<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/home/sangenya/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-channel-0.5.1/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.rs - source</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled ><script id="default-settings"></script><script src="../../storage.js"></script><script src="../../crates.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../favicon.svg">
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</pre><pre class="rust">
<span class="doccomment">//! Multi-producer multi-consumer channels for message passing.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This crate is an alternative to [`std::sync::mpsc`] with more features and better performance.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Hello, world!</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::unbounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Create a channel of unbounded capacity.</span>
<span class="doccomment">//! let (s, r) = unbounded();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Send a message into the channel.</span>
<span class="doccomment">//! s.send("Hello, world!").unwrap();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Receive the message from the channel.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok("Hello, world!"));</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Channel types</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Channels can be created using two functions:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! * [`bounded`] creates a channel of bounded capacity, i.e. there is a limit to how many messages</span>
<span class="doccomment">//! it can hold at a time.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! * [`unbounded`] creates a channel of unbounded capacity, i.e. it can hold any number of</span>
<span class="doccomment">//! messages at a time.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Both functions return a [`Sender`] and a [`Receiver`], which represent the two opposite sides</span>
<span class="doccomment">//! of a channel.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Creating a bounded channel:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::bounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Create a channel that can hold at most 5 messages at a time.</span>
<span class="doccomment">//! let (s, r) = bounded(5);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Can send only 5 messages without blocking.</span>
<span class="doccomment">//! for i in 0..5 {</span>
<span class="doccomment">//! s.send(i).unwrap();</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Another call to `send` would block because the channel is full.</span>
<span class="doccomment">//! // s.send(5).unwrap();</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Creating an unbounded channel:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::unbounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Create an unbounded channel.</span>
<span class="doccomment">//! let (s, r) = unbounded();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Can send any number of messages into the channel without blocking.</span>
<span class="doccomment">//! for i in 0..1000 {</span>
<span class="doccomment">//! s.send(i).unwrap();</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A special case is zero-capacity channel, which cannot hold any messages. Instead, send and</span>
<span class="doccomment">//! receive operations must appear at the same time in order to pair up and pass the message over:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::thread;</span>
<span class="doccomment">//! use crossbeam_channel::bounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Create a zero-capacity channel.</span>
<span class="doccomment">//! let (s, r) = bounded(0);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Sending blocks until a receive operation appears on the other side.</span>
<span class="doccomment">//! thread::spawn(move || s.send("Hi!").unwrap());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Receiving blocks until a send operation appears on the other side.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok("Hi!"));</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Sharing channels</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Senders and receivers can be cloned and sent to other threads:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::thread;</span>
<span class="doccomment">//! use crossbeam_channel::bounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s1, r1) = bounded(0);</span>
<span class="doccomment">//! let (s2, r2) = (s1.clone(), r1.clone());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Spawn a thread that receives a message and then sends one.</span>
<span class="doccomment">//! thread::spawn(move || {</span>
<span class="doccomment">//! r2.recv().unwrap();</span>
<span class="doccomment">//! s2.send(2).unwrap();</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Send a message and then receive one.</span>
<span class="doccomment">//! s1.send(1).unwrap();</span>
<span class="doccomment">//! r1.recv().unwrap();</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Note that cloning only creates a new handle to the same sending or receiving side. It does not</span>
<span class="doccomment">//! create a separate stream of messages in any way:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::unbounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s1, r1) = unbounded();</span>
<span class="doccomment">//! let (s2, r2) = (s1.clone(), r1.clone());</span>
<span class="doccomment">//! let (s3, r3) = (s2.clone(), r2.clone());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! s1.send(10).unwrap();</span>
<span class="doccomment">//! s2.send(20).unwrap();</span>
<span class="doccomment">//! s3.send(30).unwrap();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! assert_eq!(r3.recv(), Ok(10));</span>
<span class="doccomment">//! assert_eq!(r1.recv(), Ok(20));</span>
<span class="doccomment">//! assert_eq!(r2.recv(), Ok(30));</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! It's also possible to share senders and receivers by reference:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::bounded;</span>
<span class="doccomment">//! use crossbeam_utils::thread::scope;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s, r) = bounded(0);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! scope(|scope| {</span>
<span class="doccomment">//! // Spawn a thread that receives a message and then sends one.</span>
<span class="doccomment">//! scope.spawn(|_| {</span>
<span class="doccomment">//! r.recv().unwrap();</span>
<span class="doccomment">//! s.send(2).unwrap();</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Send a message and then receive one.</span>
<span class="doccomment">//! s.send(1).unwrap();</span>
<span class="doccomment">//! r.recv().unwrap();</span>
<span class="doccomment">//! }).unwrap();</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Disconnection</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! When all senders or all receivers associated with a channel get dropped, the channel becomes</span>
<span class="doccomment">//! disconnected. No more messages can be sent, but any remaining messages can still be received.</span>
<span class="doccomment">//! Send and receive operations on a disconnected channel never block.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::{unbounded, RecvError};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s, r) = unbounded();</span>
<span class="doccomment">//! s.send(1).unwrap();</span>
<span class="doccomment">//! s.send(2).unwrap();</span>
<span class="doccomment">//! s.send(3).unwrap();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // The only sender is dropped, disconnecting the channel.</span>
<span class="doccomment">//! drop(s);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // The remaining messages can be received.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok(1));</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok(2));</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok(3));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // There are no more messages in the channel.</span>
<span class="doccomment">//! assert!(r.is_empty());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Note that calling `r.recv()` does not block.</span>
<span class="doccomment">//! // Instead, `Err(RecvError)` is returned immediately.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Err(RecvError));</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Blocking operations</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Send and receive operations come in three flavors:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! * Non-blocking (returns immediately with success or failure).</span>
<span class="doccomment">//! * Blocking (waits until the operation succeeds or the channel becomes disconnected).</span>
<span class="doccomment">//! * Blocking with a timeout (blocks only for a certain duration of time).</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A simple example showing the difference between non-blocking and blocking operations:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::{bounded, RecvError, TryRecvError};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s, r) = bounded(1);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Send a message into the channel.</span>
<span class="doccomment">//! s.send("foo").unwrap();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // This call would block because the channel is full.</span>
<span class="doccomment">//! // s.send("bar").unwrap();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Receive the message.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Ok("foo"));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // This call would block because the channel is empty.</span>
<span class="doccomment">//! // r.recv();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Try receiving a message without blocking.</span>
<span class="doccomment">//! assert_eq!(r.try_recv(), Err(TryRecvError::Empty));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Disconnect the channel.</span>
<span class="doccomment">//! drop(s);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // This call doesn't block because the channel is now disconnected.</span>
<span class="doccomment">//! assert_eq!(r.recv(), Err(RecvError));</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Iteration</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Receivers can be used as iterators. For example, method [`iter`] creates an iterator that</span>
<span class="doccomment">//! receives messages until the channel becomes empty and disconnected. Note that iteration may</span>
<span class="doccomment">//! block waiting for next message to arrive.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::thread;</span>
<span class="doccomment">//! use crossbeam_channel::unbounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s, r) = unbounded();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! thread::spawn(move || {</span>
<span class="doccomment">//! s.send(1).unwrap();</span>
<span class="doccomment">//! s.send(2).unwrap();</span>
<span class="doccomment">//! s.send(3).unwrap();</span>
<span class="doccomment">//! drop(s); // Disconnect the channel.</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Collect all messages from the channel.</span>
<span class="doccomment">//! // Note that the call to `collect` blocks until the sender is dropped.</span>
<span class="doccomment">//! let v: Vec<_> = r.iter().collect();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! assert_eq!(v, [1, 2, 3]);</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A non-blocking iterator can be created using [`try_iter`], which receives all available</span>
<span class="doccomment">//! messages without blocking:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_channel::unbounded;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s, r) = unbounded();</span>
<span class="doccomment">//! s.send(1).unwrap();</span>
<span class="doccomment">//! s.send(2).unwrap();</span>
<span class="doccomment">//! s.send(3).unwrap();</span>
<span class="doccomment">//! // No need to drop the sender.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Receive all messages currently in the channel.</span>
<span class="doccomment">//! let v: Vec<_> = r.try_iter().collect();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! assert_eq!(v, [1, 2, 3]);</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Selection</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! The [`select!`] macro allows you to define a set of channel operations, wait until any one of</span>
<span class="doccomment">//! them becomes ready, and finally execute it. If multiple operations are ready at the same time,</span>
<span class="doccomment">//! a random one among them is selected.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! It is also possible to define a `default` case that gets executed if none of the operations are</span>
<span class="doccomment">//! ready, either right away or for a certain duration of time.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! An operation is considered to be ready if it doesn't have to block. Note that it is ready even</span>
<span class="doccomment">//! when it will simply return an error because the channel is disconnected.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! An example of receiving a message from two channels:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::thread;</span>
<span class="doccomment">//! use std::time::Duration;</span>
<span class="doccomment">//! use crossbeam_channel::{select, unbounded};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let (s1, r1) = unbounded();</span>
<span class="doccomment">//! let (s2, r2) = unbounded();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! thread::spawn(move || s1.send(10).unwrap());</span>
<span class="doccomment">//! thread::spawn(move || s2.send(20).unwrap());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // At most one of these two receive operations will be executed.</span>
<span class="doccomment">//! select! {</span>
<span class="doccomment">//! recv(r1) -> msg => assert_eq!(msg, Ok(10)),</span>
<span class="doccomment">//! recv(r2) -> msg => assert_eq!(msg, Ok(20)),</span>
<span class="doccomment">//! default(Duration::from_secs(1)) => println!("timed out"),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! If you need to select over a dynamically created list of channel operations, use [`Select`]</span>
<span class="doccomment">//! instead. The [`select!`] macro is just a convenience wrapper around [`Select`].</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Extra channels</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Three functions can create special kinds of channels, all of which return just a [`Receiver`]</span>
<span class="doccomment">//! handle:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! * [`after`] creates a channel that delivers a single message after a certain duration of time.</span>
<span class="doccomment">//! * [`tick`] creates a channel that delivers messages periodically.</span>
<span class="doccomment">//! * [`never`](never()) creates a channel that never delivers messages.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! These channels are very efficient because messages get lazily generated on receive operations.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! An example that prints elapsed time every 50 milliseconds for the duration of 1 second:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use std::time::{Duration, Instant};</span>
<span class="doccomment">//! use crossbeam_channel::{after, select, tick};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let start = Instant::now();</span>
<span class="doccomment">//! let ticker = tick(Duration::from_millis(50));</span>
<span class="doccomment">//! let timeout = after(Duration::from_secs(1));</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! loop {</span>
<span class="doccomment">//! select! {</span>
<span class="doccomment">//! recv(ticker) -> _ => println!("elapsed: {:?}", start.elapsed()),</span>
<span class="doccomment">//! recv(timeout) -> _ => break,</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`send`]: Sender::send</span>
<span class="doccomment">//! [`recv`]: Receiver::recv</span>
<span class="doccomment">//! [`iter`]: Receiver::iter</span>
<span class="doccomment">//! [`try_iter`]: Receiver::try_iter</span>
<span class="attribute">#![<span class="ident">doc</span>(<span class="ident">test</span>(
<span class="ident">no_crate_inject</span>,
<span class="ident">attr</span>(
<span class="ident">deny</span>(<span class="ident">warnings</span>, <span class="ident">rust_2018_idioms</span>),
<span class="ident">allow</span>(<span class="ident">dead_code</span>, <span class="ident">unused_assignments</span>, <span class="ident">unused_variables</span>)
)
))]</span>
<span class="attribute">#![<span class="ident">warn</span>(
<span class="ident">missing_docs</span>,
<span class="ident">missing_debug_implementations</span>,
<span class="ident">rust_2018_idioms</span>,
<span class="ident">unreachable_pub</span>
)]</span>
<span class="attribute">#![<span class="ident">cfg_attr</span>(<span class="ident">not</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std"</span>), <span class="ident">no_std</span>)]</span>
<span class="kw">use</span> <span class="ident">cfg_if::cfg_if</span>;
<span class="macro">cfg_if!</span> {
<span class="kw">if</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std"</span>)]</span> {
<span class="kw">mod</span> <span class="ident">channel</span>;
<span class="kw">mod</span> <span class="ident">context</span>;
<span class="kw">mod</span> <span class="ident">counter</span>;
<span class="kw">mod</span> <span class="ident">err</span>;
<span class="kw">mod</span> <span class="ident">flavors</span>;
<span class="kw">mod</span> <span class="ident">select</span>;
<span class="kw">mod</span> <span class="ident">select_macro</span>;
<span class="kw">mod</span> <span class="ident">utils</span>;
<span class="kw">mod</span> <span class="ident">waker</span>;
<span class="doccomment">/// Crate internals used by the `select!` macro.</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">internal</span> {
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::select::SelectHandle</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::select</span>::{<span class="ident">select</span>, <span class="ident">select_timeout</span>, <span class="ident">try_select</span>};
}
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::channel</span>::{<span class="ident">after</span>, <span class="ident">at</span>, <span class="ident">never</span>, <span class="ident">tick</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::channel</span>::{<span class="ident">bounded</span>, <span class="ident">unbounded</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::channel</span>::{<span class="ident">IntoIter</span>, <span class="ident">Iter</span>, <span class="ident">TryIter</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::channel</span>::{<span class="ident">Receiver</span>, <span class="ident">Sender</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::select</span>::{<span class="ident">Select</span>, <span class="ident">SelectedOperation</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">ReadyTimeoutError</span>, <span class="ident">SelectTimeoutError</span>, <span class="ident">TryReadyError</span>, <span class="ident">TrySelectError</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">RecvError</span>, <span class="ident">RecvTimeoutError</span>, <span class="ident">TryRecvError</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="kw">crate</span><span class="ident">::err</span>::{<span class="ident">SendError</span>, <span class="ident">SendTimeoutError</span>, <span class="ident">TrySendError</span>};
}
}
</pre></div>
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