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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 &lt;LICENSE-APACHE or</span>
<span class="comment">// https://www.apache.org/licenses/LICENSE-2.0&gt; or the MIT license</span>
<span class="comment">// &lt;LICENSE-MIT or https://opensource.org/licenses/MIT&gt;, 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">//! Little-Endian utilities</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Little-Endian order has been chosen for internal usage; this makes some</span>
<span class="doccomment">//! useful functions available.</span>
<span class="kw">use</span> <span class="ident">core::convert::TryInto</span>;
<span class="doccomment">/// Reads unsigned 32 bit integers from `src` into `dst`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">read_u32_into</span>(<span class="ident">src</span>: <span class="kw-2">&amp;</span>[<span class="ident">u8</span>], <span class="ident">dst</span>: <span class="kw-2">&amp;mut</span> [<span class="ident">u32</span>]) {
<span class="macro">assert!</span>(<span class="ident">src</span>.<span class="ident">len</span>() <span class="op">&gt;</span><span class="op">=</span> <span class="number">4</span> <span class="op">*</span> <span class="ident">dst</span>.<span class="ident">len</span>());
<span class="kw">for</span> (<span class="ident">out</span>, <span class="ident">chunk</span>) <span class="kw">in</span> <span class="ident">dst</span>.<span class="ident">iter_mut</span>().<span class="ident">zip</span>(<span class="ident">src</span>.<span class="ident">chunks_exact</span>(<span class="number">4</span>)) {
<span class="kw-2">*</span><span class="ident">out</span> <span class="op">=</span> <span class="ident">u32::from_le_bytes</span>(<span class="ident">chunk</span>.<span class="ident">try_into</span>().<span class="ident">unwrap</span>());
}
}
<span class="doccomment">/// Reads unsigned 64 bit integers from `src` into `dst`.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">read_u64_into</span>(<span class="ident">src</span>: <span class="kw-2">&amp;</span>[<span class="ident">u8</span>], <span class="ident">dst</span>: <span class="kw-2">&amp;mut</span> [<span class="ident">u64</span>]) {
<span class="macro">assert!</span>(<span class="ident">src</span>.<span class="ident">len</span>() <span class="op">&gt;</span><span class="op">=</span> <span class="number">8</span> <span class="op">*</span> <span class="ident">dst</span>.<span class="ident">len</span>());
<span class="kw">for</span> (<span class="ident">out</span>, <span class="ident">chunk</span>) <span class="kw">in</span> <span class="ident">dst</span>.<span class="ident">iter_mut</span>().<span class="ident">zip</span>(<span class="ident">src</span>.<span class="ident">chunks_exact</span>(<span class="number">8</span>)) {
<span class="kw-2">*</span><span class="ident">out</span> <span class="op">=</span> <span class="ident">u64::from_le_bytes</span>(<span class="ident">chunk</span>.<span class="ident">try_into</span>().<span class="ident">unwrap</span>());
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_read</span>() {
<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>, <span class="number">10</span>, <span class="number">11</span>, <span class="number">12</span>, <span class="number">13</span>, <span class="number">14</span>, <span class="number">15</span>, <span class="number">16</span>];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> [<span class="number">0u32</span>; <span class="number">4</span>];
<span class="ident">read_u32_into</span>(<span class="kw-2">&amp;</span><span class="ident">bytes</span>, <span class="kw-2">&amp;mut</span> <span class="ident">buf</span>);
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">0</span>], <span class="number">0x04030201</span>);
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">3</span>], <span class="number">0x100F0E0D</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> [<span class="number">0u32</span>; <span class="number">3</span>];
<span class="ident">read_u32_into</span>(<span class="kw-2">&amp;</span><span class="ident">bytes</span>[<span class="number">1</span>..<span class="number">13</span>], <span class="kw-2">&amp;mut</span> <span class="ident">buf</span>); <span class="comment">// unaligned</span>
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">0</span>], <span class="number">0x05040302</span>);
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">2</span>], <span class="number">0x0D0C0B0A</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> [<span class="number">0u64</span>; <span class="number">2</span>];
<span class="ident">read_u64_into</span>(<span class="kw-2">&amp;</span><span class="ident">bytes</span>, <span class="kw-2">&amp;mut</span> <span class="ident">buf</span>);
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">0</span>], <span class="number">0x0807060504030201</span>);
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">1</span>], <span class="number">0x100F0E0D0C0B0A09</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> [<span class="number">0u64</span>; <span class="number">1</span>];
<span class="ident">read_u64_into</span>(<span class="kw-2">&amp;</span><span class="ident">bytes</span>[<span class="number">7</span>..<span class="number">15</span>], <span class="kw-2">&amp;mut</span> <span class="ident">buf</span>); <span class="comment">// unaligned</span>
<span class="macro">assert_eq!</span>(<span class="ident">buf</span>[<span class="number">0</span>], <span class="number">0x0F0E0D0C0B0A0908</span>);
}
</code></pre></div>
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