| <!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/biguint/subtraction.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>subtraction.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="attribute">#[cfg(not(u64_digit))] |
| </span><span class="kw">use </span><span class="kw">super</span>::u32_from_u128; |
| <span class="kw">use </span><span class="kw">super</span>::BigUint; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::big_digit::{<span class="self">self</span>, BigDigit}; |
| <span class="kw">use </span><span class="kw">crate</span>::UsizePromotion; |
| |
| <span class="kw">use </span>core::cmp::Ordering::{Equal, Greater, Less}; |
| <span class="kw">use </span>core::ops::{Sub, SubAssign}; |
| <span class="kw">use </span>num_traits::{CheckedSub, Zero}; |
| |
| <span class="attribute">#[cfg(all(use_addcarry, target_arch = <span class="string">"x86_64"</span>))] |
| </span><span class="kw">use </span>core::arch::x86_64 <span class="kw">as </span>arch; |
| |
| <span class="attribute">#[cfg(all(use_addcarry, target_arch = <span class="string">"x86"</span>))] |
| </span><span class="kw">use </span>core::arch::x86 <span class="kw">as </span>arch; |
| |
| <span class="comment">// Subtract with borrow: |
| </span><span class="attribute">#[cfg(all(use_addcarry, u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sbb(borrow: u8, a: u64, b: u64, out: <span class="kw-2">&mut </span>u64) -> u8 { |
| <span class="comment">// Safety: There are absolutely no safety concerns with calling `_subborrow_u64`. |
| // It's just unsafe for API consistency with other intrinsics. |
| </span><span class="kw">unsafe </span>{ arch::_subborrow_u64(borrow, a, b, out) } |
| } |
| |
| <span class="attribute">#[cfg(all(use_addcarry, not(u64_digit)))] |
| #[inline] |
| </span><span class="kw">fn </span>sbb(borrow: u8, a: u32, b: u32, out: <span class="kw-2">&mut </span>u32) -> u8 { |
| <span class="comment">// Safety: There are absolutely no safety concerns with calling `_subborrow_u32`. |
| // It's just unsafe for API consistency with other intrinsics. |
| </span><span class="kw">unsafe </span>{ arch::_subborrow_u32(borrow, a, b, out) } |
| } |
| |
| <span class="comment">// fallback for environments where we don't have a subborrow intrinsic |
| </span><span class="attribute">#[cfg(not(use_addcarry))] |
| #[inline] |
| </span><span class="kw">fn </span>sbb(borrow: u8, a: BigDigit, b: BigDigit, out: <span class="kw-2">&mut </span>BigDigit) -> u8 { |
| <span class="kw">use </span><span class="kw">crate</span>::big_digit::SignedDoubleBigDigit; |
| |
| <span class="kw">let </span>difference = SignedDoubleBigDigit::from(a) |
| - SignedDoubleBigDigit::from(b) |
| - SignedDoubleBigDigit::from(borrow); |
| <span class="kw-2">*</span>out = difference <span class="kw">as </span>BigDigit; |
| u8::from(difference < <span class="number">0</span>) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>sub2(a: <span class="kw-2">&mut </span>[BigDigit], b: <span class="kw-2">&</span>[BigDigit]) { |
| <span class="kw">let </span><span class="kw-2">mut </span>borrow = <span class="number">0</span>; |
| |
| <span class="kw">let </span>len = Ord::min(a.len(), b.len()); |
| <span class="kw">let </span>(a_lo, a_hi) = a.split_at_mut(len); |
| <span class="kw">let </span>(b_lo, b_hi) = b.split_at(len); |
| |
| <span class="kw">for </span>(a, b) <span class="kw">in </span>a_lo.iter_mut().zip(b_lo) { |
| borrow = sbb(borrow, <span class="kw-2">*</span>a, <span class="kw-2">*</span>b, a); |
| } |
| |
| <span class="kw">if </span>borrow != <span class="number">0 </span>{ |
| <span class="kw">for </span>a <span class="kw">in </span>a_hi { |
| borrow = sbb(borrow, <span class="kw-2">*</span>a, <span class="number">0</span>, a); |
| <span class="kw">if </span>borrow == <span class="number">0 </span>{ |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| |
| <span class="comment">// note: we're _required_ to fail on underflow |
| </span><span class="macro">assert!</span>( |
| borrow == <span class="number">0 </span>&& b_hi.iter().all(|x| <span class="kw-2">*</span>x == <span class="number">0</span>), |
| <span class="string">"Cannot subtract b from a because b is larger than a." |
| </span>); |
| } |
| |
| <span class="comment">// Only for the Sub impl. `a` and `b` must have same length. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">fn </span>__sub2rev(a: <span class="kw-2">&</span>[BigDigit], b: <span class="kw-2">&mut </span>[BigDigit]) -> u8 { |
| <span class="macro">debug_assert!</span>(b.len() == a.len()); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>borrow = <span class="number">0</span>; |
| |
| <span class="kw">for </span>(ai, bi) <span class="kw">in </span>a.iter().zip(b) { |
| borrow = sbb(borrow, <span class="kw-2">*</span>ai, <span class="kw-2">*</span>bi, bi); |
| } |
| |
| borrow |
| } |
| |
| <span class="kw">fn </span>sub2rev(a: <span class="kw-2">&</span>[BigDigit], b: <span class="kw-2">&mut </span>[BigDigit]) { |
| <span class="macro">debug_assert!</span>(b.len() >= a.len()); |
| |
| <span class="kw">let </span>len = Ord::min(a.len(), b.len()); |
| <span class="kw">let </span>(a_lo, a_hi) = a.split_at(len); |
| <span class="kw">let </span>(b_lo, b_hi) = b.split_at_mut(len); |
| |
| <span class="kw">let </span>borrow = __sub2rev(a_lo, b_lo); |
| |
| <span class="macro">assert!</span>(a_hi.is_empty()); |
| |
| <span class="comment">// note: we're _required_ to fail on underflow |
| </span><span class="macro">assert!</span>( |
| borrow == <span class="number">0 </span>&& b_hi.iter().all(|x| <span class="kw-2">*</span>x == <span class="number">0</span>), |
| <span class="string">"Cannot subtract b from a because b is larger than a." |
| </span>); |
| } |
| |
| <span class="macro">forward_val_val_binop!</span>(<span class="kw">impl </span>Sub <span class="kw">for </span>BigUint, sub); |
| <span class="macro">forward_ref_ref_binop!</span>(<span class="kw">impl </span>Sub <span class="kw">for </span>BigUint, sub); |
| <span class="macro">forward_val_assign!</span>(<span class="kw">impl </span>SubAssign <span class="kw">for </span>BigUint, sub_assign); |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Sub<<span class="kw-2">&</span><span class="lifetime">'a </span>BigUint> <span class="kw">for </span>BigUint { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="kw">fn </span>sub(<span class="kw-2">mut </span><span class="self">self</span>, other: <span class="kw-2">&</span>BigUint) -> BigUint { |
| <span class="self">self </span>-= other; |
| <span class="self">self |
| </span>} |
| } |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> SubAssign<<span class="kw-2">&</span><span class="lifetime">'a </span>BigUint> <span class="kw">for </span>BigUint { |
| <span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: <span class="kw-2">&</span><span class="lifetime">'a </span>BigUint) { |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>other.data[..]); |
| <span class="self">self</span>.normalize(); |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Sub<BigUint> <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span>BigUint { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">let </span>other_len = other.data.len(); |
| <span class="kw">if </span>other_len < <span class="self">self</span>.data.len() { |
| <span class="kw">let </span>lo_borrow = __sub2rev(<span class="kw-2">&</span><span class="self">self</span>.data[..other_len], <span class="kw-2">&mut </span>other.data); |
| other.data.extend_from_slice(<span class="kw-2">&</span><span class="self">self</span>.data[other_len..]); |
| <span class="kw">if </span>lo_borrow != <span class="number">0 </span>{ |
| sub2(<span class="kw-2">&mut </span>other.data[other_len..], <span class="kw-2">&</span>[<span class="number">1</span>]) |
| } |
| } <span class="kw">else </span>{ |
| sub2rev(<span class="kw-2">&</span><span class="self">self</span>.data[..], <span class="kw-2">&mut </span>other.data[..]); |
| } |
| other.normalized() |
| } |
| } |
| |
| <span class="macro">promote_unsigned_scalars!</span>(<span class="kw">impl </span>Sub <span class="kw">for </span>BigUint, sub); |
| <span class="macro">promote_unsigned_scalars_assign!</span>(<span class="kw">impl </span>SubAssign <span class="kw">for </span>BigUint, sub_assign); |
| <span class="macro">forward_all_scalar_binop_to_val_val!</span>(<span class="kw">impl </span>Sub<u32> <span class="kw">for </span>BigUint, sub); |
| <span class="macro">forward_all_scalar_binop_to_val_val!</span>(<span class="kw">impl </span>Sub<u64> <span class="kw">for </span>BigUint, sub); |
| <span class="macro">forward_all_scalar_binop_to_val_val!</span>(<span class="kw">impl </span>Sub<u128> <span class="kw">for </span>BigUint, sub); |
| |
| <span class="kw">impl </span>Sub<u32> <span class="kw">for </span>BigUint { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>sub(<span class="kw-2">mut </span><span class="self">self</span>, other: u32) -> BigUint { |
| <span class="self">self </span>-= other; |
| <span class="self">self |
| </span>} |
| } |
| |
| <span class="kw">impl </span>SubAssign<u32> <span class="kw">for </span>BigUint { |
| <span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: u32) { |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>[other <span class="kw">as </span>BigDigit]); |
| <span class="self">self</span>.normalize(); |
| } |
| } |
| |
| <span class="kw">impl </span>Sub<BigUint> <span class="kw">for </span>u32 { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[cfg(not(u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">if </span>other.data.len() == <span class="number">0 </span>{ |
| other.data.push(<span class="self">self</span>); |
| } <span class="kw">else </span>{ |
| sub2rev(<span class="kw-2">&</span>[<span class="self">self</span>], <span class="kw-2">&mut </span>other.data[..]); |
| } |
| other.normalized() |
| } |
| |
| <span class="attribute">#[cfg(u64_digit)] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">if </span>other.data.is_empty() { |
| other.data.push(<span class="self">self </span><span class="kw">as </span>BigDigit); |
| } <span class="kw">else </span>{ |
| sub2rev(<span class="kw-2">&</span>[<span class="self">self </span><span class="kw">as </span>BigDigit], <span class="kw-2">&mut </span>other.data[..]); |
| } |
| other.normalized() |
| } |
| } |
| |
| <span class="kw">impl </span>Sub<u64> <span class="kw">for </span>BigUint { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>sub(<span class="kw-2">mut </span><span class="self">self</span>, other: u64) -> BigUint { |
| <span class="self">self </span>-= other; |
| <span class="self">self |
| </span>} |
| } |
| |
| <span class="kw">impl </span>SubAssign<u64> <span class="kw">for </span>BigUint { |
| <span class="attribute">#[cfg(not(u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: u64) { |
| <span class="kw">let </span>(hi, lo) = big_digit::from_doublebigdigit(other); |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>[lo, hi]); |
| <span class="self">self</span>.normalize(); |
| } |
| |
| <span class="attribute">#[cfg(u64_digit)] |
| #[inline] |
| </span><span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: u64) { |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>[other <span class="kw">as </span>BigDigit]); |
| <span class="self">self</span>.normalize(); |
| } |
| } |
| |
| <span class="kw">impl </span>Sub<BigUint> <span class="kw">for </span>u64 { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[cfg(not(u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">while </span>other.data.len() < <span class="number">2 </span>{ |
| other.data.push(<span class="number">0</span>); |
| } |
| |
| <span class="kw">let </span>(hi, lo) = big_digit::from_doublebigdigit(<span class="self">self</span>); |
| sub2rev(<span class="kw-2">&</span>[lo, hi], <span class="kw-2">&mut </span>other.data[..]); |
| other.normalized() |
| } |
| |
| <span class="attribute">#[cfg(u64_digit)] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">if </span>other.data.is_empty() { |
| other.data.push(<span class="self">self</span>); |
| } <span class="kw">else </span>{ |
| sub2rev(<span class="kw-2">&</span>[<span class="self">self</span>], <span class="kw-2">&mut </span>other.data[..]); |
| } |
| other.normalized() |
| } |
| } |
| |
| <span class="kw">impl </span>Sub<u128> <span class="kw">for </span>BigUint { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>sub(<span class="kw-2">mut </span><span class="self">self</span>, other: u128) -> BigUint { |
| <span class="self">self </span>-= other; |
| <span class="self">self |
| </span>} |
| } |
| |
| <span class="kw">impl </span>SubAssign<u128> <span class="kw">for </span>BigUint { |
| <span class="attribute">#[cfg(not(u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: u128) { |
| <span class="kw">let </span>(a, b, c, d) = u32_from_u128(other); |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>[d, c, b, a]); |
| <span class="self">self</span>.normalize(); |
| } |
| |
| <span class="attribute">#[cfg(u64_digit)] |
| #[inline] |
| </span><span class="kw">fn </span>sub_assign(<span class="kw-2">&mut </span><span class="self">self</span>, other: u128) { |
| <span class="kw">let </span>(hi, lo) = big_digit::from_doublebigdigit(other); |
| sub2(<span class="kw-2">&mut </span><span class="self">self</span>.data[..], <span class="kw-2">&</span>[lo, hi]); |
| <span class="self">self</span>.normalize(); |
| } |
| } |
| |
| <span class="kw">impl </span>Sub<BigUint> <span class="kw">for </span>u128 { |
| <span class="kw">type </span>Output = BigUint; |
| |
| <span class="attribute">#[cfg(not(u64_digit))] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">while </span>other.data.len() < <span class="number">4 </span>{ |
| other.data.push(<span class="number">0</span>); |
| } |
| |
| <span class="kw">let </span>(a, b, c, d) = u32_from_u128(<span class="self">self</span>); |
| sub2rev(<span class="kw-2">&</span>[d, c, b, a], <span class="kw-2">&mut </span>other.data[..]); |
| other.normalized() |
| } |
| |
| <span class="attribute">#[cfg(u64_digit)] |
| #[inline] |
| </span><span class="kw">fn </span>sub(<span class="self">self</span>, <span class="kw-2">mut </span>other: BigUint) -> BigUint { |
| <span class="kw">while </span>other.data.len() < <span class="number">2 </span>{ |
| other.data.push(<span class="number">0</span>); |
| } |
| |
| <span class="kw">let </span>(hi, lo) = big_digit::from_doublebigdigit(<span class="self">self</span>); |
| sub2rev(<span class="kw-2">&</span>[lo, hi], <span class="kw-2">&mut </span>other.data[..]); |
| other.normalized() |
| } |
| } |
| |
| <span class="kw">impl </span>CheckedSub <span class="kw">for </span>BigUint { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>checked_sub(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span>BigUint) -> <span class="prelude-ty">Option</span><BigUint> { |
| <span class="kw">match </span><span class="self">self</span>.cmp(v) { |
| Less => <span class="prelude-val">None</span>, |
| Equal => <span class="prelude-val">Some</span>(Zero::zero()), |
| Greater => <span class="prelude-val">Some</span>(<span class="self">self</span>.sub(v)), |
| } |
| } |
| } |
| </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> |
