| <!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 `/home/fmp/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-0.1.80/src/backtrack.rs`."> |
| <meta name="keywords" content="rust, rustlang, rust-lang"> |
| |
| <title>backtrack.rs.html -- source</title> |
| |
| <link rel="stylesheet" type="text/css" href="../../normalize.css"> |
| <link rel="stylesheet" type="text/css" href="../../rustdoc.css"> |
| <link rel="stylesheet" type="text/css" href="../../main.css"> |
| |
| |
| <link rel="shortcut icon" href="https://www.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"> |
| <a href='../../regex/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> |
| |
| </nav> |
| |
| <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"> |
| </div> |
| </form> |
| </nav> |
| |
| <section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span> |
| <span id="2"> 2</span> |
| <span id="3"> 3</span> |
| <span id="4"> 4</span> |
| <span id="5"> 5</span> |
| <span id="6"> 6</span> |
| <span id="7"> 7</span> |
| <span id="8"> 8</span> |
| <span id="9"> 9</span> |
| <span id="10"> 10</span> |
| <span id="11"> 11</span> |
| <span id="12"> 12</span> |
| <span id="13"> 13</span> |
| <span id="14"> 14</span> |
| <span id="15"> 15</span> |
| <span id="16"> 16</span> |
| <span id="17"> 17</span> |
| <span id="18"> 18</span> |
| <span id="19"> 19</span> |
| <span id="20"> 20</span> |
| <span id="21"> 21</span> |
| <span id="22"> 22</span> |
| <span id="23"> 23</span> |
| <span id="24"> 24</span> |
| <span id="25"> 25</span> |
| <span id="26"> 26</span> |
| <span id="27"> 27</span> |
| <span id="28"> 28</span> |
| <span id="29"> 29</span> |
| <span id="30"> 30</span> |
| <span id="31"> 31</span> |
| <span id="32"> 32</span> |
| <span id="33"> 33</span> |
| <span id="34"> 34</span> |
| <span id="35"> 35</span> |
| <span id="36"> 36</span> |
| <span id="37"> 37</span> |
| <span id="38"> 38</span> |
| <span id="39"> 39</span> |
| <span id="40"> 40</span> |
| <span id="41"> 41</span> |
| <span id="42"> 42</span> |
| <span id="43"> 43</span> |
| <span id="44"> 44</span> |
| <span id="45"> 45</span> |
| <span id="46"> 46</span> |
| <span id="47"> 47</span> |
| <span id="48"> 48</span> |
| <span id="49"> 49</span> |
| <span id="50"> 50</span> |
| <span id="51"> 51</span> |
| <span id="52"> 52</span> |
| <span id="53"> 53</span> |
| <span id="54"> 54</span> |
| <span id="55"> 55</span> |
| <span id="56"> 56</span> |
| <span id="57"> 57</span> |
| <span id="58"> 58</span> |
| <span id="59"> 59</span> |
| <span id="60"> 60</span> |
| <span id="61"> 61</span> |
| <span id="62"> 62</span> |
| <span id="63"> 63</span> |
| <span id="64"> 64</span> |
| <span id="65"> 65</span> |
| <span id="66"> 66</span> |
| <span id="67"> 67</span> |
| <span id="68"> 68</span> |
| <span id="69"> 69</span> |
| <span id="70"> 70</span> |
| <span id="71"> 71</span> |
| <span id="72"> 72</span> |
| <span id="73"> 73</span> |
| <span id="74"> 74</span> |
| <span id="75"> 75</span> |
| <span id="76"> 76</span> |
| <span id="77"> 77</span> |
| <span id="78"> 78</span> |
| <span id="79"> 79</span> |
| <span id="80"> 80</span> |
| <span id="81"> 81</span> |
| <span id="82"> 82</span> |
| <span id="83"> 83</span> |
| <span id="84"> 84</span> |
| <span id="85"> 85</span> |
| <span id="86"> 86</span> |
| <span id="87"> 87</span> |
| <span id="88"> 88</span> |
| <span id="89"> 89</span> |
| <span id="90"> 90</span> |
| <span id="91"> 91</span> |
| <span id="92"> 92</span> |
| <span id="93"> 93</span> |
| <span id="94"> 94</span> |
| <span id="95"> 95</span> |
| <span id="96"> 96</span> |
| <span id="97"> 97</span> |
| <span id="98"> 98</span> |
| <span id="99"> 99</span> |
| <span id="100">100</span> |
| <span id="101">101</span> |
| <span id="102">102</span> |
| <span id="103">103</span> |
| <span id="104">104</span> |
| <span id="105">105</span> |
| <span id="106">106</span> |
| <span id="107">107</span> |
| <span id="108">108</span> |
| <span id="109">109</span> |
| <span id="110">110</span> |
| <span id="111">111</span> |
| <span id="112">112</span> |
| <span id="113">113</span> |
| <span id="114">114</span> |
| <span id="115">115</span> |
| <span id="116">116</span> |
| <span id="117">117</span> |
| <span id="118">118</span> |
| <span id="119">119</span> |
| <span id="120">120</span> |
| <span id="121">121</span> |
| <span id="122">122</span> |
| <span id="123">123</span> |
| <span id="124">124</span> |
| <span id="125">125</span> |
| <span id="126">126</span> |
| <span id="127">127</span> |
| <span id="128">128</span> |
| <span id="129">129</span> |
| <span id="130">130</span> |
| <span id="131">131</span> |
| <span id="132">132</span> |
| <span id="133">133</span> |
| <span id="134">134</span> |
| <span id="135">135</span> |
| <span id="136">136</span> |
| <span id="137">137</span> |
| <span id="138">138</span> |
| <span id="139">139</span> |
| <span id="140">140</span> |
| <span id="141">141</span> |
| <span id="142">142</span> |
| <span id="143">143</span> |
| <span id="144">144</span> |
| <span id="145">145</span> |
| <span id="146">146</span> |
| <span id="147">147</span> |
| <span id="148">148</span> |
| <span id="149">149</span> |
| <span id="150">150</span> |
| <span id="151">151</span> |
| <span id="152">152</span> |
| <span id="153">153</span> |
| <span id="154">154</span> |
| <span id="155">155</span> |
| <span id="156">156</span> |
| <span id="157">157</span> |
| <span id="158">158</span> |
| <span id="159">159</span> |
| <span id="160">160</span> |
| <span id="161">161</span> |
| <span id="162">162</span> |
| <span id="163">163</span> |
| <span id="164">164</span> |
| <span id="165">165</span> |
| <span id="166">166</span> |
| <span id="167">167</span> |
| <span id="168">168</span> |
| <span id="169">169</span> |
| <span id="170">170</span> |
| <span id="171">171</span> |
| <span id="172">172</span> |
| <span id="173">173</span> |
| <span id="174">174</span> |
| <span id="175">175</span> |
| <span id="176">176</span> |
| <span id="177">177</span> |
| <span id="178">178</span> |
| <span id="179">179</span> |
| <span id="180">180</span> |
| <span id="181">181</span> |
| <span id="182">182</span> |
| <span id="183">183</span> |
| <span id="184">184</span> |
| <span id="185">185</span> |
| <span id="186">186</span> |
| <span id="187">187</span> |
| <span id="188">188</span> |
| <span id="189">189</span> |
| <span id="190">190</span> |
| <span id="191">191</span> |
| <span id="192">192</span> |
| <span id="193">193</span> |
| <span id="194">194</span> |
| <span id="195">195</span> |
| <span id="196">196</span> |
| <span id="197">197</span> |
| <span id="198">198</span> |
| <span id="199">199</span> |
| <span id="200">200</span> |
| <span id="201">201</span> |
| <span id="202">202</span> |
| <span id="203">203</span> |
| <span id="204">204</span> |
| <span id="205">205</span> |
| <span id="206">206</span> |
| <span id="207">207</span> |
| <span id="208">208</span> |
| <span id="209">209</span> |
| <span id="210">210</span> |
| <span id="211">211</span> |
| <span id="212">212</span> |
| <span id="213">213</span> |
| <span id="214">214</span> |
| <span id="215">215</span> |
| <span id="216">216</span> |
| <span id="217">217</span> |
| <span id="218">218</span> |
| <span id="219">219</span> |
| <span id="220">220</span> |
| <span id="221">221</span> |
| <span id="222">222</span> |
| <span id="223">223</span> |
| <span id="224">224</span> |
| <span id="225">225</span> |
| <span id="226">226</span> |
| <span id="227">227</span> |
| <span id="228">228</span> |
| <span id="229">229</span> |
| <span id="230">230</span> |
| <span id="231">231</span> |
| <span id="232">232</span> |
| <span id="233">233</span> |
| <span id="234">234</span> |
| <span id="235">235</span> |
| <span id="236">236</span> |
| <span id="237">237</span> |
| <span id="238">238</span> |
| <span id="239">239</span> |
| <span id="240">240</span> |
| <span id="241">241</span> |
| <span id="242">242</span> |
| <span id="243">243</span> |
| <span id="244">244</span> |
| <span id="245">245</span> |
| <span id="246">246</span> |
| <span id="247">247</span> |
| <span id="248">248</span> |
| <span id="249">249</span> |
| <span id="250">250</span> |
| <span id="251">251</span> |
| <span id="252">252</span> |
| <span id="253">253</span> |
| <span id="254">254</span> |
| <span id="255">255</span> |
| <span id="256">256</span> |
| <span id="257">257</span> |
| <span id="258">258</span> |
| <span id="259">259</span> |
| <span id="260">260</span> |
| <span id="261">261</span> |
| <span id="262">262</span> |
| <span id="263">263</span> |
| <span id="264">264</span> |
| <span id="265">265</span> |
| <span id="266">266</span> |
| <span id="267">267</span> |
| <span id="268">268</span> |
| <span id="269">269</span> |
| <span id="270">270</span> |
| <span id="271">271</span> |
| <span id="272">272</span> |
| <span id="273">273</span> |
| <span id="274">274</span> |
| <span id="275">275</span> |
| <span id="276">276</span> |
| <span id="277">277</span> |
| <span id="278">278</span> |
| <span id="279">279</span> |
| <span id="280">280</span> |
| <span id="281">281</span> |
| <span id="282">282</span> |
| <span id="283">283</span> |
| <span id="284">284</span> |
| <span id="285">285</span> |
| <span id="286">286</span> |
| <span id="287">287</span> |
| <span id="288">288</span> |
| <span id="289">289</span> |
| <span id="290">290</span> |
| <span id="291">291</span> |
| <span id="292">292</span> |
| <span id="293">293</span> |
| <span id="294">294</span> |
| <span id="295">295</span> |
| <span id="296">296</span> |
| <span id="297">297</span> |
| <span id="298">298</span> |
| <span id="299">299</span> |
| <span id="300">300</span> |
| <span id="301">301</span> |
| <span id="302">302</span> |
| </pre><pre class="rust "> |
| <span class="comment">// Copyright 2014-2015 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="comment">// This is the backtracking matching engine. It has the same exact capability</span> |
| <span class="comment">// as the full NFA simulation, except it is artificially restricted to small</span> |
| <span class="comment">// regexes on small inputs because of its memory requirements.</span> |
| <span class="comment">//</span> |
| <span class="comment">// In particular, this is a *bounded* backtracking engine. It retains worst</span> |
| <span class="comment">// case linear time by keeping track of the states that is has visited (using a</span> |
| <span class="comment">// bitmap). Namely, once a state is visited, it is never visited again. Since a</span> |
| <span class="comment">// state is keyed by `(instruction index, input index)`, we have that its time</span> |
| <span class="comment">// complexity is `O(mn)` (i.e., linear in the size of the search text).</span> |
| <span class="comment">//</span> |
| <span class="comment">// The backtracking engine can beat out the NFA simulation on small</span> |
| <span class="comment">// regexes/inputs because it doesn't have to keep track of multiple copies of</span> |
| <span class="comment">// the capture groups. In benchmarks, the backtracking engine is roughly twice</span> |
| <span class="comment">// as fast as the full NFA simulation. Note though that its performance doesn't</span> |
| <span class="comment">// scale, even if you're willing to live with the memory requirements. Namely,</span> |
| <span class="comment">// the bitset has to be zeroed on each execution, which becomes quite expensive</span> |
| <span class="comment">// on large bitsets.</span> |
| |
| <span class="kw">use</span> <span class="ident">exec</span>::<span class="ident">ProgramCache</span>; |
| <span class="kw">use</span> <span class="ident">input</span>::{<span class="ident">Input</span>, <span class="ident">InputAt</span>}; |
| <span class="kw">use</span> <span class="ident">prog</span>::{<span class="ident">Program</span>, <span class="ident">InstPtr</span>}; |
| <span class="kw">use</span> <span class="ident">re_trait</span>::<span class="ident">Slot</span>; |
| |
| <span class="kw">type</span> <span class="ident">Bits</span> <span class="op">=</span> <span class="ident">u32</span>; |
| |
| <span class="kw">const</span> <span class="ident">BIT_SIZE</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">32</span>; |
| <span class="kw">const</span> <span class="ident">MAX_SIZE_BYTES</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">256</span> <span class="op">*</span> (<span class="number">1</span> <span class="op"><<</span> <span class="number">10</span>); <span class="comment">// 256 KB</span> |
| |
| <span class="doccomment">/// Returns true iff the given regex and input should be executed by this</span> |
| <span class="doccomment">/// engine with reasonable memory usage.</span> |
| <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">should_exec</span>(<span class="ident">num_insts</span>: <span class="ident">usize</span>, <span class="ident">text_len</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">bool</span> { |
| <span class="comment">// Total memory usage in bytes is determined by:</span> |
| <span class="comment">//</span> |
| <span class="comment">// ((len(insts) * (len(input) + 1) + bits - 1) / bits) * (size_of(u32))</span> |
| <span class="comment">//</span> |
| <span class="comment">// The actual limit picked is pretty much a heuristic.</span> |
| <span class="comment">// See: https://github.com/rust-lang-nursery/regex/issues/215</span> |
| <span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> ((<span class="ident">num_insts</span> <span class="op">*</span> (<span class="ident">text_len</span> <span class="op">+</span> <span class="number">1</span>) <span class="op">+</span> <span class="ident">BIT_SIZE</span> <span class="op">-</span> <span class="number">1</span>) <span class="op">/</span> <span class="ident">BIT_SIZE</span>) <span class="op">*</span> <span class="number">4</span>; |
| <span class="ident">size</span> <span class="op"><=</span> <span class="ident">MAX_SIZE_BYTES</span> |
| } |
| |
| <span class="doccomment">/// A backtracking 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">Bounded</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'m</span>, <span class="lifetime">'r</span>, <span class="lifetime">'s</span>, <span class="ident">I</span><span class="op">></span> { |
| <span class="ident">prog</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">Program</span>, |
| <span class="ident">input</span>: <span class="ident">I</span>, |
| <span class="ident">matches</span>: <span class="kw-2">&</span><span class="lifetime">'m</span> <span class="kw-2">mut</span> [<span class="ident">bool</span>], |
| <span class="ident">slots</span>: <span class="kw-2">&</span><span class="lifetime">'s</span> <span class="kw-2">mut</span> [<span class="ident">Slot</span>], |
| <span class="ident">m</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">Cache</span>, |
| } |
| |
| <span class="doccomment">/// Shared cached state between multiple invocations of a backtracking engine</span> |
| <span class="doccomment">/// in the same thread.</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="ident">jobs</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">Job</span><span class="op">></span>, |
| <span class="ident">visited</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">Bits</span><span class="op">></span>, |
| } |
| |
| <span class="kw">impl</span> <span class="ident">Cache</span> { |
| <span class="doccomment">/// Create new empty cache for the backtracking engine.</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="op">-></span> <span class="self">Self</span> { |
| <span class="ident">Cache</span> { <span class="ident">jobs</span>: <span class="macro">vec</span><span class="macro">!</span>[], <span class="ident">visited</span>: <span class="macro">vec</span><span class="macro">!</span>[] } |
| } |
| } |
| |
| <span class="doccomment">/// A job is an explicit unit of stack space in the backtracking engine.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// The "normal" representation is a single state transition, which corresponds</span> |
| <span class="doccomment">/// to an NFA state and a character in the input. However, the backtracking</span> |
| <span class="doccomment">/// engine must keep track of old capture group values. We use the explicit</span> |
| <span class="doccomment">/// stack to do it.</span> |
| <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>)]</span> |
| <span class="kw">enum</span> <span class="ident">Job</span> { |
| <span class="ident">Inst</span> { <span class="ident">ip</span>: <span class="ident">InstPtr</span>, <span class="ident">at</span>: <span class="ident">InputAt</span> }, |
| <span class="ident">SaveRestore</span> { <span class="ident">slot</span>: <span class="ident">usize</span>, <span class="ident">old_pos</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span> }, |
| } |
| |
| <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'m</span>, <span class="lifetime">'r</span>, <span class="lifetime">'s</span>, <span class="ident">I</span>: <span class="ident">Input</span><span class="op">></span> <span class="ident">Bounded</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="lifetime">'m</span>, <span class="lifetime">'r</span>, <span class="lifetime">'s</span>, <span class="ident">I</span><span class="op">></span> { |
| <span class="doccomment">/// Execute the backtracking 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">&</span><span class="lifetime">'m</span> <span class="kw-2">mut</span> [<span class="ident">bool</span>], |
| <span class="ident">slots</span>: <span class="kw-2">&</span><span class="lifetime">'s</span> <span class="kw-2">mut</span> [<span class="ident">Slot</span>], |
| <span class="ident">input</span>: <span class="ident">I</span>, |
| <span class="ident">start</span>: <span class="ident">usize</span>, |
| ) <span class="op">-></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="kw-2">mut</span> <span class="ident">cache</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">cache</span>.<span class="ident">backtrack</span>; |
| <span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">at</span>(<span class="ident">start</span>); |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">b</span> <span class="op">=</span> <span class="ident">Bounded</span> { |
| <span class="ident">prog</span>: <span class="ident">prog</span>, |
| <span class="ident">input</span>: <span class="ident">input</span>, |
| <span class="ident">matches</span>: <span class="ident">matches</span>, |
| <span class="ident">slots</span>: <span class="ident">slots</span>, |
| <span class="ident">m</span>: <span class="ident">cache</span>, |
| }; |
| <span class="ident">b</span>.<span class="ident">exec_</span>(<span class="ident">start</span>) |
| } |
| |
| <span class="doccomment">/// Clears the cache such that the backtracking engine can be executed</span> |
| <span class="doccomment">/// on some input of fixed length.</span> |
| <span class="kw">fn</span> <span class="ident">clear</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) { |
| <span class="comment">// Reset the job memory so that we start fresh.</span> |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">jobs</span>.<span class="ident">clear</span>(); |
| |
| <span class="comment">// Now we need to clear the bit state set.</span> |
| <span class="comment">// We do this by figuring out how much space we need to keep track</span> |
| <span class="comment">// of the states we've visited.</span> |
| <span class="comment">// Then we reset all existing allocated space to 0.</span> |
| <span class="comment">// Finally, we request more space if we need it.</span> |
| <span class="comment">//</span> |
| <span class="comment">// This is all a little circuitous, but doing this unsafely</span> |
| <span class="comment">// doesn't seem to have a measurable impact on performance.</span> |
| <span class="comment">// (Probably because backtracking is limited to such small</span> |
| <span class="comment">// inputs/regexes in the first place.)</span> |
| <span class="kw">let</span> <span class="ident">visited_len</span> <span class="op">=</span> |
| (<span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">len</span>() <span class="op">*</span> (<span class="self">self</span>.<span class="ident">input</span>.<span class="ident">len</span>() <span class="op">+</span> <span class="number">1</span>) <span class="op">+</span> <span class="ident">BIT_SIZE</span> <span class="op">-</span> <span class="number">1</span>) |
| <span class="op">/</span> |
| <span class="ident">BIT_SIZE</span>; |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>.<span class="ident">truncate</span>(<span class="ident">visited_len</span>); |
| <span class="kw">for</span> <span class="ident">v</span> <span class="kw">in</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span> { |
| <span class="kw-2">*</span><span class="ident">v</span> <span class="op">=</span> <span class="number">0</span>; |
| } |
| <span class="kw">if</span> <span class="ident">visited_len</span> <span class="op">></span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>.<span class="ident">len</span>() { |
| <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>.<span class="ident">len</span>(); |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>.<span class="ident">reserve_exact</span>(<span class="ident">visited_len</span> <span class="op">-</span> <span class="ident">len</span>); |
| <span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..(<span class="ident">visited_len</span> <span class="op">-</span> <span class="ident">len</span>) { |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>.<span class="ident">push</span>(<span class="number">0</span>); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Start backtracking at the given position in the input, but also look</span> |
| <span class="doccomment">/// for literal prefixes.</span> |
| <span class="kw">fn</span> <span class="ident">exec_</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="kw-2">mut</span> <span class="ident">at</span>: <span class="ident">InputAt</span>) <span class="op">-></span> <span class="ident">bool</span> { |
| <span class="self">self</span>.<span class="ident">clear</span>(); |
| <span class="comment">// If this is an anchored regex at the beginning of the input, then</span> |
| <span class="comment">// we're either already done or we only need to try backtracking once.</span> |
| <span class="kw">if</span> <span class="self">self</span>.<span class="ident">prog</span>.<span class="ident">is_anchored_start</span> { |
| <span class="kw">return</span> <span class="kw">if</span> <span class="op">!</span><span class="ident">at</span>.<span class="ident">is_start</span>() { |
| <span class="bool-val">false</span> |
| } <span class="kw">else</span> { |
| <span class="self">self</span>.<span class="ident">backtrack</span>(<span class="ident">at</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">loop</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="op">=></span> <span class="kw">break</span>, |
| <span class="prelude-val">Some</span>(<span class="ident">at</span>) <span class="op">=></span> <span class="ident">at</span>, |
| }; |
| } |
| <span class="ident">matched</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">backtrack</span>(<span class="ident">at</span>) <span class="op">||</span> <span class="ident">matched</span>; |
| <span class="kw">if</span> <span class="ident">matched</span> <span class="op">&&</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="kw">return</span> <span class="bool-val">true</span>; |
| } |
| <span class="kw">if</span> <span class="ident">at</span>.<span class="ident">is_end</span>() { |
| <span class="kw">break</span>; |
| } |
| <span class="ident">at</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="ident">matched</span> |
| } |
| |
| <span class="doccomment">/// The main backtracking loop starting at the given input position.</span> |
| <span class="kw">fn</span> <span class="ident">backtrack</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">start</span>: <span class="ident">InputAt</span>) <span class="op">-></span> <span class="ident">bool</span> { |
| <span class="comment">// N.B. We use an explicit stack to avoid recursion.</span> |
| <span class="comment">// To avoid excessive pushing and popping, most transitions are handled</span> |
| <span class="comment">// in the `step` helper function, which only pushes to the stack when</span> |
| <span class="comment">// there's a capture or a branch.</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="self">self</span>.<span class="ident">m</span>.<span class="ident">jobs</span>.<span class="ident">push</span>(<span class="ident">Job</span>::<span class="ident">Inst</span> { <span class="ident">ip</span>: <span class="number">0</span>, <span class="ident">at</span>: <span class="ident">start</span> }); |
| <span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">job</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">jobs</span>.<span class="ident">pop</span>() { |
| <span class="kw">match</span> <span class="ident">job</span> { |
| <span class="ident">Job</span>::<span class="ident">Inst</span> { <span class="ident">ip</span>, <span class="ident">at</span> } <span class="op">=></span> { |
| <span class="kw">if</span> <span class="self">self</span>.<span class="ident">step</span>(<span class="ident">ip</span>, <span class="ident">at</span>) { |
| <span class="comment">// Only quit if we're matching one regex.</span> |
| <span class="comment">// If we're matching a regex set, then mush on and</span> |
| <span class="comment">// try to find other matches (if we want them).</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="kw">return</span> <span class="bool-val">true</span>; |
| } |
| <span class="ident">matched</span> <span class="op">=</span> <span class="bool-val">true</span>; |
| } |
| } |
| <span class="ident">Job</span>::<span class="ident">SaveRestore</span> { <span class="ident">slot</span>, <span class="ident">old_pos</span> } <span class="op">=></span> { |
| <span class="kw">if</span> <span class="ident">slot</span> <span class="op"><</span> <span class="self">self</span>.<span class="ident">slots</span>.<span class="ident">len</span>() { |
| <span class="self">self</span>.<span class="ident">slots</span>[<span class="ident">slot</span>] <span class="op">=</span> <span class="ident">old_pos</span>; |
| } |
| } |
| } |
| } |
| <span class="ident">matched</span> |
| } |
| |
| <span class="kw">fn</span> <span class="ident">step</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="kw-2">mut</span> <span class="ident">ip</span>: <span class="ident">InstPtr</span>, <span class="kw-2">mut</span> <span class="ident">at</span>: <span class="ident">InputAt</span>) <span class="op">-></span> <span class="ident">bool</span> { |
| <span class="kw">use</span> <span class="ident">prog</span>::<span class="ident">Inst</span>::<span class="kw-2">*</span>; |
| <span class="kw">loop</span> { |
| <span class="comment">// This loop is an optimization to avoid constantly pushing/popping</span> |
| <span class="comment">// from the stack. Namely, if we're pushing a job only to run it</span> |
| <span class="comment">// next, avoid the push and just mutate `ip` (and possibly `at`)</span> |
| <span class="comment">// in place.</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">slot</span>) <span class="op">=></span> { |
| <span class="kw">if</span> <span class="ident">slot</span> <span class="op"><</span> <span class="self">self</span>.<span class="ident">matches</span>.<span class="ident">len</span>() { |
| <span class="self">self</span>.<span class="ident">matches</span>[<span class="ident">slot</span>] <span class="op">=</span> <span class="bool-val">true</span>; |
| } |
| <span class="kw">return</span> <span class="bool-val">true</span>; |
| } |
| <span class="ident">Save</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=></span> { |
| <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="kw-2">&</span><span class="ident">old_pos</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">slots</span>.<span class="ident">get</span>(<span class="ident">inst</span>.<span class="ident">slot</span>) { |
| <span class="comment">// If this path doesn't work out, then we save the old</span> |
| <span class="comment">// capture index (if one exists) in an alternate</span> |
| <span class="comment">// job. If the next path fails, then the alternate</span> |
| <span class="comment">// job is popped and the old capture index is restored.</span> |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">jobs</span>.<span class="ident">push</span>(<span class="ident">Job</span>::<span class="ident">SaveRestore</span> { |
| <span class="ident">slot</span>: <span class="ident">inst</span>.<span class="ident">slot</span>, |
| <span class="ident">old_pos</span>: <span class="ident">old_pos</span>, |
| }); |
| <span class="self">self</span>.<span class="ident">slots</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="op">=></span> { |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">jobs</span>.<span class="ident">push</span>(<span class="ident">Job</span>::<span class="ident">Inst</span> { <span class="ident">ip</span>: <span class="ident">inst</span>.<span class="ident">goto2</span>, <span class="ident">at</span>: <span class="ident">at</span> }); |
| <span class="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto1</span>; |
| } |
| <span class="ident">EmptyLook</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=></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="kw">else</span> { |
| <span class="kw">return</span> <span class="bool-val">false</span>; |
| } |
| } |
| <span class="ident">Char</span>(<span class="kw-2">ref</span> <span class="ident">inst</span>) <span class="op">=></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="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto</span>; |
| <span class="ident">at</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">else</span> { |
| <span class="kw">return</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="op">=></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="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto</span>; |
| <span class="ident">at</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">else</span> { |
| <span class="kw">return</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="op">=></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="ident">ip</span> <span class="op">=</span> <span class="ident">inst</span>.<span class="ident">goto</span>; |
| <span class="ident">at</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">continue</span>; |
| } |
| } |
| <span class="kw">return</span> <span class="bool-val">false</span>; |
| } |
| } |
| <span class="kw">if</span> <span class="self">self</span>.<span class="ident">has_visited</span>(<span class="ident">ip</span>, <span class="ident">at</span>) { |
| <span class="kw">return</span> <span class="bool-val">false</span>; |
| } |
| } |
| } |
| |
| <span class="kw">fn</span> <span class="ident">has_visited</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">ip</span>: <span class="ident">InstPtr</span>, <span class="ident">at</span>: <span class="ident">InputAt</span>) <span class="op">-></span> <span class="ident">bool</span> { |
| <span class="kw">let</span> <span class="ident">k</span> <span class="op">=</span> <span class="ident">ip</span> <span class="op">*</span> (<span class="self">self</span>.<span class="ident">input</span>.<span class="ident">len</span>() <span class="op">+</span> <span class="number">1</span>) <span class="op">+</span> <span class="ident">at</span>.<span class="ident">pos</span>(); |
| <span class="kw">let</span> <span class="ident">k1</span> <span class="op">=</span> <span class="ident">k</span> <span class="op">/</span> <span class="ident">BIT_SIZE</span>; |
| <span class="kw">let</span> <span class="ident">k2</span> <span class="op">=</span> <span class="ident">usize_to_u32</span>(<span class="number">1</span> <span class="op"><<</span> (<span class="ident">k</span> <span class="op">&</span> (<span class="ident">BIT_SIZE</span> <span class="op">-</span> <span class="number">1</span>))); |
| <span class="kw">if</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>[<span class="ident">k1</span>] <span class="op">&</span> <span class="ident">k2</span> <span class="op">==</span> <span class="number">0</span> { |
| <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">visited</span>[<span class="ident">k1</span>] <span class="op">|=</span> <span class="ident">k2</span>; |
| <span class="bool-val">false</span> |
| } <span class="kw">else</span> { |
| <span class="bool-val">true</span> |
| } |
| } |
| } |
| |
| <span class="kw">fn</span> <span class="ident">usize_to_u32</span>(<span class="ident">n</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">u32</span> { |
| <span class="kw">if</span> (<span class="ident">n</span> <span class="kw">as</span> <span class="ident">u64</span>) <span class="op">></span> (::<span class="ident">std</span>::<span class="ident">u32</span>::<span class="ident">MAX</span> <span class="kw">as</span> <span class="ident">u64</span>) { |
| <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"BUG: {} is too big to fit into u32"</span>, <span class="ident">n</span>) |
| } |
| <span class="ident">n</span> <span class="kw">as</span> <span class="ident">u32</span> |
| } |
| </pre> |
| </section> |
| <section id='search' class="content hidden"></section> |
| |
| <section class="footer"></section> |
| |
| <aside id="help" class="hidden"> |
| <div> |
| <h1 class="hidden">Help</h1> |
| |
| <div class="shortcuts"> |
| <h2>Keyboard Shortcuts</h2> |
| |
| <dl> |
| <dt>?</dt> |
| <dd>Show this help dialog</dd> |
| <dt>S</dt> |
| <dd>Focus the search field</dd> |
| <dt>⇤</dt> |
| <dd>Move up in search results</dd> |
| <dt>⇥</dt> |
| <dd>Move down in search results</dd> |
| <dt>⏎</dt> |
| <dd>Go to active search result</dd> |
| <dt>+</dt> |
| <dd>Collapse/expand all sections</dd> |
| </dl> |
| </div> |
| |
| <div class="infos"> |
| <h2>Search Tricks</h2> |
| |
| <p> |
| Prefix searches with a type followed by a colon (e.g. |
| <code>fn:</code>) to restrict the search to a given type. |
| </p> |
| |
| <p> |
| Accepted types are: <code>fn</code>, <code>mod</code>, |
| <code>struct</code>, <code>enum</code>, |
| <code>trait</code>, <code>type</code>, <code>macro</code>, |
| and <code>const</code>. |
| </p> |
| |
| <p> |
| Search functions by type signature (e.g. |
| <code>vec -> usize</code> or <code>* -> vec</code>) |
| </p> |
| </div> |
| </div> |
| </aside> |
| |
| |
| |
| <script> |
| window.rootPath = "../../"; |
| window.currentCrate = "regex"; |
| </script> |
| <script src="../../main.js"></script> |
| <script defer src="../../search-index.js"></script> |
| </body> |
| </html> |
