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<!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 `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-1.5.6/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" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../../dark.css" disabled><link rel="stylesheet" type="text/css" 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="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../regex/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div>
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</pre><pre class="rust"><code><span class="comment">// This module implements the Pike VM. That is, it guarantees linear time</span>
<span class="comment">// search of a regex on any text with memory use proportional to the size of</span>
<span class="comment">// the regex.</span>
<span class="comment">//</span>
<span class="comment">// It is equal in power to the backtracking engine in this crate, except the</span>
<span class="comment">// backtracking engine is typically faster on small regexes/texts at the</span>
<span class="comment">// expense of a bigger memory footprint.</span>
<span class="comment">//</span>
<span class="comment">// It can do more than the DFA can (specifically, record capture locations</span>
<span class="comment">// and execute Unicode word boundary assertions), but at a slower speed.</span>
<span class="comment">// Specifically, the Pike VM executes a DFA implicitly by repeatedly expanding</span>
<span class="comment">// epsilon transitions. That is, the Pike VM engine can be in multiple states</span>
<span class="comment">// at once where as the DFA is only ever in one state at a time.</span>
<span class="comment">//</span>
<span class="comment">// Therefore, the Pike VM is generally treated as the fallback when the other</span>
<span class="comment">// matching engines either aren't feasible to run or are insufficient.</span>
<span class="kw">use</span> <span class="ident">std::mem</span>;
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::exec::ProgramCache</span>;
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::input</span>::{<span class="ident">Input</span>, <span class="ident">InputAt</span>};
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::prog</span>::{<span class="ident">InstPtr</span>, <span class="ident">Program</span>};
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::re_trait::Slot</span>;
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::sparse::SparseSet</span>;
<span class="doccomment">/// An NFA simulation matching engine.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Fsm</span><span class="op"><</span><span class="lifetime">'r</span>, <span class="ident">I</span><span class="op">></span> {
<span class="doccomment">/// The sequence of opcodes (among other things) that is actually executed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The program may be byte oriented or Unicode codepoint oriented.</span>
<span class="ident">prog</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">Program</span>,
<span class="doccomment">/// An explicit stack used for following epsilon transitions. (This is</span>
<span class="doccomment">/// borrowed from the cache.)</span>
<span class="ident">stack</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="kw-2">mut</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">FollowEpsilon</span><span class="op">></span>,
<span class="doccomment">/// The input to search.</span>
<span class="ident">input</span>: <span class="ident">I</span>,
}
<span class="doccomment">/// A cached allocation that can be reused on each execution.</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">Cache</span> {
<span class="doccomment">/// A pair of ordered sets for tracking NFA states.</span>
<span class="ident">clist</span>: <span class="ident">Threads</span>,
<span class="ident">nlist</span>: <span class="ident">Threads</span>,
<span class="doccomment">/// An explicit stack used for following epsilon transitions.</span>
<span class="ident">stack</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">FollowEpsilon</span><span class="op">></span>,
}
<span class="doccomment">/// An ordered set of NFA states and their captures.</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">Threads</span> {
<span class="doccomment">/// An ordered set of opcodes (each opcode is an NFA state).</span>
<span class="ident">set</span>: <span class="ident">SparseSet</span>,
<span class="doccomment">/// Captures for every NFA state.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It is stored in row-major order, where the columns are the capture</span>
<span class="doccomment">/// slots and the rows are the states.</span>
<span class="ident">caps</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">Slot</span><span class="op">></span>,
<span class="doccomment">/// The number of capture slots stored per thread. (Every capture has</span>
<span class="doccomment">/// two slots.)</span>
<span class="ident">slots_per_thread</span>: <span class="ident">usize</span>,
}
<span class="doccomment">/// A representation of an explicit stack frame when following epsilon</span>
<span class="doccomment">/// transitions. This is used to avoid recursion.</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">FollowEpsilon</span> {
<span class="doccomment">/// Follow transitions at the given instruction pointer.</span>
<span class="ident">IP</span>(<span class="ident">InstPtr</span>),
<span class="doccomment">/// Restore the capture slot with the given position in the input.</span>
<span class="ident">Capture</span> { <span class="ident">slot</span>: <span class="ident">usize</span>, <span class="ident">pos</span>: <span class="ident">Slot</span> },
}
<span class="kw">impl</span> <span class="ident">Cache</span> {
<span class="doccomment">/// Create a new allocation used by the NFA machine to record execution</span>
<span class="doccomment">/// and captures.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">_prog</span>: <span class="kw-2">&</span><span class="ident">Program</span>) -> <span class="self">Self</span> {
<span class="ident">Cache</span> { <span class="ident">clist</span>: <span class="ident">Threads::new</span>(), <span class="ident">nlist</span>: <span class="ident">Threads::new</span>(), <span class="ident">stack</span>: <span class="macro">vec!</span>[] }
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'r</span>, <span class="ident">I</span>: <span class="ident">Input</span><span class="op">></span> <span class="ident">Fsm</span><span class="op"><</span><span class="lifetime">'r</span>, <span class="ident">I</span><span class="op">></span> {
<span class="doccomment">/// Execute the NFA matching engine.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If there's a match, `exec` returns `true` and populates the given</span>
<span class="doccomment">/// captures accordingly.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">exec</span>(
<span class="ident">prog</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">Program</span>,
<span class="ident">cache</span>: <span class="kw-2">&</span><span class="ident">ProgramCache</span>,
<span class="ident">matches</span>: <span class="kw-2">&mut</span> [<span class="ident">bool</span>],
<span class="ident">slots</span>: <span class="kw-2">&mut</span> [<span class="ident">Slot</span>],
<span class="ident">quit_after_match</span>: <span class="ident">bool</span>,
<span class="ident">input</span>: <span class="ident">I</span>,
<span class="ident">start</span>: <span class="ident">usize</span>,
<span class="ident">end</span>: <span class="ident">usize</span>,
) -> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cache</span> <span class="op">=</span> <span class="ident">cache</span>.<span class="ident">borrow_mut</span>();
<span class="kw">let</span> <span class="ident">cache</span> <span class="op">=</span> <span class="kw-2">&mut</span> <span class="ident">cache</span>.<span class="ident">pikevm</span>;
<span class="ident">cache</span>.<span class="ident">clist</span>.<span class="ident">resize</span>(<span class="ident">prog</span>.<span class="ident">len</span>(), <span class="ident">prog</span>.<span class="ident">captures</span>.<span class="ident">len</span>());
<span class="ident">cache</span>.<span class="ident">nlist</span>.<span class="ident">resize</span>(<span class="ident">prog</span>.<span class="ident">len</span>(), <span class="ident">prog</span>.<span class="ident">captures</span>.<span class="ident">len</span>());
<span class="kw">let</span> <span class="ident">at</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">at</span>(<span class="ident">start</span>);
<span class="ident">Fsm</span> { <span class="ident">prog</span>: <span class="ident">prog</span>, <span class="ident">stack</span>: <span class="kw-2">&mut</span> <span class="ident">cache</span>.<span class="ident">stack</span>, <span class="ident">input</span>: <span class="ident">input</span> }.<span class="ident">exec_</span>(
<span class="kw-2">&mut</span> <span class="ident">cache</span>.<span class="ident">clist</span>,
<span class="kw-2">&mut</span> <span class="ident">cache</span>.<span class="ident">nlist</span>,
<span class="ident">matches</span>,
<span class="ident">slots</span>,
<span class="ident">quit_after_match</span>,
<span class="ident">at</span>,
<span class="ident">end</span>,
)
}
<span class="kw">fn</span> <span class="ident">exec_</span>(
<span class="kw-2">&mut</span> <span class="self">self</span>,
<span class="kw-2">mut</span> <span class="ident">clist</span>: <span class="kw-2">&mut</span> <span class="ident">Threads</span>,
<span class="kw-2">mut</span> <span class="ident">nlist</span>: <span class="kw-2">&mut</span> <span class="ident">Threads</span>,
<span class="ident">matches</span>: <span class="kw-2">&mut</span> [<span class="ident">bool</span>],
<span class="ident">slots</span>: <span class="kw-2">&mut</span> [<span class="ident">Slot</span>],
<span class="ident">quit_after_match</span>: <span class="ident">bool</span>,
<span class="kw-2">mut</span> <span class="ident">at</span>: <span class="ident">InputAt</span>,
<span class="ident">end</span>: <span class="ident">usize</span>,
) -> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">matched</span> <span class="op">=</span> <span class="bool-val">false</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">all_matched</span> <span class="op">=</span> <span class="bool-val">false</span>;
<span class="ident">clist</span>.<span class="ident">set</span>.<span class="ident">clear</span>();
<span class="ident">nlist</span>.<span class="ident">set</span>.<span class="ident">clear</span>();
<span class="lifetime">'LOOP</span>: <span class="kw">loop</span> {
<span class="kw">if</span> <span class="ident">clist</span>.<span class="ident">set</span>.<span class="ident">is_empty</span>() {
<span class="comment">// Three ways to bail out when our current set of threads is</span>
<span class="comment">// empty.</span>
<span class="comment">//</span>
<span class="comment">// 1. We have a match---so we're done exploring any possible</span>
<span class="comment">// alternatives. Time to quit. (We can't do this if we're</span>
<span class="comment">// looking for matches for multiple regexes, unless we know</span>
<span class="comment">// they all matched.)</span>
<span class="comment">//</span>
<span class="comment">// 2. If the expression starts with a '^' we can terminate as</span>
<span class="comment">// soon as the last thread dies.</span>
<span class="kw">if</span> (<span class="ident">matched</span> <span class="op">&&</span> <span class="ident">matches</span>.<span class="ident">len</span>() <span class="op"><</span><span class="op">=</span> <span class="number">1</span>)
<span class="op">|</span><span class="op">|</span> <span class="ident">all_matched</span>
<span class="op">|</span><span class="op">|</span> (<span class="op">!</span><span class="ident">at</span>.<span class="ident">is_start</span>() <span class="op">&&</span> <span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">is_anchored_start</span>)
{
<span class="kw">break</span>;
}
<span class="comment">// 3. If there's a literal prefix for the program, try to</span>
<span class="comment">// jump ahead quickly. If it can't be found, then we can</span>
<span class="comment">// bail out early.</span>
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">prefixes</span>.<span class="ident">is_empty</span>() {
<span class="ident">at</span> <span class="op">=</span> <span class="kw">match</span> <span class="self">self</span>.<span class="ident">input</span>.<span class="ident">prefix_at</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">prefixes</span>, <span class="ident">at</span>) {
<span class="prelude-val">None</span> => <span class="kw">break</span>,
<span class="prelude-val">Some</span>(<span class="ident">at</span>) => <span class="ident">at</span>,
};
}
}
<span class="comment">// This simulates a preceding '.*?' for every regex by adding</span>
<span class="comment">// a state starting at the current position in the input for the</span>
<span class="comment">// beginning of the program only if we don't already have a match.</span>
<span class="kw">if</span> <span class="ident">clist</span>.<span class="ident">set</span>.<span class="ident">is_empty</span>()
<span class="op">|</span><span class="op">|</span> (<span class="op">!</span><span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">is_anchored_start</span> <span class="op">&&</span> <span class="op">!</span><span class="ident">all_matched</span>)
{
<span class="self">self</span>.<span class="ident">add</span>(<span class="kw-2">&mut</span> <span class="ident">clist</span>, <span class="ident">slots</span>, <span class="number">0</span>, <span class="ident">at</span>);
}
<span class="comment">// The previous call to "add" actually inspects the position just</span>
<span class="comment">// before the current character. For stepping through the machine,</span>
<span class="comment">// we can to look at the current character, so we advance the</span>
<span class="comment">// input.</span>
<span class="kw">let</span> <span class="ident">at_next</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">input</span>.<span class="ident">at</span>(<span class="ident">at</span>.<span class="ident">next_pos</span>());
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">clist</span>.<span class="ident">set</span>.<span class="ident">len</span>() {
<span class="kw">let</span> <span class="ident">ip</span> <span class="op">=</span> <span class="ident">clist</span>.<span class="ident">set</span>[<span class="ident">i</span>];
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">step</span>(
<span class="kw-2">&mut</span> <span class="ident">nlist</span>,
<span class="ident">matches</span>,
<span class="ident">slots</span>,
<span class="ident">clist</span>.<span class="ident">caps</span>(<span class="ident">ip</span>),
<span class="ident">ip</span>,
<span class="ident">at</span>,
<span class="ident">at_next</span>,
) {
<span class="ident">matched</span> <span class="op">=</span> <span class="bool-val">true</span>;
<span class="ident">all_matched</span> <span class="op">=</span> <span class="ident">all_matched</span> <span class="op">|</span><span class="op">|</span> <span class="ident">matches</span>.<span class="ident">iter</span>().<span class="ident">all</span>(<span class="op">|</span><span class="kw-2">&</span><span class="ident">b</span><span class="op">|</span> <span class="ident">b</span>);
<span class="kw">if</span> <span class="ident">quit_after_match</span> {
<span class="comment">// If we only care if a match occurs (not its</span>
<span class="comment">// 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>.<span class="ident">prog</span>.<span class="ident">matches</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="number">1</span> {
<span class="comment">// We don't need to check the rest of the threads</span>
<span class="comment">// in this set because we've matched something</span>
<span class="comment">// ("leftmost-first"). However, we still need to check</span>
<span class="comment">// threads in the next set to support things like</span>
<span class="comment">// greedy matching.</span>
<span class="comment">//</span>
<span class="comment">// This is only true on normal regexes. For regex sets,</span>
<span class="comment">// we need to mush on to observe other matches.</span>
<span class="kw">break</span>;
}
}
}
<span class="kw">if</span> <span class="ident">at</span>.<span class="ident">pos</span>() <span class="op">></span><span class="op">=</span> <span class="ident">end</span> {
<span class="kw">break</span>;
}
<span class="ident">at</span> <span class="op">=</span> <span class="ident">at_next</span>;
<span class="ident">mem::swap</span>(<span class="ident">clist</span>, <span class="ident">nlist</span>);
<span class="ident">nlist</span>.<span class="ident">set</span>.<span class="ident">clear</span>();
}
<span class="ident">matched</span>
}
<span class="doccomment">/// Step through the input, one token (byte or codepoint) at a time.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// nlist is the set of states that will be processed on the next token</span>
<span class="doccomment">/// in the input.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// caps is the set of captures passed by the caller of the NFA. They are</span>
<span class="doccomment">/// written to only when a match state is visited.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread_caps is the set of captures set for the current NFA state, ip.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// at and at_next are the current and next positions in the input. at or</span>
<span class="doccomment">/// at_next may be EOF.</span>
<span class="kw">fn</span> <span class="ident">step</span>(
<span class="kw-2">&mut</span> <span class="self">self</span>,
<span class="ident">nlist</span>: <span class="kw-2">&mut</span> <span class="ident">Threads</span>,
<span class="ident">matches</span>: <span class="kw-2">&mut</span> [<span class="ident">bool</span>],
<span class="ident">slots</span>: <span class="kw-2">&mut</span> [<span class="ident">Slot</span>],
<span class="ident">thread_caps</span>: <span class="kw-2">&mut</span> [<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>],
<span class="ident">ip</span>: <span class="ident">usize</span>,
<span class="ident">at</span>: <span class="ident">InputAt</span>,
<span class="ident">at_next</span>: <span class="ident">InputAt</span>,
) -> <span class="ident">bool</span> {
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::prog::Inst</span>::<span class="kw-2">*</span>;
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">prog</span>[<span class="ident">ip</span>] {
<span class="ident">Match</span>(<span class="ident">match_slot</span>) => {
<span class="kw">if</span> <span class="ident">match_slot</span> <span class="op"><</span> <span class="ident">matches</span>.<span class="ident">len</span>() {
<span class="ident">matches</span>[<span class="ident">match_slot</span>] <span class="op">=</span> <span class="bool-val">true</span>;
}
<span class="kw">for</span> (<span class="ident">slot</span>, <span class="ident">val</span>) <span class="kw">in</span> <span class="ident">slots</span>.<span class="ident">iter_mut</span>().<span class="ident">zip</span>(<span class="ident">thread_caps</span>.<span class="ident">iter</span>()) {
<span class="kw-2">*</span><span class="ident">slot</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">val</span>;
}
<span class="bool-val">true</span>
}
<span class="ident">Char</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="kw">if</span> <span class="ident">inst</span>.<span class="ident">c</span> <span class="op">==</span> <span class="ident">at</span>.<span class="ident">char</span>() {
<span class="self">self</span>.<span class="ident">add</span>(<span class="ident">nlist</span>, <span class="ident">thread_caps</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">at_next</span>);
}
<span class="bool-val">false</span>
}
<span class="ident">Ranges</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="kw">if</span> <span class="ident">inst</span>.<span class="ident">matches</span>(<span class="ident">at</span>.<span class="ident">char</span>()) {
<span class="self">self</span>.<span class="ident">add</span>(<span class="ident">nlist</span>, <span class="ident">thread_caps</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">at_next</span>);
}
<span class="bool-val">false</span>
}
<span class="ident">Bytes</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">b</span>) <span class="op">=</span> <span class="ident">at</span>.<span class="ident">byte</span>() {
<span class="kw">if</span> <span class="ident">inst</span>.<span class="ident">matches</span>(<span class="ident">b</span>) {
<span class="self">self</span>.<span class="ident">add</span>(<span class="ident">nlist</span>, <span class="ident">thread_caps</span>, <span class="ident">inst</span>.<span class="ident">goto</span>, <span class="ident">at_next</span>);
}
}
<span class="bool-val">false</span>
}
<span class="ident">EmptyLook</span>(<span class="kw">_</span>) <span class="op">|</span> <span class="ident">Save</span>(<span class="kw">_</span>) <span class="op">|</span> <span class="ident">Split</span>(<span class="kw">_</span>) => <span class="bool-val">false</span>,
}
}
<span class="doccomment">/// Follows epsilon transitions and adds them for processing to nlist,</span>
<span class="doccomment">/// starting at and including ip.</span>
<span class="kw">fn</span> <span class="ident">add</span>(
<span class="kw-2">&mut</span> <span class="self">self</span>,
<span class="ident">nlist</span>: <span class="kw-2">&mut</span> <span class="ident">Threads</span>,
<span class="ident">thread_caps</span>: <span class="kw-2">&mut</span> [<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>],
<span class="ident">ip</span>: <span class="ident">usize</span>,
<span class="ident">at</span>: <span class="ident">InputAt</span>,
) {
<span class="self">self</span>.<span class="ident">stack</span>.<span class="ident">push</span>(<span class="ident">FollowEpsilon::IP</span>(<span class="ident">ip</span>));
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">frame</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">stack</span>.<span class="ident">pop</span>() {
<span class="kw">match</span> <span class="ident">frame</span> {
<span class="ident">FollowEpsilon::IP</span>(<span class="ident">ip</span>) => {
<span class="self">self</span>.<span class="ident">add_step</span>(<span class="ident">nlist</span>, <span class="ident">thread_caps</span>, <span class="ident">ip</span>, <span class="ident">at</span>);
}
<span class="ident">FollowEpsilon::Capture</span> { <span class="ident">slot</span>, <span class="ident">pos</span> } => {
<span class="ident">thread_caps</span>[<span class="ident">slot</span>] <span class="op">=</span> <span class="ident">pos</span>;
}
}
}
}
<span class="doccomment">/// A helper function for add that avoids excessive pushing to the stack.</span>
<span class="kw">fn</span> <span class="ident">add_step</span>(
<span class="kw-2">&mut</span> <span class="self">self</span>,
<span class="ident">nlist</span>: <span class="kw-2">&mut</span> <span class="ident">Threads</span>,
<span class="ident">thread_caps</span>: <span class="kw-2">&mut</span> [<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>],
<span class="kw-2">mut</span> <span class="ident">ip</span>: <span class="ident">usize</span>,
<span class="ident">at</span>: <span class="ident">InputAt</span>,
) {
<span class="comment">// Instead of pushing and popping to the stack, we mutate ip as we</span>
<span class="comment">// traverse the set of states. We only push to the stack when we</span>
<span class="comment">// absolutely need recursion (restoring captures or following a</span>
<span class="comment">// branch).</span>
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::prog::Inst</span>::<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> <span class="ident">nlist</span>.<span class="ident">set</span>.<span class="ident">contains</span>(<span class="ident">ip</span>) {
<span class="kw">return</span>;
}
<span class="ident">nlist</span>.<span class="ident">set</span>.<span class="ident">insert</span>(<span class="ident">ip</span>);
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">prog</span>[<span class="ident">ip</span>] {
<span class="ident">EmptyLook</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">input</span>.<span class="ident">is_empty_match</span>(<span class="ident">at</span>, <span class="ident">inst</span>) {
<span class="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto</span>;
}
}
<span class="ident">Save</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="kw">if</span> <span class="ident">inst</span>.<span class="ident">slot</span> <span class="op"><</span> <span class="ident">thread_caps</span>.<span class="ident">len</span>() {
<span class="self">self</span>.<span class="ident">stack</span>.<span class="ident">push</span>(<span class="ident">FollowEpsilon::Capture</span> {
<span class="ident">slot</span>: <span class="ident">inst</span>.<span class="ident">slot</span>,
<span class="ident">pos</span>: <span class="ident">thread_caps</span>[<span class="ident">inst</span>.<span class="ident">slot</span>],
});
<span class="ident">thread_caps</span>[<span class="ident">inst</span>.<span class="ident">slot</span>] <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">at</span>.<span class="ident">pos</span>());
}
<span class="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto</span>;
}
<span class="ident">Split</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) => {
<span class="self">self</span>.<span class="ident">stack</span>.<span class="ident">push</span>(<span class="ident">FollowEpsilon::IP</span>(<span class="ident">inst</span>.<span class="ident">goto2</span>));
<span class="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto1</span>;
}
<span class="ident">Match</span>(<span class="kw">_</span>) <span class="op">|</span> <span class="ident">Char</span>(<span class="kw">_</span>) <span class="op">|</span> <span class="ident">Ranges</span>(<span class="kw">_</span>) <span class="op">|</span> <span class="ident">Bytes</span>(<span class="kw">_</span>) => {
<span class="kw">let</span> <span class="ident">t</span> <span class="op">=</span> <span class="kw-2">&mut</span> <span class="ident">nlist</span>.<span class="ident">caps</span>(<span class="ident">ip</span>);
<span class="kw">for</span> (<span class="ident">slot</span>, <span class="ident">val</span>) <span class="kw">in</span> <span class="ident">t</span>.<span class="ident">iter_mut</span>().<span class="ident">zip</span>(<span class="ident">thread_caps</span>.<span class="ident">iter</span>()) {
<span class="kw-2">*</span><span class="ident">slot</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">val</span>;
}
<span class="kw">return</span>;
}
}
}
}
}
<span class="kw">impl</span> <span class="ident">Threads</span> {
<span class="kw">fn</span> <span class="ident">new</span>() -> <span class="self">Self</span> {
<span class="ident">Threads</span> { <span class="ident">set</span>: <span class="ident">SparseSet::new</span>(<span class="number">0</span>), <span class="ident">caps</span>: <span class="macro">vec!</span>[], <span class="ident">slots_per_thread</span>: <span class="number">0</span> }
}
<span class="kw">fn</span> <span class="ident">resize</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">num_insts</span>: <span class="ident">usize</span>, <span class="ident">ncaps</span>: <span class="ident">usize</span>) {
<span class="kw">if</span> <span class="ident">num_insts</span> <span class="op">==</span> <span class="self">self</span>.<span class="ident">set</span>.<span class="ident">capacity</span>() {
<span class="kw">return</span>;
}
<span class="self">self</span>.<span class="ident">slots_per_thread</span> <span class="op">=</span> <span class="ident">ncaps</span> <span class="op">*</span> <span class="number">2</span>;
<span class="self">self</span>.<span class="ident">set</span> <span class="op">=</span> <span class="ident">SparseSet::new</span>(<span class="ident">num_insts</span>);
<span class="self">self</span>.<span class="ident">caps</span> <span class="op">=</span> <span class="macro">vec!</span>[<span class="prelude-val">None</span>; <span class="self">self</span>.<span class="ident">slots_per_thread</span> <span class="op">*</span> <span class="ident">num_insts</span>];
}
<span class="kw">fn</span> <span class="ident">caps</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">pc</span>: <span class="ident">usize</span>) -> <span class="kw-2">&mut</span> [<span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>] {
<span class="kw">let</span> <span class="ident">i</span> <span class="op">=</span> <span class="ident">pc</span> <span class="op">*</span> <span class="self">self</span>.<span class="ident">slots_per_thread</span>;
<span class="kw-2">&mut</span> <span class="self">self</span>.<span class="ident">caps</span>[<span class="ident">i</span>..<span class="ident">i</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">slots_per_thread</span>]
}
}
</code></pre></div>
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