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</pre><pre class="rust ">
<span class="comment">// Copyright 2013 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! Utilities for random number generation</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! The key functions are `random()` and `Rng::gen()`. These are polymorphic</span>
<span class="doccomment">//! and so can be used to generate any type that implements `Rand`. Type inference</span>
<span class="doccomment">//! means that often a simple call to `rand::random()` or `rng.gen()` will</span>
<span class="doccomment">//! suffice, but sometimes an annotation is required, e.g. `rand::random::<f64>()`.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! See the `distributions` submodule for sampling random numbers from</span>
<span class="doccomment">//! distributions like normal and exponential.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Thread-local RNG</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! There is built-in support for a RNG associated with each thread stored</span>
<span class="doccomment">//! in thread-local storage. This RNG can be accessed via `thread_rng`, or</span>
<span class="doccomment">//! used implicitly via `random`. This RNG is normally randomly seeded</span>
<span class="doccomment">//! from an operating-system source of randomness, e.g. `/dev/urandom` on</span>
<span class="doccomment">//! Unix systems, and will automatically reseed itself from this source</span>
<span class="doccomment">//! after generating 32 KiB of random data.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Cryptographic security</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! An application that requires an entropy source for cryptographic purposes</span>
<span class="doccomment">//! must use `OsRng`, which reads randomness from the source that the operating</span>
<span class="doccomment">//! system provides (e.g. `/dev/urandom` on Unixes or `CryptGenRandom()` on Windows).</span>
<span class="doccomment">//! The other random number generators provided by this module are not suitable</span>
<span class="doccomment">//! for such purposes.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! *Note*: many Unix systems provide `/dev/random` as well as `/dev/urandom`.</span>
<span class="doccomment">//! This module uses `/dev/urandom` for the following reasons:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! - On Linux, `/dev/random` may block if entropy pool is empty; `/dev/urandom` will not block.</span>
<span class="doccomment">//! This does not mean that `/dev/random` provides better output than</span>
<span class="doccomment">//! `/dev/urandom`; the kernel internally runs a cryptographically secure pseudorandom</span>
<span class="doccomment">//! number generator (CSPRNG) based on entropy pool for random number generation,</span>
<span class="doccomment">//! so the "quality" of `/dev/random` is not better than `/dev/urandom` in most cases.</span>
<span class="doccomment">//! However, this means that `/dev/urandom` can yield somewhat predictable randomness</span>
<span class="doccomment">//! if the entropy pool is very small, such as immediately after first booting.</span>
<span class="doccomment">//! Linux 3.17 added the `getrandom(2)` system call which solves the issue: it blocks if entropy</span>
<span class="doccomment">//! pool is not initialized yet, but it does not block once initialized.</span>
<span class="doccomment">//! `getrandom(2)` was based on `getentropy(2)`, an existing system call in OpenBSD.</span>
<span class="doccomment">//! `OsRng` tries to use `getrandom(2)` if available, and use `/dev/urandom` fallback if not.</span>
<span class="doccomment">//! If an application does not have `getrandom` and likely to be run soon after first booting,</span>
<span class="doccomment">//! or on a system with very few entropy sources, one should consider using `/dev/random` via</span>
<span class="doccomment">//! `ReaderRng`.</span>
<span class="doccomment">//! - On some systems (e.g. FreeBSD, OpenBSD and macOS) there is no difference</span>
<span class="doccomment">//! between the two sources. (Also note that, on some systems e.g. FreeBSD, both `/dev/random`</span>
<span class="doccomment">//! and `/dev/urandom` may block once if the CSPRNG has not seeded yet.)</span>
<span class="attribute">#<span class="op">!</span>[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rand"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"0"</span>)]</span>
<span class="kw">use</span> <span class="ident">cell</span>::<span class="ident">RefCell</span>;
<span class="kw">use</span> <span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">io</span>;
<span class="kw">use</span> <span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">rc</span>::<span class="ident">Rc</span>;
<span class="kw">use</span> <span class="ident">sys</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">"32"</span>)]</span>
<span class="kw">use</span> <span class="ident">core_rand</span>::<span class="ident">IsaacRng</span> <span class="kw">as</span> <span class="ident">IsaacWordRng</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">"64"</span>)]</span>
<span class="kw">use</span> <span class="ident">core_rand</span>::<span class="ident">Isaac64Rng</span> <span class="kw">as</span> <span class="ident">IsaacWordRng</span>;
<span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core_rand</span>::{<span class="ident">Rand</span>, <span class="ident">Rng</span>, <span class="ident">SeedableRng</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core_rand</span>::{<span class="ident">XorShiftRng</span>, <span class="ident">IsaacRng</span>, <span class="ident">Isaac64Rng</span>};
<span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core_rand</span>::<span class="ident">reseeding</span>;
<span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">reader</span>;
<span class="doccomment">/// The standard RNG. This is designed to be efficient on the current</span>
<span class="doccomment">/// platform.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Copy</span>, <span class="ident">Clone</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">StdRng</span> {
<span class="ident">rng</span>: <span class="ident">IsaacWordRng</span>,
}
<span class="kw">impl</span> <span class="ident">StdRng</span> {
<span class="doccomment">/// Create a randomly seeded instance of `StdRng`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is a very expensive operation as it has to read</span>
<span class="doccomment">/// randomness from the operating system and use this in an</span>
<span class="doccomment">/// expensive seeding operation. If one is only generating a small</span>
<span class="doccomment">/// number of random numbers, or doesn't need the utmost speed for</span>
<span class="doccomment">/// generating each number, `thread_rng` and/or `random` may be more</span>
<span class="doccomment">/// appropriate.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Reading the randomness from the OS may fail, and any error is</span>
<span class="doccomment">/// propagated via the `io::Result` return value.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-></span> <span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">StdRng</span><span class="op">></span> {
<span class="ident">OsRng</span>::<span class="ident">new</span>().<span class="ident">map</span>(<span class="op">|</span><span class="kw-2">mut</span> <span class="ident">r</span><span class="op">|</span> <span class="ident">StdRng</span> { <span class="ident">rng</span>: <span class="ident">r</span>.<span class="ident">gen</span>() })
}
}
<span class="kw">impl</span> <span class="ident">Rng</span> <span class="kw">for</span> <span class="ident">StdRng</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u32</span> {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">next_u32</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">next_u64</span>()
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">SeedableRng</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> [<span class="ident">usize</span>]<span class="op">></span> <span class="kw">for</span> <span class="ident">StdRng</span> {
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">seed</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> [<span class="ident">usize</span>]) {
<span class="comment">// the internal RNG can just be seeded from the above</span>
<span class="comment">// randomness.</span>
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">reseed</span>(<span class="kw">unsafe</span> {<span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">seed</span>)})
}
<span class="kw">fn</span> <span class="ident">from_seed</span>(<span class="ident">seed</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> [<span class="ident">usize</span>]) <span class="op">-></span> <span class="ident">StdRng</span> {
<span class="ident">StdRng</span> { <span class="ident">rng</span>: <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="kw">unsafe</span> {<span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">seed</span>)}) }
}
}
<span class="doccomment">/// Controls how the thread-local RNG is reseeded.</span>
<span class="kw">struct</span> <span class="ident">ThreadRngReseeder</span>;
<span class="kw">impl</span> <span class="ident">reseeding</span>::<span class="ident">Reseeder</span><span class="op"><</span><span class="ident">StdRng</span><span class="op">></span> <span class="kw">for</span> <span class="ident">ThreadRngReseeder</span> {
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">rng</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">StdRng</span>) {
<span class="kw-2">*</span><span class="ident">rng</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">StdRng</span>::<span class="ident">new</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">r</span>) <span class="op">=></span> <span class="ident">r</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"could not reseed thread_rng: {}"</span>, <span class="ident">e</span>)
}
}
}
<span class="kw">const</span> <span class="ident">THREAD_RNG_RESEED_THRESHOLD</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">32_768</span>;
<span class="kw">type</span> <span class="ident">ThreadRngInner</span> <span class="op">=</span> <span class="ident">reseeding</span>::<span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">StdRng</span>, <span class="ident">ThreadRngReseeder</span><span class="op">></span>;
<span class="doccomment">/// The thread-local RNG.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ThreadRng</span> {
<span class="ident">rng</span>: <span class="ident">Rc</span><span class="op"><</span><span class="ident">RefCell</span><span class="op"><</span><span class="ident">ThreadRngInner</span><span class="op">>></span>,
}
<span class="kw">impl</span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">ThreadRng</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="ident">f</span>.<span class="ident">pad</span>(<span class="string">"ThreadRng { .. }"</span>)
}
}
<span class="doccomment">/// Retrieve the lazily-initialized thread-local random number</span>
<span class="doccomment">/// generator, seeded by the system. Intended to be used in method</span>
<span class="doccomment">/// chaining style, e.g. `thread_rng().gen::<isize>()`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The RNG provided will reseed itself from the operating system</span>
<span class="doccomment">/// after generating a certain amount of randomness.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The internal RNG used is platform and architecture dependent, even</span>
<span class="doccomment">/// if the operating system random number generator is rigged to give</span>
<span class="doccomment">/// the same sequence always. If absolute consistency is required,</span>
<span class="doccomment">/// explicitly select an RNG, e.g. `IsaacRng` or `Isaac64Rng`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">thread_rng</span>() <span class="op">-></span> <span class="ident">ThreadRng</span> {
<span class="comment">// used to make space in TLS for a random number generator</span>
<span class="macro">thread_local</span><span class="macro">!</span>(<span class="kw">static</span> <span class="ident">THREAD_RNG_KEY</span>: <span class="ident">Rc</span><span class="op"><</span><span class="ident">RefCell</span><span class="op"><</span><span class="ident">ThreadRngInner</span><span class="op">>></span> <span class="op">=</span> {
<span class="kw">let</span> <span class="ident">r</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">StdRng</span>::<span class="ident">new</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">r</span>) <span class="op">=></span> <span class="ident">r</span>,
<span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"could not initialize thread_rng: {}"</span>, <span class="ident">e</span>)
};
<span class="kw">let</span> <span class="ident">rng</span> <span class="op">=</span> <span class="ident">reseeding</span>::<span class="ident">ReseedingRng</span>::<span class="ident">new</span>(<span class="ident">r</span>,
<span class="ident">THREAD_RNG_RESEED_THRESHOLD</span>,
<span class="ident">ThreadRngReseeder</span>);
<span class="ident">Rc</span>::<span class="ident">new</span>(<span class="ident">RefCell</span>::<span class="ident">new</span>(<span class="ident">rng</span>))
});
<span class="ident">ThreadRng</span> { <span class="ident">rng</span>: <span class="ident">THREAD_RNG_KEY</span>.<span class="ident">with</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">clone</span>()) }
}
<span class="kw">impl</span> <span class="ident">Rng</span> <span class="kw">for</span> <span class="ident">ThreadRng</span> {
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u32</span> {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">borrow_mut</span>().<span class="ident">next_u32</span>()
}
<span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">borrow_mut</span>().<span class="ident">next_u64</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">bytes</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">borrow_mut</span>().<span class="ident">fill_bytes</span>(<span class="ident">bytes</span>)
}
}
<span class="doccomment">/// A random number generator that retrieves randomness straight from</span>
<span class="doccomment">/// the operating system. Platform sources:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - Unix-like systems (Linux, Android, macOS): read directly from</span>
<span class="doccomment">/// `/dev/urandom`, or from `getrandom(2)` system call if available.</span>
<span class="doccomment">/// - Windows: calls `CryptGenRandom`, using the default cryptographic</span>
<span class="doccomment">/// service provider with the `PROV_RSA_FULL` type.</span>
<span class="doccomment">/// - iOS: calls SecRandomCopyBytes as /dev/(u)random is sandboxed.</span>
<span class="doccomment">/// - OpenBSD: uses the `getentropy(2)` system call.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This does not block.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">OsRng</span>(<span class="ident">sys</span>::<span class="ident">rand</span>::<span class="ident">OsRng</span>);
<span class="kw">impl</span> <span class="ident">OsRng</span> {
<span class="doccomment">/// Create a new `OsRng`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-></span> <span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">OsRng</span><span class="op">></span> {
<span class="ident">sys</span>::<span class="ident">rand</span>::<span class="ident">OsRng</span>::<span class="ident">new</span>().<span class="ident">map</span>(<span class="ident">OsRng</span>)
}
}
<span class="kw">impl</span> <span class="ident">Rng</span> <span class="kw">for</span> <span class="ident">OsRng</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u32</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_u32</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_u64</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">bytes</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">fill_bytes</span>(<span class="ident">bytes</span>)
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">mpsc</span>::<span class="ident">channel</span>;
<span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">Rng</span>;
<span class="kw">use</span> <span class="kw">super</span>::<span class="ident">OsRng</span>;
<span class="kw">use</span> <span class="ident">thread</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_os_rng</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">OsRng</span>::<span class="ident">new</span>().<span class="ident">unwrap</span>();
<span class="ident">r</span>.<span class="ident">next_u32</span>();
<span class="ident">r</span>.<span class="ident">next_u64</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">1000</span>];
<span class="ident">r</span>.<span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"emscripten"</span>, <span class="ident">ignore</span>)]</span>
<span class="kw">fn</span> <span class="ident">test_os_rng_tasks</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">txs</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[];
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="number">20</span> {
<span class="kw">let</span> (<span class="ident">tx</span>, <span class="ident">rx</span>) <span class="op">=</span> <span class="ident">channel</span>();
<span class="ident">txs</span>.<span class="ident">push</span>(<span class="ident">tx</span>);
<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span><span class="op">||</span> {
<span class="comment">// wait until all the threads are ready to go.</span>
<span class="ident">rx</span>.<span class="ident">recv</span>().<span class="ident">unwrap</span>();
<span class="comment">// deschedule to attempt to interleave things as much</span>
<span class="comment">// as possible (XXX: is this a good test?)</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">OsRng</span>::<span class="ident">new</span>().<span class="ident">unwrap</span>();
<span class="ident">thread</span>::<span class="ident">yield_now</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">1000</span>];
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="number">100</span> {
<span class="ident">r</span>.<span class="ident">next_u32</span>();
<span class="ident">thread</span>::<span class="ident">yield_now</span>();
<span class="ident">r</span>.<span class="ident">next_u64</span>();
<span class="ident">thread</span>::<span class="ident">yield_now</span>();
<span class="ident">r</span>.<span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>);
<span class="ident">thread</span>::<span class="ident">yield_now</span>();
}
});
}
<span class="comment">// start all the threads</span>
<span class="kw">for</span> <span class="ident">tx</span> <span class="kw">in</span> <span class="kw-2">&</span><span class="ident">txs</span> {
<span class="ident">tx</span>.<span class="ident">send</span>(()).<span class="ident">unwrap</span>();
}
}
}
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