| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-1.8.3/src/pikevm.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>pikevm.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../regex/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../regex/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="comment">// This module implements the Pike VM. That is, it guarantees linear time |
| // search of a regex on any text with memory use proportional to the size of |
| // the regex. |
| // |
| // It is equal in power to the backtracking engine in this crate, except the |
| // backtracking engine is typically faster on small regexes/texts at the |
| // expense of a bigger memory footprint. |
| // |
| // It can do more than the DFA can (specifically, record capture locations |
| // and execute Unicode word boundary assertions), but at a slower speed. |
| // Specifically, the Pike VM executes a DFA implicitly by repeatedly expanding |
| // epsilon transitions. That is, the Pike VM engine can be in multiple states |
| // at once where as the DFA is only ever in one state at a time. |
| // |
| // Therefore, the Pike VM is generally treated as the fallback when the other |
| // matching engines either aren't feasible to run or are insufficient. |
| |
| </span><span class="kw">use </span>std::mem; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::exec::ProgramCache; |
| <span class="kw">use </span><span class="kw">crate</span>::input::{Input, InputAt}; |
| <span class="kw">use </span><span class="kw">crate</span>::prog::{InstPtr, Program}; |
| <span class="kw">use </span><span class="kw">crate</span>::re_trait::Slot; |
| <span class="kw">use </span><span class="kw">crate</span>::sparse::SparseSet; |
| |
| <span class="doccomment">/// An NFA simulation matching engine. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>Fsm<<span class="lifetime">'r</span>, I> { |
| <span class="doccomment">/// The sequence of opcodes (among other things) that is actually executed. |
| /// |
| /// The program may be byte oriented or Unicode codepoint oriented. |
| </span>prog: <span class="kw-2">&</span><span class="lifetime">'r </span>Program, |
| <span class="doccomment">/// An explicit stack used for following epsilon transitions. (This is |
| /// borrowed from the cache.) |
| </span>stack: <span class="kw-2">&</span><span class="lifetime">'r </span><span class="kw-2">mut </span>Vec<FollowEpsilon>, |
| <span class="doccomment">/// The input to search. |
| </span>input: I, |
| } |
| |
| <span class="doccomment">/// A cached allocation that can be reused on each execution. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub struct </span>Cache { |
| <span class="doccomment">/// A pair of ordered sets for tracking NFA states. |
| </span>clist: Threads, |
| nlist: Threads, |
| <span class="doccomment">/// An explicit stack used for following epsilon transitions. |
| </span>stack: Vec<FollowEpsilon>, |
| } |
| |
| <span class="doccomment">/// An ordered set of NFA states and their captures. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">struct </span>Threads { |
| <span class="doccomment">/// An ordered set of opcodes (each opcode is an NFA state). |
| </span>set: SparseSet, |
| <span class="doccomment">/// Captures for every NFA state. |
| /// |
| /// It is stored in row-major order, where the columns are the capture |
| /// slots and the rows are the states. |
| </span>caps: Vec<Slot>, |
| <span class="doccomment">/// The number of capture slots stored per thread. (Every capture has |
| /// two slots.) |
| </span>slots_per_thread: usize, |
| } |
| |
| <span class="doccomment">/// A representation of an explicit stack frame when following epsilon |
| /// transitions. This is used to avoid recursion. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">enum </span>FollowEpsilon { |
| <span class="doccomment">/// Follow transitions at the given instruction pointer. |
| </span>IP(InstPtr), |
| <span class="doccomment">/// Restore the capture slot with the given position in the input. |
| </span>Capture { slot: usize, pos: Slot }, |
| } |
| |
| <span class="kw">impl </span>Cache { |
| <span class="doccomment">/// Create a new allocation used by the NFA machine to record execution |
| /// and captures. |
| </span><span class="kw">pub fn </span>new(_prog: <span class="kw-2">&</span>Program) -> <span class="self">Self </span>{ |
| Cache { clist: Threads::new(), nlist: Threads::new(), stack: <span class="macro">vec!</span>[] } |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'r</span>, I: Input> Fsm<<span class="lifetime">'r</span>, I> { |
| <span class="doccomment">/// Execute the NFA matching engine. |
| /// |
| /// If there's a match, `exec` returns `true` and populates the given |
| /// captures accordingly. |
| </span><span class="kw">pub fn </span>exec( |
| prog: <span class="kw-2">&</span><span class="lifetime">'r </span>Program, |
| cache: <span class="kw-2">&</span>ProgramCache, |
| matches: <span class="kw-2">&mut </span>[bool], |
| slots: <span class="kw-2">&mut </span>[Slot], |
| quit_after_match: bool, |
| input: I, |
| start: usize, |
| end: usize, |
| ) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>cache = cache.borrow_mut(); |
| <span class="kw">let </span>cache = <span class="kw-2">&mut </span>cache.pikevm; |
| cache.clist.resize(prog.len(), prog.captures.len()); |
| cache.nlist.resize(prog.len(), prog.captures.len()); |
| <span class="kw">let </span>at = input.at(start); |
| Fsm { prog, stack: <span class="kw-2">&mut </span>cache.stack, input }.exec_( |
| <span class="kw-2">&mut </span>cache.clist, |
| <span class="kw-2">&mut </span>cache.nlist, |
| matches, |
| slots, |
| quit_after_match, |
| at, |
| end, |
| ) |
| } |
| |
| <span class="kw">fn </span>exec_( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| <span class="kw-2">mut </span>clist: <span class="kw-2">&mut </span>Threads, |
| <span class="kw-2">mut </span>nlist: <span class="kw-2">&mut </span>Threads, |
| matches: <span class="kw-2">&mut </span>[bool], |
| slots: <span class="kw-2">&mut </span>[Slot], |
| quit_after_match: bool, |
| <span class="kw-2">mut </span>at: InputAt, |
| end: usize, |
| ) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>matched = <span class="bool-val">false</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>all_matched = <span class="bool-val">false</span>; |
| clist.set.clear(); |
| nlist.set.clear(); |
| <span class="lifetime">'LOOP</span>: <span class="kw">loop </span>{ |
| <span class="kw">if </span>clist.set.is_empty() { |
| <span class="comment">// Three ways to bail out when our current set of threads is |
| // empty. |
| // |
| // 1. We have a match---so we're done exploring any possible |
| // alternatives. Time to quit. (We can't do this if we're |
| // looking for matches for multiple regexes, unless we know |
| // they all matched.) |
| // |
| // 2. If the expression starts with a '^' we can terminate as |
| // soon as the last thread dies. |
| </span><span class="kw">if </span>(matched && matches.len() <= <span class="number">1</span>) |
| || all_matched |
| || (!at.is_start() && <span class="self">self</span>.prog.is_anchored_start) |
| { |
| <span class="kw">break</span>; |
| } |
| |
| <span class="comment">// 3. If there's a literal prefix for the program, try to |
| // jump ahead quickly. If it can't be found, then we can |
| // bail out early. |
| </span><span class="kw">if </span>!<span class="self">self</span>.prog.prefixes.is_empty() { |
| at = <span class="kw">match </span><span class="self">self</span>.input.prefix_at(<span class="kw-2">&</span><span class="self">self</span>.prog.prefixes, at) { |
| <span class="prelude-val">None </span>=> <span class="kw">break</span>, |
| <span class="prelude-val">Some</span>(at) => at, |
| }; |
| } |
| } |
| |
| <span class="comment">// This simulates a preceding '.*?' for every regex by adding |
| // a state starting at the current position in the input for the |
| // beginning of the program only if we don't already have a match. |
| </span><span class="kw">if </span>clist.set.is_empty() |
| || (!<span class="self">self</span>.prog.is_anchored_start && !all_matched) |
| { |
| <span class="self">self</span>.add(<span class="kw-2">&mut </span>clist, slots, <span class="number">0</span>, at); |
| } |
| <span class="comment">// The previous call to "add" actually inspects the position just |
| // before the current character. For stepping through the machine, |
| // we can to look at the current character, so we advance the |
| // input. |
| </span><span class="kw">let </span>at_next = <span class="self">self</span>.input.at(at.next_pos()); |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..clist.set.len() { |
| <span class="kw">let </span>ip = clist.set[i]; |
| <span class="kw">if </span><span class="self">self</span>.step( |
| <span class="kw-2">&mut </span>nlist, |
| matches, |
| slots, |
| clist.caps(ip), |
| ip, |
| at, |
| at_next, |
| ) { |
| matched = <span class="bool-val">true</span>; |
| all_matched = all_matched || matches.iter().all(|<span class="kw-2">&</span>b| b); |
| <span class="kw">if </span>quit_after_match { |
| <span class="comment">// If we only care if a match occurs (not its |
| // position), then we can quit right now. |
| </span><span class="kw">break </span><span class="lifetime">'LOOP</span>; |
| } |
| <span class="kw">if </span><span class="self">self</span>.prog.matches.len() == <span class="number">1 </span>{ |
| <span class="comment">// We don't need to check the rest of the threads |
| // in this set because we've matched something |
| // ("leftmost-first"). However, we still need to check |
| // threads in the next set to support things like |
| // greedy matching. |
| // |
| // This is only true on normal regexes. For regex sets, |
| // we need to mush on to observe other matches. |
| </span><span class="kw">break</span>; |
| } |
| } |
| } |
| <span class="kw">if </span>at.pos() >= end { |
| <span class="kw">break</span>; |
| } |
| at = at_next; |
| mem::swap(clist, nlist); |
| nlist.set.clear(); |
| } |
| matched |
| } |
| |
| <span class="doccomment">/// Step through the input, one token (byte or codepoint) at a time. |
| /// |
| /// nlist is the set of states that will be processed on the next token |
| /// in the input. |
| /// |
| /// caps is the set of captures passed by the caller of the NFA. They are |
| /// written to only when a match state is visited. |
| /// |
| /// thread_caps is the set of captures set for the current NFA state, ip. |
| /// |
| /// at and at_next are the current and next positions in the input. at or |
| /// at_next may be EOF. |
| </span><span class="kw">fn </span>step( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| nlist: <span class="kw-2">&mut </span>Threads, |
| matches: <span class="kw-2">&mut </span>[bool], |
| slots: <span class="kw-2">&mut </span>[Slot], |
| thread_caps: <span class="kw-2">&mut </span>[<span class="prelude-ty">Option</span><usize>], |
| ip: usize, |
| at: InputAt, |
| at_next: InputAt, |
| ) -> bool { |
| <span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| <span class="kw">match </span><span class="self">self</span>.prog[ip] { |
| Match(match_slot) => { |
| <span class="kw">if </span>match_slot < matches.len() { |
| matches[match_slot] = <span class="bool-val">true</span>; |
| } |
| <span class="kw">for </span>(slot, val) <span class="kw">in </span>slots.iter_mut().zip(thread_caps.iter()) { |
| <span class="kw-2">*</span>slot = <span class="kw-2">*</span>val; |
| } |
| <span class="bool-val">true |
| </span>} |
| Char(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if </span>inst.c == at.char() { |
| <span class="self">self</span>.add(nlist, thread_caps, inst.goto, at_next); |
| } |
| <span class="bool-val">false |
| </span>} |
| Ranges(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if </span>inst.matches(at.char()) { |
| <span class="self">self</span>.add(nlist, thread_caps, inst.goto, at_next); |
| } |
| <span class="bool-val">false |
| </span>} |
| Bytes(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(b) = at.byte() { |
| <span class="kw">if </span>inst.matches(b) { |
| <span class="self">self</span>.add(nlist, thread_caps, inst.goto, at_next); |
| } |
| } |
| <span class="bool-val">false |
| </span>} |
| EmptyLook(<span class="kw">_</span>) | Save(<span class="kw">_</span>) | Split(<span class="kw">_</span>) => <span class="bool-val">false</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Follows epsilon transitions and adds them for processing to nlist, |
| /// starting at and including ip. |
| </span><span class="kw">fn </span>add( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| nlist: <span class="kw-2">&mut </span>Threads, |
| thread_caps: <span class="kw-2">&mut </span>[<span class="prelude-ty">Option</span><usize>], |
| ip: usize, |
| at: InputAt, |
| ) { |
| <span class="self">self</span>.stack.push(FollowEpsilon::IP(ip)); |
| <span class="kw">while let </span><span class="prelude-val">Some</span>(frame) = <span class="self">self</span>.stack.pop() { |
| <span class="kw">match </span>frame { |
| FollowEpsilon::IP(ip) => { |
| <span class="self">self</span>.add_step(nlist, thread_caps, ip, at); |
| } |
| FollowEpsilon::Capture { slot, pos } => { |
| thread_caps[slot] = pos; |
| } |
| } |
| } |
| } |
| |
| <span class="doccomment">/// A helper function for add that avoids excessive pushing to the stack. |
| </span><span class="kw">fn </span>add_step( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| nlist: <span class="kw-2">&mut </span>Threads, |
| thread_caps: <span class="kw-2">&mut </span>[<span class="prelude-ty">Option</span><usize>], |
| <span class="kw-2">mut </span>ip: usize, |
| at: InputAt, |
| ) { |
| <span class="comment">// Instead of pushing and popping to the stack, we mutate ip as we |
| // traverse the set of states. We only push to the stack when we |
| // absolutely need recursion (restoring captures or following a |
| // branch). |
| </span><span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| <span class="kw">loop </span>{ |
| <span class="comment">// Don't visit states we've already added. |
| </span><span class="kw">if </span>nlist.set.contains(ip) { |
| <span class="kw">return</span>; |
| } |
| nlist.set.insert(ip); |
| <span class="kw">match </span><span class="self">self</span>.prog[ip] { |
| EmptyLook(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if </span><span class="self">self</span>.input.is_empty_match(at, inst) { |
| ip = inst.goto; |
| } |
| } |
| Save(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if </span>inst.slot < thread_caps.len() { |
| <span class="self">self</span>.stack.push(FollowEpsilon::Capture { |
| slot: inst.slot, |
| pos: thread_caps[inst.slot], |
| }); |
| thread_caps[inst.slot] = <span class="prelude-val">Some</span>(at.pos()); |
| } |
| ip = inst.goto; |
| } |
| Split(<span class="kw-2">ref </span>inst) => { |
| <span class="self">self</span>.stack.push(FollowEpsilon::IP(inst.goto2)); |
| ip = inst.goto1; |
| } |
| Match(<span class="kw">_</span>) | Char(<span class="kw">_</span>) | Ranges(<span class="kw">_</span>) | Bytes(<span class="kw">_</span>) => { |
| <span class="kw">let </span>t = <span class="kw-2">&mut </span>nlist.caps(ip); |
| <span class="kw">for </span>(slot, val) <span class="kw">in </span>t.iter_mut().zip(thread_caps.iter()) { |
| <span class="kw-2">*</span>slot = <span class="kw-2">*</span>val; |
| } |
| <span class="kw">return</span>; |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Threads { |
| <span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| Threads { set: SparseSet::new(<span class="number">0</span>), caps: <span class="macro">vec!</span>[], slots_per_thread: <span class="number">0 </span>} |
| } |
| |
| <span class="kw">fn </span>resize(<span class="kw-2">&mut </span><span class="self">self</span>, num_insts: usize, ncaps: usize) { |
| <span class="kw">if </span>num_insts == <span class="self">self</span>.set.capacity() { |
| <span class="kw">return</span>; |
| } |
| <span class="self">self</span>.slots_per_thread = ncaps * <span class="number">2</span>; |
| <span class="self">self</span>.set = SparseSet::new(num_insts); |
| <span class="self">self</span>.caps = <span class="macro">vec!</span>[<span class="prelude-val">None</span>; <span class="self">self</span>.slots_per_thread * num_insts]; |
| } |
| |
| <span class="kw">fn </span>caps(<span class="kw-2">&mut </span><span class="self">self</span>, pc: usize) -> <span class="kw-2">&mut </span>[<span class="prelude-ty">Option</span><usize>] { |
| <span class="kw">let </span>i = pc * <span class="self">self</span>.slots_per_thread; |
| <span class="kw-2">&mut </span><span class="self">self</span>.caps[i..i + <span class="self">self</span>.slots_per_thread] |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="regex" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
