), iter.next().unwrap());</span>
<span class="doccomment">/// assert_eq!(Ok(18), iter.next().unwrap());</span>
<span class="doccomment">/// assert_eq!(Ok(19), iter.next().unwrap());</span>
<span class="doccomment">/// assert_eq!(None, iter.next());</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">flatten_stream</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">FlattenStream</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="op"><</span><span class="self">Self</span> <span class="kw">as</span> <span class="ident">Future</span><span class="op">></span>::<span class="ident">Item</span>: <span class="ident">stream</span>::<span class="ident">Stream</span><span class="op"><</span><span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>,
<span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="ident">flatten_stream</span>::<span class="ident">new</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Fuse a future such that `poll` will never again be called once it has</span>
<span class="doccomment">/// completed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Currently once a future has returned `Ready` or `Err` from</span>
<span class="doccomment">/// `poll` any further calls could exhibit bad behavior such as blocking</span>
<span class="doccomment">/// forever, panicking, never returning, etc. If it is known that `poll`</span>
<span class="doccomment">/// may be called too often then this method can be used to ensure that it</span>
<span class="doccomment">/// has defined semantics.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Once a future has been `fuse`d and it returns a completion from `poll`,</span>
<span class="doccomment">/// then it will forever return `NotReady` from `poll` again (never</span>
<span class="doccomment">/// resolve). This, unlike the trait's `poll` method, is guaranteed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This combinator will drop this future as soon as it's been completed to</span>
<span class="doccomment">/// ensure resources are reclaimed as soon as possible.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut future = future::ok::<i32, u32>(2);</span>
<span class="doccomment">/// assert_eq!(future.poll(), Ok(Async::Ready(2)));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Normally, a call such as this would panic:</span>
<span class="doccomment">/// //future.poll();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // This, however, is guaranteed to not panic</span>
<span class="doccomment">/// let mut future = future::ok::<i32, u32>(2).fuse();</span>
<span class="doccomment">/// assert_eq!(future.poll(), Ok(Async::Ready(2)));</span>
<span class="doccomment">/// assert_eq!(future.poll(), Ok(Async::NotReady));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">fuse</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Fuse</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="kw">let</span> <span class="ident">f</span> <span class="op">=</span> <span class="ident">fuse</span>::<span class="ident">new</span>(<span class="self">self</span>);
<span class="ident">assert_future</span>::<span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">f</span>)
}
<span class="doccomment">/// Do something with the item of a future, passing it on.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// When using futures, you'll often chain several of them together.</span>
<span class="doccomment">/// While working on such code, you might want to check out what's happening at</span>
<span class="doccomment">/// various parts in the pipeline. To do that, insert a call to inspect().</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::ok::<u32, u32>(1);</span>
<span class="doccomment">/// let new_future = future.inspect(|&x| println!("about to resolve: {}", x));</span>
<span class="doccomment">/// assert_eq!(new_future.wait(), Ok(1));</span>
<span class="doccomment">/// ```</span>
<span class="kw">fn</span> <span class="ident">inspect</span><span class="op"><</span><span class="ident">F</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">Inspect</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="self">Self</span>::<span class="ident">Item</span>) <span class="op">-></span> (),
<span class="self">Self</span>: <span class="ident">Sized</span>,
{
<span class="ident">assert_future</span>::<span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span>, _<span class="op">></span>(<span class="ident">inspect</span>::<span class="ident">new</span>(<span class="self">self</span>, <span class="ident">f</span>))
}
<span class="doccomment">/// Catches unwinding panics while polling the future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In general, panics within a future can propagate all the way out to the</span>
<span class="doccomment">/// task level. This combinator makes it possible to halt unwinding within</span>
<span class="doccomment">/// the future itself. It's most commonly used within task executors. It's</span>
<span class="doccomment">/// not recommended to use this for error handling.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this method requires the `UnwindSafe` bound from the standard</span>
<span class="doccomment">/// library. This isn't always applied automatically, and the standard</span>
<span class="doccomment">/// library provides an `AssertUnwindSafe` wrapper type to apply it</span>
<span class="doccomment">/// after-the fact. To assist using this method, the `Future` trait is also</span>
<span class="doccomment">/// implemented for `AssertUnwindSafe<F>` where `F` implements `Future`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is only available when the `use_std` feature of this</span>
<span class="doccomment">/// library is activated, and it is activated by default.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future::{self, FutureResult};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut future = future::ok::<i32, u32>(2);</span>
<span class="doccomment">/// assert!(future.catch_unwind().wait().is_ok());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut future = future::lazy(|| -> FutureResult<i32, u32> {</span>
<span class="doccomment">/// panic!();</span>
<span class="doccomment">/// future::ok::<i32, u32>(2)</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert!(future.catch_unwind().wait().is_err());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"use_std"</span>)]</span>
<span class="kw">fn</span> <span class="ident">catch_unwind</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">CatchUnwind</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span> <span class="op">+</span> ::<span class="ident">std</span>::<span class="ident">panic</span>::<span class="ident">UnwindSafe</span>
{
<span class="ident">catch_unwind</span>::<span class="ident">new</span>(<span class="self">self</span>)
}
<span class="doccomment">/// Create a cloneable handle to this future where all handles will resolve</span>
<span class="doccomment">/// to the same result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The shared() method provides a method to convert any future into a</span>
<span class="doccomment">/// cloneable future. It enables a future to be polled by multiple threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The returned `Shared` future resolves successfully with</span>
<span class="doccomment">/// `SharedItem<Self::Item>` or erroneously with `SharedError<Self::Error>`.</span>
<span class="doccomment">/// Both `SharedItem` and `SharedError` implements `Deref` to allow shared</span>
<span class="doccomment">/// access to the underlying result. Ownership of `Self::Item` and</span>
<span class="doccomment">/// `Self::Error` cannot currently be reclaimed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is only available when the `use_std` feature of this</span>
<span class="doccomment">/// library is activated, and it is activated by default.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::ok::<_, bool>(6);</span>
<span class="doccomment">/// let shared1 = future.shared();</span>
<span class="doccomment">/// let shared2 = shared1.clone();</span>
<span class="doccomment">/// assert_eq!(6, *shared1.wait().unwrap());</span>
<span class="doccomment">/// assert_eq!(6, *shared2.wait().unwrap());</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::thread;</span>
<span class="doccomment">/// use futures::prelude::*;</span>
<span class="doccomment">/// use futures::future;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let future = future::ok::<_, bool>(6);</span>
<span class="doccomment">/// let shared1 = future.shared();</span>
<span class="doccomment">/// let shared2 = shared1.clone();</span>
<span class="doccomment">/// let join_handle = thread::spawn(move || {</span>
<span class="doccomment">/// assert_eq!(6, *shared2.wait().unwrap());</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// assert_eq!(6, *shared1.wait().unwrap());</span>
<span class="doccomment">/// join_handle.join().unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"use_std"</span>)]</span>
<span class="kw">fn</span> <span class="ident">shared</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Shared</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>
<span class="kw">where</span> <span class="self">Self</span>: <span class="ident">Sized</span>
{
<span class="ident">shared</span>::<span class="ident">new</span>(<span class="self">self</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Future</span><span class="op">></span> <span class="ident">Future</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">F</span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Item</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Error</span>;
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> {
(<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">poll</span>()
}
}
<span class="comment">// Just a helper function to ensure the futures we're returning all have the</span>
<span class="comment">// right implementations.</span>
<span class="kw">fn</span> <span class="ident">assert_future</span><span class="op"><</span><span class="ident">A</span>, <span class="ident">B</span>, <span class="ident">F</span><span class="op">></span>(<span class="ident">t</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">F</span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">A</span>, <span class="ident">Error</span><span class="op">=</span><span class="ident">B</span><span class="op">></span>,
{
<span class="ident">t</span>
}
<span class="doccomment">/// Class of types which can be converted into a future.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This trait is very similar to the `IntoIterator` trait and is intended to be</span>
<span class="doccomment">/// used in a very similar fashion.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">IntoFuture</span> {
<span class="doccomment">/// The future that this type can be converted into.</span>
<span class="kw">type</span> <span class="ident">Future</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Item</span>, <span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>;
<span class="doccomment">/// The item that the future may resolve with.</span>
<span class="kw">type</span> <span class="ident">Item</span>;
<span class="doccomment">/// The error that the future may resolve with.</span>
<span class="kw">type</span> <span class="ident">Error</span>;
<span class="doccomment">/// Consumes this object and produces a future.</span>
<span class="kw">fn</span> <span class="ident">into_future</span>(<span class="self">self</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Future</span>;
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">Future</span><span class="op">></span> <span class="ident">IntoFuture</span> <span class="kw">for</span> <span class="ident">F</span> {
<span class="kw">type</span> <span class="ident">Future</span> <span class="op">=</span> <span class="ident">F</span>;
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Item</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">F</span>::<span class="ident">Error</span>;
<span class="kw">fn</span> <span class="ident">into_future</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">F</span> {
<span class="self">self</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> <span class="ident">IntoFuture</span> <span class="kw">for</span> <span class="ident">result</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Future</span> <span class="op">=</span> <span class="ident">FutureResult</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span>;
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">E</span>;
<span class="kw">fn</span> <span class="ident">into_future</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">FutureResult</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="ident">result</span>(<span class="self">self</span>)
}
}
<span class="doccomment">/// Asynchronous conversion from a type `T`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This trait is analogous to `std::convert::From`, adapted to asynchronous</span>
<span class="doccomment">/// computation.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">FutureFrom</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Sized</span> {
<span class="doccomment">/// The future for the conversion.</span>
<span class="kw">type</span> <span class="ident">Future</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="self">Self</span>, <span class="ident">Error</span><span class="op">=</span><span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>;
<span class="doccomment">/// Possible errors during conversion.</span>
<span class="kw">type</span> <span class="ident">Error</span>;
<span class="doccomment">/// Consume the given value, beginning the conversion.</span>
<span class="kw">fn</span> <span class="ident">future_from</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Future</span>;
}
<span class="doccomment">/// A trait for types which can spawn fresh futures.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This trait is typically implemented for "executors", or those types which</span>
<span class="doccomment">/// can execute futures to completion. Futures passed to `Spawn::spawn`</span>
<span class="doccomment">/// typically get turned into a *task* and are then driven to completion.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// On spawn, the executor takes ownership of the future and becomes responsible</span>
<span class="doccomment">/// to call `Future::poll()` whenever a readiness notification is raised.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Executor</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span> <span class="op">=</span> (), <span class="ident">Error</span> <span class="op">=</span> ()<span class="op">>></span> {
<span class="doccomment">/// Spawns a future to run on this `Executor`, typically in the</span>
<span class="doccomment">/// "background".</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will return immediately, and schedule the future `future`</span>
<span class="doccomment">/// to run on `self`. The details of scheduling and execution are left to</span>
<span class="doccomment">/// the implementations of `Executor`, but this is typically a primary point</span>
<span class="doccomment">/// for injecting concurrency in a futures-based system. Futures spawned</span>
<span class="doccomment">/// through this `execute` function tend to run concurrently while they're</span>
<span class="doccomment">/// waiting on events.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Errors</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Implementers of this trait are allowed to reject accepting this future</span>
<span class="doccomment">/// as well. This can happen for various reason such as:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * The executor is shut down</span>
<span class="doccomment">/// * The executor has run out of capacity to execute futures</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The decision is left to the caller how to work with this form of error.</span>
<span class="doccomment">/// The error returned transfers ownership of the future back to the caller.</span>
<span class="kw">fn</span> <span class="ident">execute</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">future</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">ExecuteError</span><span class="op"><</span><span class="ident">F</span><span class="op">>></span>;
}
<span class="doccomment">/// Errors returned from the `Spawn::spawn` function.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ExecuteError</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="ident">future</span>: <span class="ident">F</span>,
<span class="ident">kind</span>: <span class="ident">ExecuteErrorKind</span>,
}
<span class="doccomment">/// Kinds of errors that can be returned from the `Execute::spawn` function.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Executors which may not always be able to accept a future may return one of</span>
<span class="doccomment">/// these errors, indicating why it was unable to spawn a future.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Copy</span>, <span class="ident">Clone</span>, <span class="ident">PartialEq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">ExecuteErrorKind</span> {
<span class="doccomment">/// This executor has shut down and will no longer accept new futures to</span>
<span class="doccomment">/// spawn.</span>
<span class="ident">Shutdown</span>,
<span class="doccomment">/// This executor has no more capacity to run more futures. Other futures</span>
<span class="doccomment">/// need to finish before this executor can accept another.</span>
<span class="ident">NoCapacity</span>,
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="ident">__Nonexhaustive</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> <span class="ident">ExecuteError</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="doccomment">/// Create a new `ExecuteError`</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">kind</span>: <span class="ident">ExecuteErrorKind</span>, <span class="ident">future</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">ExecuteError</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="ident">ExecuteError</span> {
<span class="ident">future</span>: <span class="ident">future</span>,
<span class="ident">kind</span>: <span class="ident">kind</span>,
}
}
<span class="doccomment">/// Returns the associated reason for the error</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">kind</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">ExecuteErrorKind</span> {
<span class="self">self</span>.<span class="ident">kind</span>
}
<span class="doccomment">/// Consumes self and returns the original future that was spawned.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_future</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">F</span> {
<span class="self">self</span>.<span class="ident">future</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">ExecuteError</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">kind</span> {
<span class="ident">ExecuteErrorKind</span>::<span class="ident">Shutdown</span> <span class="op">=></span> <span class="string">"executor has shut down"</span>.<span class="ident">fmt</span>(<span class="ident">f</span>),
<span class="ident">ExecuteErrorKind</span>::<span class="ident">NoCapacity</span> <span class="op">=></span> <span class="string">"executor has no more capacity"</span>.<span class="ident">fmt</span>(<span class="ident">f</span>),
<span class="ident">ExecuteErrorKind</span>::<span class="ident">__Nonexhaustive</span> <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(),
}
}
}
</pre>
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