| <!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/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.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="doccomment">//! Fast, SIMD-accelerated CRC32 (IEEE) checksum computation. |
| //! |
| //! ## Usage |
| //! |
| //! ### Simple usage |
| //! |
| //! For simple use-cases, you can call the [`hash()`] convenience function to |
| //! directly compute the CRC32 checksum for a given byte slice: |
| //! |
| //! ```rust |
| //! let checksum = crc32fast::hash(b"foo bar baz"); |
| //! ``` |
| //! |
| //! ### Advanced usage |
| //! |
| //! For use-cases that require more flexibility or performance, for example when |
| //! processing large amounts of data, you can create and manipulate a [`Hasher`]: |
| //! |
| //! ```rust |
| //! use crc32fast::Hasher; |
| //! |
| //! let mut hasher = Hasher::new(); |
| //! hasher.update(b"foo bar baz"); |
| //! let checksum = hasher.finalize(); |
| //! ``` |
| //! |
| //! ## Performance |
| //! |
| //! This crate contains multiple CRC32 implementations: |
| //! |
| //! - A fast baseline implementation which processes up to 16 bytes per iteration |
| //! - An optimized implementation for modern `x86` using `sse` and `pclmulqdq` instructions |
| //! |
| //! Calling the [`Hasher::new`] constructor at runtime will perform a feature detection to select the most |
| //! optimal implementation for the current CPU feature set. |
| |
| </span><span class="attribute">#![cfg_attr(not(feature = <span class="string">"std"</span>), no_std)] |
| #![cfg_attr( |
| all(feature = <span class="string">"nightly"</span>, target_arch = <span class="string">"aarch64"</span>), |
| feature(stdsimd, aarch64_target_feature) |
| )] |
| |
| #[deny(missing_docs)] |
| #[cfg(test)] |
| #[macro_use] |
| </span><span class="kw">extern crate </span>quickcheck; |
| |
| <span class="attribute">#[macro_use] |
| </span><span class="kw">extern crate </span>cfg_if; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">use </span>std <span class="kw">as </span>core; |
| |
| <span class="kw">use </span>core::fmt; |
| <span class="kw">use </span>core::hash; |
| |
| <span class="kw">mod </span>baseline; |
| <span class="kw">mod </span>combine; |
| <span class="kw">mod </span>specialized; |
| <span class="kw">mod </span>table; |
| |
| <span class="doccomment">/// Computes the CRC32 hash of a byte slice. |
| /// |
| /// Check out [`Hasher`] for more advanced use-cases. |
| </span><span class="kw">pub fn </span>hash(buf: <span class="kw-2">&</span>[u8]) -> u32 { |
| <span class="kw">let </span><span class="kw-2">mut </span>h = Hasher::new(); |
| h.update(buf); |
| h.finalize() |
| } |
| |
| <span class="attribute">#[derive(Clone)] |
| </span><span class="kw">enum </span>State { |
| Baseline(baseline::State), |
| Specialized(specialized::State), |
| } |
| |
| <span class="attribute">#[derive(Clone)] |
| </span><span class="doccomment">/// Represents an in-progress CRC32 computation. |
| </span><span class="kw">pub struct </span>Hasher { |
| amount: u64, |
| state: State, |
| } |
| |
| <span class="kw">const </span>DEFAULT_INIT_STATE: u32 = <span class="number">0</span>; |
| |
| <span class="kw">impl </span>Hasher { |
| <span class="doccomment">/// Create a new `Hasher`. |
| /// |
| /// This will perform a CPU feature detection at runtime to select the most |
| /// optimal implementation for the current processor architecture. |
| </span><span class="kw">pub fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::new_with_initial(DEFAULT_INIT_STATE) |
| } |
| |
| <span class="doccomment">/// Create a new `Hasher` with an initial CRC32 state. |
| /// |
| /// This works just like `Hasher::new`, except that it allows for an initial |
| /// CRC32 state to be passed in. |
| </span><span class="kw">pub fn </span>new_with_initial(init: u32) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::new_with_initial_len(init, <span class="number">0</span>) |
| } |
| |
| <span class="doccomment">/// Create a new `Hasher` with an initial CRC32 state. |
| /// |
| /// As `new_with_initial`, but also accepts a length (in bytes). The |
| /// resulting object can then be used with `combine` to compute `crc(a || |
| /// b)` from `crc(a)`, `crc(b)`, and `len(b)`. |
| </span><span class="kw">pub fn </span>new_with_initial_len(init: u32, amount: u64) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::internal_new_specialized(init, amount) |
| .unwrap_or_else(|| <span class="self">Self</span>::internal_new_baseline(init, amount)) |
| } |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="comment">// Internal-only API. Don't use. |
| </span><span class="kw">pub fn </span>internal_new_baseline(init: u32, amount: u64) -> <span class="self">Self </span>{ |
| Hasher { |
| amount, |
| state: State::Baseline(baseline::State::new(init)), |
| } |
| } |
| |
| <span class="attribute">#[doc(hidden)] |
| </span><span class="comment">// Internal-only API. Don't use. |
| </span><span class="kw">pub fn </span>internal_new_specialized(init: u32, amount: u64) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>> { |
| { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(state) = specialized::State::new(init) { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(Hasher { |
| amount, |
| state: State::Specialized(state), |
| }); |
| } |
| } |
| <span class="prelude-val">None |
| </span>} |
| |
| <span class="doccomment">/// Process the given byte slice and update the hash state. |
| </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="self">self</span>.amount += buf.len() <span class="kw">as </span>u64; |
| <span class="kw">match </span><span class="self">self</span>.state { |
| State::Baseline(<span class="kw-2">ref mut </span>state) => state.update(buf), |
| State::Specialized(<span class="kw-2">ref mut </span>state) => state.update(buf), |
| } |
| } |
| |
| <span class="doccomment">/// Finalize the hash state and return the computed CRC32 value. |
| </span><span class="kw">pub fn </span>finalize(<span class="self">self</span>) -> u32 { |
| <span class="kw">match </span><span class="self">self</span>.state { |
| State::Baseline(state) => state.finalize(), |
| State::Specialized(state) => state.finalize(), |
| } |
| } |
| |
| <span class="doccomment">/// Reset the hash state. |
| </span><span class="kw">pub fn </span>reset(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.amount = <span class="number">0</span>; |
| <span class="kw">match </span><span class="self">self</span>.state { |
| State::Baseline(<span class="kw-2">ref mut </span>state) => state.reset(), |
| State::Specialized(<span class="kw-2">ref mut </span>state) => state.reset(), |
| } |
| } |
| |
| <span class="doccomment">/// Combine the hash state with the hash state for the subsequent block of bytes. |
| </span><span class="kw">pub fn </span>combine(<span class="kw-2">&mut </span><span class="self">self</span>, other: <span class="kw-2">&</span><span class="self">Self</span>) { |
| <span class="self">self</span>.amount += other.amount; |
| <span class="kw">let </span>other_crc = other.clone().finalize(); |
| <span class="kw">match </span><span class="self">self</span>.state { |
| State::Baseline(<span class="kw-2">ref mut </span>state) => state.combine(other_crc, other.amount), |
| State::Specialized(<span class="kw-2">ref mut </span>state) => state.combine(other_crc, other.amount), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Hasher { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| f.debug_struct(<span class="string">"crc32fast::Hasher"</span>).finish() |
| } |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>Hasher { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::new() |
| } |
| } |
| |
| <span class="kw">impl </span>hash::Hasher <span class="kw">for </span>Hasher { |
| <span class="kw">fn </span>write(<span class="kw-2">&mut </span><span class="self">self</span>, bytes: <span class="kw-2">&</span>[u8]) { |
| <span class="self">self</span>.update(bytes) |
| } |
| |
| <span class="kw">fn </span>finish(<span class="kw-2">&</span><span class="self">self</span>) -> u64 { |
| u64::from(<span class="self">self</span>.clone().finalize()) |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test { |
| <span class="kw">use </span><span class="kw">super</span>::Hasher; |
| |
| <span class="macro">quickcheck! </span>{ |
| <span class="kw">fn </span>combine(bytes_1: Vec<u8>, bytes_2: Vec<u8>) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_a = Hasher::new(); |
| hash_a.update(<span class="kw-2">&</span>bytes_1); |
| hash_a.update(<span class="kw-2">&</span>bytes_2); |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_b = Hasher::new(); |
| hash_b.update(<span class="kw-2">&</span>bytes_2); |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_c = Hasher::new(); |
| hash_c.update(<span class="kw-2">&</span>bytes_1); |
| hash_c.combine(<span class="kw-2">&</span>hash_b); |
| |
| hash_a.finalize() == hash_c.finalize() |
| } |
| |
| <span class="kw">fn </span>combine_from_len(bytes_1: Vec<u8>, bytes_2: Vec<u8>) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_a = Hasher::new(); |
| hash_a.update(<span class="kw-2">&</span>bytes_1); |
| <span class="kw">let </span>a = hash_a.finalize(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_b = Hasher::new(); |
| hash_b.update(<span class="kw-2">&</span>bytes_2); |
| <span class="kw">let </span>b = hash_b.finalize(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>hash_ab = Hasher::new(); |
| hash_ab.update(<span class="kw-2">&</span>bytes_1); |
| hash_ab.update(<span class="kw-2">&</span>bytes_2); |
| <span class="kw">let </span>ab = hash_ab.finalize(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>reconstructed = Hasher::new_with_initial_len(a, bytes_1.len() <span class="kw">as </span>u64); |
| <span class="kw">let </span>hash_b_reconstructed = Hasher::new_with_initial_len(b, bytes_2.len() <span class="kw">as </span>u64); |
| |
| reconstructed.combine(<span class="kw-2">&</span>hash_b_reconstructed); |
| |
| reconstructed.finalize() == ab |
| } |
| } |
| } |
| </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> |
