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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 to the Rust file `src/common.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>common.rs.html -- 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="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">&#9776;</div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
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<span class="comment">// Translated from C to Rust. The original C code can be found at</span>
<span class="comment">// https://github.com/ulfjack/ryu and carries the following license:</span>
<span class="comment">//</span>
<span class="comment">// Copyright 2018 Ulf Adams</span>
<span class="comment">//</span>
<span class="comment">// The contents of this file may be used under the terms of the Apache License,</span>
<span class="comment">// Version 2.0.</span>
<span class="comment">//</span>
<span class="comment">// (See accompanying file LICENSE-Apache or copy at</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0)</span>
<span class="comment">//</span>
<span class="comment">// Alternatively, the contents of this file may be used under the terms of</span>
<span class="comment">// the Boost Software License, Version 1.0.</span>
<span class="comment">// (See accompanying file LICENSE-Boost or copy at</span>
<span class="comment">// https://www.boost.org/LICENSE_1_0.txt)</span>
<span class="comment">//</span>
<span class="comment">// Unless required by applicable law or agreed to in writing, this software</span>
<span class="comment">// is distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY</span>
<span class="comment">// KIND, either express or implied.</span>
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ptr</span>;
<span class="comment">// Returns e == 0 ? 1 : ceil(log_2(5^e)).</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;no-panic&quot;</span>, <span class="ident">inline</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">pow5bits</span>(<span class="ident">e</span>: <span class="ident">i32</span>) <span class="op">-&gt;</span> <span class="ident">u32</span> {
<span class="comment">// This approximation works up to the point that the multiplication overflows at e = 3529.</span>
<span class="comment">// If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater</span>
<span class="comment">// than 2^9297.</span>
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&gt;=</span> <span class="number">0</span>);
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&lt;=</span> <span class="number">3528</span>);
((<span class="ident">e</span> <span class="kw">as</span> <span class="ident">u32</span> <span class="op">*</span> <span class="number">1217359</span>) <span class="op">&gt;&gt;</span> <span class="number">19</span>) <span class="op">+</span> <span class="number">1</span>
}
<span class="comment">// Returns floor(log_10(2^e)).</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;no-panic&quot;</span>, <span class="ident">inline</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">log10_pow2</span>(<span class="ident">e</span>: <span class="ident">i32</span>) <span class="op">-&gt;</span> <span class="ident">i32</span> {
<span class="comment">// The first value this approximation fails for is 2^1651 which is just greater than 10^297.</span>
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&gt;=</span> <span class="number">0</span>);
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&lt;=</span> <span class="number">1650</span>);
((<span class="ident">e</span> <span class="kw">as</span> <span class="ident">u32</span> <span class="op">*</span> <span class="number">78913</span>) <span class="op">&gt;&gt;</span> <span class="number">18</span>) <span class="kw">as</span> <span class="ident">i32</span>
}
<span class="comment">// Returns floor(log_10(5^e)).</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;no-panic&quot;</span>, <span class="ident">inline</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">log10_pow5</span>(<span class="ident">e</span>: <span class="ident">i32</span>) <span class="op">-&gt;</span> <span class="ident">i32</span> {
<span class="comment">// The first value this approximation fails for is 5^2621 which is just greater than 10^1832.</span>
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&gt;=</span> <span class="number">0</span>);
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">e</span> <span class="op">&lt;=</span> <span class="number">2620</span>);
((<span class="ident">e</span> <span class="kw">as</span> <span class="ident">u32</span> <span class="op">*</span> <span class="number">732923</span>) <span class="op">&gt;&gt;</span> <span class="number">20</span>) <span class="kw">as</span> <span class="ident">i32</span>
}
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;no-panic&quot;</span>, <span class="ident">inline</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">copy_special_str</span>(
<span class="ident">result</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>,
<span class="ident">sign</span>: <span class="ident">bool</span>,
<span class="ident">exponent</span>: <span class="ident">bool</span>,
<span class="ident">mantissa</span>: <span class="ident">bool</span>,
) <span class="op">-&gt;</span> <span class="ident">usize</span> {
<span class="kw">if</span> <span class="ident">mantissa</span> {
<span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="string">b&quot;NaN&quot;</span>.<span class="ident">as_ptr</span>(), <span class="ident">result</span>, <span class="number">3</span>);
<span class="kw">return</span> <span class="number">3</span>;
}
<span class="kw">if</span> <span class="ident">sign</span> {
<span class="kw-2">*</span><span class="ident">result</span> <span class="op">=</span> <span class="string">b&#39;-&#39;</span>;
}
<span class="kw">if</span> <span class="ident">exponent</span> {
<span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="string">b&quot;Infinity&quot;</span>.<span class="ident">as_ptr</span>(), <span class="ident">result</span>.<span class="ident">offset</span>(<span class="ident">sign</span> <span class="kw">as</span> <span class="ident">isize</span>), <span class="number">8</span>);
<span class="kw">return</span> <span class="ident">sign</span> <span class="kw">as</span> <span class="ident">usize</span> <span class="op">+</span> <span class="number">8</span>;
}
<span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="string">b&quot;0E0&quot;</span>.<span class="ident">as_ptr</span>(), <span class="ident">result</span>.<span class="ident">offset</span>(<span class="ident">sign</span> <span class="kw">as</span> <span class="ident">isize</span>), <span class="number">3</span>);
<span class="ident">sign</span> <span class="kw">as</span> <span class="ident">usize</span> <span class="op">+</span> <span class="number">3</span>
}
</pre>
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