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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 `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/num-bigint-0.3.3/src/bigint/bits.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>bits.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" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" 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="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></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="sidebar"><a class="sidebar-logo" href="../../../num_bigint/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../num_bigint/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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</pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::BigInt;
<span class="kw">use </span><span class="kw">super</span>::Sign::{Minus, NoSign, Plus};
<span class="kw">use </span><span class="kw">crate</span>::big_digit::{<span class="self">self</span>, BigDigit, DoubleBigDigit};
<span class="kw">use </span><span class="kw">crate</span>::biguint::IntDigits;
<span class="kw">use </span><span class="kw">crate</span>::std_alloc::Vec;
<span class="kw">use </span>core::cmp::Ordering::{Equal, Greater, Less};
<span class="kw">use </span>core::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign};
<span class="kw">use </span>num_traits::{ToPrimitive, Zero};
<span class="comment">// Negation in two&#39;s complement.
// acc must be initialized as 1 for least-significant digit.
//
// When negating, a carry (acc == 1) means that all the digits
// considered to this point were zero. This means that if all the
// digits of a negative BigInt have been considered, carry must be
// zero as we cannot have negative zero.
//
// 01 -&gt; ...f ff
// ff -&gt; ...f 01
// 01 00 -&gt; ...f ff 00
// 01 01 -&gt; ...f fe ff
// 01 ff -&gt; ...f fe 01
// ff 00 -&gt; ...f 01 00
// ff 01 -&gt; ...f 00 ff
// ff ff -&gt; ...f 00 01
</span><span class="attribute">#[inline]
</span><span class="kw">fn </span>negate_carry(a: BigDigit, acc: <span class="kw-2">&amp;mut </span>DoubleBigDigit) -&gt; BigDigit {
<span class="kw-2">*</span>acc += DoubleBigDigit::from(!a);
<span class="kw">let </span>lo = <span class="kw-2">*</span>acc <span class="kw">as </span>BigDigit;
<span class="kw-2">*</span>acc &gt;&gt;= big_digit::BITS;
lo
}
<span class="comment">// + 1 &amp; -ff = ...0 01 &amp; ...f 01 = ...0 01 = + 1
// +ff &amp; - 1 = ...0 ff &amp; ...f ff = ...0 ff = +ff
// answer is pos, has length of a
</span><span class="kw">fn </span>bitand_pos_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai &amp;= twos_b;
}
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
}
<span class="comment">// - 1 &amp; +ff = ...f ff &amp; ...0 ff = ...0 ff = +ff
// -ff &amp; + 1 = ...f 01 &amp; ...0 01 = ...0 01 = + 1
// answer is pos, has length of b
</span><span class="kw">fn </span>bitand_neg_pos(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = twos_a &amp; bi;
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; a.truncate(b.len()),
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().cloned());
}
}
}
<span class="comment">// - 1 &amp; -ff = ...f ff &amp; ...f 01 = ...f 01 = - ff
// -ff &amp; - 1 = ...f 01 &amp; ...f ff = ...f 01 = - ff
// -ff &amp; -fe = ...f 01 &amp; ...f 02 = ...f 00 = -100
// answer is neg, has length of longest with a possible carry
</span><span class="kw">fn </span>bitand_neg_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_and = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai = negate_carry(twos_a &amp; twos_b, <span class="kw-2">&amp;mut </span>carry_and);
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; {
<span class="kw">for </span>ai <span class="kw">in </span>a[b.len()..].iter_mut() {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = negate_carry(twos_a, <span class="kw-2">&amp;mut </span>carry_and);
}
<span class="macro">debug_assert!</span>(carry_a == <span class="number">0</span>);
}
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().map(|<span class="kw-2">&amp;</span>bi| {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
negate_carry(twos_b, <span class="kw-2">&amp;mut </span>carry_and)
}));
<span class="macro">debug_assert!</span>(carry_b == <span class="number">0</span>);
}
}
<span class="kw">if </span>carry_and != <span class="number">0 </span>{
a.push(<span class="number">1</span>);
}
}
<span class="macro">forward_val_val_binop!</span>(<span class="kw">impl </span>BitAnd <span class="kw">for </span>BigInt, bitand);
<span class="macro">forward_ref_val_binop!</span>(<span class="kw">impl </span>BitAnd <span class="kw">for </span>BigInt, bitand);
<span class="comment">// do not use forward_ref_ref_binop_commutative! for bitand so that we can
// clone as needed, avoiding over-allocation
</span><span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>, <span class="lifetime">&#39;b</span>&gt; BitAnd&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;b </span>BigInt&gt; <span class="kw">for </span><span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt {
<span class="kw">type </span>Output = BigInt;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>bitand(<span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) -&gt; BigInt {
<span class="kw">match </span>(<span class="self">self</span>.sign, other.sign) {
(NoSign, <span class="kw">_</span>) | (<span class="kw">_</span>, NoSign) =&gt; BigInt::zero(),
(Plus, Plus) =&gt; BigInt::from(<span class="kw-2">&amp;</span><span class="self">self</span>.data &amp; <span class="kw-2">&amp;</span>other.data),
(Plus, Minus) =&gt; <span class="self">self</span>.clone() &amp; other,
(Minus, Plus) =&gt; other.clone() &amp; <span class="self">self</span>,
(Minus, Minus) =&gt; {
<span class="comment">// forward to val-ref, choosing the larger to clone
</span><span class="kw">if </span><span class="self">self</span>.len() &gt;= other.len() {
<span class="self">self</span>.clone() &amp; other
} <span class="kw">else </span>{
other.clone() &amp; <span class="self">self
</span>}
}
}
}
}
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitAnd&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">type </span>Output = BigInt;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>bitand(<span class="kw-2">mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) -&gt; BigInt {
<span class="self">self </span>&amp;= other;
<span class="self">self
</span>}
}
<span class="macro">forward_val_assign!</span>(<span class="kw">impl </span>BitAndAssign <span class="kw">for </span>BigInt, bitand_assign);
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitAndAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">fn </span>bitand_assign(<span class="kw-2">&amp;mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) {
<span class="kw">match </span>(<span class="self">self</span>.sign, other.sign) {
(NoSign, <span class="kw">_</span>) =&gt; {}
(<span class="kw">_</span>, NoSign) =&gt; <span class="self">self</span>.set_zero(),
(Plus, Plus) =&gt; {
<span class="self">self</span>.data &amp;= <span class="kw-2">&amp;</span>other.data;
<span class="kw">if </span><span class="self">self</span>.data.is_zero() {
<span class="self">self</span>.sign = NoSign;
}
}
(Plus, Minus) =&gt; {
bitand_pos_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.normalize();
}
(Minus, Plus) =&gt; {
bitand_neg_pos(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.sign = Plus;
<span class="self">self</span>.normalize();
}
(Minus, Minus) =&gt; {
bitand_neg_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.normalize();
}
}
}
}
<span class="comment">// + 1 | -ff = ...0 01 | ...f 01 = ...f 01 = -ff
// +ff | - 1 = ...0 ff | ...f ff = ...f ff = - 1
// answer is neg, has length of b
</span><span class="kw">fn </span>bitor_pos_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_or = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai = negate_carry(<span class="kw-2">*</span>ai | twos_b, <span class="kw-2">&amp;mut </span>carry_or);
}
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; {
a.truncate(b.len());
}
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().map(|<span class="kw-2">&amp;</span>bi| {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
negate_carry(twos_b, <span class="kw-2">&amp;mut </span>carry_or)
}));
<span class="macro">debug_assert!</span>(carry_b == <span class="number">0</span>);
}
}
<span class="comment">// for carry_or to be non-zero, we would need twos_b == 0
</span><span class="macro">debug_assert!</span>(carry_or == <span class="number">0</span>);
}
<span class="comment">// - 1 | +ff = ...f ff | ...0 ff = ...f ff = - 1
// -ff | + 1 = ...f 01 | ...0 01 = ...f 01 = -ff
// answer is neg, has length of a
</span><span class="kw">fn </span>bitor_neg_pos(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_or = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = negate_carry(twos_a | bi, <span class="kw-2">&amp;mut </span>carry_or);
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="kw">if </span>a.len() &gt; b.len() {
<span class="kw">for </span>ai <span class="kw">in </span>a[b.len()..].iter_mut() {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = negate_carry(twos_a, <span class="kw-2">&amp;mut </span>carry_or);
}
<span class="macro">debug_assert!</span>(carry_a == <span class="number">0</span>);
}
<span class="comment">// for carry_or to be non-zero, we would need twos_a == 0
</span><span class="macro">debug_assert!</span>(carry_or == <span class="number">0</span>);
}
<span class="comment">// - 1 | -ff = ...f ff | ...f 01 = ...f ff = -1
// -ff | - 1 = ...f 01 | ...f ff = ...f ff = -1
// answer is neg, has length of shortest
</span><span class="kw">fn </span>bitor_neg_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_or = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai = negate_carry(twos_a | twos_b, <span class="kw-2">&amp;mut </span>carry_or);
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
<span class="kw">if </span>a.len() &gt; b.len() {
a.truncate(b.len());
}
<span class="comment">// for carry_or to be non-zero, we would need twos_a == 0 or twos_b == 0
</span><span class="macro">debug_assert!</span>(carry_or == <span class="number">0</span>);
}
<span class="macro">forward_val_val_binop!</span>(<span class="kw">impl </span>BitOr <span class="kw">for </span>BigInt, bitor);
<span class="macro">forward_ref_val_binop!</span>(<span class="kw">impl </span>BitOr <span class="kw">for </span>BigInt, bitor);
<span class="comment">// do not use forward_ref_ref_binop_commutative! for bitor so that we can
// clone as needed, avoiding over-allocation
</span><span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>, <span class="lifetime">&#39;b</span>&gt; BitOr&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;b </span>BigInt&gt; <span class="kw">for </span><span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt {
<span class="kw">type </span>Output = BigInt;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>bitor(<span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) -&gt; BigInt {
<span class="kw">match </span>(<span class="self">self</span>.sign, other.sign) {
(NoSign, <span class="kw">_</span>) =&gt; other.clone(),
(<span class="kw">_</span>, NoSign) =&gt; <span class="self">self</span>.clone(),
(Plus, Plus) =&gt; BigInt::from(<span class="kw-2">&amp;</span><span class="self">self</span>.data | <span class="kw-2">&amp;</span>other.data),
(Plus, Minus) =&gt; other.clone() | <span class="self">self</span>,
(Minus, Plus) =&gt; <span class="self">self</span>.clone() | other,
(Minus, Minus) =&gt; {
<span class="comment">// forward to val-ref, choosing the smaller to clone
</span><span class="kw">if </span><span class="self">self</span>.len() &lt;= other.len() {
<span class="self">self</span>.clone() | other
} <span class="kw">else </span>{
other.clone() | <span class="self">self
</span>}
}
}
}
}
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitOr&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">type </span>Output = BigInt;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>bitor(<span class="kw-2">mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) -&gt; BigInt {
<span class="self">self </span>|= other;
<span class="self">self
</span>}
}
<span class="macro">forward_val_assign!</span>(<span class="kw">impl </span>BitOrAssign <span class="kw">for </span>BigInt, bitor_assign);
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitOrAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">fn </span>bitor_assign(<span class="kw-2">&amp;mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) {
<span class="kw">match </span>(<span class="self">self</span>.sign, other.sign) {
(<span class="kw">_</span>, NoSign) =&gt; {}
(NoSign, <span class="kw">_</span>) =&gt; <span class="self">self</span>.clone_from(other),
(Plus, Plus) =&gt; <span class="self">self</span>.data |= <span class="kw-2">&amp;</span>other.data,
(Plus, Minus) =&gt; {
bitor_pos_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.sign = Minus;
<span class="self">self</span>.normalize();
}
(Minus, Plus) =&gt; {
bitor_neg_pos(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.normalize();
}
(Minus, Minus) =&gt; {
bitor_neg_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.normalize();
}
}
}
}
<span class="comment">// + 1 ^ -ff = ...0 01 ^ ...f 01 = ...f 00 = -100
// +ff ^ - 1 = ...0 ff ^ ...f ff = ...f 00 = -100
// answer is neg, has length of longest with a possible carry
</span><span class="kw">fn </span>bitxor_pos_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_xor = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai = negate_carry(<span class="kw-2">*</span>ai ^ twos_b, <span class="kw-2">&amp;mut </span>carry_xor);
}
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; {
<span class="kw">for </span>ai <span class="kw">in </span>a[b.len()..].iter_mut() {
<span class="kw">let </span>twos_b = !<span class="number">0</span>;
<span class="kw-2">*</span>ai = negate_carry(<span class="kw-2">*</span>ai ^ twos_b, <span class="kw-2">&amp;mut </span>carry_xor);
}
}
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().map(|<span class="kw-2">&amp;</span>bi| {
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
negate_carry(twos_b, <span class="kw-2">&amp;mut </span>carry_xor)
}));
<span class="macro">debug_assert!</span>(carry_b == <span class="number">0</span>);
}
}
<span class="kw">if </span>carry_xor != <span class="number">0 </span>{
a.push(<span class="number">1</span>);
}
}
<span class="comment">// - 1 ^ +ff = ...f ff ^ ...0 ff = ...f 00 = -100
// -ff ^ + 1 = ...f 01 ^ ...0 01 = ...f 00 = -100
// answer is neg, has length of longest with a possible carry
</span><span class="kw">fn </span>bitxor_neg_pos(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_xor = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = negate_carry(twos_a ^ bi, <span class="kw-2">&amp;mut </span>carry_xor);
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; {
<span class="kw">for </span>ai <span class="kw">in </span>a[b.len()..].iter_mut() {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw-2">*</span>ai = negate_carry(twos_a, <span class="kw-2">&amp;mut </span>carry_xor);
}
<span class="macro">debug_assert!</span>(carry_a == <span class="number">0</span>);
}
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().map(|<span class="kw-2">&amp;</span>bi| {
<span class="kw">let </span>twos_a = !<span class="number">0</span>;
negate_carry(twos_a ^ bi, <span class="kw-2">&amp;mut </span>carry_xor)
}));
}
}
<span class="kw">if </span>carry_xor != <span class="number">0 </span>{
a.push(<span class="number">1</span>);
}
}
<span class="comment">// - 1 ^ -ff = ...f ff ^ ...f 01 = ...0 fe = +fe
// -ff &amp; - 1 = ...f 01 ^ ...f ff = ...0 fe = +fe
// answer is pos, has length of longest
</span><span class="kw">fn </span>bitxor_neg_neg(a: <span class="kw-2">&amp;mut </span>Vec&lt;BigDigit&gt;, b: <span class="kw-2">&amp;</span>[BigDigit]) {
<span class="kw">let </span><span class="kw-2">mut </span>carry_a = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_b = <span class="number">1</span>;
<span class="kw">for </span>(ai, <span class="kw-2">&amp;</span>bi) <span class="kw">in </span>a.iter_mut().zip(b.iter()) {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
<span class="kw-2">*</span>ai = twos_a ^ twos_b;
}
<span class="macro">debug_assert!</span>(a.len() &gt; b.len() || carry_a == <span class="number">0</span>);
<span class="macro">debug_assert!</span>(b.len() &gt; a.len() || carry_b == <span class="number">0</span>);
<span class="kw">match </span>Ord::cmp(<span class="kw-2">&amp;</span>a.len(), <span class="kw-2">&amp;</span>b.len()) {
Greater =&gt; {
<span class="kw">for </span>ai <span class="kw">in </span>a[b.len()..].iter_mut() {
<span class="kw">let </span>twos_a = negate_carry(<span class="kw-2">*</span>ai, <span class="kw-2">&amp;mut </span>carry_a);
<span class="kw">let </span>twos_b = !<span class="number">0</span>;
<span class="kw-2">*</span>ai = twos_a ^ twos_b;
}
<span class="macro">debug_assert!</span>(carry_a == <span class="number">0</span>);
}
Equal =&gt; {}
Less =&gt; {
<span class="kw">let </span>extra = <span class="kw-2">&amp;</span>b[a.len()..];
a.extend(extra.iter().map(|<span class="kw-2">&amp;</span>bi| {
<span class="kw">let </span>twos_a = !<span class="number">0</span>;
<span class="kw">let </span>twos_b = negate_carry(bi, <span class="kw-2">&amp;mut </span>carry_b);
twos_a ^ twos_b
}));
<span class="macro">debug_assert!</span>(carry_b == <span class="number">0</span>);
}
}
}
<span class="macro">forward_all_binop_to_val_ref_commutative!</span>(<span class="kw">impl </span>BitXor <span class="kw">for </span>BigInt, bitxor);
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitXor&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">type </span>Output = BigInt;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>bitxor(<span class="kw-2">mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) -&gt; BigInt {
<span class="self">self </span>^= other;
<span class="self">self
</span>}
}
<span class="macro">forward_val_assign!</span>(<span class="kw">impl </span>BitXorAssign <span class="kw">for </span>BigInt, bitxor_assign);
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; BitXorAssign&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>BigInt&gt; <span class="kw">for </span>BigInt {
<span class="kw">fn </span>bitxor_assign(<span class="kw-2">&amp;mut </span><span class="self">self</span>, other: <span class="kw-2">&amp;</span>BigInt) {
<span class="kw">match </span>(<span class="self">self</span>.sign, other.sign) {
(<span class="kw">_</span>, NoSign) =&gt; {}
(NoSign, <span class="kw">_</span>) =&gt; <span class="self">self</span>.clone_from(other),
(Plus, Plus) =&gt; {
<span class="self">self</span>.data ^= <span class="kw-2">&amp;</span>other.data;
<span class="kw">if </span><span class="self">self</span>.data.is_zero() {
<span class="self">self</span>.sign = NoSign;
}
}
(Plus, Minus) =&gt; {
bitxor_pos_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.sign = Minus;
<span class="self">self</span>.normalize();
}
(Minus, Plus) =&gt; {
bitxor_neg_pos(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.normalize();
}
(Minus, Minus) =&gt; {
bitxor_neg_neg(<span class="self">self</span>.digits_mut(), other.digits());
<span class="self">self</span>.sign = Plus;
<span class="self">self</span>.normalize();
}
}
}
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>set_negative_bit(x: <span class="kw-2">&amp;mut </span>BigInt, bit: u64, value: bool) {
<span class="macro">debug_assert_eq!</span>(x.sign, Minus);
<span class="kw">let </span>data = <span class="kw-2">&amp;mut </span>x.data;
<span class="kw">let </span>bits_per_digit = u64::from(big_digit::BITS);
<span class="kw">if </span>bit &gt;= bits_per_digit * data.len() <span class="kw">as </span>u64 {
<span class="kw">if </span>!value {
data.set_bit(bit, <span class="bool-val">true</span>);
}
} <span class="kw">else </span>{
<span class="comment">// If the Uint number is
// ... 0 x 1 0 ... 0
// then the two&#39;s complement is
// ... 1 !x 1 0 ... 0
// |-- bit at position &#39;trailing_zeros&#39;
// where !x is obtained from x by flipping each bit
</span><span class="kw">let </span>trailing_zeros = data.trailing_zeros().unwrap();
<span class="kw">if </span>bit &gt; trailing_zeros {
data.set_bit(bit, !value);
} <span class="kw">else if </span>bit == trailing_zeros &amp;&amp; !value {
<span class="comment">// Clearing the bit at position `trailing_zeros` is dealt with by doing
// similarly to what `bitand_neg_pos` does, except we start at digit
// `bit_index`. All digits below `bit_index` are guaranteed to be zero,
// so initially we have `carry_in` = `carry_out` = 1. Furthermore, we
// stop traversing the digits when there are no more carries.
</span><span class="kw">let </span>bit_index = (bit / bits_per_digit).to_usize().unwrap();
<span class="kw">let </span>bit_mask = (<span class="number">1 </span><span class="kw">as </span>BigDigit) &lt;&lt; (bit % bits_per_digit);
<span class="kw">let </span><span class="kw-2">mut </span>digit_iter = data.digits_mut().iter_mut().skip(bit_index);
<span class="kw">let </span><span class="kw-2">mut </span>carry_in = <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>carry_out = <span class="number">1</span>;
<span class="kw">let </span>digit = digit_iter.next().unwrap();
<span class="kw">let </span>twos_in = negate_carry(<span class="kw-2">*</span>digit, <span class="kw-2">&amp;mut </span>carry_in);
<span class="kw">let </span>twos_out = twos_in &amp; !bit_mask;
<span class="kw-2">*</span>digit = negate_carry(twos_out, <span class="kw-2">&amp;mut </span>carry_out);
<span class="kw">for </span>digit <span class="kw">in </span>digit_iter {
<span class="kw">if </span>carry_in == <span class="number">0 </span>&amp;&amp; carry_out == <span class="number">0 </span>{
<span class="comment">// Exit the loop since no more digits can change
</span><span class="kw">break</span>;
}
<span class="kw">let </span>twos = negate_carry(<span class="kw-2">*</span>digit, <span class="kw-2">&amp;mut </span>carry_in);
<span class="kw-2">*</span>digit = negate_carry(twos, <span class="kw-2">&amp;mut </span>carry_out);
}
<span class="kw">if </span>carry_out != <span class="number">0 </span>{
<span class="comment">// All digits have been traversed and there is a carry
</span><span class="macro">debug_assert_eq!</span>(carry_in, <span class="number">0</span>);
data.digits_mut().push(<span class="number">1</span>);
}
} <span class="kw">else if </span>bit &lt; trailing_zeros &amp;&amp; value {
<span class="comment">// Flip each bit from position &#39;bit&#39; to &#39;trailing_zeros&#39;, both inclusive
// ... 1 !x 1 0 ... 0 ... 0
// |-- bit at position &#39;bit&#39;
// |-- bit at position &#39;trailing_zeros&#39;
// bit_mask: 1 1 ... 1 0 .. 0
// This is done by xor&#39;ing with the bit_mask
</span><span class="kw">let </span>index_lo = (bit / bits_per_digit).to_usize().unwrap();
<span class="kw">let </span>index_hi = (trailing_zeros / bits_per_digit).to_usize().unwrap();
<span class="kw">let </span>bit_mask_lo = big_digit::MAX &lt;&lt; (bit % bits_per_digit);
<span class="kw">let </span>bit_mask_hi =
big_digit::MAX &gt;&gt; (bits_per_digit - <span class="number">1 </span>- (trailing_zeros % bits_per_digit));
<span class="kw">let </span>digits = data.digits_mut();
<span class="kw">if </span>index_lo == index_hi {
digits[index_lo] ^= bit_mask_lo &amp; bit_mask_hi;
} <span class="kw">else </span>{
digits[index_lo] = bit_mask_lo;
<span class="kw">for </span>index <span class="kw">in </span>(index_lo + <span class="number">1</span>)..index_hi {
digits[index] = big_digit::MAX;
}
digits[index_hi] ^= bit_mask_hi;
}
} <span class="kw">else </span>{
<span class="comment">// We end up here in two cases:
// bit == trailing_zeros &amp;&amp; value: Bit is already set
// bit &lt; trailing_zeros &amp;&amp; !value: Bit is already cleared
</span>}
}
}
</code></pre></div>
</section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="num_bigint" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html>