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<!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/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/getrandom-0.2.7/src/use_file.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>use_file.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><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="../../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../../dark.css" disabled><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../getrandom/index.html"><div class="logo-container"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></div>
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</pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or https://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">//! Implementations that just need to read from a file</span>
<span class="kw">use</span> <span class="kw">crate</span>::{
<span class="ident">util::LazyUsize</span>,
<span class="ident">util_libc</span>::{<span class="ident">open_readonly</span>, <span class="ident">sys_fill_exact</span>},
<span class="ident">Error</span>,
};
<span class="kw">use</span> <span class="ident">core</span>::{
<span class="ident">cell::UnsafeCell</span>,
<span class="ident">sync::atomic</span>::{<span class="ident">AtomicUsize</span>, <span class="ident">Ordering::Relaxed</span>},
};
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"dragonfly"</span>,
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"emscripten"</span>,
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"haiku"</span>,
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"macos"</span>,
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"solaris"</span>,
<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"illumos"</span>
))]</span>
<span class="kw">const</span> <span class="ident">FILE_PATH</span>: <span class="kw-2">&</span><span class="ident">str</span> <span class="op">=</span> <span class="string">"/dev/random\0"</span>;
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"android"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"linux"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"redox"</span>))]</span>
<span class="kw">const</span> <span class="ident">FILE_PATH</span>: <span class="kw-2">&</span><span class="ident">str</span> <span class="op">=</span> <span class="string">"/dev/urandom\0"</span>;
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">getrandom_inner</span>(<span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Error</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">fd</span> <span class="op">=</span> <span class="ident">get_rng_fd</span>()<span class="question-mark">?</span>;
<span class="kw">let</span> <span class="ident">read</span> <span class="op">=</span> <span class="op">|</span><span class="ident">buf</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]<span class="op">|</span> <span class="kw">unsafe</span> { <span class="ident">libc::read</span>(<span class="ident">fd</span>, <span class="ident">buf</span>.<span class="ident">as_mut_ptr</span>() <span class="kw">as</span> <span class="kw-2">*mut</span> <span class="kw">_</span>, <span class="ident">buf</span>.<span class="ident">len</span>()) };
<span class="kw">if</span> <span class="macro">cfg!</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"emscripten"</span>) {
<span class="comment">// `Crypto.getRandomValues` documents `dest` should be at most 65536 bytes.</span>
<span class="kw">for</span> <span class="ident">chunk</span> <span class="kw">in</span> <span class="ident">dest</span>.<span class="ident">chunks_mut</span>(<span class="number">65536</span>) {
<span class="ident">sys_fill_exact</span>(<span class="ident">chunk</span>, <span class="ident">read</span>)<span class="question-mark">?</span>;
}
} <span class="kw">else</span> {
<span class="ident">sys_fill_exact</span>(<span class="ident">dest</span>, <span class="ident">read</span>)<span class="question-mark">?</span>;
}
<span class="prelude-val">Ok</span>(())
}
<span class="comment">// Returns the file descriptor for the device file used to retrieve random</span>
<span class="comment">// bytes. The file will be opened exactly once. All subsequent calls will</span>
<span class="comment">// return the same file descriptor. This file descriptor is never closed.</span>
<span class="kw">fn</span> <span class="ident">get_rng_fd</span>() -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">libc::c_int</span>, <span class="ident">Error</span><span class="op">></span> {
<span class="kw">static</span> <span class="ident">FD</span>: <span class="ident">AtomicUsize</span> <span class="op">=</span> <span class="ident">AtomicUsize::new</span>(<span class="ident">LazyUsize::UNINIT</span>);
<span class="kw">fn</span> <span class="ident">get_fd</span>() -> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">libc::c_int</span><span class="op">></span> {
<span class="kw">match</span> <span class="ident">FD</span>.<span class="ident">load</span>(<span class="ident">Relaxed</span>) {
<span class="ident">LazyUsize::UNINIT</span> => <span class="prelude-val">None</span>,
<span class="ident">val</span> => <span class="prelude-val">Some</span>(<span class="ident">val</span> <span class="kw">as</span> <span class="ident">libc::c_int</span>),
}
}
<span class="comment">// Use double-checked locking to avoid acquiring the lock if possible.</span>
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">fd</span>) <span class="op">=</span> <span class="ident">get_fd</span>() {
<span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">fd</span>);
}
<span class="comment">// SAFETY: We use the mutex only in this method, and we always unlock it</span>
<span class="comment">// before returning, making sure we don't violate the pthread_mutex_t API.</span>
<span class="kw">static</span> <span class="ident">MUTEX</span>: <span class="ident">Mutex</span> <span class="op">=</span> <span class="ident">Mutex::new</span>();
<span class="kw">unsafe</span> { <span class="ident">MUTEX</span>.<span class="ident">lock</span>() };
<span class="kw">let</span> <span class="ident">_guard</span> <span class="op">=</span> <span class="ident">DropGuard</span>(<span class="op">|</span><span class="op">|</span> <span class="kw">unsafe</span> { <span class="ident">MUTEX</span>.<span class="ident">unlock</span>() });
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">fd</span>) <span class="op">=</span> <span class="ident">get_fd</span>() {
<span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">fd</span>);
}
<span class="comment">// On Linux, /dev/urandom might return insecure values.</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"android"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"linux"</span>))]</span>
<span class="ident">wait_until_rng_ready</span>()<span class="question-mark">?</span>;
<span class="kw">let</span> <span class="ident">fd</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">open_readonly</span>(<span class="ident">FILE_PATH</span>)<span class="question-mark">?</span> };
<span class="comment">// The fd always fits in a usize without conflicting with UNINIT.</span>
<span class="macro">debug_assert!</span>(<span class="ident">fd</span> <span class="op">></span><span class="op">=</span> <span class="number">0</span> <span class="op">&&</span> (<span class="ident">fd</span> <span class="kw">as</span> <span class="ident">usize</span>) <span class="op"><</span> <span class="ident">LazyUsize::UNINIT</span>);
<span class="ident">FD</span>.<span class="ident">store</span>(<span class="ident">fd</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">Relaxed</span>);
<span class="prelude-val">Ok</span>(<span class="ident">fd</span>)
}
<span class="comment">// Succeeds once /dev/urandom is safe to read from</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_os</span> <span class="op">=</span> <span class="string">"android"</span>, <span class="ident">target_os</span> <span class="op">=</span> <span class="string">"linux"</span>))]</span>
<span class="kw">fn</span> <span class="ident">wait_until_rng_ready</span>() -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Error</span><span class="op">></span> {
<span class="comment">// Poll /dev/random to make sure it is ok to read from /dev/urandom.</span>
<span class="kw">let</span> <span class="ident">fd</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">open_readonly</span>(<span class="string">"/dev/random\0"</span>)<span class="question-mark">?</span> };
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pfd</span> <span class="op">=</span> <span class="ident">libc::pollfd</span> {
<span class="ident">fd</span>,
<span class="ident">events</span>: <span class="ident">libc::POLLIN</span>,
<span class="ident">revents</span>: <span class="number">0</span>,
};
<span class="kw">let</span> <span class="ident">_guard</span> <span class="op">=</span> <span class="ident">DropGuard</span>(<span class="op">|</span><span class="op">|</span> <span class="kw">unsafe</span> {
<span class="ident">libc::close</span>(<span class="ident">fd</span>);
});
<span class="kw">loop</span> {
<span class="comment">// A negative timeout means an infinite timeout.</span>
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">libc::poll</span>(<span class="kw-2">&mut</span> <span class="ident">pfd</span>, <span class="number">1</span>, <span class="op">-</span><span class="number">1</span>) };
<span class="kw">if</span> <span class="ident">res</span> <span class="op">></span><span class="op">=</span> <span class="number">0</span> {
<span class="macro">debug_assert_eq!</span>(<span class="ident">res</span>, <span class="number">1</span>); <span class="comment">// We only used one fd, and cannot timeout.</span>
<span class="kw">return</span> <span class="prelude-val">Ok</span>(());
}
<span class="kw">let</span> <span class="ident">err</span> <span class="op">=</span> <span class="ident"><span class="kw">crate</span>::util_libc::last_os_error</span>();
<span class="kw">match</span> <span class="ident">err</span>.<span class="ident">raw_os_error</span>() {
<span class="prelude-val">Some</span>(<span class="ident">libc::EINTR</span>) <span class="op">|</span> <span class="prelude-val">Some</span>(<span class="ident">libc::EAGAIN</span>) => <span class="kw">continue</span>,
<span class="kw">_</span> => <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">err</span>),
}
}
}
<span class="kw">struct</span> <span class="ident">Mutex</span>(<span class="ident">UnsafeCell</span><span class="op"><</span><span class="ident">libc::pthread_mutex_t</span><span class="op">></span>);
<span class="kw">impl</span> <span class="ident">Mutex</span> {
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">new</span>() -> <span class="self">Self</span> {
<span class="self">Self</span>(<span class="ident">UnsafeCell::new</span>(<span class="ident">libc::PTHREAD_MUTEX_INITIALIZER</span>))
}
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">lock</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">libc::pthread_mutex_lock</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">get</span>());
<span class="macro">debug_assert_eq!</span>(<span class="ident">r</span>, <span class="number">0</span>);
}
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">unlock</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">libc::pthread_mutex_unlock</span>(<span class="self">self</span>.<span class="number">0</span>.<span class="ident">get</span>());
<span class="macro">debug_assert_eq!</span>(<span class="ident">r</span>, <span class="number">0</span>);
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Mutex</span> {}
<span class="kw">struct</span> <span class="ident">DropGuard</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnMut</span>()<span class="op">></span>(<span class="ident">F</span>);
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnMut</span>()<span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">DropGuard</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) {
<span class="self">self</span>.<span class="number">0</span>()
}
}
</code></pre></div>
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