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</pre><pre class="rust"><code><span class="comment">/* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */</span>
<span class="comment">/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
* Optimized by Bruce D. Evans.
*/</span>
<span class="comment">/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/</span>
<span class="kw">use</span> <span class="kw">super</span>::{<span class="ident">k_cosf</span>, <span class="ident">k_sinf</span>, <span class="ident">rem_pio2f</span>};
<span class="kw">use</span> <span class="ident">core::f64::consts::FRAC_PI_2</span>;
<span class="comment">/* Small multiples of pi/2 rounded to double precision. */</span>
<span class="kw">const</span> <span class="ident">C1_PIO2</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="number">1.</span> <span class="op">*</span> <span class="ident">FRAC_PI_2</span>; <span class="comment">/* 0x3FF921FB, 0x54442D18 */</span>
<span class="kw">const</span> <span class="ident">C2_PIO2</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="number">2.</span> <span class="op">*</span> <span class="ident">FRAC_PI_2</span>; <span class="comment">/* 0x400921FB, 0x54442D18 */</span>
<span class="kw">const</span> <span class="ident">C3_PIO2</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="number">3.</span> <span class="op">*</span> <span class="ident">FRAC_PI_2</span>; <span class="comment">/* 0x4012D97C, 0x7F3321D2 */</span>
<span class="kw">const</span> <span class="ident">C4_PIO2</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="number">4.</span> <span class="op">*</span> <span class="ident">FRAC_PI_2</span>; <span class="comment">/* 0x401921FB, 0x54442D18 */</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">all</span>(<span class="ident">test</span>, <span class="ident">assert_no_panic</span>), <span class="ident">no_panic::no_panic</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">cosf</span>(<span class="ident">x</span>: <span class="ident">f32</span>) -&gt; <span class="ident">f32</span> {
<span class="kw">let</span> <span class="ident">x64</span> <span class="op">=</span> <span class="ident">x</span> <span class="kw">as</span> <span class="ident">f64</span>;
<span class="kw">let</span> <span class="ident">x1p120</span> <span class="op">=</span> <span class="ident">f32::from_bits</span>(<span class="number">0x7b800000</span>); <span class="comment">// 0x1p120f === 2 ^ 120</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">ix</span> <span class="op">=</span> <span class="ident">x</span>.<span class="ident">to_bits</span>();
<span class="kw">let</span> <span class="ident">sign</span> <span class="op">=</span> (<span class="ident">ix</span> <span class="op">&gt;</span><span class="op">&gt;</span> <span class="number">31</span>) <span class="op">!</span><span class="op">=</span> <span class="number">0</span>;
<span class="ident">ix</span> <span class="op">&amp;=</span> <span class="number">0x7fffffff</span>;
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&lt;</span><span class="op">=</span> <span class="number">0x3f490fda</span> {
<span class="comment">/* |x| ~&lt;= pi/4 */</span>
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&lt;</span> <span class="number">0x39800000</span> {
<span class="comment">/* |x| &lt; 2**-12 */</span>
<span class="comment">/* raise inexact if x != 0 */</span>
<span class="macro">force_eval!</span>(<span class="ident">x</span> <span class="op">+</span> <span class="ident">x1p120</span>);
<span class="kw">return</span> <span class="number">1.</span>;
}
<span class="kw">return</span> <span class="ident">k_cosf</span>(<span class="ident">x64</span>);
}
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&lt;</span><span class="op">=</span> <span class="number">0x407b53d1</span> {
<span class="comment">/* |x| ~&lt;= 5*pi/4 */</span>
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&gt;</span> <span class="number">0x4016cbe3</span> {
<span class="comment">/* |x| ~&gt; 3*pi/4 */</span>
<span class="kw">return</span> <span class="op">-</span><span class="ident">k_cosf</span>(<span class="kw">if</span> <span class="ident">sign</span> { <span class="ident">x64</span> <span class="op">+</span> <span class="ident">C2_PIO2</span> } <span class="kw">else</span> { <span class="ident">x64</span> <span class="op">-</span> <span class="ident">C2_PIO2</span> });
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">sign</span> {
<span class="kw">return</span> <span class="ident">k_sinf</span>(<span class="ident">x64</span> <span class="op">+</span> <span class="ident">C1_PIO2</span>);
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="ident">k_sinf</span>(<span class="ident">C1_PIO2</span> <span class="op">-</span> <span class="ident">x64</span>);
}
}
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&lt;</span><span class="op">=</span> <span class="number">0x40e231d5</span> {
<span class="comment">/* |x| ~&lt;= 9*pi/4 */</span>
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&gt;</span> <span class="number">0x40afeddf</span> {
<span class="comment">/* |x| ~&gt; 7*pi/4 */</span>
<span class="kw">return</span> <span class="ident">k_cosf</span>(<span class="kw">if</span> <span class="ident">sign</span> { <span class="ident">x64</span> <span class="op">+</span> <span class="ident">C4_PIO2</span> } <span class="kw">else</span> { <span class="ident">x64</span> <span class="op">-</span> <span class="ident">C4_PIO2</span> });
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">sign</span> {
<span class="kw">return</span> <span class="ident">k_sinf</span>(<span class="op">-</span><span class="ident">x64</span> <span class="op">-</span> <span class="ident">C3_PIO2</span>);
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="ident">k_sinf</span>(<span class="ident">x64</span> <span class="op">-</span> <span class="ident">C3_PIO2</span>);
}
}
<span class="comment">/* cos(Inf or NaN) is NaN */</span>
<span class="kw">if</span> <span class="ident">ix</span> <span class="op">&gt;</span><span class="op">=</span> <span class="number">0x7f800000</span> {
<span class="kw">return</span> <span class="ident">x</span> <span class="op">-</span> <span class="ident">x</span>;
}
<span class="comment">/* general argument reduction needed */</span>
<span class="kw">let</span> (<span class="ident">n</span>, <span class="ident">y</span>) <span class="op">=</span> <span class="ident">rem_pio2f</span>(<span class="ident">x</span>);
<span class="kw">match</span> <span class="ident">n</span> <span class="op">&amp;</span> <span class="number">3</span> {
<span class="number">0</span> =&gt; <span class="ident">k_cosf</span>(<span class="ident">y</span>),
<span class="number">1</span> =&gt; <span class="ident">k_sinf</span>(<span class="op">-</span><span class="ident">y</span>),
<span class="number">2</span> =&gt; <span class="op">-</span><span class="ident">k_cosf</span>(<span class="ident">y</span>),
<span class="kw">_</span> =&gt; <span class="ident">k_sinf</span>(<span class="ident">y</span>),
}
}
</code></pre></div>
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