<!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 `liballoc/slice.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>slice.rs.html -- source</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../alloc/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span> <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> <span id="303">303</span> <span id="304">304</span> <span id="305">305</span> <span id="306">306</span> <span id="307">307</span> <span id="308">308</span> <span id="309">309</span> <span id="310">310</span> <span id="311">311</span> <span id="312">312</span> <span id="313">313</span> <span id="314">314</span> <span id="315">315</span> <span id="316">316</span> <span id="317">317</span> <span id="318">318</span> <span id="319">319</span> <span id="320">320</span> <span id="321">321</span> <span id="322">322</span> <span id="323">323</span> <span id="324">324</span> <span id="325">325</span> <span id="326">326</span> <span id="327">327</span> <span id="328">328</span> <span id="329">329</span> <span id="330">330</span> <span id="331">331</span> <span id="332">332</span> <span id="333">333</span> <span id="334">334</span> <span id="335">335</span> <span id="336">336</span> <span id="337">337</span> <span id="338">338</span> <span id="339">339</span> <span id="340">340</span> <span id="341">341</span> <span id="342">342</span> <span id="343">343</span> <span id="344">344</span> <span id="345">345</span> <span id="346">346</span> <span id="347">347</span> <span id="348">348</span> <span id="349">349</span> <span id="350">350</span> <span id="351">351</span> <span id="352">352</span> <span id="353">353</span> <span id="354">354</span> <span id="355">355</span> <span id="356">356</span> <span id="357">357</span> <span id="358">358</span> <span id="359">359</span> <span id="360">360</span> <span id="361">361</span> <span id="362">362</span> <span id="363">363</span> <span id="364">364</span> <span id="365">365</span> <span id="366">366</span> <span id="367">367</span> <span id="368">368</span> <span id="369">369</span> <span id="370">370</span> <span id="371">371</span> <span id="372">372</span> <span id="373">373</span> <span id="374">374</span> <span id="375">375</span> <span id="376">376</span> <span id="377">377</span> <span id="378">378</span> <span id="379">379</span> <span id="380">380</span> <span id="381">381</span> <span id="382">382</span> <span id="383">383</span> <span id="384">384</span> <span id="385">385</span> <span id="386">386</span> <span id="387">387</span> <span id="388">388</span> <span id="389">389</span> <span id="390">390</span> <span id="391">391</span> <span id="392">392</span> <span id="393">393</span> <span id="394">394</span> <span id="395">395</span> <span id="396">396</span> <span id="397">397</span> <span id="398">398</span> <span id="399">399</span> <span id="400">400</span> <span id="401">401</span> <span id="402">402</span> <span id="403">403</span> <span id="404">404</span> <span id="405">405</span> <span id="406">406</span> <span id="407">407</span> <span id="408">408</span> <span id="409">409</span> <span id="410">410</span> <span id="411">411</span> <span id="412">412</span> <span id="413">413</span> <span id="414">414</span> <span id="415">415</span> <span id="416">416</span> <span id="417">417</span> <span id="418">418</span> <span id="419">419</span> <span id="420">420</span> <span id="421">421</span> <span id="422">422</span> <span id="423">423</span> <span id="424">424</span> <span id="425">425</span> <span id="426">426</span> <span id="427">427</span> <span id="428">428</span> <span id="429">429</span> <span id="430">430</span> <span id="431">431</span> <span id="432">432</span> <span id="433">433</span> <span id="434">434</span> <span id="435">435</span> <span id="436">436</span> <span id="437">437</span> <span id="438">438</span> <span id="439">439</span> <span id="440">440</span> <span id="441">441</span> <span id="442">442</span> <span id="443">443</span> <span id="444">444</span> <span id="445">445</span> <span id="446">446</span> <span id="447">447</span> <span id="448">448</span> <span id="449">449</span> <span id="450">450</span> <span id="451">451</span> <span id="452">452</span> <span id="453">453</span> <span id="454">454</span> <span id="455">455</span> <span id="456">456</span> <span id="457">457</span> <span id="458">458</span> <span id="459">459</span> <span id="460">460</span> <span id="461">461</span> <span id="462">462</span> <span id="463">463</span> <span id="464">464</span> <span id="465">465</span> <span id="466">466</span> <span id="467">467</span> <span id="468">468</span> <span id="469">469</span> <span id="470">470</span> <span id="471">471</span> <span id="472">472</span> <span id="473">473</span> <span id="474">474</span> <span id="475">475</span> <span id="476">476</span> <span id="477">477</span> <span id="478">478</span> <span id="479">479</span> <span id="480">480</span> <span id="481">481</span> <span id="482">482</span> <span id="483">483</span> <span id="484">484</span> <span id="485">485</span> <span id="486">486</span> <span id="487">487</span> <span id="488">488</span> <span id="489">489</span> <span id="490">490</span> <span id="491">491</span> <span id="492">492</span> <span id="493">493</span> <span id="494">494</span> <span id="495">495</span> <span id="496">496</span> <span id="497">497</span> <span id="498">498</span> <span id="499">499</span> <span id="500">500</span> <span id="501">501</span> <span id="502">502</span> <span id="503">503</span> <span id="504">504</span> <span id="505">505</span> <span id="506">506</span> <span id="507">507</span> <span id="508">508</span> <span id="509">509</span> <span id="510">510</span> <span id="511">511</span> <span id="512">512</span> <span id="513">513</span> <span id="514">514</span> <span id="515">515</span> <span id="516">516</span> <span id="517">517</span> <span id="518">518</span> <span id="519">519</span> <span id="520">520</span> <span id="521">521</span> <span id="522">522</span> <span id="523">523</span> <span id="524">524</span> <span id="525">525</span> <span id="526">526</span> <span id="527">527</span> <span id="528">528</span> <span id="529">529</span> <span id="530">530</span> <span id="531">531</span> <span id="532">532</span> <span id="533">533</span> <span id="534">534</span> <span id="535">535</span> <span id="536">536</span> <span id="537">537</span> <span id="538">538</span> <span id="539">539</span> <span id="540">540</span> <span id="541">541</span> <span id="542">542</span> <span id="543">543</span> <span id="544">544</span> <span id="545">545</span> <span id="546">546</span> <span id="547">547</span> <span id="548">548</span> <span id="549">549</span> <span id="550">550</span> <span id="551">551</span> <span id="552">552</span> <span id="553">553</span> <span id="554">554</span> <span id="555">555</span> <span id="556">556</span> <span id="557">557</span> <span id="558">558</span> <span id="559">559</span> <span id="560">560</span> <span id="561">561</span> <span id="562">562</span> <span id="563">563</span> <span id="564">564</span> <span id="565">565</span> <span id="566">566</span> <span id="567">567</span> <span id="568">568</span> <span id="569">569</span> <span id="570">570</span> <span id="571">571</span> <span id="572">572</span> <span id="573">573</span> <span id="574">574</span> <span id="575">575</span> <span id="576">576</span> <span id="577">577</span> <span id="578">578</span> <span id="579">579</span> <span id="580">580</span> <span id="581">581</span> <span id="582">582</span> <span id="583">583</span> <span id="584">584</span> <span id="585">585</span> <span id="586">586</span> <span id="587">587</span> <span id="588">588</span> <span id="589">589</span> <span id="590">590</span> <span id="591">591</span> <span id="592">592</span> <span id="593">593</span> <span id="594">594</span> <span id="595">595</span> <span id="596">596</span> <span id="597">597</span> <span id="598">598</span> <span id="599">599</span> <span id="600">600</span> <span id="601">601</span> <span id="602">602</span> <span id="603">603</span> <span id="604">604</span> <span id="605">605</span> <span id="606">606</span> <span id="607">607</span> <span id="608">608</span> <span id="609">609</span> <span id="610">610</span> <span id="611">611</span> <span id="612">612</span> <span id="613">613</span> <span id="614">614</span> <span id="615">615</span> <span id="616">616</span> <span id="617">617</span> <span id="618">618</span> <span id="619">619</span> <span id="620">620</span> <span id="621">621</span> <span id="622">622</span> <span id="623">623</span> <span id="624">624</span> <span id="625">625</span> <span id="626">626</span> <span id="627">627</span> <span id="628">628</span> <span id="629">629</span> <span id="630">630</span> <span id="631">631</span> <span id="632">632</span> <span id="633">633</span> <span id="634">634</span> <span id="635">635</span> <span id="636">636</span> <span id="637">637</span> <span id="638">638</span> <span id="639">639</span> <span id="640">640</span> <span id="641">641</span> <span id="642">642</span> <span id="643">643</span> <span id="644">644</span> <span id="645">645</span> <span id="646">646</span> <span id="647">647</span> <span id="648">648</span> <span id="649">649</span> <span id="650">650</span> <span id="651">651</span> <span id="652">652</span> <span id="653">653</span> <span id="654">654</span> <span id="655">655</span> <span id="656">656</span> <span id="657">657</span> <span id="658">658</span> <span id="659">659</span> <span id="660">660</span> <span id="661">661</span> <span id="662">662</span> <span id="663">663</span> <span id="664">664</span> <span id="665">665</span> <span id="666">666</span> <span id="667">667</span> <span id="668">668</span> <span id="669">669</span> <span id="670">670</span> <span id="671">671</span> <span id="672">672</span> <span id="673">673</span> <span id="674">674</span> <span id="675">675</span> <span id="676">676</span> <span id="677">677</span> <span id="678">678</span> <span id="679">679</span> <span id="680">680</span> <span id="681">681</span> <span id="682">682</span> <span id="683">683</span> <span id="684">684</span> <span id="685">685</span> <span id="686">686</span> <span id="687">687</span> <span id="688">688</span> <span id="689">689</span> <span id="690">690</span> <span id="691">691</span> <span id="692">692</span> <span id="693">693</span> <span id="694">694</span> <span id="695">695</span> <span id="696">696</span> <span id="697">697</span> <span id="698">698</span> <span id="699">699</span> <span id="700">700</span> <span id="701">701</span> <span id="702">702</span> <span id="703">703</span> <span id="704">704</span> <span id="705">705</span> <span id="706">706</span> <span id="707">707</span> <span id="708">708</span> <span id="709">709</span> <span id="710">710</span> <span id="711">711</span> <span id="712">712</span> <span id="713">713</span> <span id="714">714</span> <span id="715">715</span> <span id="716">716</span> <span id="717">717</span> <span id="718">718</span> <span id="719">719</span> <span id="720">720</span> <span id="721">721</span> <span id="722">722</span> <span id="723">723</span> <span id="724">724</span> <span id="725">725</span> <span id="726">726</span> <span id="727">727</span> <span id="728">728</span> <span id="729">729</span> <span id="730">730</span> <span id="731">731</span> <span id="732">732</span> <span id="733">733</span> <span id="734">734</span> <span id="735">735</span> <span id="736">736</span> <span id="737">737</span> <span id="738">738</span> <span id="739">739</span> <span id="740">740</span> <span id="741">741</span> <span id="742">742</span> <span id="743">743</span> <span id="744">744</span> <span id="745">745</span> <span id="746">746</span> <span id="747">747</span> <span id="748">748</span> <span id="749">749</span> <span id="750">750</span> <span id="751">751</span> <span id="752">752</span> <span id="753">753</span> <span id="754">754</span> <span id="755">755</span> <span id="756">756</span> <span id="757">757</span> <span id="758">758</span> <span id="759">759</span> <span id="760">760</span> <span id="761">761</span> <span id="762">762</span> <span id="763">763</span> <span id="764">764</span> <span id="765">765</span> <span id="766">766</span> <span id="767">767</span> <span id="768">768</span> <span id="769">769</span> <span id="770">770</span> <span id="771">771</span> <span id="772">772</span> <span id="773">773</span> <span id="774">774</span> <span id="775">775</span> <span id="776">776</span> <span id="777">777</span> <span id="778">778</span> <span id="779">779</span> <span id="780">780</span> <span id="781">781</span> <span id="782">782</span> <span id="783">783</span> <span id="784">784</span> <span id="785">785</span> <span id="786">786</span> <span id="787">787</span> <span id="788">788</span> <span id="789">789</span> <span id="790">790</span> <span id="791">791</span> <span id="792">792</span> <span id="793">793</span> <span id="794">794</span> <span id="795">795</span> <span id="796">796</span> <span id="797">797</span> <span id="798">798</span> <span id="799">799</span> <span id="800">800</span> <span id="801">801</span> <span id="802">802</span> <span id="803">803</span> <span id="804">804</span> <span id="805">805</span> <span id="806">806</span> <span id="807">807</span> <span id="808">808</span> <span id="809">809</span> <span id="810">810</span> <span id="811">811</span> <span id="812">812</span> <span id="813">813</span> <span id="814">814</span> <span id="815">815</span> <span id="816">816</span> <span id="817">817</span> <span id="818">818</span> <span id="819">819</span> <span id="820">820</span> <span id="821">821</span> <span id="822">822</span> <span id="823">823</span> <span id="824">824</span> <span id="825">825</span> <span id="826">826</span> <span id="827">827</span> <span id="828">828</span> <span id="829">829</span> <span id="830">830</span> <span id="831">831</span> <span id="832">832</span> <span id="833">833</span> <span id="834">834</span> <span id="835">835</span> <span id="836">836</span> <span id="837">837</span> <span id="838">838</span> <span id="839">839</span> <span id="840">840</span> <span id="841">841</span> <span id="842">842</span> <span id="843">843</span> <span id="844">844</span> <span id="845">845</span> <span id="846">846</span> <span id="847">847</span> <span id="848">848</span> <span id="849">849</span> <span id="850">850</span> <span id="851">851</span> <span id="852">852</span> <span id="853">853</span> <span id="854">854</span> <span id="855">855</span> <span id="856">856</span> <span id="857">857</span> <span id="858">858</span> <span id="859">859</span> <span id="860">860</span> <span id="861">861</span> <span id="862">862</span> <span id="863">863</span> <span id="864">864</span> <span id="865">865</span> <span id="866">866</span> <span id="867">867</span> <span id="868">868</span> <span id="869">869</span> <span id="870">870</span> <span id="871">871</span> <span id="872">872</span> <span id="873">873</span> <span id="874">874</span> <span id="875">875</span> <span id="876">876</span> <span id="877">877</span> <span id="878">878</span> <span id="879">879</span> <span id="880">880</span> <span id="881">881</span> <span id="882">882</span> <span id="883">883</span> <span id="884">884</span> <span id="885">885</span> <span id="886">886</span> <span id="887">887</span> <span id="888">888</span> <span id="889">889</span> <span id="890">890</span> <span id="891">891</span> <span id="892">892</span> <span id="893">893</span> <span id="894">894</span> <span id="895">895</span> <span id="896">896</span> <span id="897">897</span> <span id="898">898</span> <span id="899">899</span> <span id="900">900</span> <span id="901">901</span> <span id="902">902</span> <span id="903">903</span> <span id="904">904</span> <span id="905">905</span> <span id="906">906</span> <span id="907">907</span> <span id="908">908</span> <span id="909">909</span> <span id="910">910</span> <span id="911">911</span> <span id="912">912</span> <span id="913">913</span> <span id="914">914</span> <span id="915">915</span> <span id="916">916</span> <span id="917">917</span> <span id="918">918</span> <span id="919">919</span> <span id="920">920</span> <span id="921">921</span> <span id="922">922</span> <span id="923">923</span> <span id="924">924</span> <span id="925">925</span> <span id="926">926</span> <span id="927">927</span> <span id="928">928</span> <span id="929">929</span> <span id="930">930</span> <span id="931">931</span> <span id="932">932</span> <span id="933">933</span> <span id="934">934</span> <span id="935">935</span> <span id="936">936</span> <span id="937">937</span> <span id="938">938</span> <span id="939">939</span> <span id="940">940</span> <span id="941">941</span> <span id="942">942</span> <span id="943">943</span> <span id="944">944</span> <span id="945">945</span> <span id="946">946</span> <span id="947">947</span> <span id="948">948</span> <span id="949">949</span> <span id="950">950</span> <span id="951">951</span> <span id="952">952</span> <span id="953">953</span> <span id="954">954</span> <span id="955">955</span> <span id="956">956</span> <span id="957">957</span> <span id="958">958</span> <span id="959">959</span> <span id="960">960</span> <span id="961">961</span> <span id="962">962</span> <span id="963">963</span> <span id="964">964</span> <span id="965">965</span> </pre><pre class="rust "> <span class="comment">// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT</span> <span class="comment">// file at the top-level directory of this distribution and at</span> <span class="comment">// http://rust-lang.org/COPYRIGHT.</span> <span class="comment">//</span> <span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span> <span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span> <span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span> <span class="comment">// option. This file may not be copied, modified, or distributed</span> <span class="comment">// except according to those terms.</span> <span class="doccomment">//! A dynamically-sized view into a contiguous sequence, `[T]`.</span> <span class="doccomment">//!</span> <span class="doccomment">//! Slices are a view into a block of memory represented as a pointer and a</span> <span class="doccomment">//! length.</span> <span class="doccomment">//!</span> <span class="doccomment">//! ```</span> <span class="doccomment">//! // slicing a Vec</span> <span class="doccomment">//! let vec = vec![1, 2, 3];</span> <span class="doccomment">//! let int_slice = &vec[..];</span> <span class="doccomment">//! // coercing an array to a slice</span> <span class="doccomment">//! let str_slice: &[&str] = &["one", "two", "three"];</span> <span class="doccomment">//! ```</span> <span class="doccomment">//!</span> <span class="doccomment">//! Slices are either mutable or shared. The shared slice type is `&[T]`,</span> <span class="doccomment">//! while the mutable slice type is `&mut [T]`, where `T` represents the element</span> <span class="doccomment">//! type. For example, you can mutate the block of memory that a mutable slice</span> <span class="doccomment">//! points to:</span> <span class="doccomment">//!</span> <span class="doccomment">//! ```</span> <span class="doccomment">//! let x = &mut [1, 2, 3];</span> <span class="doccomment">//! x[1] = 7;</span> <span class="doccomment">//! assert_eq!(x, &[1, 7, 3]);</span> <span class="doccomment">//! ```</span> <span class="doccomment">//!</span> <span class="doccomment">//! Here are some of the things this module contains:</span> <span class="doccomment">//!</span> <span class="doccomment">//! ## Structs</span> <span class="doccomment">//!</span> <span class="doccomment">//! There are several structs that are useful for slices, such as [`Iter`], which</span> <span class="doccomment">//! represents iteration over a slice.</span> <span class="doccomment">//!</span> <span class="doccomment">//! ## Trait Implementations</span> <span class="doccomment">//!</span> <span class="doccomment">//! There are several implementations of common traits for slices. Some examples</span> <span class="doccomment">//! include:</span> <span class="doccomment">//!</span> <span class="doccomment">//! * [`Clone`]</span> <span class="doccomment">//! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].</span> <span class="doccomment">//! * [`Hash`] - for slices whose element type is [`Hash`].</span> <span class="doccomment">//!</span> <span class="doccomment">//! ## Iteration</span> <span class="doccomment">//!</span> <span class="doccomment">//! The slices implement `IntoIterator`. The iterator yields references to the</span> <span class="doccomment">//! slice elements.</span> <span class="doccomment">//!</span> <span class="doccomment">//! ```</span> <span class="doccomment">//! let numbers = &[0, 1, 2];</span> <span class="doccomment">//! for n in numbers {</span> <span class="doccomment">//! println!("{} is a number!", n);</span> <span class="doccomment">//! }</span> <span class="doccomment">//! ```</span> <span class="doccomment">//!</span> <span class="doccomment">//! The mutable slice yields mutable references to the elements:</span> <span class="doccomment">//!</span> <span class="doccomment">//! ```</span> <span class="doccomment">//! let mut scores = [7, 8, 9];</span> <span class="doccomment">//! for score in &mut scores[..] {</span> <span class="doccomment">//! *score += 1;</span> <span class="doccomment">//! }</span> <span class="doccomment">//! ```</span> <span class="doccomment">//!</span> <span class="doccomment">//! This iterator yields mutable references to the slice's elements, so while</span> <span class="doccomment">//! the element type of the slice is `i32`, the element type of the iterator is</span> <span class="doccomment">//! `&mut i32`.</span> <span class="doccomment">//!</span> <span class="doccomment">//! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default</span> <span class="doccomment">//! iterators.</span> <span class="doccomment">//! * Further methods that return iterators are [`.split`], [`.splitn`],</span> <span class="doccomment">//! [`.chunks`], [`.windows`] and more.</span> <span class="doccomment">//!</span> <span class="doccomment">//! *[See also the slice primitive type](../../std/primitive.slice.html).*</span> <span class="doccomment">//!</span> <span class="doccomment">//! [`Clone`]: ../../std/clone/trait.Clone.html</span> <span class="doccomment">//! [`Eq`]: ../../std/cmp/trait.Eq.html</span> <span class="doccomment">//! [`Ord`]: ../../std/cmp/trait.Ord.html</span> <span class="doccomment">//! [`Iter`]: struct.Iter.html</span> <span class="doccomment">//! [`Hash`]: ../../std/hash/trait.Hash.html</span> <span class="doccomment">//! [`.iter`]: ../../std/primitive.slice.html#method.iter</span> <span class="doccomment">//! [`.iter_mut`]: ../../std/primitive.slice.html#method.iter_mut</span> <span class="doccomment">//! [`.split`]: ../../std/primitive.slice.html#method.split</span> <span class="doccomment">//! [`.splitn`]: ../../std/primitive.slice.html#method.splitn</span> <span class="doccomment">//! [`.chunks`]: ../../std/primitive.slice.html#method.chunks</span> <span class="doccomment">//! [`.windows`]: ../../std/primitive.slice.html#method.windows</span> <span class="attribute">#![<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="comment">// Many of the usings in this module are only used in the test configuration.</span> <span class="comment">// It's cleaner to just turn off the unused_imports warning than to fix them.</span> <span class="attribute">#![<span class="ident">cfg_attr</span>(<span class="ident">test</span>, <span class="ident">allow</span>(<span class="ident">unused_imports</span>, <span class="ident">dead_code</span>))]</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">cmp</span>::<span class="ident">Ordering</span>::{<span class="self">self</span>, <span class="ident">Less</span>}; <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>::<span class="ident">size_of</span>; <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>; <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ptr</span>; <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">stage0</span>)]</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::<span class="ident">SliceExt</span>; <span class="kw">use</span> <span class="ident">core</span>::{<span class="ident">u8</span>, <span class="ident">u16</span>, <span class="ident">u32</span>}; <span class="kw">use</span> <span class="ident">borrow</span>::{<span class="ident">Borrow</span>, <span class="ident">BorrowMut</span>, <span class="ident">ToOwned</span>}; <span class="kw">use</span> <span class="ident">boxed</span>::<span class="ident">Box</span>; <span class="kw">use</span> <span class="ident">vec</span>::<span class="ident">Vec</span>; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">Chunks</span>, <span class="ident">Windows</span>}; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">Iter</span>, <span class="ident">IterMut</span>}; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">SplitMut</span>, <span class="ident">ChunksMut</span>, <span class="ident">Split</span>}; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">SplitN</span>, <span class="ident">RSplitN</span>, <span class="ident">SplitNMut</span>, <span class="ident">RSplitNMut</span>}; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_rsplit"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.27.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">RSplit</span>, <span class="ident">RSplitMut</span>}; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">from_raw_parts</span>, <span class="ident">from_raw_parts_mut</span>}; <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"from_ref"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"45703"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">from_ref</span>, <span class="ident">from_ref_mut</span>}; <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_get_slice"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35729"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::<span class="ident">SliceIndex</span>; <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"exact_chunks"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"47115"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>::{<span class="ident">ExactChunks</span>, <span class="ident">ExactChunksMut</span>}; <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// Basic slice extension methods</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// HACK(japaric) needed for the implementation of `vec!` macro during testing</span> <span class="comment">// NB see the hack module in this file for more details</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">hack</span>::<span class="ident">into_vec</span>; <span class="comment">// HACK(japaric) needed for the implementation of `Vec::clone` during testing</span> <span class="comment">// NB see the hack module in this file for more details</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="self">self</span>::<span class="ident">hack</span>::<span class="ident">to_vec</span>; <span class="comment">// HACK(japaric): With cfg(test) `impl [T]` is not available, these three</span> <span class="comment">// functions are actually methods that are in `impl [T]` but not in</span> <span class="comment">// `core::slice::SliceExt` - we need to supply these functions for the</span> <span class="comment">// `test_permutations` test</span> <span class="kw">mod</span> <span class="ident">hack</span> { <span class="kw">use</span> <span class="ident">boxed</span>::<span class="ident">Box</span>; <span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>; <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span> <span class="kw">use</span> <span class="ident">string</span>::<span class="ident">ToString</span>; <span class="kw">use</span> <span class="ident">vec</span>::<span class="ident">Vec</span>; <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="kw-2">mut</span> <span class="ident">b</span>: <span class="ident">Box</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">unsafe</span> { <span class="kw">let</span> <span class="ident">xs</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">from_raw_parts</span>(<span class="ident">b</span>.<span class="ident">as_mut_ptr</span>(), <span class="ident">b</span>.<span class="ident">len</span>(), <span class="ident">b</span>.<span class="ident">len</span>()); <span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">b</span>); <span class="ident">xs</span> } } <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">s</span>: <span class="kw-2">&</span>[<span class="ident">T</span>]) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">Clone</span> { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">vector</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">s</span>.<span class="ident">len</span>()); <span class="ident">vector</span>.<span class="ident">extend_from_slice</span>(<span class="ident">s</span>); <span class="ident">vector</span> } } <span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">stage0</span>, <span class="ident">lang</span> <span class="op">=</span> <span class="string">"slice"</span>)]</span> <span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">not</span>(<span class="ident">stage0</span>), <span class="ident">lang</span> <span class="op">=</span> <span class="string">"slice_alloc"</span>)]</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> [<span class="ident">T</span>] { <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">stage0</span>)]</span> <span class="macro">slice_core_methods</span><span class="macro">!</span>(); <span class="doccomment">/// Sorts the slice.</span> <span class="doccomment">///</span> <span class="doccomment">/// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.</span> <span class="doccomment">///</span> <span class="doccomment">/// When applicable, unstable sorting is preferred because it is generally faster than stable</span> <span class="doccomment">/// sorting and it doesn't allocate auxiliary memory.</span> <span class="doccomment">/// See [`sort_unstable`](#method.sort_unstable).</span> <span class="doccomment">///</span> <span class="doccomment">/// # Current implementation</span> <span class="doccomment">///</span> <span class="doccomment">/// The current algorithm is an adaptive, iterative merge sort inspired by</span> <span class="doccomment">/// [timsort](https://en.wikipedia.org/wiki/Timsort).</span> <span class="doccomment">/// It is designed to be very fast in cases where the slice is nearly sorted, or consists of</span> <span class="doccomment">/// two or more sorted sequences concatenated one after another.</span> <span class="doccomment">///</span> <span class="doccomment">/// Also, it allocates temporary storage half the size of `self`, but for short slices a</span> <span class="doccomment">/// non-allocating insertion sort is used instead.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let mut v = [-5, 4, 1, -3, 2];</span> <span class="doccomment">///</span> <span class="doccomment">/// v.sort();</span> <span class="doccomment">/// assert!(v == [-5, -3, 1, 2, 4]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">sort</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">Ord</span> { <span class="ident">merge_sort</span>(<span class="self">self</span>, <span class="op">|</span><span class="ident">a</span>, <span class="ident">b</span><span class="op">|</span> <span class="ident">a</span>.<span class="ident">lt</span>(<span class="ident">b</span>)); } <span class="doccomment">/// Sorts the slice with a comparator function.</span> <span class="doccomment">///</span> <span class="doccomment">/// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.</span> <span class="doccomment">///</span> <span class="doccomment">/// When applicable, unstable sorting is preferred because it is generally faster than stable</span> <span class="doccomment">/// sorting and it doesn't allocate auxiliary memory.</span> <span class="doccomment">/// See [`sort_unstable_by`](#method.sort_unstable_by).</span> <span class="doccomment">///</span> <span class="doccomment">/// # Current implementation</span> <span class="doccomment">///</span> <span class="doccomment">/// The current algorithm is an adaptive, iterative merge sort inspired by</span> <span class="doccomment">/// [timsort](https://en.wikipedia.org/wiki/Timsort).</span> <span class="doccomment">/// It is designed to be very fast in cases where the slice is nearly sorted, or consists of</span> <span class="doccomment">/// two or more sorted sequences concatenated one after another.</span> <span class="doccomment">///</span> <span class="doccomment">/// Also, it allocates temporary storage half the size of `self`, but for short slices a</span> <span class="doccomment">/// non-allocating insertion sort is used instead.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let mut v = [5, 4, 1, 3, 2];</span> <span class="doccomment">/// v.sort_by(|a, b| a.cmp(b));</span> <span class="doccomment">/// assert!(v == [1, 2, 3, 4, 5]);</span> <span class="doccomment">///</span> <span class="doccomment">/// // reverse sorting</span> <span class="doccomment">/// v.sort_by(|a, b| b.cmp(a));</span> <span class="doccomment">/// assert!(v == [5, 4, 3, 2, 1]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">sort_by</span><span class="op"><</span><span class="ident">F</span><span class="op">></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">compare</span>: <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>, <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">Ordering</span> { <span class="ident">merge_sort</span>(<span class="self">self</span>, <span class="op">|</span><span class="ident">a</span>, <span class="ident">b</span><span class="op">|</span> <span class="ident">compare</span>(<span class="ident">a</span>, <span class="ident">b</span>) <span class="op">==</span> <span class="ident">Less</span>); } <span class="doccomment">/// Sorts the slice with a key extraction function.</span> <span class="doccomment">///</span> <span class="doccomment">/// This sort is stable (i.e. does not reorder equal elements) and `O(m n log(m n))`</span> <span class="doccomment">/// worst-case, where the key function is `O(m)`.</span> <span class="doccomment">///</span> <span class="doccomment">/// When applicable, unstable sorting is preferred because it is generally faster than stable</span> <span class="doccomment">/// sorting and it doesn't allocate auxiliary memory.</span> <span class="doccomment">/// See [`sort_unstable_by_key`](#method.sort_unstable_by_key).</span> <span class="doccomment">///</span> <span class="doccomment">/// # Current implementation</span> <span class="doccomment">///</span> <span class="doccomment">/// The current algorithm is an adaptive, iterative merge sort inspired by</span> <span class="doccomment">/// [timsort](https://en.wikipedia.org/wiki/Timsort).</span> <span class="doccomment">/// It is designed to be very fast in cases where the slice is nearly sorted, or consists of</span> <span class="doccomment">/// two or more sorted sequences concatenated one after another.</span> <span class="doccomment">///</span> <span class="doccomment">/// Also, it allocates temporary storage half the size of `self`, but for short slices a</span> <span class="doccomment">/// non-allocating insertion sort is used instead.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let mut v = [-5i32, 4, 1, -3, 2];</span> <span class="doccomment">///</span> <span class="doccomment">/// v.sort_by_key(|k| k.abs());</span> <span class="doccomment">/// assert!(v == [1, 2, -3, 4, -5]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_sort_by_key"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.7.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">sort_by_key</span><span class="op"><</span><span class="ident">K</span>, <span class="ident">F</span><span class="op">></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">f</span>: <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">K</span>, <span class="ident">K</span>: <span class="ident">Ord</span> { <span class="ident">merge_sort</span>(<span class="self">self</span>, <span class="op">|</span><span class="ident">a</span>, <span class="ident">b</span><span class="op">|</span> <span class="ident">f</span>(<span class="ident">a</span>).<span class="ident">lt</span>(<span class="kw-2">&</span><span class="ident">f</span>(<span class="ident">b</span>))); } <span class="doccomment">/// Sorts the slice with a key extraction function.</span> <span class="doccomment">///</span> <span class="doccomment">/// During sorting, the key function is called only once per element.</span> <span class="doccomment">///</span> <span class="doccomment">/// This sort is stable (i.e. does not reorder equal elements) and `O(m n + n log n)`</span> <span class="doccomment">/// worst-case, where the key function is `O(m)`.</span> <span class="doccomment">///</span> <span class="doccomment">/// For simple key functions (e.g. functions that are property accesses or</span> <span class="doccomment">/// basic operations), [`sort_by_key`](#method.sort_by_key) is likely to be</span> <span class="doccomment">/// faster.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Current implementation</span> <span class="doccomment">///</span> <span class="doccomment">/// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters,</span> <span class="doccomment">/// which combines the fast average case of randomized quicksort with the fast worst case of</span> <span class="doccomment">/// heapsort, while achieving linear time on slices with certain patterns. It uses some</span> <span class="doccomment">/// randomization to avoid degenerate cases, but with a fixed seed to always provide</span> <span class="doccomment">/// deterministic behavior.</span> <span class="doccomment">///</span> <span class="doccomment">/// In the worst case, the algorithm allocates temporary storage in a `Vec<(K, usize)>` the</span> <span class="doccomment">/// length of the slice.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// #![feature(slice_sort_by_cached_key)]</span> <span class="doccomment">/// let mut v = [-5i32, 4, 32, -3, 2];</span> <span class="doccomment">///</span> <span class="doccomment">/// v.sort_by_cached_key(|k| k.to_string());</span> <span class="doccomment">/// assert!(v == [-3, -5, 2, 32, 4]);</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// [pdqsort]: https://github.com/orlp/pdqsort</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_sort_by_cached_key"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"34447"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">sort_by_cached_key</span><span class="op"><</span><span class="ident">K</span>, <span class="ident">F</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">K</span>, <span class="ident">K</span>: <span class="ident">Ord</span> { <span class="comment">// Helper macro for indexing our vector by the smallest possible type, to reduce allocation.</span> <span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">sort_by_key</span> { (<span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">slice</span>:<span class="ident">ident</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">f</span>:<span class="ident">ident</span>) <span class="op">=></span> ({ <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">indices</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw">_</span><span class="op">></span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">slice</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">f</span>).<span class="ident">enumerate</span>().<span class="ident">map</span>(<span class="op">|</span>(<span class="ident">i</span>, <span class="ident">k</span>)<span class="op">|</span> (<span class="ident">k</span>, <span class="ident">i</span> <span class="kw">as</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>)).<span class="ident">collect</span>(); <span class="comment">// The elements of `indices` are unique, as they are indexed, so any sort will be</span> <span class="comment">// stable with respect to the original slice. We use `sort_unstable` here because</span> <span class="comment">// it requires less memory allocation.</span> <span class="ident">indices</span>.<span class="ident">sort_unstable</span>(); <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="macro-nonterminal">$</span><span class="macro-nonterminal">slice</span>.<span class="ident">len</span>() { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">index</span> <span class="op">=</span> <span class="ident">indices</span>[<span class="ident">i</span>].<span class="number">1</span>; <span class="kw">while</span> (<span class="ident">index</span> <span class="kw">as</span> <span class="ident">usize</span>) <span class="op"><</span> <span class="ident">i</span> { <span class="ident">index</span> <span class="op">=</span> <span class="ident">indices</span>[<span class="ident">index</span> <span class="kw">as</span> <span class="ident">usize</span>].<span class="number">1</span>; } <span class="ident">indices</span>[<span class="ident">i</span>].<span class="number">1</span> <span class="op">=</span> <span class="ident">index</span>; <span class="macro-nonterminal">$</span><span class="macro-nonterminal">slice</span>.<span class="ident">swap</span>(<span class="ident">i</span>, <span class="ident">index</span> <span class="kw">as</span> <span class="ident">usize</span>); } }) } <span class="kw">let</span> <span class="ident">sz_u8</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span>(<span class="ident">K</span>, <span class="ident">u8</span>)<span class="op">></span>(); <span class="kw">let</span> <span class="ident">sz_u16</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span>(<span class="ident">K</span>, <span class="ident">u16</span>)<span class="op">></span>(); <span class="kw">let</span> <span class="ident">sz_u32</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span>(<span class="ident">K</span>, <span class="ident">u32</span>)<span class="op">></span>(); <span class="kw">let</span> <span class="ident">sz_usize</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span>(<span class="ident">K</span>, <span class="ident">usize</span>)<span class="op">></span>(); <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">len</span>(); <span class="kw">if</span> <span class="ident">len</span> <span class="op"><</span> <span class="number">2</span> { <span class="kw">return</span> } <span class="kw">if</span> <span class="ident">sz_u8</span> <span class="op"><</span> <span class="ident">sz_u16</span> <span class="op">&&</span> <span class="ident">len</span> <span class="op"><=</span> ( <span class="ident">u8</span>::<span class="ident">MAX</span> <span class="kw">as</span> <span class="ident">usize</span>) { <span class="kw">return</span> <span class="macro">sort_by_key</span><span class="macro">!</span>( <span class="ident">u8</span>, <span class="self">self</span>, <span class="ident">f</span>) } <span class="kw">if</span> <span class="ident">sz_u16</span> <span class="op"><</span> <span class="ident">sz_u32</span> <span class="op">&&</span> <span class="ident">len</span> <span class="op"><=</span> (<span class="ident">u16</span>::<span class="ident">MAX</span> <span class="kw">as</span> <span class="ident">usize</span>) { <span class="kw">return</span> <span class="macro">sort_by_key</span><span class="macro">!</span>(<span class="ident">u16</span>, <span class="self">self</span>, <span class="ident">f</span>) } <span class="kw">if</span> <span class="ident">sz_u32</span> <span class="op"><</span> <span class="ident">sz_usize</span> <span class="op">&&</span> <span class="ident">len</span> <span class="op"><=</span> (<span class="ident">u32</span>::<span class="ident">MAX</span> <span class="kw">as</span> <span class="ident">usize</span>) { <span class="kw">return</span> <span class="macro">sort_by_key</span><span class="macro">!</span>(<span class="ident">u32</span>, <span class="self">self</span>, <span class="ident">f</span>) } <span class="macro">sort_by_key</span><span class="macro">!</span>(<span class="ident">usize</span>, <span class="self">self</span>, <span class="ident">f</span>) } <span class="doccomment">/// Copies `self` into a new `Vec`.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let s = [10, 40, 30];</span> <span class="doccomment">/// let x = s.to_vec();</span> <span class="doccomment">/// // Here, `s` and `x` can be modified independently.</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">rustc_conversion_suggestion</span>]</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_vec</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">Clone</span> { <span class="comment">// NB see hack module in this file</span> <span class="ident">hack</span>::<span class="ident">to_vec</span>(<span class="self">self</span>) } <span class="doccomment">/// Converts `self` into a vector without clones or allocation.</span> <span class="doccomment">///</span> <span class="doccomment">/// The resulting vector can be converted back into a box via</span> <span class="doccomment">/// `Vec<T>`'s `into_boxed_slice` method.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let s: Box<[i32]> = Box::new([10, 40, 30]);</span> <span class="doccomment">/// let x = s.into_vec();</span> <span class="doccomment">/// // `s` cannot be used anymore because it has been converted into `x`.</span> <span class="doccomment">///</span> <span class="doccomment">/// assert_eq!(x, vec![10, 40, 30]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_vec</span>(<span class="self">self</span>: <span class="ident">Box</span><span class="op"><</span><span class="self">Self</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="comment">// NB see hack module in this file</span> <span class="ident">hack</span>::<span class="ident">into_vec</span>(<span class="self">self</span>) } <span class="doccomment">/// Creates a vector by repeating a slice `n` times.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// Basic usage:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// #![feature(repeat_generic_slice)]</span> <span class="doccomment">///</span> <span class="doccomment">/// fn main() {</span> <span class="doccomment">/// assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);</span> <span class="doccomment">/// }</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"repeat_generic_slice"</span>, <span class="ident">reason</span> <span class="op">=</span> <span class="string">"it's on str, why not on slice?"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"48784"</span>)]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">repeat</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">n</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">Copy</span> { <span class="kw">if</span> <span class="ident">n</span> <span class="op">==</span> <span class="number">0</span> { <span class="kw">return</span> <span class="ident">Vec</span>::<span class="ident">new</span>(); } <span class="comment">// If `n` is larger than zero, it can be split as</span> <span class="comment">// `n = 2^expn + rem (2^expn > rem, expn >= 0, rem >= 0)`.</span> <span class="comment">// `2^expn` is the number represented by the leftmost '1' bit of `n`,</span> <span class="comment">// and `rem` is the remaining part of `n`.</span> <span class="comment">// Using `Vec` to access `set_len()`.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="self">self</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">n</span>); <span class="comment">// `2^expn` repetition is done by doubling `buf` `expn`-times.</span> <span class="ident">buf</span>.<span class="ident">extend</span>(<span class="self">self</span>); { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">m</span> <span class="op">=</span> <span class="ident">n</span> <span class="op">>></span> <span class="number">1</span>; <span class="comment">// If `m > 0`, there are remaining bits up to the leftmost '1'.</span> <span class="kw">while</span> <span class="ident">m</span> <span class="op">></span> <span class="number">0</span> { <span class="comment">// `buf.extend(buf)`:</span> <span class="kw">unsafe</span> { <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>( <span class="ident">buf</span>.<span class="ident">as_ptr</span>(), (<span class="ident">buf</span>.<span class="ident">as_mut_ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>).<span class="ident">add</span>(<span class="ident">buf</span>.<span class="ident">len</span>()), <span class="ident">buf</span>.<span class="ident">len</span>(), ); <span class="comment">// `buf` has capacity of `self.len() * n`.</span> <span class="kw">let</span> <span class="ident">buf_len</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">len</span>(); <span class="ident">buf</span>.<span class="ident">set_len</span>(<span class="ident">buf_len</span> <span class="op">*</span> <span class="number">2</span>); } <span class="ident">m</span> <span class="op">>>=</span> <span class="number">1</span>; } } <span class="comment">// `rem` (`= n - 2^expn`) repetition is done by copying</span> <span class="comment">// first `rem` repetitions from `buf` itself.</span> <span class="kw">let</span> <span class="ident">rem_len</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">len</span>() <span class="op">*</span> <span class="ident">n</span> <span class="op">-</span> <span class="ident">buf</span>.<span class="ident">len</span>(); <span class="comment">// `self.len() * rem`</span> <span class="kw">if</span> <span class="ident">rem_len</span> <span class="op">></span> <span class="number">0</span> { <span class="comment">// `buf.extend(buf[0 .. rem_len])`:</span> <span class="kw">unsafe</span> { <span class="comment">// This is non-overlapping since `2^expn > rem`.</span> <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>( <span class="ident">buf</span>.<span class="ident">as_ptr</span>(), (<span class="ident">buf</span>.<span class="ident">as_mut_ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>).<span class="ident">add</span>(<span class="ident">buf</span>.<span class="ident">len</span>()), <span class="ident">rem_len</span>, ); <span class="comment">// `buf.len() + rem_len` equals to `buf.capacity()` (`= self.len() * n`).</span> <span class="kw">let</span> <span class="ident">buf_cap</span> <span class="op">=</span> <span class="ident">buf</span>.<span class="ident">capacity</span>(); <span class="ident">buf</span>.<span class="ident">set_len</span>(<span class="ident">buf_cap</span>); } } <span class="ident">buf</span> } } <span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">stage0</span>, <span class="ident">lang</span> <span class="op">=</span> <span class="string">"slice_u8"</span>)]</span> <span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">not</span>(<span class="ident">stage0</span>), <span class="ident">lang</span> <span class="op">=</span> <span class="string">"slice_u8_alloc"</span>)]</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span> <span class="kw">impl</span> [<span class="ident">u8</span>] { <span class="doccomment">/// Returns a vector containing a copy of this slice where each byte</span> <span class="doccomment">/// is mapped to its ASCII upper case equivalent.</span> <span class="doccomment">///</span> <span class="doccomment">/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',</span> <span class="doccomment">/// but non-ASCII letters are unchanged.</span> <span class="doccomment">///</span> <span class="doccomment">/// To uppercase the value in-place, use [`make_ascii_uppercase`].</span> <span class="doccomment">///</span> <span class="doccomment">/// [`make_ascii_uppercase`]: #method.make_ascii_uppercase</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"ascii_methods_on_intrinsics"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.23.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_ascii_uppercase</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">me</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">to_vec</span>(); <span class="ident">me</span>.<span class="ident">make_ascii_uppercase</span>(); <span class="ident">me</span> } <span class="doccomment">/// Returns a vector containing a copy of this slice where each byte</span> <span class="doccomment">/// is mapped to its ASCII lower case equivalent.</span> <span class="doccomment">///</span> <span class="doccomment">/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',</span> <span class="doccomment">/// but non-ASCII letters are unchanged.</span> <span class="doccomment">///</span> <span class="doccomment">/// To lowercase the value in-place, use [`make_ascii_lowercase`].</span> <span class="doccomment">///</span> <span class="doccomment">/// [`make_ascii_lowercase`]: #method.make_ascii_lowercase</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"ascii_methods_on_intrinsics"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.23.0"</span>)]</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_ascii_lowercase</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> { <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">me</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">to_vec</span>(); <span class="ident">me</span>.<span class="ident">make_ascii_lowercase</span>(); <span class="ident">me</span> } <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">stage0</span>)]</span> <span class="macro">slice_u8_core_methods</span><span class="macro">!</span>(); } <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// Extension traits for slices over specific kinds of data</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_concat_ext"</span>, <span class="ident">reason</span> <span class="op">=</span> <span class="string">"trait should not have to exist"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27747"</span>)]</span> <span class="doccomment">/// An extension trait for concatenating slices</span> <span class="doccomment">///</span> <span class="doccomment">/// While this trait is unstable, the methods are stable. `SliceConcatExt` is</span> <span class="doccomment">/// included in the [standard library prelude], so you can use [`join()`] and</span> <span class="doccomment">/// [`concat()`] as if they existed on `[T]` itself.</span> <span class="doccomment">///</span> <span class="doccomment">/// [standard library prelude]: ../../std/prelude/index.html</span> <span class="doccomment">/// [`join()`]: #tymethod.join</span> <span class="doccomment">/// [`concat()`]: #tymethod.concat</span> <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">SliceConcatExt</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> { <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_concat_ext"</span>, <span class="ident">reason</span> <span class="op">=</span> <span class="string">"trait should not have to exist"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27747"</span>)]</span> <span class="doccomment">/// The resulting type after concatenation</span> <span class="kw">type</span> <span class="ident">Output</span>; <span class="doccomment">/// Flattens a slice of `T` into a single value `Self::Output`.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// assert_eq!(["hello", "world"].concat(), "helloworld");</span> <span class="doccomment">/// assert_eq!([[1, 2], [3, 4]].concat(), [1, 2, 3, 4]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">fn</span> <span class="ident">concat</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span>; <span class="doccomment">/// Flattens a slice of `T` into a single value `Self::Output`, placing a</span> <span class="doccomment">/// given separator between each.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// assert_eq!(["hello", "world"].join(" "), "hello world");</span> <span class="doccomment">/// assert_eq!([[1, 2], [3, 4]].join(&0), [1, 2, 0, 3, 4]);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rename_connect_to_join"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.3.0"</span>)]</span> <span class="kw">fn</span> <span class="ident">join</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">sep</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span>; <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="attribute">#[<span class="ident">rustc_deprecated</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.3.0"</span>, <span class="ident">reason</span> <span class="op">=</span> <span class="string">"renamed to join"</span>)]</span> <span class="kw">fn</span> <span class="ident">connect</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">sep</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span>::<span class="ident">Output</span>; } <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"slice_concat_ext"</span>, <span class="ident">reason</span> <span class="op">=</span> <span class="string">"trait should not have to exist"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27747"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Clone</span>, <span class="ident">V</span>: <span class="ident">Borrow</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">>></span> <span class="ident">SliceConcatExt</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> [<span class="ident">V</span>] { <span class="kw">type</span> <span class="ident">Output</span> <span class="op">=</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>; <span class="kw">fn</span> <span class="ident">concat</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">iter</span>().<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">v</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">v</span>.<span class="ident">borrow</span>().<span class="ident">len</span>()); <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">size</span>); <span class="kw">for</span> <span class="ident">v</span> <span class="kw">in</span> <span class="self">self</span> { <span class="ident">result</span>.<span class="ident">extend_from_slice</span>(<span class="ident">v</span>.<span class="ident">borrow</span>()) } <span class="ident">result</span> } <span class="kw">fn</span> <span class="ident">join</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">sep</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">iter</span>().<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">v</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">v</span>.<span class="ident">borrow</span>().<span class="ident">len</span>()); <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">size</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">len</span>()); <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">true</span>; <span class="kw">for</span> <span class="ident">v</span> <span class="kw">in</span> <span class="self">self</span> { <span class="kw">if</span> <span class="ident">first</span> { <span class="ident">first</span> <span class="op">=</span> <span class="bool-val">false</span> } <span class="kw">else</span> { <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">sep</span>.<span class="ident">clone</span>()) } <span class="ident">result</span>.<span class="ident">extend_from_slice</span>(<span class="ident">v</span>.<span class="ident">borrow</span>()) } <span class="ident">result</span> } <span class="kw">fn</span> <span class="ident">connect</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">sep</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">join</span>(<span class="ident">sep</span>) } } <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// Standard trait implementations for slices</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Borrow</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> <span class="kw">for</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">borrow</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span>[<span class="ident">T</span>] { <span class="kw-2">&</span><span class="self">self</span>[..] } } <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">BorrowMut</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> <span class="kw">for</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">borrow_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">T</span>] { <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>[..] } } <span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="ident">ToOwned</span> <span class="kw">for</span> [<span class="ident">T</span>] { <span class="kw">type</span> <span class="ident">Owned</span> <span class="op">=</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>; <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span> <span class="kw">fn</span> <span class="ident">to_owned</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">to_vec</span>() } <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span> <span class="kw">fn</span> <span class="ident">to_owned</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="ident">hack</span>::<span class="ident">to_vec</span>(<span class="self">self</span>) } <span class="kw">fn</span> <span class="ident">clone_into</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">target</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) { <span class="comment">// drop anything in target that will not be overwritten</span> <span class="ident">target</span>.<span class="ident">truncate</span>(<span class="self">self</span>.<span class="ident">len</span>()); <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">target</span>.<span class="ident">len</span>(); <span class="comment">// reuse the contained values' allocations/resources.</span> <span class="ident">target</span>.<span class="ident">clone_from_slice</span>(<span class="kw-2">&</span><span class="self">self</span>[..<span class="ident">len</span>]); <span class="comment">// target.len <= self.len due to the truncate above, so the</span> <span class="comment">// slice here is always in-bounds.</span> <span class="ident">target</span>.<span class="ident">extend_from_slice</span>(<span class="kw-2">&</span><span class="self">self</span>[<span class="ident">len</span>..]); } } <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// Sorting</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="doccomment">/// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted.</span> <span class="doccomment">///</span> <span class="doccomment">/// This is the integral subroutine of insertion sort.</span> <span class="kw">fn</span> <span class="ident">insert_head</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span>(<span class="ident">v</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">T</span>], <span class="ident">is_less</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>, <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">bool</span> { <span class="kw">if</span> <span class="ident">v</span>.<span class="ident">len</span>() <span class="op">>=</span> <span class="number">2</span> <span class="op">&&</span> <span class="ident">is_less</span>(<span class="kw-2">&</span><span class="ident">v</span>[<span class="number">1</span>], <span class="kw-2">&</span><span class="ident">v</span>[<span class="number">0</span>]) { <span class="kw">unsafe</span> { <span class="comment">// There are three ways to implement insertion here:</span> <span class="comment">//</span> <span class="comment">// 1. Swap adjacent elements until the first one gets to its final destination.</span> <span class="comment">// However, this way we copy data around more than is necessary. If elements are big</span> <span class="comment">// structures (costly to copy), this method will be slow.</span> <span class="comment">//</span> <span class="comment">// 2. Iterate until the right place for the first element is found. Then shift the</span> <span class="comment">// elements succeeding it to make room for it and finally place it into the</span> <span class="comment">// remaining hole. This is a good method.</span> <span class="comment">//</span> <span class="comment">// 3. Copy the first element into a temporary variable. Iterate until the right place</span> <span class="comment">// for it is found. As we go along, copy every traversed element into the slot</span> <span class="comment">// preceding it. Finally, copy data from the temporary variable into the remaining</span> <span class="comment">// hole. This method is very good. Benchmarks demonstrated slightly better</span> <span class="comment">// performance than with the 2nd method.</span> <span class="comment">//</span> <span class="comment">// All methods were benchmarked, and the 3rd showed best results. So we chose that one.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">tmp</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">ManuallyDrop</span>::<span class="ident">new</span>(<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="kw-2">&</span><span class="ident">v</span>[<span class="number">0</span>])); <span class="comment">// Intermediate state of the insertion process is always tracked by `hole`, which</span> <span class="comment">// serves two purposes:</span> <span class="comment">// 1. Protects integrity of `v` from panics in `is_less`.</span> <span class="comment">// 2. Fills the remaining hole in `v` in the end.</span> <span class="comment">//</span> <span class="comment">// Panic safety:</span> <span class="comment">//</span> <span class="comment">// If `is_less` panics at any point during the process, `hole` will get dropped and</span> <span class="comment">// fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it</span> <span class="comment">// initially held exactly once.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">hole</span> <span class="op">=</span> <span class="ident">InsertionHole</span> { <span class="ident">src</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">tmp</span>, <span class="ident">dest</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="number">1</span>], }; <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="kw-2">&</span><span class="ident">v</span>[<span class="number">1</span>], <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="number">0</span>], <span class="number">1</span>); <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">2</span>..<span class="ident">v</span>.<span class="ident">len</span>() { <span class="kw">if</span> <span class="op">!</span><span class="ident">is_less</span>(<span class="kw-2">&</span><span class="ident">v</span>[<span class="ident">i</span>], <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">tmp</span>) { <span class="kw">break</span>; } <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="kw-2">&</span><span class="ident">v</span>[<span class="ident">i</span>], <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="ident">i</span> <span class="op">-</span> <span class="number">1</span>], <span class="number">1</span>); <span class="ident">hole</span>.<span class="ident">dest</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="ident">i</span>]; } <span class="comment">// `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`.</span> } } <span class="comment">// When dropped, copies from `src` into `dest`.</span> <span class="kw">struct</span> <span class="ident">InsertionHole</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="ident">src</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">dest</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, } <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">InsertionHole</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) { <span class="kw">unsafe</span> { <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="self">self</span>.<span class="ident">src</span>, <span class="self">self</span>.<span class="ident">dest</span>, <span class="number">1</span>); } } } } <span class="doccomment">/// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and</span> <span class="doccomment">/// stores the result into `v[..]`.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Safety</span> <span class="doccomment">///</span> <span class="doccomment">/// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough</span> <span class="doccomment">/// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type.</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">merge</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span>(<span class="ident">v</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">T</span>], <span class="ident">mid</span>: <span class="ident">usize</span>, <span class="ident">buf</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">is_less</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>, <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">bool</span> { <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">len</span>(); <span class="kw">let</span> <span class="ident">v</span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">as_mut_ptr</span>(); <span class="kw">let</span> <span class="ident">v_mid</span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">offset</span>(<span class="ident">mid</span> <span class="kw">as</span> <span class="ident">isize</span>); <span class="kw">let</span> <span class="ident">v_end</span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">offset</span>(<span class="ident">len</span> <span class="kw">as</span> <span class="ident">isize</span>); <span class="comment">// The merge process first copies the shorter run into `buf`. Then it traces the newly copied</span> <span class="comment">// run and the longer run forwards (or backwards), comparing their next unconsumed elements and</span> <span class="comment">// copying the lesser (or greater) one into `v`.</span> <span class="comment">//</span> <span class="comment">// As soon as the shorter run is fully consumed, the process is done. If the longer run gets</span> <span class="comment">// consumed first, then we must copy whatever is left of the shorter run into the remaining</span> <span class="comment">// hole in `v`.</span> <span class="comment">//</span> <span class="comment">// Intermediate state of the process is always tracked by `hole`, which serves two purposes:</span> <span class="comment">// 1. Protects integrity of `v` from panics in `is_less`.</span> <span class="comment">// 2. Fills the remaining hole in `v` if the longer run gets consumed first.</span> <span class="comment">//</span> <span class="comment">// Panic safety:</span> <span class="comment">//</span> <span class="comment">// If `is_less` panics at any point during the process, `hole` will get dropped and fill the</span> <span class="comment">// hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every</span> <span class="comment">// object it initially held exactly once.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">hole</span>; <span class="kw">if</span> <span class="ident">mid</span> <span class="op"><=</span> <span class="ident">len</span> <span class="op">-</span> <span class="ident">mid</span> { <span class="comment">// The left run is shorter.</span> <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="ident">v</span>, <span class="ident">buf</span>, <span class="ident">mid</span>); <span class="ident">hole</span> <span class="op">=</span> <span class="ident">MergeHole</span> { <span class="ident">start</span>: <span class="ident">buf</span>, <span class="ident">end</span>: <span class="ident">buf</span>.<span class="ident">offset</span>(<span class="ident">mid</span> <span class="kw">as</span> <span class="ident">isize</span>), <span class="ident">dest</span>: <span class="ident">v</span>, }; <span class="comment">// Initially, these pointers point to the beginnings of their arrays.</span> <span class="kw">let</span> <span class="ident">left</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">hole</span>.<span class="ident">start</span>; <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">right</span> <span class="op">=</span> <span class="ident">v_mid</span>; <span class="kw">let</span> <span class="ident">out</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">hole</span>.<span class="ident">dest</span>; <span class="kw">while</span> <span class="kw-2">*</span><span class="ident">left</span> <span class="op"><</span> <span class="ident">hole</span>.<span class="ident">end</span> <span class="op">&&</span> <span class="ident">right</span> <span class="op"><</span> <span class="ident">v_end</span> { <span class="comment">// Consume the lesser side.</span> <span class="comment">// If equal, prefer the left run to maintain stability.</span> <span class="kw">let</span> <span class="ident">to_copy</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">is_less</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">right</span>, <span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">left</span>) { <span class="ident">get_and_increment</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">right</span>) } <span class="kw">else</span> { <span class="ident">get_and_increment</span>(<span class="ident">left</span>) }; <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="ident">to_copy</span>, <span class="ident">get_and_increment</span>(<span class="ident">out</span>), <span class="number">1</span>); } } <span class="kw">else</span> { <span class="comment">// The right run is shorter.</span> <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="ident">v_mid</span>, <span class="ident">buf</span>, <span class="ident">len</span> <span class="op">-</span> <span class="ident">mid</span>); <span class="ident">hole</span> <span class="op">=</span> <span class="ident">MergeHole</span> { <span class="ident">start</span>: <span class="ident">buf</span>, <span class="ident">end</span>: <span class="ident">buf</span>.<span class="ident">offset</span>((<span class="ident">len</span> <span class="op">-</span> <span class="ident">mid</span>) <span class="kw">as</span> <span class="ident">isize</span>), <span class="ident">dest</span>: <span class="ident">v_mid</span>, }; <span class="comment">// Initially, these pointers point past the ends of their arrays.</span> <span class="kw">let</span> <span class="ident">left</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">hole</span>.<span class="ident">dest</span>; <span class="kw">let</span> <span class="ident">right</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">hole</span>.<span class="ident">end</span>; <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">out</span> <span class="op">=</span> <span class="ident">v_end</span>; <span class="kw">while</span> <span class="ident">v</span> <span class="op"><</span> <span class="kw-2">*</span><span class="ident">left</span> <span class="op">&&</span> <span class="ident">buf</span> <span class="op"><</span> <span class="kw-2">*</span><span class="ident">right</span> { <span class="comment">// Consume the greater side.</span> <span class="comment">// If equal, prefer the right run to maintain stability.</span> <span class="kw">let</span> <span class="ident">to_copy</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">is_less</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">right</span>.<span class="ident">offset</span>(<span class="op">-</span><span class="number">1</span>), <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">left</span>.<span class="ident">offset</span>(<span class="op">-</span><span class="number">1</span>)) { <span class="ident">decrement_and_get</span>(<span class="ident">left</span>) } <span class="kw">else</span> { <span class="ident">decrement_and_get</span>(<span class="ident">right</span>) }; <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="ident">to_copy</span>, <span class="ident">decrement_and_get</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">out</span>), <span class="number">1</span>); } } <span class="comment">// Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of</span> <span class="comment">// it will now be copied into the hole in `v`.</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">get_and_increment</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">ptr</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> { <span class="kw">let</span> <span class="ident">old</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">ptr</span>; <span class="kw-2">*</span><span class="ident">ptr</span> <span class="op">=</span> <span class="ident">ptr</span>.<span class="ident">offset</span>(<span class="number">1</span>); <span class="ident">old</span> } <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">decrement_and_get</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">ptr</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> { <span class="kw-2">*</span><span class="ident">ptr</span> <span class="op">=</span> <span class="ident">ptr</span>.<span class="ident">offset</span>(<span class="op">-</span><span class="number">1</span>); <span class="kw-2">*</span><span class="ident">ptr</span> } <span class="comment">// When dropped, copies the range `start..end` into `dest..`.</span> <span class="kw">struct</span> <span class="ident">MergeHole</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="ident">start</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">end</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">dest</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, } <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">MergeHole</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) { <span class="comment">// `T` is not a zero-sized type, so it's okay to divide by its size.</span> <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> (<span class="self">self</span>.<span class="ident">end</span> <span class="kw">as</span> <span class="ident">usize</span> <span class="op">-</span> <span class="self">self</span>.<span class="ident">start</span> <span class="kw">as</span> <span class="ident">usize</span>) <span class="op">/</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>(); <span class="kw">unsafe</span> { <span class="ident">ptr</span>::<span class="ident">copy_nonoverlapping</span>(<span class="self">self</span>.<span class="ident">start</span>, <span class="self">self</span>.<span class="ident">dest</span>, <span class="ident">len</span>); } } } } <span class="doccomment">/// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail</span> <span class="doccomment">/// [here](http://svn.python.org/projects/python/trunk/Objects/listsort.txt).</span> <span class="doccomment">///</span> <span class="doccomment">/// The algorithm identifies strictly descending and non-descending subsequences, which are called</span> <span class="doccomment">/// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed</span> <span class="doccomment">/// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are</span> <span class="doccomment">/// satisfied:</span> <span class="doccomment">///</span> <span class="doccomment">/// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`</span> <span class="doccomment">/// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`</span> <span class="doccomment">///</span> <span class="doccomment">/// The invariants ensure that the total running time is `O(n log n)` worst-case.</span> <span class="kw">fn</span> <span class="ident">merge_sort</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">F</span><span class="op">></span>(<span class="ident">v</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">T</span>], <span class="kw-2">mut</span> <span class="ident">is_less</span>: <span class="ident">F</span>) <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnMut</span>(<span class="kw-2">&</span><span class="ident">T</span>, <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">bool</span> { <span class="comment">// Slices of up to this length get sorted using insertion sort.</span> <span class="kw">const</span> <span class="ident">MAX_INSERTION</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">20</span>; <span class="comment">// Very short runs are extended using insertion sort to span at least this many elements.</span> <span class="kw">const</span> <span class="ident">MIN_RUN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">10</span>; <span class="comment">// Sorting has no meaningful behavior on zero-sized types.</span> <span class="kw">if</span> <span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">==</span> <span class="number">0</span> { <span class="kw">return</span>; } <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">v</span>.<span class="ident">len</span>(); <span class="comment">// Short arrays get sorted in-place via insertion sort to avoid allocations.</span> <span class="kw">if</span> <span class="ident">len</span> <span class="op"><=</span> <span class="ident">MAX_INSERTION</span> { <span class="kw">if</span> <span class="ident">len</span> <span class="op">>=</span> <span class="number">2</span> { <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> (<span class="number">0</span>..<span class="ident">len</span><span class="op">-</span><span class="number">1</span>).<span class="ident">rev</span>() { <span class="ident">insert_head</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="ident">i</span>..], <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">is_less</span>); } } <span class="kw">return</span>; } <span class="comment">// Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it</span> <span class="comment">// shallow copies of the contents of `v` without risking the dtors running on copies if</span> <span class="comment">// `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run,</span> <span class="comment">// which will always have length at most `len / 2`.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">len</span> <span class="op">/</span> <span class="number">2</span>); <span class="comment">// In order to identify natural runs in `v`, we traverse it backwards. That might seem like a</span> <span class="comment">// strange decision, but consider the fact that merges more often go in the opposite direction</span> <span class="comment">// (forwards). According to benchmarks, merging forwards is slightly faster than merging</span> <span class="comment">// backwards. To conclude, identifying runs by traversing backwards improves performance.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">runs</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[]; <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">end</span> <span class="op">=</span> <span class="ident">len</span>; <span class="kw">while</span> <span class="ident">end</span> <span class="op">></span> <span class="number">0</span> { <span class="comment">// Find the next natural run, and reverse it if it's strictly descending.</span> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">start</span> <span class="op">=</span> <span class="ident">end</span> <span class="op">-</span> <span class="number">1</span>; <span class="kw">if</span> <span class="ident">start</span> <span class="op">></span> <span class="number">0</span> { <span class="ident">start</span> <span class="op">-=</span> <span class="number">1</span>; <span class="kw">unsafe</span> { <span class="kw">if</span> <span class="ident">is_less</span>(<span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span> <span class="op">+</span> <span class="number">1</span>), <span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span>)) { <span class="kw">while</span> <span class="ident">start</span> <span class="op">></span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">is_less</span>(<span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span>), <span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span> <span class="op">-</span> <span class="number">1</span>)) { <span class="ident">start</span> <span class="op">-=</span> <span class="number">1</span>; } <span class="ident">v</span>[<span class="ident">start</span>..<span class="ident">end</span>].<span class="ident">reverse</span>(); } <span class="kw">else</span> { <span class="kw">while</span> <span class="ident">start</span> <span class="op">></span> <span class="number">0</span> <span class="op">&&</span> <span class="op">!</span><span class="ident">is_less</span>(<span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span>), <span class="ident">v</span>.<span class="ident">get_unchecked</span>(<span class="ident">start</span> <span class="op">-</span> <span class="number">1</span>)) { <span class="ident">start</span> <span class="op">-=</span> <span class="number">1</span>; } } } } <span class="comment">// Insert some more elements into the run if it's too short. Insertion sort is faster than</span> <span class="comment">// merge sort on short sequences, so this significantly improves performance.</span> <span class="kw">while</span> <span class="ident">start</span> <span class="op">></span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">end</span> <span class="op">-</span> <span class="ident">start</span> <span class="op"><</span> <span class="ident">MIN_RUN</span> { <span class="ident">start</span> <span class="op">-=</span> <span class="number">1</span>; <span class="ident">insert_head</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="ident">start</span>..<span class="ident">end</span>], <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">is_less</span>); } <span class="comment">// Push this run onto the stack.</span> <span class="ident">runs</span>.<span class="ident">push</span>(<span class="ident">Run</span> { <span class="ident">start</span>, <span class="ident">len</span>: <span class="ident">end</span> <span class="op">-</span> <span class="ident">start</span>, }); <span class="ident">end</span> <span class="op">=</span> <span class="ident">start</span>; <span class="comment">// Merge some pairs of adjacent runs to satisfy the invariants.</span> <span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">r</span>) <span class="op">=</span> <span class="ident">collapse</span>(<span class="kw-2">&</span><span class="ident">runs</span>) { <span class="kw">let</span> <span class="ident">left</span> <span class="op">=</span> <span class="ident">runs</span>[<span class="ident">r</span> <span class="op">+</span> <span class="number">1</span>]; <span class="kw">let</span> <span class="ident">right</span> <span class="op">=</span> <span class="ident">runs</span>[<span class="ident">r</span>]; <span class="kw">unsafe</span> { <span class="ident">merge</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>[<span class="ident">left</span>.<span class="ident">start</span> .. <span class="ident">right</span>.<span class="ident">start</span> <span class="op">+</span> <span class="ident">right</span>.<span class="ident">len</span>], <span class="ident">left</span>.<span class="ident">len</span>, <span class="ident">buf</span>.<span class="ident">as_mut_ptr</span>(), <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">is_less</span>); } <span class="ident">runs</span>[<span class="ident">r</span>] <span class="op">=</span> <span class="ident">Run</span> { <span class="ident">start</span>: <span class="ident">left</span>.<span class="ident">start</span>, <span class="ident">len</span>: <span class="ident">left</span>.<span class="ident">len</span> <span class="op">+</span> <span class="ident">right</span>.<span class="ident">len</span>, }; <span class="ident">runs</span>.<span class="ident">remove</span>(<span class="ident">r</span> <span class="op">+</span> <span class="number">1</span>); } } <span class="comment">// Finally, exactly one run must remain in the stack.</span> <span class="macro">debug_assert</span><span class="macro">!</span>(<span class="ident">runs</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="number">1</span> <span class="op">&&</span> <span class="ident">runs</span>[<span class="number">0</span>].<span class="ident">start</span> <span class="op">==</span> <span class="number">0</span> <span class="op">&&</span> <span class="ident">runs</span>[<span class="number">0</span>].<span class="ident">len</span> <span class="op">==</span> <span class="ident">len</span>); <span class="comment">// Examines the stack of runs and identifies the next pair of runs to merge. More specifically,</span> <span class="comment">// if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the</span> <span class="comment">// algorithm should continue building a new run instead, `None` is returned.</span> <span class="comment">//</span> <span class="comment">// TimSort is infamous for its buggy implementations, as described here:</span> <span class="comment">// http://envisage-project.eu/timsort-specification-and-verification/</span> <span class="comment">//</span> <span class="comment">// The gist of the story is: we must enforce the invariants on the top four runs on the stack.</span> <span class="comment">// Enforcing them on just top three is not sufficient to ensure that the invariants will still</span> <span class="comment">// hold for *all* runs in the stack.</span> <span class="comment">//</span> <span class="comment">// This function correctly checks invariants for the top four runs. Additionally, if the top</span> <span class="comment">// run starts at index 0, it will always demand a merge operation until the stack is fully</span> <span class="comment">// collapsed, in order to complete the sort.</span> <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">fn</span> <span class="ident">collapse</span>(<span class="ident">runs</span>: <span class="kw-2">&</span>[<span class="ident">Run</span>]) <span class="op">-></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">n</span> <span class="op">=</span> <span class="ident">runs</span>.<span class="ident">len</span>(); <span class="kw">if</span> <span class="ident">n</span> <span class="op">>=</span> <span class="number">2</span> <span class="op">&&</span> (<span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">start</span> <span class="op">==</span> <span class="number">0</span> <span class="op">||</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">2</span>].<span class="ident">len</span> <span class="op"><=</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">len</span> <span class="op">||</span> (<span class="ident">n</span> <span class="op">>=</span> <span class="number">3</span> <span class="op">&&</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">3</span>].<span class="ident">len</span> <span class="op"><=</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">2</span>].<span class="ident">len</span> <span class="op">+</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">len</span>) <span class="op">||</span> (<span class="ident">n</span> <span class="op">>=</span> <span class="number">4</span> <span class="op">&&</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">4</span>].<span class="ident">len</span> <span class="op"><=</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">3</span>].<span class="ident">len</span> <span class="op">+</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">2</span>].<span class="ident">len</span>)) { <span class="kw">if</span> <span class="ident">n</span> <span class="op">>=</span> <span class="number">3</span> <span class="op">&&</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">3</span>].<span class="ident">len</span> <span class="op"><</span> <span class="ident">runs</span>[<span class="ident">n</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">len</span> { <span class="prelude-val">Some</span>(<span class="ident">n</span> <span class="op">-</span> <span class="number">3</span>) } <span class="kw">else</span> { <span class="prelude-val">Some</span>(<span class="ident">n</span> <span class="op">-</span> <span class="number">2</span>) } } <span class="kw">else</span> { <span class="prelude-val">None</span> } } <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>)]</span> <span class="kw">struct</span> <span class="ident">Run</span> { <span class="ident">start</span>: <span class="ident">usize</span>, <span class="ident">len</span>: <span class="ident">usize</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><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse 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><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../";window.currentCrate = "alloc";</script><script src="../../aliases.js"></script><script src="../../main.js"></script><script defer src="../../search-index.js"></script></body></html>