| <!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/crc32fast-1.3.2/src/specialized/pclmulqdq.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>pclmulqdq.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="../../../crc32fast/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="../../../crc32fast/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(target_arch = <span class="string">"x86"</span>)] |
| </span><span class="kw">use </span>core::arch::x86 <span class="kw">as </span>arch; |
| <span class="attribute">#[cfg(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">#[derive(Clone)] |
| </span><span class="kw">pub struct </span>State { |
| state: u32, |
| } |
| |
| <span class="kw">impl </span>State { |
| <span class="attribute">#[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="kw">pub fn </span>new(state: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>> { |
| <span class="kw">if </span><span class="macro">cfg!</span>(target_feature = <span class="string">"pclmulqdq"</span>) |
| && <span class="macro">cfg!</span>(target_feature = <span class="string">"sse2"</span>) |
| && <span class="macro">cfg!</span>(target_feature = <span class="string">"sse4.1"</span>) |
| { |
| <span class="comment">// SAFETY: The conditions above ensure that all |
| // required instructions are supported by the CPU. |
| </span><span class="prelude-val">Some</span>(<span class="self">Self </span>{ state }) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">pub fn </span>new(state: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>> { |
| <span class="kw">if </span><span class="macro">is_x86_feature_detected!</span>(<span class="string">"pclmulqdq"</span>) |
| && <span class="macro">is_x86_feature_detected!</span>(<span class="string">"sse2"</span>) |
| && <span class="macro">is_x86_feature_detected!</span>(<span class="string">"sse4.1"</span>) |
| { |
| <span class="comment">// SAFETY: The conditions above ensure that all |
| // required instructions are supported by the CPU. |
| </span><span class="prelude-val">Some</span>(<span class="self">Self </span>{ state }) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="kw">pub fn </span>update(<span class="kw-2">&mut </span><span class="self">self</span>, buf: <span class="kw-2">&</span>[u8]) { |
| <span class="comment">// SAFETY: The `State::new` constructor ensures that all |
| // required instructions are supported by the CPU. |
| </span><span class="self">self</span>.state = <span class="kw">unsafe </span>{ calculate(<span class="self">self</span>.state, buf) } |
| } |
| |
| <span class="kw">pub fn </span>finalize(<span class="self">self</span>) -> u32 { |
| <span class="self">self</span>.state |
| } |
| |
| <span class="kw">pub fn </span>reset(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.state = <span class="number">0</span>; |
| } |
| |
| <span class="kw">pub fn </span>combine(<span class="kw-2">&mut </span><span class="self">self</span>, other: u32, amount: u64) { |
| <span class="self">self</span>.state = ::combine::combine(<span class="self">self</span>.state, other, amount); |
| } |
| } |
| |
| <span class="kw">const </span>K1: i64 = <span class="number">0x154442bd4</span>; |
| <span class="kw">const </span>K2: i64 = <span class="number">0x1c6e41596</span>; |
| <span class="kw">const </span>K3: i64 = <span class="number">0x1751997d0</span>; |
| <span class="kw">const </span>K4: i64 = <span class="number">0x0ccaa009e</span>; |
| <span class="kw">const </span>K5: i64 = <span class="number">0x163cd6124</span>; |
| <span class="kw">const </span>K6: i64 = <span class="number">0x1db710640</span>; |
| |
| <span class="kw">const </span>P_X: i64 = <span class="number">0x1DB710641</span>; |
| <span class="kw">const </span>U_PRIME: i64 = <span class="number">0x1F7011641</span>; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">unsafe fn </span>debug(s: <span class="kw-2">&</span>str, a: arch::__m128i) -> arch::__m128i { |
| <span class="kw">if </span><span class="bool-val">false </span>{ |
| <span class="kw">union </span>A { |
| a: arch::__m128i, |
| b: [u8; <span class="number">16</span>], |
| } |
| <span class="kw">let </span>x = A { a }.b; |
| <span class="macro">print!</span>(<span class="string">" {:20} | "</span>, s); |
| <span class="kw">for </span>x <span class="kw">in </span>x.iter() { |
| <span class="macro">print!</span>(<span class="string">"{:02x} "</span>, x); |
| } |
| <span class="macro">println!</span>(); |
| } |
| <span class="kw">return </span>a; |
| } |
| |
| <span class="attribute">#[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="kw">unsafe fn </span>debug(_s: <span class="kw-2">&</span>str, a: arch::__m128i) -> arch::__m128i { |
| a |
| } |
| |
| <span class="attribute">#[target_feature(enable = <span class="string">"pclmulqdq"</span>, enable = <span class="string">"sse2"</span>, enable = <span class="string">"sse4.1"</span>)] |
| </span><span class="kw">unsafe fn </span>calculate(crc: u32, <span class="kw-2">mut </span>data: <span class="kw-2">&</span>[u8]) -> u32 { |
| <span class="comment">// In theory we can accelerate smaller chunks too, but for now just rely on |
| // the fallback implementation as it's too much hassle and doesn't seem too |
| // beneficial. |
| </span><span class="kw">if </span>data.len() < <span class="number">128 </span>{ |
| <span class="kw">return </span>::baseline::update_fast_16(crc, data); |
| } |
| |
| <span class="comment">// Step 1: fold by 4 loop |
| </span><span class="kw">let </span><span class="kw-2">mut </span>x3 = get(<span class="kw-2">&mut </span>data); |
| <span class="kw">let </span><span class="kw-2">mut </span>x2 = get(<span class="kw-2">&mut </span>data); |
| <span class="kw">let </span><span class="kw-2">mut </span>x1 = get(<span class="kw-2">&mut </span>data); |
| <span class="kw">let </span><span class="kw-2">mut </span>x0 = get(<span class="kw-2">&mut </span>data); |
| |
| <span class="comment">// fold in our initial value, part of the incremental crc checksum |
| </span>x3 = arch::_mm_xor_si128(x3, arch::_mm_cvtsi32_si128(!crc <span class="kw">as </span>i32)); |
| |
| <span class="kw">let </span>k1k2 = arch::_mm_set_epi64x(K2, K1); |
| <span class="kw">while </span>data.len() >= <span class="number">64 </span>{ |
| x3 = reduce128(x3, get(<span class="kw-2">&mut </span>data), k1k2); |
| x2 = reduce128(x2, get(<span class="kw-2">&mut </span>data), k1k2); |
| x1 = reduce128(x1, get(<span class="kw-2">&mut </span>data), k1k2); |
| x0 = reduce128(x0, get(<span class="kw-2">&mut </span>data), k1k2); |
| } |
| |
| <span class="kw">let </span>k3k4 = arch::_mm_set_epi64x(K4, K3); |
| <span class="kw">let </span><span class="kw-2">mut </span>x = reduce128(x3, x2, k3k4); |
| x = reduce128(x, x1, k3k4); |
| x = reduce128(x, x0, k3k4); |
| |
| <span class="comment">// Step 2: fold by 1 loop |
| </span><span class="kw">while </span>data.len() >= <span class="number">16 </span>{ |
| x = reduce128(x, get(<span class="kw-2">&mut </span>data), k3k4); |
| } |
| |
| debug(<span class="string">"128 > 64 init"</span>, x); |
| |
| <span class="comment">// Perform step 3, reduction from 128 bits to 64 bits. This is |
| // significantly different from the paper and basically doesn't follow it |
| // at all. It's not really clear why, but implementations of this algorithm |
| // in Chrome/Linux diverge in the same way. It is beyond me why this is |
| // different than the paper, maybe the paper has like errata or something? |
| // Unclear. |
| // |
| // It's also not clear to me what's actually happening here and/or why, but |
| // algebraically what's happening is: |
| // |
| // x = (x[0:63] • K4) ^ x[64:127] // 96 bit result |
| // x = ((x[0:31] as u64) • K5) ^ x[32:95] // 64 bit result |
| // |
| // It's... not clear to me what's going on here. The paper itself is pretty |
| // vague on this part but definitely uses different constants at least. |
| // It's not clear to me, reading the paper, where the xor operations are |
| // happening or why things are shifting around. This implementation... |
| // appears to work though! |
| </span>drop(K6); |
| <span class="kw">let </span>x = arch::_mm_xor_si128( |
| arch::_mm_clmulepi64_si128(x, k3k4, <span class="number">0x10</span>), |
| arch::_mm_srli_si128(x, <span class="number">8</span>), |
| ); |
| <span class="kw">let </span>x = arch::_mm_xor_si128( |
| arch::_mm_clmulepi64_si128( |
| arch::_mm_and_si128(x, arch::_mm_set_epi32(<span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, !<span class="number">0</span>)), |
| arch::_mm_set_epi64x(<span class="number">0</span>, K5), |
| <span class="number">0x00</span>, |
| ), |
| arch::_mm_srli_si128(x, <span class="number">4</span>), |
| ); |
| debug(<span class="string">"128 > 64 xx"</span>, x); |
| |
| <span class="comment">// Perform a Barrett reduction from our now 64 bits to 32 bits. The |
| // algorithm for this is described at the end of the paper, and note that |
| // this also implements the "bit reflected input" variant. |
| </span><span class="kw">let </span>pu = arch::_mm_set_epi64x(U_PRIME, P_X); |
| |
| <span class="comment">// T1(x) = ⌊(R(x) % x^32)⌋ • μ |
| </span><span class="kw">let </span>t1 = arch::_mm_clmulepi64_si128( |
| arch::_mm_and_si128(x, arch::_mm_set_epi32(<span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, !<span class="number">0</span>)), |
| pu, |
| <span class="number">0x10</span>, |
| ); |
| <span class="comment">// T2(x) = ⌊(T1(x) % x^32)⌋ • P(x) |
| </span><span class="kw">let </span>t2 = arch::_mm_clmulepi64_si128( |
| arch::_mm_and_si128(t1, arch::_mm_set_epi32(<span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, !<span class="number">0</span>)), |
| pu, |
| <span class="number">0x00</span>, |
| ); |
| <span class="comment">// We're doing the bit-reflected variant, so get the upper 32-bits of the |
| // 64-bit result instead of the lower 32-bits. |
| // |
| // C(x) = R(x) ^ T2(x) / x^32 |
| </span><span class="kw">let </span>c = arch::_mm_extract_epi32(arch::_mm_xor_si128(x, t2), <span class="number">1</span>) <span class="kw">as </span>u32; |
| |
| <span class="kw">if </span>!data.is_empty() { |
| ::baseline::update_fast_16(!c, data) |
| } <span class="kw">else </span>{ |
| !c |
| } |
| } |
| |
| <span class="kw">unsafe fn </span>reduce128(a: arch::__m128i, b: arch::__m128i, keys: arch::__m128i) -> arch::__m128i { |
| <span class="kw">let </span>t1 = arch::_mm_clmulepi64_si128(a, keys, <span class="number">0x00</span>); |
| <span class="kw">let </span>t2 = arch::_mm_clmulepi64_si128(a, keys, <span class="number">0x11</span>); |
| arch::_mm_xor_si128(arch::_mm_xor_si128(b, t1), t2) |
| } |
| |
| <span class="kw">unsafe fn </span>get(a: <span class="kw-2">&mut &</span>[u8]) -> arch::__m128i { |
| <span class="macro">debug_assert!</span>(a.len() >= <span class="number">16</span>); |
| <span class="kw">let </span>r = arch::_mm_loadu_si128(a.as_ptr() <span class="kw">as </span><span class="kw-2">*const </span>arch::__m128i); |
| <span class="kw-2">*</span>a = <span class="kw-2">&</span>a[<span class="number">16</span>..]; |
| <span class="kw">return </span>r; |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test { |
| <span class="macro">quickcheck! </span>{ |
| <span class="kw">fn </span>check_against_baseline(init: u32, chunks: Vec<(Vec<u8>, usize)>) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>baseline = <span class="kw">super</span>::<span class="kw">super</span>::<span class="kw">super</span>::baseline::State::new(init); |
| <span class="kw">let </span><span class="kw-2">mut </span>pclmulqdq = <span class="kw">super</span>::State::new(init).expect(<span class="string">"not supported"</span>); |
| <span class="kw">for </span>(chunk, <span class="kw-2">mut </span>offset) <span class="kw">in </span>chunks { |
| <span class="comment">// simulate random alignments by offsetting the slice by up to 15 bytes |
| </span>offset &= <span class="number">0xF</span>; |
| <span class="kw">if </span>chunk.len() <= offset { |
| baseline.update(<span class="kw-2">&</span>chunk); |
| pclmulqdq.update(<span class="kw-2">&</span>chunk); |
| } <span class="kw">else </span>{ |
| baseline.update(<span class="kw-2">&</span>chunk[offset..]); |
| pclmulqdq.update(<span class="kw-2">&</span>chunk[offset..]); |
| } |
| } |
| pclmulqdq.finalize() == baseline.finalize() |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="crc32fast" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
