| <!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/regex-1.8.3/src/utf8.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>utf8.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="../../regex/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="../../regex/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">/// A few elementary UTF-8 encoding and decoding functions used by the matching |
| /// engines. |
| /// |
| /// In an ideal world, the matching engines operate on `&str` and we can just |
| /// lean on the standard library for all our UTF-8 needs. However, to support |
| /// byte based regexes (that can match on arbitrary bytes which may contain |
| /// UTF-8), we need to be capable of searching and decoding UTF-8 on a `&[u8]`. |
| /// The standard library doesn't really recognize this use case, so we have |
| /// to build it out ourselves. |
| /// |
| /// Should this be factored out into a separate crate? It seems independently |
| /// useful. There are other crates that already exist (e.g., `utf-8`) that have |
| /// overlapping use cases. Not sure what to do. |
| </span><span class="kw">use </span>std::char; |
| |
| <span class="kw">const </span>TAG_CONT: u8 = <span class="number">0b1000_0000</span>; |
| <span class="kw">const </span>TAG_TWO: u8 = <span class="number">0b1100_0000</span>; |
| <span class="kw">const </span>TAG_THREE: u8 = <span class="number">0b1110_0000</span>; |
| <span class="kw">const </span>TAG_FOUR: u8 = <span class="number">0b1111_0000</span>; |
| |
| <span class="doccomment">/// Returns the smallest possible index of the next valid UTF-8 sequence |
| /// starting after `i`. |
| </span><span class="kw">pub fn </span>next_utf8(text: <span class="kw-2">&</span>[u8], i: usize) -> usize { |
| <span class="kw">let </span>b = <span class="kw">match </span>text.get(i) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>i + <span class="number">1</span>, |
| <span class="prelude-val">Some</span>(<span class="kw-2">&</span>b) => b, |
| }; |
| <span class="kw">let </span>inc = <span class="kw">if </span>b <= <span class="number">0x7F </span>{ |
| <span class="number">1 |
| </span>} <span class="kw">else if </span>b <= <span class="number">0b110_11111 </span>{ |
| <span class="number">2 |
| </span>} <span class="kw">else if </span>b <= <span class="number">0b1110_1111 </span>{ |
| <span class="number">3 |
| </span>} <span class="kw">else </span>{ |
| <span class="number">4 |
| </span>}; |
| i + inc |
| } |
| |
| <span class="doccomment">/// Decode a single UTF-8 sequence into a single Unicode codepoint from `src`. |
| /// |
| /// If no valid UTF-8 sequence could be found, then `None` is returned. |
| /// Otherwise, the decoded codepoint and the number of bytes read is returned. |
| /// The number of bytes read (for a valid UTF-8 sequence) is guaranteed to be |
| /// 1, 2, 3 or 4. |
| /// |
| /// Note that a UTF-8 sequence is invalid if it is incorrect UTF-8, encodes a |
| /// codepoint that is out of range (surrogate codepoints are out of range) or |
| /// is not the shortest possible UTF-8 sequence for that codepoint. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>decode_utf8(src: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><(char, usize)> { |
| <span class="kw">let </span>b0 = <span class="kw">match </span>src.get(<span class="number">0</span>) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>(<span class="kw-2">&</span>b) <span class="kw">if </span>b <= <span class="number">0x7F </span>=> <span class="kw">return </span><span class="prelude-val">Some</span>((b <span class="kw">as </span>char, <span class="number">1</span>)), |
| <span class="prelude-val">Some</span>(<span class="kw-2">&</span>b) => b, |
| }; |
| <span class="kw">match </span>b0 { |
| <span class="number">0b110_00000</span>..=<span class="number">0b110_11111 </span>=> { |
| <span class="kw">if </span>src.len() < <span class="number">2 </span>{ |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>b1 = src[<span class="number">1</span>]; |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b1 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>cp = ((b0 & !TAG_TWO) <span class="kw">as </span>u32) << <span class="number">6 </span>| ((b1 & !TAG_CONT) <span class="kw">as </span>u32); |
| <span class="kw">match </span>cp { |
| <span class="number">0x80</span>..=<span class="number">0x7FF </span>=> char::from_u32(cp).map(|cp| (cp, <span class="number">2</span>)), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="number">0b1110_0000</span>..=<span class="number">0b1110_1111 </span>=> { |
| <span class="kw">if </span>src.len() < <span class="number">3 </span>{ |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>(b1, b2) = (src[<span class="number">1</span>], src[<span class="number">2</span>]); |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b1 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b2 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>cp = ((b0 & !TAG_THREE) <span class="kw">as </span>u32) << <span class="number">12 |
| </span>| ((b1 & !TAG_CONT) <span class="kw">as </span>u32) << <span class="number">6 |
| </span>| ((b2 & !TAG_CONT) <span class="kw">as </span>u32); |
| <span class="kw">match </span>cp { |
| <span class="comment">// char::from_u32 will disallow surrogate codepoints. |
| </span><span class="number">0x800</span>..=<span class="number">0xFFFF </span>=> char::from_u32(cp).map(|cp| (cp, <span class="number">3</span>)), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="number">0b11110_000</span>..=<span class="number">0b11110_111 </span>=> { |
| <span class="kw">if </span>src.len() < <span class="number">4 </span>{ |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>(b1, b2, b3) = (src[<span class="number">1</span>], src[<span class="number">2</span>], src[<span class="number">3</span>]); |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b1 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b2 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">if </span><span class="number">0b11_000000 </span>& b3 != TAG_CONT { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>cp = ((b0 & !TAG_FOUR) <span class="kw">as </span>u32) << <span class="number">18 |
| </span>| ((b1 & !TAG_CONT) <span class="kw">as </span>u32) << <span class="number">12 |
| </span>| ((b2 & !TAG_CONT) <span class="kw">as </span>u32) << <span class="number">6 |
| </span>| ((b3 & !TAG_CONT) <span class="kw">as </span>u32); |
| <span class="kw">match </span>cp { |
| <span class="number">0x10000</span>..=<span class="number">0x0010_FFFF </span>=> char::from_u32(cp).map(|cp| (cp, <span class="number">4</span>)), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Like `decode_utf8`, but decodes the last UTF-8 sequence in `src` instead |
| /// of the first. |
| </span><span class="kw">pub fn </span>decode_last_utf8(src: <span class="kw-2">&</span>[u8]) -> <span class="prelude-ty">Option</span><(char, usize)> { |
| <span class="kw">if </span>src.is_empty() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span><span class="kw-2">mut </span>start = src.len() - <span class="number">1</span>; |
| <span class="kw">if </span>src[start] <= <span class="number">0x7F </span>{ |
| <span class="kw">return </span><span class="prelude-val">Some</span>((src[start] <span class="kw">as </span>char, <span class="number">1</span>)); |
| } |
| <span class="kw">while </span>start > src.len().saturating_sub(<span class="number">4</span>) { |
| start -= <span class="number">1</span>; |
| <span class="kw">if </span>is_start_byte(src[start]) { |
| <span class="kw">break</span>; |
| } |
| } |
| <span class="kw">match </span>decode_utf8(<span class="kw-2">&</span>src[start..]) { |
| <span class="prelude-val">None </span>=> <span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>((<span class="kw">_</span>, n)) <span class="kw">if </span>n < src.len() - start => <span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>((cp, n)) => <span class="prelude-val">Some</span>((cp, n)), |
| } |
| } |
| |
| <span class="kw">fn </span>is_start_byte(b: u8) -> bool { |
| b & <span class="number">0b11_000000 </span>!= <span class="number">0b1_0000000 |
| </span>} |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span>std::str; |
| |
| <span class="kw">use </span>quickcheck::quickcheck; |
| |
| <span class="kw">use super</span>::{ |
| decode_last_utf8, decode_utf8, TAG_CONT, TAG_FOUR, TAG_THREE, TAG_TWO, |
| }; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_roundtrip() { |
| <span class="kw">fn </span>p(given_cp: char) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>tmp = [<span class="number">0</span>; <span class="number">4</span>]; |
| <span class="kw">let </span>encoded_len = given_cp.encode_utf8(<span class="kw-2">&mut </span>tmp).len(); |
| <span class="kw">let </span>(got_cp, got_len) = decode_utf8(<span class="kw-2">&</span>tmp[..encoded_len]).unwrap(); |
| encoded_len == got_len && given_cp == got_cp |
| } |
| quickcheck(p <span class="kw">as fn</span>(char) -> bool) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_roundtrip_last() { |
| <span class="kw">fn </span>p(given_cp: char) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>tmp = [<span class="number">0</span>; <span class="number">4</span>]; |
| <span class="kw">let </span>encoded_len = given_cp.encode_utf8(<span class="kw-2">&mut </span>tmp).len(); |
| <span class="kw">let </span>(got_cp, got_len) = |
| decode_last_utf8(<span class="kw-2">&</span>tmp[..encoded_len]).unwrap(); |
| encoded_len == got_len && given_cp == got_cp |
| } |
| quickcheck(p <span class="kw">as fn</span>(char) -> bool) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_encode_matches_std() { |
| <span class="kw">fn </span>p(cp: char) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>got = [<span class="number">0</span>; <span class="number">4</span>]; |
| <span class="kw">let </span>n = cp.encode_utf8(<span class="kw-2">&mut </span>got).len(); |
| <span class="kw">let </span>expected = cp.to_string(); |
| <span class="kw-2">&</span>got[..n] == expected.as_bytes() |
| } |
| quickcheck(p <span class="kw">as fn</span>(char) -> bool) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_decode_matches_std() { |
| <span class="kw">fn </span>p(given_cp: char) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>tmp = [<span class="number">0</span>; <span class="number">4</span>]; |
| <span class="kw">let </span>n = given_cp.encode_utf8(<span class="kw-2">&mut </span>tmp).len(); |
| <span class="kw">let </span>(got_cp, <span class="kw">_</span>) = decode_utf8(<span class="kw-2">&</span>tmp[..n]).unwrap(); |
| <span class="kw">let </span>expected_cp = |
| str::from_utf8(<span class="kw-2">&</span>tmp[..n]).unwrap().chars().next().unwrap(); |
| got_cp == expected_cp |
| } |
| quickcheck(p <span class="kw">as fn</span>(char) -> bool) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_decode_last_matches_std() { |
| <span class="kw">fn </span>p(given_cp: char) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>tmp = [<span class="number">0</span>; <span class="number">4</span>]; |
| <span class="kw">let </span>n = given_cp.encode_utf8(<span class="kw-2">&mut </span>tmp).len(); |
| <span class="kw">let </span>(got_cp, <span class="kw">_</span>) = decode_last_utf8(<span class="kw-2">&</span>tmp[..n]).unwrap(); |
| <span class="kw">let </span>expected_cp = str::from_utf8(<span class="kw-2">&</span>tmp[..n]) |
| .unwrap() |
| .chars() |
| .rev() |
| .next() |
| .unwrap(); |
| got_cp == expected_cp |
| } |
| quickcheck(p <span class="kw">as fn</span>(char) -> bool) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>reject_invalid() { |
| <span class="comment">// Invalid start byte |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xFF</span>]), <span class="prelude-val">None</span>); |
| <span class="comment">// Surrogate pair |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xED</span>, <span class="number">0xA0</span>, <span class="number">0x81</span>]), <span class="prelude-val">None</span>); |
| <span class="comment">// Invalid continuation byte. |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xD4</span>, <span class="number">0xC2</span>]), <span class="prelude-val">None</span>); |
| <span class="comment">// Bad lengths |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xC3</span>]), <span class="prelude-val">None</span>); <span class="comment">// 2 bytes |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xEF</span>, <span class="number">0xBF</span>]), <span class="prelude-val">None</span>); <span class="comment">// 3 bytes |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[<span class="number">0xF4</span>, <span class="number">0x8F</span>, <span class="number">0xBF</span>]), <span class="prelude-val">None</span>); <span class="comment">// 4 bytes |
| // Not a minimal UTF-8 sequence |
| </span><span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[TAG_TWO, TAG_CONT | <span class="string">b'a'</span>]), <span class="prelude-val">None</span>); |
| <span class="macro">assert_eq!</span>(decode_utf8(<span class="kw-2">&</span>[TAG_THREE, TAG_CONT, TAG_CONT | <span class="string">b'a'</span>]), <span class="prelude-val">None</span>); |
| <span class="macro">assert_eq!</span>( |
| decode_utf8(<span class="kw-2">&</span>[TAG_FOUR, TAG_CONT, TAG_CONT, TAG_CONT | <span class="string">b'a'</span>,]), |
| <span class="prelude-val">None |
| </span>); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>reject_invalid_last() { |
| <span class="comment">// Invalid start byte |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[<span class="number">0xFF</span>]), <span class="prelude-val">None</span>); |
| <span class="comment">// Surrogate pair |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[<span class="number">0xED</span>, <span class="number">0xA0</span>, <span class="number">0x81</span>]), <span class="prelude-val">None</span>); |
| <span class="comment">// Bad lengths |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[<span class="number">0xC3</span>]), <span class="prelude-val">None</span>); <span class="comment">// 2 bytes |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[<span class="number">0xEF</span>, <span class="number">0xBF</span>]), <span class="prelude-val">None</span>); <span class="comment">// 3 bytes |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[<span class="number">0xF4</span>, <span class="number">0x8F</span>, <span class="number">0xBF</span>]), <span class="prelude-val">None</span>); <span class="comment">// 4 bytes |
| // Not a minimal UTF-8 sequence |
| </span><span class="macro">assert_eq!</span>(decode_last_utf8(<span class="kw-2">&</span>[TAG_TWO, TAG_CONT | <span class="string">b'a'</span>]), <span class="prelude-val">None</span>); |
| <span class="macro">assert_eq!</span>( |
| decode_last_utf8(<span class="kw-2">&</span>[TAG_THREE, TAG_CONT, TAG_CONT | <span class="string">b'a'</span>,]), |
| <span class="prelude-val">None |
| </span>); |
| <span class="macro">assert_eq!</span>( |
| decode_last_utf8( |
| <span class="kw-2">&</span>[TAG_FOUR, TAG_CONT, TAG_CONT, TAG_CONT | <span class="string">b'a'</span>,] |
| ), |
| <span class="prelude-val">None |
| </span>); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="regex" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
