<!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 to the Rust file `libcore/str/pattern.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>pattern.rs.html -- source</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css"><link rel="stylesheet" type="text/css" href="../../../light.css" id="themeStyle"><script src="../../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../../settings.html"><img src="../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><pre class="rust ">
<span class="comment">// Copyright 2015 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! The string Pattern API.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! For more details, see the traits `Pattern`, `Searcher`,</span>
<span class="doccomment">//! `ReverseSearcher` and `DoubleEndedSearcher`.</span>
<span class="attribute">#![<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pattern"</span>,
<span class="ident">reason</span> <span class="op">=</span> <span class="string">"API not fully fleshed out and ready to be stabilized"</span>,
<span class="ident">issue</span> <span class="op">=</span> <span class="string">"27721"</span>)]</span>
<span class="kw">use</span> <span class="ident">cmp</span>;
<span class="kw">use</span> <span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">slice</span>::<span class="ident">memchr</span>;
<span class="kw">use</span> <span class="ident">usize</span>;
<span class="comment">// Pattern</span>
<span class="doccomment">/// A string pattern.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A `Pattern<'a>` expresses that the implementing type</span>
<span class="doccomment">/// can be used as a string pattern for searching in a `&'a str`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For example, both `'a'` and `"aa"` are patterns that</span>
<span class="doccomment">/// would match at index `1` in the string `"baaaab"`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The trait itself acts as a builder for an associated</span>
<span class="doccomment">/// `Searcher` type, which does the actual work of finding</span>
<span class="doccomment">/// occurrences of the pattern in a string.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>: <span class="ident">Sized</span> {
<span class="doccomment">/// Associated searcher for this pattern</span>
<span class="kw">type</span> <span class="ident">Searcher</span>: <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>;
<span class="doccomment">/// Constructs the associated searcher from</span>
<span class="doccomment">/// `self` and the `haystack` to search in.</span>
<span class="kw">fn</span> <span class="ident">into_searcher</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Searcher</span>;
<span class="doccomment">/// Checks whether the pattern matches anywhere in the haystack</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_contained_in</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">into_searcher</span>(<span class="ident">haystack</span>).<span class="ident">next_match</span>().<span class="ident">is_some</span>()
}
<span class="doccomment">/// Checks whether the pattern matches at the front of the haystack</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_prefix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">into_searcher</span>(<span class="ident">haystack</span>).<span class="ident">next</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="number">0</span>, <span class="kw">_</span>) <span class="op">=></span> <span class="bool-val">true</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="bool-val">false</span>,
}
}
<span class="doccomment">/// Checks whether the pattern matches at the back of the haystack</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_suffix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span>
<span class="kw">where</span> <span class="self">Self</span>::<span class="ident">Searcher</span>: <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>
{
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">into_searcher</span>(<span class="ident">haystack</span>).<span class="ident">next_back</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="kw">_</span>, <span class="ident">j</span>) <span class="kw">if</span> <span class="ident">haystack</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="ident">j</span> <span class="op">=></span> <span class="bool-val">true</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="bool-val">false</span>,
}
}
}
<span class="comment">// Searcher</span>
<span class="doccomment">/// Result of calling `Searcher::next()` or `ReverseSearcher::next_back()`.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Copy</span>, <span class="ident">Clone</span>, <span class="ident">Eq</span>, <span class="ident">PartialEq</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">SearchStep</span> {
<span class="doccomment">/// Expresses that a match of the pattern has been found at</span>
<span class="doccomment">/// `haystack[a..b]`.</span>
<span class="ident">Match</span>(<span class="ident">usize</span>, <span class="ident">usize</span>),
<span class="doccomment">/// Expresses that `haystack[a..b]` has been rejected as a possible match</span>
<span class="doccomment">/// of the pattern.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that there might be more than one `Reject` between two `Match`es,</span>
<span class="doccomment">/// there is no requirement for them to be combined into one.</span>
<span class="ident">Reject</span>(<span class="ident">usize</span>, <span class="ident">usize</span>),
<span class="doccomment">/// Expresses that every byte of the haystack has been visited, ending</span>
<span class="doccomment">/// the iteration.</span>
<span class="ident">Done</span>
}
<span class="doccomment">/// A searcher for a string pattern.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This trait provides methods for searching for non-overlapping</span>
<span class="doccomment">/// matches of a pattern starting from the front (left) of a string.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It will be implemented by associated `Searcher`</span>
<span class="doccomment">/// types of the `Pattern` trait.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The trait is marked unsafe because the indices returned by the</span>
<span class="doccomment">/// `next()` methods are required to lie on valid utf8 boundaries in</span>
<span class="doccomment">/// the haystack. This enables consumers of this trait to</span>
<span class="doccomment">/// slice the haystack without additional runtime checks.</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">trait</span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// Getter for the underlying string to be searched in</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Will always return the same `&str`</span>
<span class="kw">fn</span> <span class="ident">haystack</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>;
<span class="doccomment">/// Performs the next search step starting from the front.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - Returns `Match(a, b)` if `haystack[a..b]` matches the pattern.</span>
<span class="doccomment">/// - Returns `Reject(a, b)` if `haystack[a..b]` can not match the</span>
<span class="doccomment">/// pattern, even partially.</span>
<span class="doccomment">/// - Returns `Done` if every byte of the haystack has been visited</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The stream of `Match` and `Reject` values up to a `Done`</span>
<span class="doccomment">/// will contain index ranges that are adjacent, non-overlapping,</span>
<span class="doccomment">/// covering the whole haystack, and laying on utf8 boundaries.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A `Match` result needs to contain the whole matched pattern,</span>
<span class="doccomment">/// however `Reject` results may be split up into arbitrary</span>
<span class="doccomment">/// many adjacent fragments. Both ranges may have zero length.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// As an example, the pattern `"aaa"` and the haystack `"cbaaaaab"`</span>
<span class="doccomment">/// might produce the stream</span>
<span class="doccomment">/// `[Reject(0, 1), Reject(1, 2), Match(2, 5), Reject(5, 8)]`</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span>;
<span class="doccomment">/// Find the next `Match` result. See `next()`</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike next(), there is no guarantee that the returned ranges</span>
<span class="doccomment">/// of this and next_reject will overlap. This will return (start_match, end_match),</span>
<span class="doccomment">/// where start_match is the index of where the match begins, and end_match is</span>
<span class="doccomment">/// the index after the end of the match.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="kw">continue</span>,
}
}
}
<span class="doccomment">/// Find the next `Reject` result. See `next()` and `next_match()`</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike next(), there is no guarantee that the returned ranges</span>
<span class="doccomment">/// of this and next_match will overlap.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_reject</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="kw">continue</span>,
}
}
}
}
<span class="doccomment">/// A reverse searcher for a string pattern.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This trait provides methods for searching for non-overlapping</span>
<span class="doccomment">/// matches of a pattern starting from the back (right) of a string.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It will be implemented by associated `Searcher`</span>
<span class="doccomment">/// types of the `Pattern` trait if the pattern supports searching</span>
<span class="doccomment">/// for it from the back.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The index ranges returned by this trait are not required</span>
<span class="doccomment">/// to exactly match those of the forward search in reverse.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For the reason why this trait is marked unsafe, see them</span>
<span class="doccomment">/// parent trait `Searcher`.</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">trait</span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>: <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="doccomment">/// Performs the next search step starting from the back.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - Returns `Match(a, b)` if `haystack[a..b]` matches the pattern.</span>
<span class="doccomment">/// - Returns `Reject(a, b)` if `haystack[a..b]` can not match the</span>
<span class="doccomment">/// pattern, even partially.</span>
<span class="doccomment">/// - Returns `Done` if every byte of the haystack has been visited</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The stream of `Match` and `Reject` values up to a `Done`</span>
<span class="doccomment">/// will contain index ranges that are adjacent, non-overlapping,</span>
<span class="doccomment">/// covering the whole haystack, and laying on utf8 boundaries.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A `Match` result needs to contain the whole matched pattern,</span>
<span class="doccomment">/// however `Reject` results may be split up into arbitrary</span>
<span class="doccomment">/// many adjacent fragments. Both ranges may have zero length.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// As an example, the pattern `"aaa"` and the haystack `"cbaaaaab"`</span>
<span class="doccomment">/// might produce the stream</span>
<span class="doccomment">/// `[Reject(7, 8), Match(4, 7), Reject(1, 4), Reject(0, 1)]`</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span>;
<span class="doccomment">/// Find the next `Match` result. See `next_back()`</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span>{
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next_back</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="kw">continue</span>,
}
}
}
<span class="doccomment">/// Find the next `Reject` result. See `next_back()`</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_reject_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span>{
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next_back</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="kw">_</span> <span class="op">=></span> <span class="kw">continue</span>,
}
}
}
}
<span class="doccomment">/// A marker trait to express that a `ReverseSearcher`</span>
<span class="doccomment">/// can be used for a `DoubleEndedIterator` implementation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For this, the impl of `Searcher` and `ReverseSearcher` need</span>
<span class="doccomment">/// to follow these conditions:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - All results of `next()` need to be identical</span>
<span class="doccomment">/// to the results of `next_back()` in reverse order.</span>
<span class="doccomment">/// - `next()` and `next_back()` need to behave as</span>
<span class="doccomment">/// the two ends of a range of values, that is they</span>
<span class="doccomment">/// can not "walk past each other".</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `char::Searcher` is a `DoubleEndedSearcher` because searching for a</span>
<span class="doccomment">/// `char` only requires looking at one at a time, which behaves the same</span>
<span class="doccomment">/// from both ends.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `(&str)::Searcher` is not a `DoubleEndedSearcher` because</span>
<span class="doccomment">/// the pattern `"aa"` in the haystack `"aaa"` matches as either</span>
<span class="doccomment">/// `"[aa]a"` or `"a[aa]"`, depending from which side it is searched.</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">DoubleEndedSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>: <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for char</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Associated type for `<char as Pattern<'a>>::Searcher`.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">CharSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>,
<span class="comment">// safety invariant: `finger`/`finger_back` must be a valid utf8 byte index of `haystack`</span>
<span class="comment">// This invariant can be broken *within* next_match and next_match_back, however</span>
<span class="comment">// they must exit with fingers on valid code point boundaries.</span>
<span class="doccomment">/// `finger` is the current byte index of the forward search.</span>
<span class="doccomment">/// Imagine that it exists before the byte at its index, i.e.</span>
<span class="doccomment">/// `haystack[finger]` is the first byte of the slice we must inspect during</span>
<span class="doccomment">/// forward searching</span>
<span class="ident">finger</span>: <span class="ident">usize</span>,
<span class="doccomment">/// `finger_back` is the current byte index of the reverse search.</span>
<span class="doccomment">/// Imagine that it exists after the byte at its index, i.e.</span>
<span class="doccomment">/// haystack[finger_back - 1] is the last byte of the slice we must inspect during</span>
<span class="doccomment">/// forward searching (and thus the first byte to be inspected when calling next_back())</span>
<span class="ident">finger_back</span>: <span class="ident">usize</span>,
<span class="doccomment">/// The character being searched for</span>
<span class="ident">needle</span>: <span class="ident">char</span>,
<span class="comment">// safety invariant: `utf8_size` must be less than 5</span>
<span class="doccomment">/// The number of bytes `needle` takes up when encoded in utf8</span>
<span class="ident">utf8_size</span>: <span class="ident">usize</span>,
<span class="doccomment">/// A utf8 encoded copy of the `needle`</span>
<span class="ident">utf8_encoded</span>: [<span class="ident">u8</span>; <span class="number">4</span>],
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">haystack</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span> {
<span class="self">self</span>.<span class="ident">haystack</span>
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">let</span> <span class="ident">old_finger</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger</span>;
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">get_unchecked</span>(<span class="ident">old_finger</span>..<span class="self">self</span>.<span class="ident">finger_back</span>) };
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">iter</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">chars</span>();
<span class="kw">let</span> <span class="ident">old_len</span> <span class="op">=</span> <span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=</span> <span class="ident">iter</span>.<span class="ident">next</span>() {
<span class="comment">// add byte offset of current character</span>
<span class="comment">// without re-encoding as utf-8</span>
<span class="self">self</span>.<span class="ident">finger</span> <span class="op">+=</span> <span class="ident">old_len</span> <span class="op">-</span> <span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="ident">ch</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">needle</span> {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">old_finger</span>, <span class="self">self</span>.<span class="ident">finger</span>)
} <span class="kw">else</span> {
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">old_finger</span>, <span class="self">self</span>.<span class="ident">finger</span>)
}
} <span class="kw">else</span> {
<span class="ident">SearchStep</span>::<span class="ident">Done</span>
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">loop</span> {
<span class="comment">// get the haystack after the last character found</span>
<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">slice</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>()
.<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">finger</span>..<span class="self">self</span>.<span class="ident">finger_back</span>) {
<span class="ident">slice</span>
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
};
<span class="comment">// the last byte of the utf8 encoded needle</span>
<span class="kw">let</span> <span class="ident">last_byte</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">utf8_encoded</span>.<span class="ident">get_unchecked</span>(<span class="self">self</span>.<span class="ident">utf8_size</span> <span class="op">-</span> <span class="number">1</span>) };
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">index</span>) <span class="op">=</span> <span class="ident">memchr</span>::<span class="ident">memchr</span>(<span class="ident">last_byte</span>, <span class="ident">bytes</span>) {
<span class="comment">// The new finger is the index of the byte we found,</span>
<span class="comment">// plus one, since we memchr'd for the last byte of the character.</span>
<span class="comment">//</span>
<span class="comment">// Note that this doesn't always give us a finger on a UTF8 boundary.</span>
<span class="comment">// If we *didn't* find our character</span>
<span class="comment">// we may have indexed to the non-last byte of a 3-byte or 4-byte character.</span>
<span class="comment">// We can't just skip to the next valid starting byte because a character like</span>
<span class="comment">// ꁁ (U+A041 YI SYLLABLE PA), utf-8 `EA 81 81` will have us always find</span>
<span class="comment">// the second byte when searching for the third.</span>
<span class="comment">//</span>
<span class="comment">// However, this is totally okay. While we have the invariant that</span>
<span class="comment">// self.finger is on a UTF8 boundary, this invariant is not relied upon</span>
<span class="comment">// within this method (it is relied upon in CharSearcher::next()).</span>
<span class="comment">//</span>
<span class="comment">// We only exit this method when we reach the end of the string, or if we</span>
<span class="comment">// find something. When we find something the `finger` will be set</span>
<span class="comment">// to a UTF8 boundary.</span>
<span class="self">self</span>.<span class="ident">finger</span> <span class="op">+=</span> <span class="ident">index</span> <span class="op">+</span> <span class="number">1</span>;
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">finger</span> <span class="op">>=</span> <span class="self">self</span>.<span class="ident">utf8_size</span> {
<span class="kw">let</span> <span class="ident">found_char</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger</span> <span class="op">-</span> <span class="self">self</span>.<span class="ident">utf8_size</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">slice</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>().<span class="ident">get</span>(<span class="ident">found_char</span>..<span class="self">self</span>.<span class="ident">finger</span>) {
<span class="kw">if</span> <span class="ident">slice</span> <span class="op">==</span> <span class="kw-2">&</span><span class="self">self</span>.<span class="ident">utf8_encoded</span>[<span class="number">0</span>..<span class="self">self</span>.<span class="ident">utf8_size</span>] {
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">found_char</span>, <span class="self">self</span>.<span class="ident">finger</span>));
}
}
}
} <span class="kw">else</span> {
<span class="comment">// found nothing, exit</span>
<span class="self">self</span>.<span class="ident">finger</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger_back</span>;
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
<span class="comment">// let next_reject use the default implementation from the Searcher trait</span>
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">let</span> <span class="ident">old_finger</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger_back</span>;
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">slice_unchecked</span>(<span class="self">self</span>.<span class="ident">finger</span>, <span class="ident">old_finger</span>) };
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">iter</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">chars</span>();
<span class="kw">let</span> <span class="ident">old_len</span> <span class="op">=</span> <span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=</span> <span class="ident">iter</span>.<span class="ident">next_back</span>() {
<span class="comment">// subtract byte offset of current character</span>
<span class="comment">// without re-encoding as utf-8</span>
<span class="self">self</span>.<span class="ident">finger_back</span> <span class="op">-=</span> <span class="ident">old_len</span> <span class="op">-</span> <span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="ident">ch</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">needle</span> {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="self">self</span>.<span class="ident">finger_back</span>, <span class="ident">old_finger</span>)
} <span class="kw">else</span> {
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="self">self</span>.<span class="ident">finger_back</span>, <span class="ident">old_finger</span>)
}
} <span class="kw">else</span> {
<span class="ident">SearchStep</span>::<span class="ident">Done</span>
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">let</span> <span class="ident">haystack</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>();
<span class="kw">loop</span> {
<span class="comment">// get the haystack up to but not including the last character searched</span>
<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">slice</span>) <span class="op">=</span> <span class="ident">haystack</span>.<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">finger</span>..<span class="self">self</span>.<span class="ident">finger_back</span>) {
<span class="ident">slice</span>
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="prelude-val">None</span>;
};
<span class="comment">// the last byte of the utf8 encoded needle</span>
<span class="kw">let</span> <span class="ident">last_byte</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">utf8_encoded</span>.<span class="ident">get_unchecked</span>(<span class="self">self</span>.<span class="ident">utf8_size</span> <span class="op">-</span> <span class="number">1</span>) };
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">index</span>) <span class="op">=</span> <span class="ident">memchr</span>::<span class="ident">memrchr</span>(<span class="ident">last_byte</span>, <span class="ident">bytes</span>) {
<span class="comment">// we searched a slice that was offset by self.finger,</span>
<span class="comment">// add self.finger to recoup the original index</span>
<span class="kw">let</span> <span class="ident">index</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger</span> <span class="op">+</span> <span class="ident">index</span>;
<span class="comment">// memrchr will return the index of the byte we wish to</span>
<span class="comment">// find. In case of an ASCII character, this is indeed</span>
<span class="comment">// were we wish our new finger to be ("after" the found</span>
<span class="comment">// char in the paradigm of reverse iteration). For</span>
<span class="comment">// multibyte chars we need to skip down by the number of more</span>
<span class="comment">// bytes they have than ASCII</span>
<span class="kw">let</span> <span class="ident">shift</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">utf8_size</span> <span class="op">-</span> <span class="number">1</span>;
<span class="kw">if</span> <span class="ident">index</span> <span class="op">>=</span> <span class="ident">shift</span> {
<span class="kw">let</span> <span class="ident">found_char</span> <span class="op">=</span> <span class="ident">index</span> <span class="op">-</span> <span class="ident">shift</span>;
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">slice</span>) <span class="op">=</span> <span class="ident">haystack</span>.<span class="ident">get</span>(<span class="ident">found_char</span>..(<span class="ident">found_char</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">utf8_size</span>)) {
<span class="kw">if</span> <span class="ident">slice</span> <span class="op">==</span> <span class="kw-2">&</span><span class="self">self</span>.<span class="ident">utf8_encoded</span>[<span class="number">0</span>..<span class="self">self</span>.<span class="ident">utf8_size</span>] {
<span class="comment">// move finger to before the character found (i.e. at its start index)</span>
<span class="self">self</span>.<span class="ident">finger_back</span> <span class="op">=</span> <span class="ident">found_char</span>;
<span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="self">self</span>.<span class="ident">finger_back</span>, <span class="self">self</span>.<span class="ident">finger_back</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">utf8_size</span>));
}
}
}
<span class="comment">// We can't use finger_back = index - size + 1 here. If we found the last char</span>
<span class="comment">// of a different-sized character (or the middle byte of a different character)</span>
<span class="comment">// we need to bump the finger_back down to `index`. This similarly makes</span>
<span class="comment">// `finger_back` have the potential to no longer be on a boundary,</span>
<span class="comment">// but this is OK since we only exit this function on a boundary</span>
<span class="comment">// or when the haystack has been searched completely.</span>
<span class="comment">//</span>
<span class="comment">// Unlike next_match this does not</span>
<span class="comment">// have the problem of repeated bytes in utf-8 because</span>
<span class="comment">// we're searching for the last byte, and we can only have</span>
<span class="comment">// found the last byte when searching in reverse.</span>
<span class="self">self</span>.<span class="ident">finger_back</span> <span class="op">=</span> <span class="ident">index</span>;
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">finger_back</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">finger</span>;
<span class="comment">// found nothing, exit</span>
<span class="kw">return</span> <span class="prelude-val">None</span>;
}
}
}
<span class="comment">// let next_reject_back use the default implementation from the Searcher trait</span>
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">DoubleEndedSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> {}
<span class="doccomment">/// Searches for chars that are equal to a given char</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">char</span> {
<span class="kw">type</span> <span class="ident">Searcher</span> <span class="op">=</span> <span class="ident">CharSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_searcher</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Searcher</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">utf8_encoded</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">4</span>];
<span class="self">self</span>.<span class="ident">encode_utf8</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">utf8_encoded</span>);
<span class="kw">let</span> <span class="ident">utf8_size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">len_utf8</span>();
<span class="ident">CharSearcher</span> {
<span class="ident">haystack</span>,
<span class="ident">finger</span>: <span class="number">0</span>,
<span class="ident">finger_back</span>: <span class="ident">haystack</span>.<span class="ident">len</span>(),
<span class="ident">needle</span>: <span class="self">self</span>,
<span class="ident">utf8_size</span>,
<span class="ident">utf8_encoded</span>
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_contained_in</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">if</span> (<span class="self">self</span> <span class="kw">as</span> <span class="ident">u32</span>) <span class="op"><</span> <span class="number">128</span> {
<span class="ident">haystack</span>.<span class="ident">as_bytes</span>().<span class="ident">contains</span>(<span class="kw-2">&</span>(<span class="self">self</span> <span class="kw">as</span> <span class="ident">u8</span>))
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buffer</span> <span class="op">=</span> [<span class="number">0u8</span>; <span class="number">4</span>];
<span class="self">self</span>.<span class="ident">encode_utf8</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buffer</span>).<span class="ident">is_contained_in</span>(<span class="ident">haystack</span>)
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_prefix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=</span> <span class="ident">haystack</span>.<span class="ident">chars</span>().<span class="ident">next</span>() {
<span class="self">self</span> <span class="op">==</span> <span class="ident">ch</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_suffix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> <span class="kw">where</span> <span class="self">Self</span>::<span class="ident">Searcher</span>: <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>
{
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=</span> <span class="ident">haystack</span>.<span class="ident">chars</span>().<span class="ident">next_back</span>() {
<span class="self">self</span> <span class="op">==</span> <span class="ident">ch</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for a MultiCharEq wrapper</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="kw">trait</span> <span class="ident">MultiCharEq</span> {
<span class="kw">fn</span> <span class="ident">matches</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">c</span>: <span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span>;
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> <span class="ident">MultiCharEq</span> <span class="kw">for</span> <span class="ident">F</span> <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">matches</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">c</span>: <span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span> { (<span class="kw-2">*</span><span class="self">self</span>)(<span class="ident">c</span>) }
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="ident">MultiCharEq</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> [<span class="ident">char</span>] {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">matches</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">c</span>: <span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">iter</span>().<span class="ident">any</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">m</span><span class="op">|</span> { <span class="ident">m</span> <span class="op">==</span> <span class="ident">c</span> })
}
}
<span class="kw">struct</span> <span class="ident">MultiCharEqPattern</span><span class="op"><</span><span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span>(<span class="ident">C</span>);
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span> {
<span class="ident">char_eq</span>: <span class="ident">C</span>,
<span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>,
<span class="ident">char_indices</span>: <span class="kw">super</span>::<span class="ident">CharIndices</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">MultiCharEqPattern</span><span class="op"><</span><span class="ident">C</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Searcher</span> <span class="op">=</span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span><span class="op">></span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_searcher</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span><span class="op">></span> {
<span class="ident">MultiCharEqSearcher</span> {
<span class="ident">haystack</span>,
<span class="ident">char_eq</span>: <span class="self">self</span>.<span class="number">0</span>,
<span class="ident">char_indices</span>: <span class="ident">haystack</span>.<span class="ident">char_indices</span>(),
}
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">haystack</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span> {
<span class="self">self</span>.<span class="ident">haystack</span>
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">char_indices</span>;
<span class="comment">// Compare lengths of the internal byte slice iterator</span>
<span class="comment">// to find length of current char</span>
<span class="kw">let</span> <span class="ident">pre_len</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>((<span class="ident">i</span>, <span class="ident">c</span>)) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">next</span>() {
<span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">let</span> <span class="ident">char_len</span> <span class="op">=</span> <span class="ident">pre_len</span> <span class="op">-</span> <span class="ident">len</span>;
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">char_eq</span>.<span class="ident">matches</span>(<span class="ident">c</span>) {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">i</span>, <span class="ident">i</span> <span class="op">+</span> <span class="ident">char_len</span>);
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">i</span>, <span class="ident">i</span> <span class="op">+</span> <span class="ident">char_len</span>);
}
}
<span class="ident">SearchStep</span>::<span class="ident">Done</span>
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">char_indices</span>;
<span class="comment">// Compare lengths of the internal byte slice iterator</span>
<span class="comment">// to find length of current char</span>
<span class="kw">let</span> <span class="ident">pre_len</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>((<span class="ident">i</span>, <span class="ident">c</span>)) <span class="op">=</span> <span class="ident">s</span>.<span class="ident">next_back</span>() {
<span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">s</span>.<span class="ident">iter</span>.<span class="ident">iter</span>.<span class="ident">len</span>();
<span class="kw">let</span> <span class="ident">char_len</span> <span class="op">=</span> <span class="ident">pre_len</span> <span class="op">-</span> <span class="ident">len</span>;
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">char_eq</span>.<span class="ident">matches</span>(<span class="ident">c</span>) {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">i</span>, <span class="ident">i</span> <span class="op">+</span> <span class="ident">char_len</span>);
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">i</span>, <span class="ident">i</span> <span class="op">+</span> <span class="ident">char_len</span>);
}
}
<span class="ident">SearchStep</span>::<span class="ident">Done</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span>: <span class="ident">MultiCharEq</span><span class="op">></span> <span class="ident">DoubleEndedSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">MultiCharEqSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">C</span><span class="op">></span> {}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">pattern_methods</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">pmap</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">smap</span>:<span class="ident">expr</span>) <span class="op">=></span> {
<span class="kw">type</span> <span class="ident">Searcher</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_searcher</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">smap</span>)((<span class="macro-nonterminal">$</span><span class="macro-nonterminal">pmap</span>)(<span class="self">self</span>).<span class="ident">into_searcher</span>(<span class="ident">haystack</span>))
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_contained_in</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">pmap</span>)(<span class="self">self</span>).<span class="ident">is_contained_in</span>(<span class="ident">haystack</span>)
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_prefix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">pmap</span>)(<span class="self">self</span>).<span class="ident">is_prefix_of</span>(<span class="ident">haystack</span>)
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_suffix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span>
<span class="kw">where</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>: <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span>
{
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">pmap</span>)(<span class="self">self</span>).<span class="ident">is_suffix_of</span>(<span class="ident">haystack</span>)
}
}
}
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">searcher_methods</span> {
(<span class="ident">forward</span>) <span class="op">=></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">haystack</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">haystack</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_match</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_reject</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_reject</span>()
}
};
(<span class="ident">reverse</span>) <span class="op">=></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_back</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_match_back</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_reject_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_reject_back</span>()
}
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for &[char]</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Todo: Change / Remove due to ambiguity in meaning.</span>
<span class="doccomment">/// Associated type for `<&[char] as Pattern<'a>>::Searcher`.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">CharSliceSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span>(<span class="op"><</span><span class="ident">MultiCharEqPattern</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'b</span> [<span class="ident">char</span>]<span class="op">></span> <span class="kw">as</span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">>></span>::<span class="ident">Searcher</span>);
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSliceSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="macro">searcher_methods</span><span class="macro">!</span>(<span class="ident">forward</span>);
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSliceSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="macro">searcher_methods</span><span class="macro">!</span>(<span class="ident">reverse</span>);
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">DoubleEndedSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharSliceSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {}
<span class="doccomment">/// Searches for chars that are equal to any of the chars in the array</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'b</span> [<span class="ident">char</span>] {
<span class="macro">pattern_methods</span><span class="macro">!</span>(<span class="ident">CharSliceSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span>, <span class="ident">MultiCharEqPattern</span>, <span class="ident">CharSliceSearcher</span>);
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for F: FnMut(char) -> bool</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Associated type for `<F as Pattern<'a>>::Searcher`.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>(<span class="op"><</span><span class="ident">MultiCharEqPattern</span><span class="op"><</span><span class="ident">F</span><span class="op">></span> <span class="kw">as</span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">>></span>::<span class="ident">Searcher</span>)
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span>;
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span>
{
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">f</span>.<span class="ident">debug_struct</span>(<span class="string">"CharPredicateSearcher"</span>)
.<span class="ident">field</span>(<span class="string">"haystack"</span>, <span class="kw-2">&</span><span class="self">self</span>.<span class="number">0</span>.<span class="ident">haystack</span>)
.<span class="ident">field</span>(<span class="string">"char_indices"</span>, <span class="kw-2">&</span><span class="self">self</span>.<span class="number">0</span>.<span class="ident">char_indices</span>)
.<span class="ident">finish</span>()
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span>
{
<span class="macro">searcher_methods</span><span class="macro">!</span>(<span class="ident">forward</span>);
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span>
{
<span class="macro">searcher_methods</span><span class="macro">!</span>(<span class="ident">reverse</span>);
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span> <span class="ident">DoubleEndedSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span> {}
<span class="doccomment">/// Searches for chars that match the given predicate</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">F</span> <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="ident">char</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="macro">pattern_methods</span><span class="macro">!</span>(<span class="ident">CharPredicateSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">F</span><span class="op">></span>, <span class="ident">MultiCharEqPattern</span>, <span class="ident">CharPredicateSearcher</span>);
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for &&str</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Delegates to the `&str` impl.</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span>, <span class="lifetime">'c</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'c</span> <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="ident">str</span> {
<span class="macro">pattern_methods</span><span class="macro">!</span>(<span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span>, <span class="op">|</span><span class="kw-2">&</span><span class="ident">s</span><span class="op">|</span> <span class="ident">s</span>, <span class="op">|</span><span class="ident">s</span><span class="op">|</span> <span class="ident">s</span>);
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Impl for &str</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Non-allocating substring search.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Will handle the pattern `""` as returning empty matches at each character</span>
<span class="doccomment">/// boundary.</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">Pattern</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="ident">str</span> {
<span class="kw">type</span> <span class="ident">Searcher</span> <span class="op">=</span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_searcher</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="ident">StrSearcher</span>::<span class="ident">new</span>(<span class="ident">haystack</span>, <span class="self">self</span>)
}
<span class="doccomment">/// Checks whether the pattern matches at the front of the haystack</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_prefix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="ident">haystack</span>.<span class="ident">is_char_boundary</span>(<span class="self">self</span>.<span class="ident">len</span>()) <span class="op">&&</span>
<span class="self">self</span> <span class="op">==</span> <span class="kw-2">&</span><span class="ident">haystack</span>[..<span class="self">self</span>.<span class="ident">len</span>()]
}
<span class="doccomment">/// Checks whether the pattern matches at the back of the haystack</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">is_suffix_of</span>(<span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">len</span>() <span class="op"><=</span> <span class="ident">haystack</span>.<span class="ident">len</span>() <span class="op">&&</span>
<span class="ident">haystack</span>.<span class="ident">is_char_boundary</span>(<span class="ident">haystack</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="self">self</span>.<span class="ident">len</span>()) <span class="op">&&</span>
<span class="self">self</span> <span class="op">==</span> <span class="kw-2">&</span><span class="ident">haystack</span>[<span class="ident">haystack</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="self">self</span>.<span class="ident">len</span>()..]
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Two Way substring searcher</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="doccomment">/// Associated type for `<&str as Pattern<'a>>::Searcher`.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>,
<span class="ident">needle</span>: <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="ident">str</span>,
<span class="ident">searcher</span>: <span class="ident">StrSearcherImpl</span>,
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">enum</span> <span class="ident">StrSearcherImpl</span> {
<span class="ident">Empty</span>(<span class="ident">EmptyNeedle</span>),
<span class="ident">TwoWay</span>(<span class="ident">TwoWaySearcher</span>),
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">EmptyNeedle</span> {
<span class="ident">position</span>: <span class="ident">usize</span>,
<span class="ident">end</span>: <span class="ident">usize</span>,
<span class="ident">is_match_fw</span>: <span class="ident">bool</span>,
<span class="ident">is_match_bw</span>: <span class="ident">bool</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">haystack</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>, <span class="ident">needle</span>: <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="ident">str</span>) <span class="op">-></span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">needle</span>.<span class="ident">is_empty</span>() {
<span class="ident">StrSearcher</span> {
<span class="ident">haystack</span>,
<span class="ident">needle</span>,
<span class="ident">searcher</span>: <span class="ident">StrSearcherImpl</span>::<span class="ident">Empty</span>(<span class="ident">EmptyNeedle</span> {
<span class="ident">position</span>: <span class="number">0</span>,
<span class="ident">end</span>: <span class="ident">haystack</span>.<span class="ident">len</span>(),
<span class="ident">is_match_fw</span>: <span class="bool-val">true</span>,
<span class="ident">is_match_bw</span>: <span class="bool-val">true</span>,
}),
}
} <span class="kw">else</span> {
<span class="ident">StrSearcher</span> {
<span class="ident">haystack</span>,
<span class="ident">needle</span>,
<span class="ident">searcher</span>: <span class="ident">StrSearcherImpl</span>::<span class="ident">TwoWay</span>(
<span class="ident">TwoWaySearcher</span>::<span class="ident">new</span>(<span class="ident">needle</span>.<span class="ident">as_bytes</span>(), <span class="ident">haystack</span>.<span class="ident">len</span>())
),
}
}
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">Searcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">haystack</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span> {
<span class="self">self</span>.<span class="ident">haystack</span>
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">searcher</span> {
<span class="ident">StrSearcherImpl</span>::<span class="ident">Empty</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="comment">// empty needle rejects every char and matches every empty string between them</span>
<span class="kw">let</span> <span class="ident">is_match</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">is_match_fw</span>;
<span class="ident">searcher</span>.<span class="ident">is_match_fw</span> <span class="op">=</span> <span class="op">!</span><span class="ident">searcher</span>.<span class="ident">is_match_fw</span>;
<span class="kw">let</span> <span class="ident">pos</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">position</span>;
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">haystack</span>[<span class="ident">pos</span>..].<span class="ident">chars</span>().<span class="ident">next</span>() {
<span class="kw">_</span> <span class="kw">if</span> <span class="ident">is_match</span> <span class="op">=></span> <span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">pos</span>, <span class="ident">pos</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">SearchStep</span>::<span class="ident">Done</span>,
<span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=></span> {
<span class="ident">searcher</span>.<span class="ident">position</span> <span class="op">+=</span> <span class="ident">ch</span>.<span class="ident">len_utf8</span>();
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">pos</span>, <span class="ident">searcher</span>.<span class="ident">position</span>)
}
}
}
<span class="ident">StrSearcherImpl</span>::<span class="ident">TwoWay</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="comment">// TwoWaySearcher produces valid *Match* indices that split at char boundaries</span>
<span class="comment">// as long as it does correct matching and that haystack and needle are</span>
<span class="comment">// valid UTF-8</span>
<span class="comment">// *Rejects* from the algorithm can fall on any indices, but we will walk them</span>
<span class="comment">// manually to the next character boundary, so that they are utf-8 safe.</span>
<span class="kw">if</span> <span class="ident">searcher</span>.<span class="ident">position</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">len</span>() {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Done</span>;
}
<span class="kw">let</span> <span class="ident">is_long</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">memory</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span>;
<span class="kw">match</span> <span class="ident">searcher</span>.<span class="ident">next</span>::<span class="op"><</span><span class="ident">RejectAndMatch</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="ident">is_long</span>)
{
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="kw-2">mut</span> <span class="ident">b</span>) <span class="op">=></span> {
<span class="comment">// skip to next char boundary</span>
<span class="kw">while</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">is_char_boundary</span>(<span class="ident">b</span>) {
<span class="ident">b</span> <span class="op">+=</span> <span class="number">1</span>;
}
<span class="ident">searcher</span>.<span class="ident">position</span> <span class="op">=</span> <span class="ident">cmp</span>::<span class="ident">max</span>(<span class="ident">b</span>, <span class="ident">searcher</span>.<span class="ident">position</span>);
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="ident">b</span>)
}
<span class="ident">otherwise</span> <span class="op">=></span> <span class="ident">otherwise</span>,
}
}
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">searcher</span> {
<span class="ident">StrSearcherImpl</span>::<span class="ident">Empty</span>(..) <span class="op">=></span> {
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(..) <span class="op">=></span> { }
}
}
}
<span class="ident">StrSearcherImpl</span>::<span class="ident">TwoWay</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="kw">let</span> <span class="ident">is_long</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">memory</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span>;
<span class="comment">// write out `true` and `false` cases to encourage the compiler</span>
<span class="comment">// to specialize the two cases separately.</span>
<span class="kw">if</span> <span class="ident">is_long</span> {
<span class="ident">searcher</span>.<span class="ident">next</span>::<span class="op"><</span><span class="ident">MatchOnly</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="bool-val">true</span>)
} <span class="kw">else</span> {
<span class="ident">searcher</span>.<span class="ident">next</span>::<span class="op"><</span><span class="ident">MatchOnly</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="bool-val">false</span>)
}
}
}
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> <span class="ident">ReverseSearcher</span><span class="op"><</span><span class="lifetime">'a</span><span class="op">></span> <span class="kw">for</span> <span class="ident">StrSearcher</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'b</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">SearchStep</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">searcher</span> {
<span class="ident">StrSearcherImpl</span>::<span class="ident">Empty</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="kw">let</span> <span class="ident">is_match</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">is_match_bw</span>;
<span class="ident">searcher</span>.<span class="ident">is_match_bw</span> <span class="op">=</span> <span class="op">!</span><span class="ident">searcher</span>.<span class="ident">is_match_bw</span>;
<span class="kw">let</span> <span class="ident">end</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">end</span>;
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">haystack</span>[..<span class="ident">end</span>].<span class="ident">chars</span>().<span class="ident">next_back</span>() {
<span class="kw">_</span> <span class="kw">if</span> <span class="ident">is_match</span> <span class="op">=></span> <span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">end</span>, <span class="ident">end</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">SearchStep</span>::<span class="ident">Done</span>,
<span class="prelude-val">Some</span>(<span class="ident">ch</span>) <span class="op">=></span> {
<span class="ident">searcher</span>.<span class="ident">end</span> <span class="op">-=</span> <span class="ident">ch</span>.<span class="ident">len_utf8</span>();
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">searcher</span>.<span class="ident">end</span>, <span class="ident">end</span>)
}
}
}
<span class="ident">StrSearcherImpl</span>::<span class="ident">TwoWay</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="kw">if</span> <span class="ident">searcher</span>.<span class="ident">end</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="ident">SearchStep</span>::<span class="ident">Done</span>;
}
<span class="kw">let</span> <span class="ident">is_long</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">memory</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span>;
<span class="kw">match</span> <span class="ident">searcher</span>.<span class="ident">next_back</span>::<span class="op"><</span><span class="ident">RejectAndMatch</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="ident">is_long</span>)
{
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="kw-2">mut</span> <span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> {
<span class="comment">// skip to next char boundary</span>
<span class="kw">while</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">is_char_boundary</span>(<span class="ident">a</span>) {
<span class="ident">a</span> <span class="op">-=</span> <span class="number">1</span>;
}
<span class="ident">searcher</span>.<span class="ident">end</span> <span class="op">=</span> <span class="ident">cmp</span>::<span class="ident">min</span>(<span class="ident">a</span>, <span class="ident">searcher</span>.<span class="ident">end</span>);
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="ident">b</span>)
}
<span class="ident">otherwise</span> <span class="op">=></span> <span class="ident">otherwise</span>,
}
}
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_match_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">searcher</span> {
<span class="ident">StrSearcherImpl</span>::<span class="ident">Empty</span>(..) <span class="op">=></span> {
<span class="kw">loop</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">next_back</span>() {
<span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)),
<span class="ident">SearchStep</span>::<span class="ident">Done</span> <span class="op">=></span> <span class="kw">return</span> <span class="prelude-val">None</span>,
<span class="ident">SearchStep</span>::<span class="ident">Reject</span>(..) <span class="op">=></span> { }
}
}
}
<span class="ident">StrSearcherImpl</span>::<span class="ident">TwoWay</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">searcher</span>) <span class="op">=></span> {
<span class="kw">let</span> <span class="ident">is_long</span> <span class="op">=</span> <span class="ident">searcher</span>.<span class="ident">memory</span> <span class="op">==</span> <span class="ident">usize</span>::<span class="ident">MAX</span>;
<span class="comment">// write out `true` and `false`, like `next_match`</span>
<span class="kw">if</span> <span class="ident">is_long</span> {
<span class="ident">searcher</span>.<span class="ident">next_back</span>::<span class="op"><</span><span class="ident">MatchOnly</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="bool-val">true</span>)
} <span class="kw">else</span> {
<span class="ident">searcher</span>.<span class="ident">next_back</span>::<span class="op"><</span><span class="ident">MatchOnly</span><span class="op">></span>(<span class="self">self</span>.<span class="ident">haystack</span>.<span class="ident">as_bytes</span>(),
<span class="self">self</span>.<span class="ident">needle</span>.<span class="ident">as_bytes</span>(),
<span class="bool-val">false</span>)
}
}
}
}
}
<span class="doccomment">/// The internal state of the two-way substring search algorithm.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">TwoWaySearcher</span> {
<span class="comment">// constants</span>
<span class="doccomment">/// critical factorization index</span>
<span class="ident">crit_pos</span>: <span class="ident">usize</span>,
<span class="doccomment">/// critical factorization index for reversed needle</span>
<span class="ident">crit_pos_back</span>: <span class="ident">usize</span>,
<span class="ident">period</span>: <span class="ident">usize</span>,
<span class="doccomment">/// `byteset` is an extension (not part of the two way algorithm);</span>
<span class="doccomment">/// it's a 64-bit "fingerprint" where each set bit `j` corresponds</span>
<span class="doccomment">/// to a (byte & 63) == j present in the needle.</span>
<span class="ident">byteset</span>: <span class="ident">u64</span>,
<span class="comment">// variables</span>
<span class="ident">position</span>: <span class="ident">usize</span>,
<span class="ident">end</span>: <span class="ident">usize</span>,
<span class="doccomment">/// index into needle before which we have already matched</span>
<span class="ident">memory</span>: <span class="ident">usize</span>,
<span class="doccomment">/// index into needle after which we have already matched</span>
<span class="ident">memory_back</span>: <span class="ident">usize</span>,
}
<span class="comment">/*
This is the Two-Way search algorithm, which was introduced in the paper:
Crochemore, M., Perrin, D., 1991, Two-way string-matching, Journal of the ACM 38(3):651-675.
Here's some background information.
A *word* is a string of symbols. The *length* of a word should be a familiar
notion, and here we denote it for any word x by |x|.
(We also allow for the possibility of the *empty word*, a word of length zero).
If x is any non-empty word, then an integer p with 0 < p <= |x| is said to be a
*period* for x iff for all i with 0 <= i <= |x| - p - 1, we have x[i] == x[i+p].
For example, both 1 and 2 are periods for the string "aa". As another example,
the only period of the string "abcd" is 4.
We denote by period(x) the *smallest* period of x (provided that x is non-empty).
This is always well-defined since every non-empty word x has at least one period,
|x|. We sometimes call this *the period* of x.
If u, v and x are words such that x = uv, where uv is the concatenation of u and
v, then we say that (u, v) is a *factorization* of x.
Let (u, v) be a factorization for a word x. Then if w is a non-empty word such
that both of the following hold
- either w is a suffix of u or u is a suffix of w
- either w is a prefix of v or v is a prefix of w
then w is said to be a *repetition* for the factorization (u, v).
Just to unpack this, there are four possibilities here. Let w = "abc". Then we
might have:
- w is a suffix of u and w is a prefix of v. ex: ("lolabc", "abcde")
- w is a suffix of u and v is a prefix of w. ex: ("lolabc", "ab")
- u is a suffix of w and w is a prefix of v. ex: ("bc", "abchi")
- u is a suffix of w and v is a prefix of w. ex: ("bc", "a")
Note that the word vu is a repetition for any factorization (u,v) of x = uv,
so every factorization has at least one repetition.
If x is a string and (u, v) is a factorization for x, then a *local period* for
(u, v) is an integer r such that there is some word w such that |w| = r and w is
a repetition for (u, v).
We denote by local_period(u, v) the smallest local period of (u, v). We sometimes
call this *the local period* of (u, v). Provided that x = uv is non-empty, this
is well-defined (because each non-empty word has at least one factorization, as
noted above).
It can be proven that the following is an equivalent definition of a local period
for a factorization (u, v): any positive integer r such that x[i] == x[i+r] for
all i such that |u| - r <= i <= |u| - 1 and such that both x[i] and x[i+r] are
defined. (i.e. i > 0 and i + r < |x|).
Using the above reformulation, it is easy to prove that
1 <= local_period(u, v) <= period(uv)
A factorization (u, v) of x such that local_period(u,v) = period(x) is called a
*critical factorization*.
The algorithm hinges on the following theorem, which is stated without proof:
**Critical Factorization Theorem** Any word x has at least one critical
factorization (u, v) such that |u| < period(x).
The purpose of maximal_suffix is to find such a critical factorization.
If the period is short, compute another factorization x = u' v' to use
for reverse search, chosen instead so that |v'| < period(x).
*/</span>
<span class="kw">impl</span> <span class="ident">TwoWaySearcher</span> {
<span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">needle</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">end</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">TwoWaySearcher</span> {
<span class="kw">let</span> (<span class="ident">crit_pos_false</span>, <span class="ident">period_false</span>) <span class="op">=</span> <span class="ident">TwoWaySearcher</span>::<span class="ident">maximal_suffix</span>(<span class="ident">needle</span>, <span class="bool-val">false</span>);
<span class="kw">let</span> (<span class="ident">crit_pos_true</span>, <span class="ident">period_true</span>) <span class="op">=</span> <span class="ident">TwoWaySearcher</span>::<span class="ident">maximal_suffix</span>(<span class="ident">needle</span>, <span class="bool-val">true</span>);
<span class="kw">let</span> (<span class="ident">crit_pos</span>, <span class="ident">period</span>) <span class="op">=</span>
<span class="kw">if</span> <span class="ident">crit_pos_false</span> <span class="op">></span> <span class="ident">crit_pos_true</span> {
(<span class="ident">crit_pos_false</span>, <span class="ident">period_false</span>)
} <span class="kw">else</span> {
(<span class="ident">crit_pos_true</span>, <span class="ident">period_true</span>)
};
<span class="comment">// A particularly readable explanation of what's going on here can be found</span>
<span class="comment">// in Crochemore and Rytter's book "Text Algorithms", ch 13. Specifically</span>
<span class="comment">// see the code for "Algorithm CP" on p. 323.</span>
<span class="comment">//</span>
<span class="comment">// What's going on is we have some critical factorization (u, v) of the</span>
<span class="comment">// needle, and we want to determine whether u is a suffix of</span>
<span class="comment">// &v[..period]. If it is, we use "Algorithm CP1". Otherwise we use</span>
<span class="comment">// "Algorithm CP2", which is optimized for when the period of the needle</span>
<span class="comment">// is large.</span>
<span class="kw">if</span> <span class="kw-2">&</span><span class="ident">needle</span>[..<span class="ident">crit_pos</span>] <span class="op">==</span> <span class="kw-2">&</span><span class="ident">needle</span>[<span class="ident">period</span>.. <span class="ident">period</span> <span class="op">+</span> <span class="ident">crit_pos</span>] {
<span class="comment">// short period case -- the period is exact</span>
<span class="comment">// compute a separate critical factorization for the reversed needle</span>
<span class="comment">// x = u' v' where |v'| < period(x).</span>
<span class="comment">//</span>
<span class="comment">// This is sped up by the period being known already.</span>
<span class="comment">// Note that a case like x = "acba" may be factored exactly forwards</span>
<span class="comment">// (crit_pos = 1, period = 3) while being factored with approximate</span>
<span class="comment">// period in reverse (crit_pos = 2, period = 2). We use the given</span>
<span class="comment">// reverse factorization but keep the exact period.</span>
<span class="kw">let</span> <span class="ident">crit_pos_back</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="ident">cmp</span>::<span class="ident">max</span>(
<span class="ident">TwoWaySearcher</span>::<span class="ident">reverse_maximal_suffix</span>(<span class="ident">needle</span>, <span class="ident">period</span>, <span class="bool-val">false</span>),
<span class="ident">TwoWaySearcher</span>::<span class="ident">reverse_maximal_suffix</span>(<span class="ident">needle</span>, <span class="ident">period</span>, <span class="bool-val">true</span>));
<span class="ident">TwoWaySearcher</span> {
<span class="ident">crit_pos</span>,
<span class="ident">crit_pos_back</span>,
<span class="ident">period</span>,
<span class="ident">byteset</span>: <span class="self">Self</span>::<span class="ident">byteset_create</span>(<span class="kw-2">&</span><span class="ident">needle</span>[..<span class="ident">period</span>]),
<span class="ident">position</span>: <span class="number">0</span>,
<span class="ident">end</span>,
<span class="ident">memory</span>: <span class="number">0</span>,
<span class="ident">memory_back</span>: <span class="ident">needle</span>.<span class="ident">len</span>(),
}
} <span class="kw">else</span> {
<span class="comment">// long period case -- we have an approximation to the actual period,</span>
<span class="comment">// and don't use memorization.</span>
<span class="comment">//</span>
<span class="comment">// Approximate the period by lower bound max(|u|, |v|) + 1.</span>
<span class="comment">// The critical factorization is efficient to use for both forward and</span>
<span class="comment">// reverse search.</span>
<span class="ident">TwoWaySearcher</span> {
<span class="ident">crit_pos</span>,
<span class="ident">crit_pos_back</span>: <span class="ident">crit_pos</span>,
<span class="ident">period</span>: <span class="ident">cmp</span>::<span class="ident">max</span>(<span class="ident">crit_pos</span>, <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="ident">crit_pos</span>) <span class="op">+</span> <span class="number">1</span>,
<span class="ident">byteset</span>: <span class="self">Self</span>::<span class="ident">byteset_create</span>(<span class="ident">needle</span>),
<span class="ident">position</span>: <span class="number">0</span>,
<span class="ident">end</span>,
<span class="ident">memory</span>: <span class="ident">usize</span>::<span class="ident">MAX</span>, <span class="comment">// Dummy value to signify that the period is long</span>
<span class="ident">memory_back</span>: <span class="ident">usize</span>::<span class="ident">MAX</span>,
}
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">byteset_create</span>(<span class="ident">bytes</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>]) <span class="op">-></span> <span class="ident">u64</span> {
<span class="ident">bytes</span>.<span class="ident">iter</span>().<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">a</span>, <span class="kw-2">&</span><span class="ident">b</span><span class="op">|</span> (<span class="number">1</span> <span class="op"><<</span> (<span class="ident">b</span> <span class="op">&</span> <span class="number">0x3f</span>)) <span class="op">|</span> <span class="ident">a</span>)
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">byteset_contains</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">byte</span>: <span class="ident">u8</span>) <span class="op">-></span> <span class="ident">bool</span> {
(<span class="self">self</span>.<span class="ident">byteset</span> <span class="op">>></span> ((<span class="ident">byte</span> <span class="op">&</span> <span class="number">0x3f</span>) <span class="kw">as</span> <span class="ident">usize</span>)) <span class="op">&</span> <span class="number">1</span> <span class="op">!=</span> <span class="number">0</span>
}
<span class="comment">// One of the main ideas of Two-Way is that we factorize the needle into</span>
<span class="comment">// two halves, (u, v), and begin trying to find v in the haystack by scanning</span>
<span class="comment">// left to right. If v matches, we try to match u by scanning right to left.</span>
<span class="comment">// How far we can jump when we encounter a mismatch is all based on the fact</span>
<span class="comment">// that (u, v) is a critical factorization for the needle.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span><span class="op"><</span><span class="ident">S</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">needle</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">long_period</span>: <span class="ident">bool</span>)
<span class="op">-></span> <span class="ident">S</span>::<span class="ident">Output</span>
<span class="kw">where</span> <span class="ident">S</span>: <span class="ident">TwoWayStrategy</span>
{
<span class="comment">// `next()` uses `self.position` as its cursor</span>
<span class="kw">let</span> <span class="ident">old_pos</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">position</span>;
<span class="kw">let</span> <span class="ident">needle_last</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>;
<span class="lifetime">'search</span>: <span class="kw">loop</span> {
<span class="comment">// Check that we have room to search in</span>
<span class="comment">// position + needle_last can not overflow if we assume slices</span>
<span class="comment">// are bounded by isize's range.</span>
<span class="kw">let</span> <span class="ident">tail_byte</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">haystack</span>.<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">position</span> <span class="op">+</span> <span class="ident">needle_last</span>) {
<span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">b</span>) <span class="op">=></span> <span class="ident">b</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">position</span> <span class="op">=</span> <span class="ident">haystack</span>.<span class="ident">len</span>();
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">rejecting</span>(<span class="ident">old_pos</span>, <span class="self">self</span>.<span class="ident">position</span>);
}
};
<span class="kw">if</span> <span class="ident">S</span>::<span class="ident">use_early_reject</span>() <span class="op">&&</span> <span class="ident">old_pos</span> <span class="op">!=</span> <span class="self">self</span>.<span class="ident">position</span> {
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">rejecting</span>(<span class="ident">old_pos</span>, <span class="self">self</span>.<span class="ident">position</span>);
}
<span class="comment">// Quickly skip by large portions unrelated to our substring</span>
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">byteset_contains</span>(<span class="ident">tail_byte</span>) {
<span class="self">self</span>.<span class="ident">position</span> <span class="op">+=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory</span> <span class="op">=</span> <span class="number">0</span>;
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
<span class="comment">// See if the right part of the needle matches</span>
<span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">long_period</span> { <span class="self">self</span>.<span class="ident">crit_pos</span> }
<span class="kw">else</span> { <span class="ident">cmp</span>::<span class="ident">max</span>(<span class="self">self</span>.<span class="ident">crit_pos</span>, <span class="self">self</span>.<span class="ident">memory</span>) };
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="ident">start</span>..<span class="ident">needle</span>.<span class="ident">len</span>() {
<span class="kw">if</span> <span class="ident">needle</span>[<span class="ident">i</span>] <span class="op">!=</span> <span class="ident">haystack</span>[<span class="self">self</span>.<span class="ident">position</span> <span class="op">+</span> <span class="ident">i</span>] {
<span class="self">self</span>.<span class="ident">position</span> <span class="op">+=</span> <span class="ident">i</span> <span class="op">-</span> <span class="self">self</span>.<span class="ident">crit_pos</span> <span class="op">+</span> <span class="number">1</span>;
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory</span> <span class="op">=</span> <span class="number">0</span>;
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
}
<span class="comment">// See if the left part of the needle matches</span>
<span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">long_period</span> { <span class="number">0</span> } <span class="kw">else</span> { <span class="self">self</span>.<span class="ident">memory</span> };
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> (<span class="ident">start</span>..<span class="self">self</span>.<span class="ident">crit_pos</span>).<span class="ident">rev</span>() {
<span class="kw">if</span> <span class="ident">needle</span>[<span class="ident">i</span>] <span class="op">!=</span> <span class="ident">haystack</span>[<span class="self">self</span>.<span class="ident">position</span> <span class="op">+</span> <span class="ident">i</span>] {
<span class="self">self</span>.<span class="ident">position</span> <span class="op">+=</span> <span class="self">self</span>.<span class="ident">period</span>;
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="self">self</span>.<span class="ident">period</span>;
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
}
<span class="comment">// We have found a match!</span>
<span class="kw">let</span> <span class="ident">match_pos</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">position</span>;
<span class="comment">// Note: add self.period instead of needle.len() to have overlapping matches</span>
<span class="self">self</span>.<span class="ident">position</span> <span class="op">+=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// set to needle.len() - self.period for overlapping matches</span>
}
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">matching</span>(<span class="ident">match_pos</span>, <span class="ident">match_pos</span> <span class="op">+</span> <span class="ident">needle</span>.<span class="ident">len</span>());
}
}
<span class="comment">// Follows the ideas in `next()`.</span>
<span class="comment">//</span>
<span class="comment">// The definitions are symmetrical, with period(x) = period(reverse(x))</span>
<span class="comment">// and local_period(u, v) = local_period(reverse(v), reverse(u)), so if (u, v)</span>
<span class="comment">// is a critical factorization, so is (reverse(v), reverse(u)).</span>
<span class="comment">//</span>
<span class="comment">// For the reverse case we have computed a critical factorization x = u' v'</span>
<span class="comment">// (field `crit_pos_back`). We need |u| < period(x) for the forward case and</span>
<span class="comment">// thus |v'| < period(x) for the reverse.</span>
<span class="comment">//</span>
<span class="comment">// To search in reverse through the haystack, we search forward through</span>
<span class="comment">// a reversed haystack with a reversed needle, matching first u' and then v'.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span><span class="op"><</span><span class="ident">S</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">haystack</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">needle</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">long_period</span>: <span class="ident">bool</span>)
<span class="op">-></span> <span class="ident">S</span>::<span class="ident">Output</span>
<span class="kw">where</span> <span class="ident">S</span>: <span class="ident">TwoWayStrategy</span>
{
<span class="comment">// `next_back()` uses `self.end` as its cursor -- so that `next()` and `next_back()`</span>
<span class="comment">// are independent.</span>
<span class="kw">let</span> <span class="ident">old_end</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">end</span>;
<span class="lifetime">'search</span>: <span class="kw">loop</span> {
<span class="comment">// Check that we have room to search in</span>
<span class="comment">// end - needle.len() will wrap around when there is no more room,</span>
<span class="comment">// but due to slice length limits it can never wrap all the way back</span>
<span class="comment">// into the length of haystack.</span>
<span class="kw">let</span> <span class="ident">front_byte</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">haystack</span>.<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">end</span>.<span class="ident">wrapping_sub</span>(<span class="ident">needle</span>.<span class="ident">len</span>())) {
<span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">b</span>) <span class="op">=></span> <span class="ident">b</span>,
<span class="prelude-val">None</span> <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">end</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">rejecting</span>(<span class="number">0</span>, <span class="ident">old_end</span>);
}
};
<span class="kw">if</span> <span class="ident">S</span>::<span class="ident">use_early_reject</span>() <span class="op">&&</span> <span class="ident">old_end</span> <span class="op">!=</span> <span class="self">self</span>.<span class="ident">end</span> {
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">rejecting</span>(<span class="self">self</span>.<span class="ident">end</span>, <span class="ident">old_end</span>);
}
<span class="comment">// Quickly skip by large portions unrelated to our substring</span>
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">byteset_contains</span>(<span class="ident">front_byte</span>) {
<span class="self">self</span>.<span class="ident">end</span> <span class="op">-=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory_back</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
<span class="comment">// See if the left part of the needle matches</span>
<span class="kw">let</span> <span class="ident">crit</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">long_period</span> { <span class="self">self</span>.<span class="ident">crit_pos_back</span> }
<span class="kw">else</span> { <span class="ident">cmp</span>::<span class="ident">min</span>(<span class="self">self</span>.<span class="ident">crit_pos_back</span>, <span class="self">self</span>.<span class="ident">memory_back</span>) };
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> (<span class="number">0</span>..<span class="ident">crit</span>).<span class="ident">rev</span>() {
<span class="kw">if</span> <span class="ident">needle</span>[<span class="ident">i</span>] <span class="op">!=</span> <span class="ident">haystack</span>[<span class="self">self</span>.<span class="ident">end</span> <span class="op">-</span> <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">+</span> <span class="ident">i</span>] {
<span class="self">self</span>.<span class="ident">end</span> <span class="op">-=</span> <span class="self">self</span>.<span class="ident">crit_pos_back</span> <span class="op">-</span> <span class="ident">i</span>;
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory_back</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
}
<span class="comment">// See if the right part of the needle matches</span>
<span class="kw">let</span> <span class="ident">needle_end</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">long_period</span> { <span class="ident">needle</span>.<span class="ident">len</span>() }
<span class="kw">else</span> { <span class="self">self</span>.<span class="ident">memory_back</span> };
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">crit_pos_back</span>..<span class="ident">needle_end</span> {
<span class="kw">if</span> <span class="ident">needle</span>[<span class="ident">i</span>] <span class="op">!=</span> <span class="ident">haystack</span>[<span class="self">self</span>.<span class="ident">end</span> <span class="op">-</span> <span class="ident">needle</span>.<span class="ident">len</span>() <span class="op">+</span> <span class="ident">i</span>] {
<span class="self">self</span>.<span class="ident">end</span> <span class="op">-=</span> <span class="self">self</span>.<span class="ident">period</span>;
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory_back</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">period</span>;
}
<span class="kw">continue</span> <span class="lifetime">'search</span>;
}
}
<span class="comment">// We have found a match!</span>
<span class="kw">let</span> <span class="ident">match_pos</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">end</span> <span class="op">-</span> <span class="ident">needle</span>.<span class="ident">len</span>();
<span class="comment">// Note: sub self.period instead of needle.len() to have overlapping matches</span>
<span class="self">self</span>.<span class="ident">end</span> <span class="op">-=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
<span class="kw">if</span> <span class="op">!</span><span class="ident">long_period</span> {
<span class="self">self</span>.<span class="ident">memory_back</span> <span class="op">=</span> <span class="ident">needle</span>.<span class="ident">len</span>();
}
<span class="kw">return</span> <span class="ident">S</span>::<span class="ident">matching</span>(<span class="ident">match_pos</span>, <span class="ident">match_pos</span> <span class="op">+</span> <span class="ident">needle</span>.<span class="ident">len</span>());
}
}
<span class="comment">// Compute the maximal suffix of `arr`.</span>
<span class="comment">//</span>
<span class="comment">// The maximal suffix is a possible critical factorization (u, v) of `arr`.</span>
<span class="comment">//</span>
<span class="comment">// Returns (`i`, `p`) where `i` is the starting index of v and `p` is the</span>
<span class="comment">// period of v.</span>
<span class="comment">//</span>
<span class="comment">// `order_greater` determines if lexical order is `<` or `>`. Both</span>
<span class="comment">// orders must be computed -- the ordering with the largest `i` gives</span>
<span class="comment">// a critical factorization.</span>
<span class="comment">//</span>
<span class="comment">// For long period cases, the resulting period is not exact (it is too short).</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">maximal_suffix</span>(<span class="ident">arr</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">order_greater</span>: <span class="ident">bool</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="ident">usize</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">left</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// Corresponds to i in the paper</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">right</span> <span class="op">=</span> <span class="number">1</span>; <span class="comment">// Corresponds to j in the paper</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// Corresponds to k in the paper, but starting at 0</span>
<span class="comment">// to match 0-based indexing.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">period</span> <span class="op">=</span> <span class="number">1</span>; <span class="comment">// Corresponds to p in the paper</span>
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">a</span>) <span class="op">=</span> <span class="ident">arr</span>.<span class="ident">get</span>(<span class="ident">right</span> <span class="op">+</span> <span class="ident">offset</span>) {
<span class="comment">// `left` will be inbounds when `right` is.</span>
<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">arr</span>[<span class="ident">left</span> <span class="op">+</span> <span class="ident">offset</span>];
<span class="kw">if</span> (<span class="ident">a</span> <span class="op"><</span> <span class="ident">b</span> <span class="op">&&</span> <span class="op">!</span><span class="ident">order_greater</span>) <span class="op">||</span> (<span class="ident">a</span> <span class="op">></span> <span class="ident">b</span> <span class="op">&&</span> <span class="ident">order_greater</span>) {
<span class="comment">// Suffix is smaller, period is entire prefix so far.</span>
<span class="ident">right</span> <span class="op">+=</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
<span class="ident">period</span> <span class="op">=</span> <span class="ident">right</span> <span class="op">-</span> <span class="ident">left</span>;
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">a</span> <span class="op">==</span> <span class="ident">b</span> {
<span class="comment">// Advance through repetition of the current period.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">==</span> <span class="ident">period</span> {
<span class="ident">right</span> <span class="op">+=</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
} <span class="kw">else</span> {
<span class="ident">offset</span> <span class="op">+=</span> <span class="number">1</span>;
}
} <span class="kw">else</span> {
<span class="comment">// Suffix is larger, start over from current location.</span>
<span class="ident">left</span> <span class="op">=</span> <span class="ident">right</span>;
<span class="ident">right</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
<span class="ident">period</span> <span class="op">=</span> <span class="number">1</span>;
}
}
(<span class="ident">left</span>, <span class="ident">period</span>)
}
<span class="comment">// Compute the maximal suffix of the reverse of `arr`.</span>
<span class="comment">//</span>
<span class="comment">// The maximal suffix is a possible critical factorization (u', v') of `arr`.</span>
<span class="comment">//</span>
<span class="comment">// Returns `i` where `i` is the starting index of v', from the back;</span>
<span class="comment">// returns immediately when a period of `known_period` is reached.</span>
<span class="comment">//</span>
<span class="comment">// `order_greater` determines if lexical order is `<` or `>`. Both</span>
<span class="comment">// orders must be computed -- the ordering with the largest `i` gives</span>
<span class="comment">// a critical factorization.</span>
<span class="comment">//</span>
<span class="comment">// For long period cases, the resulting period is not exact (it is too short).</span>
<span class="kw">fn</span> <span class="ident">reverse_maximal_suffix</span>(<span class="ident">arr</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">known_period</span>: <span class="ident">usize</span>,
<span class="ident">order_greater</span>: <span class="ident">bool</span>) <span class="op">-></span> <span class="ident">usize</span>
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">left</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// Corresponds to i in the paper</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">right</span> <span class="op">=</span> <span class="number">1</span>; <span class="comment">// Corresponds to j in the paper</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>; <span class="comment">// Corresponds to k in the paper, but starting at 0</span>
<span class="comment">// to match 0-based indexing.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">period</span> <span class="op">=</span> <span class="number">1</span>; <span class="comment">// Corresponds to p in the paper</span>
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">arr</span>.<span class="ident">len</span>();
<span class="kw">while</span> <span class="ident">right</span> <span class="op">+</span> <span class="ident">offset</span> <span class="op"><</span> <span class="ident">n</span> {
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">arr</span>[<span class="ident">n</span> <span class="op">-</span> (<span class="number">1</span> <span class="op">+</span> <span class="ident">right</span> <span class="op">+</span> <span class="ident">offset</span>)];
<span class="kw">let</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">arr</span>[<span class="ident">n</span> <span class="op">-</span> (<span class="number">1</span> <span class="op">+</span> <span class="ident">left</span> <span class="op">+</span> <span class="ident">offset</span>)];
<span class="kw">if</span> (<span class="ident">a</span> <span class="op"><</span> <span class="ident">b</span> <span class="op">&&</span> <span class="op">!</span><span class="ident">order_greater</span>) <span class="op">||</span> (<span class="ident">a</span> <span class="op">></span> <span class="ident">b</span> <span class="op">&&</span> <span class="ident">order_greater</span>) {
<span class="comment">// Suffix is smaller, period is entire prefix so far.</span>
<span class="ident">right</span> <span class="op">+=</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
<span class="ident">period</span> <span class="op">=</span> <span class="ident">right</span> <span class="op">-</span> <span class="ident">left</span>;
} <span class="kw">else</span> <span class="kw">if</span> <span class="ident">a</span> <span class="op">==</span> <span class="ident">b</span> {
<span class="comment">// Advance through repetition of the current period.</span>
<span class="kw">if</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span> <span class="op">==</span> <span class="ident">period</span> {
<span class="ident">right</span> <span class="op">+=</span> <span class="ident">offset</span> <span class="op">+</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
} <span class="kw">else</span> {
<span class="ident">offset</span> <span class="op">+=</span> <span class="number">1</span>;
}
} <span class="kw">else</span> {
<span class="comment">// Suffix is larger, start over from current location.</span>
<span class="ident">left</span> <span class="op">=</span> <span class="ident">right</span>;
<span class="ident">right</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="ident">offset</span> <span class="op">=</span> <span class="number">0</span>;
<span class="ident">period</span> <span class="op">=</span> <span class="number">1</span>;
}
<span class="kw">if</span> <span class="ident">period</span> <span class="op">==</span> <span class="ident">known_period</span> {
<span class="kw">break</span>;
}
}
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">period</span> <span class="op"><=</span> <span class="ident">known_period</span>);
<span class="ident">left</span>
}
}
<span class="comment">// TwoWayStrategy allows the algorithm to either skip non-matches as quickly</span>
<span class="comment">// as possible, or to work in a mode where it emits Rejects relatively quickly.</span>
<span class="kw">trait</span> <span class="ident">TwoWayStrategy</span> {
<span class="kw">type</span> <span class="ident">Output</span>;
<span class="kw">fn</span> <span class="ident">use_early_reject</span>() <span class="op">-></span> <span class="ident">bool</span>;
<span class="kw">fn</span> <span class="ident">rejecting</span>(<span class="ident">a</span>: <span class="ident">usize</span>, <span class="ident">b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span>;
<span class="kw">fn</span> <span class="ident">matching</span>(<span class="ident">a</span>: <span class="ident">usize</span>, <span class="ident">b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span>;
}
<span class="doccomment">/// Skip to match intervals as quickly as possible</span>
<span class="kw">enum</span> <span class="ident">MatchOnly</span> { }
<span class="kw">impl</span> <span class="ident">TwoWayStrategy</span> <span class="kw">for</span> <span class="ident">MatchOnly</span> {
<span class="kw">type</span> <span class="ident">Output</span> <span class="op">=</span> <span class="prelude-ty">Option</span><span class="op"><</span>(<span class="ident">usize</span>, <span class="ident">usize</span>)<span class="op">></span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">use_early_reject</span>() <span class="op">-></span> <span class="ident">bool</span> { <span class="bool-val">false</span> }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">rejecting</span>(<span class="ident">_a</span>: <span class="ident">usize</span>, <span class="ident">_b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span> { <span class="prelude-val">None</span> }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">matching</span>(<span class="ident">a</span>: <span class="ident">usize</span>, <span class="ident">b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span> { <span class="prelude-val">Some</span>((<span class="ident">a</span>, <span class="ident">b</span>)) }
}
<span class="doccomment">/// Emit Rejects regularly</span>
<span class="kw">enum</span> <span class="ident">RejectAndMatch</span> { }
<span class="kw">impl</span> <span class="ident">TwoWayStrategy</span> <span class="kw">for</span> <span class="ident">RejectAndMatch</span> {
<span class="kw">type</span> <span class="ident">Output</span> <span class="op">=</span> <span class="ident">SearchStep</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">use_early_reject</span>() <span class="op">-></span> <span class="ident">bool</span> { <span class="bool-val">true</span> }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">rejecting</span>(<span class="ident">a</span>: <span class="ident">usize</span>, <span class="ident">b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span> { <span class="ident">SearchStep</span>::<span class="ident">Reject</span>(<span class="ident">a</span>, <span class="ident">b</span>) }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">matching</span>(<span class="ident">a</span>: <span class="ident">usize</span>, <span class="ident">b</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span> { <span class="ident">SearchStep</span>::<span class="ident">Match</span>(<span class="ident">a</span>, <span class="ident">b</span>) }
}
</pre>
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