1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925
//! A double-ended queue (deque) implemented with a growable ring buffer.
//!
//! This queue has *O*(1) amortized inserts and removals from both ends of the
//! container. It also has *O*(1) indexing like a vector. The contained elements
//! are not required to be copyable, and the queue will be sendable if the
//! contained type is sendable.
#![stable(feature = "rust1", since = "1.0.0")]
use core::cmp::{self, Ordering};
use core::fmt;
use core::hash::{Hash, Hasher};
use core::iter::{repeat_n, repeat_with, ByRefSized};
use core::mem::{ManuallyDrop, SizedTypeProperties};
use core::ops::{Index, IndexMut, Range, RangeBounds};
use core::ptr;
use core::slice;
// This is used in a bunch of intra-doc links.
// FIXME: For some reason, `#[cfg(doc)]` wasn't sufficient, resulting in
// failures in linkchecker even though rustdoc built the docs just fine.
#[allow(unused_imports)]
use core::mem;
use crate::alloc::{Allocator, Global};
use crate::collections::TryReserveError;
use crate::collections::TryReserveErrorKind;
use crate::raw_vec::RawVec;
use crate::vec::Vec;
#[macro_use]
mod macros;
#[stable(feature = "drain", since = "1.6.0")]
pub use self::drain::Drain;
mod drain;
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::iter_mut::IterMut;
mod iter_mut;
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::into_iter::IntoIter;
mod into_iter;
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::iter::Iter;
mod iter;
use self::spec_extend::SpecExtend;
mod spec_extend;
use self::spec_from_iter::SpecFromIter;
mod spec_from_iter;
#[cfg(test)]
mod tests;
/// A double-ended queue implemented with a growable ring buffer.
///
/// The "default" usage of this type as a queue is to use [`push_back`] to add to
/// the queue, and [`pop_front`] to remove from the queue. [`extend`] and [`append`]
/// push onto the back in this manner, and iterating over `VecDeque` goes front
/// to back.
///
/// A `VecDeque` with a known list of items can be initialized from an array:
///
/// ```
/// use std::collections::VecDeque;
///
/// let deq = VecDeque::from([-1, 0, 1]);
/// ```
///
/// Since `VecDeque` is a ring buffer, its elements are not necessarily contiguous
/// in memory. If you want to access the elements as a single slice, such as for
/// efficient sorting, you can use [`make_contiguous`]. It rotates the `VecDeque`
/// so that its elements do not wrap, and returns a mutable slice to the
/// now-contiguous element sequence.
///
/// [`push_back`]: VecDeque::push_back
/// [`pop_front`]: VecDeque::pop_front
/// [`extend`]: VecDeque::extend
/// [`append`]: VecDeque::append
/// [`make_contiguous`]: VecDeque::make_contiguous
#[cfg_attr(not(test), rustc_diagnostic_item = "VecDeque")]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_insignificant_dtor]
pub struct VecDeque<
T,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
// `self[0]`, if it exists, is `buf[head]`.
// `head < buf.capacity()`, unless `buf.capacity() == 0` when `head == 0`.
head: usize,
// the number of initialized elements, starting from the one at `head` and potentially wrapping around.
// if `len == 0`, the exact value of `head` is unimportant.
// if `T` is zero-Sized, then `self.len <= usize::MAX`, otherwise `self.len <= isize::MAX as usize`.
len: usize,
buf: RawVec<T, A>,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Clone, A: Allocator + Clone> Clone for VecDeque<T, A> {
fn clone(&self) -> Self {
let mut deq = Self::with_capacity_in(self.len(), self.allocator().clone());
deq.extend(self.iter().cloned());
deq
}
fn clone_from(&mut self, other: &Self) {
self.clear();
self.extend(other.iter().cloned());
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<#[may_dangle] T, A: Allocator> Drop for VecDeque<T, A> {
fn drop(&mut self) {
/// Runs the destructor for all items in the slice when it gets dropped (normally or
/// during unwinding).
struct Dropper<'a, T>(&'a mut [T]);
impl<'a, T> Drop for Dropper<'a, T> {
fn drop(&mut self) {
unsafe {
ptr::drop_in_place(self.0);
}
}
}
let (front, back) = self.as_mut_slices();
unsafe {
let _back_dropper = Dropper(back);
// use drop for [T]
ptr::drop_in_place(front);
}
// RawVec handles deallocation
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Default for VecDeque<T> {
/// Creates an empty deque.
#[inline]
fn default() -> VecDeque<T> {
VecDeque::new()
}
}
impl<T, A: Allocator> VecDeque<T, A> {
/// Marginally more convenient
#[inline]
fn ptr(&self) -> *mut T {
self.buf.ptr()
}
/// Moves an element out of the buffer
#[inline]
unsafe fn buffer_read(&mut self, off: usize) -> T {
unsafe { ptr::read(self.ptr().add(off)) }
}
/// Writes an element into the buffer, moving it.
#[inline]
unsafe fn buffer_write(&mut self, off: usize, value: T) {
unsafe {
ptr::write(self.ptr().add(off), value);
}
}
/// Returns a slice pointer into the buffer.
/// `range` must lie inside `0..self.capacity()`.
#[inline]
unsafe fn buffer_range(&self, range: Range<usize>) -> *mut [T] {
unsafe {
ptr::slice_from_raw_parts_mut(self.ptr().add(range.start), range.end - range.start)
}
}
/// Returns `true` if the buffer is at full capacity.
#[inline]
fn is_full(&self) -> bool {
self.len == self.capacity()
}
/// Returns the index in the underlying buffer for a given logical element
/// index + addend.
#[inline]
fn wrap_add(&self, idx: usize, addend: usize) -> usize {
wrap_index(idx.wrapping_add(addend), self.capacity())
}
#[inline]
fn to_physical_idx(&self, idx: usize) -> usize {
self.wrap_add(self.head, idx)
}
/// Returns the index in the underlying buffer for a given logical element
/// index - subtrahend.
#[inline]
fn wrap_sub(&self, idx: usize, subtrahend: usize) -> usize {
wrap_index(idx.wrapping_sub(subtrahend).wrapping_add(self.capacity()), self.capacity())
}
/// Copies a contiguous block of memory len long from src to dst
#[inline]
unsafe fn copy(&mut self, src: usize, dst: usize, len: usize) {
debug_assert!(
dst + len <= self.capacity(),
"cpy dst={} src={} len={} cap={}",
dst,
src,
len,
self.capacity()
);
debug_assert!(
src + len <= self.capacity(),
"cpy dst={} src={} len={} cap={}",
dst,
src,
len,
self.capacity()
);
unsafe {
ptr::copy(self.ptr().add(src), self.ptr().add(dst), len);
}
}
/// Copies a contiguous block of memory len long from src to dst
#[inline]
unsafe fn copy_nonoverlapping(&mut self, src: usize, dst: usize, len: usize) {
debug_assert!(
dst + len <= self.capacity(),
"cno dst={} src={} len={} cap={}",
dst,
src,
len,
self.capacity()
);
debug_assert!(
src + len <= self.capacity(),
"cno dst={} src={} len={} cap={}",
dst,
src,
len,
self.capacity()
);
unsafe {
ptr::copy_nonoverlapping(self.ptr().add(src), self.ptr().add(dst), len);
}
}
/// Copies a potentially wrapping block of memory len long from src to dest.
/// (abs(dst - src) + len) must be no larger than capacity() (There must be at
/// most one continuous overlapping region between src and dest).
unsafe fn wrap_copy(&mut self, src: usize, dst: usize, len: usize) {
debug_assert!(
cmp::min(src.abs_diff(dst), self.capacity() - src.abs_diff(dst)) + len
<= self.capacity(),
"wrc dst={} src={} len={} cap={}",
dst,
src,
len,
self.capacity()
);
// If T is a ZST, don't do any copying.
if T::IS_ZST || src == dst || len == 0 {
return;
}
let dst_after_src = self.wrap_sub(dst, src) < len;
let src_pre_wrap_len = self.capacity() - src;
let dst_pre_wrap_len = self.capacity() - dst;
let src_wraps = src_pre_wrap_len < len;
let dst_wraps = dst_pre_wrap_len < len;
match (dst_after_src, src_wraps, dst_wraps) {
(_, false, false) => {
// src doesn't wrap, dst doesn't wrap
//
// S . . .
// 1 [_ _ A A B B C C _]
// 2 [_ _ A A A A B B _]
// D . . .
//
unsafe {
self.copy(src, dst, len);
}
}
(false, false, true) => {
// dst before src, src doesn't wrap, dst wraps
//
// S . . .
// 1 [A A B B _ _ _ C C]
// 2 [A A B B _ _ _ A A]
// 3 [B B B B _ _ _ A A]
// . . D .
//
unsafe {
self.copy(src, dst, dst_pre_wrap_len);
self.copy(src + dst_pre_wrap_len, 0, len - dst_pre_wrap_len);
}
}
(true, false, true) => {
// src before dst, src doesn't wrap, dst wraps
//
// S . . .
// 1 [C C _ _ _ A A B B]
// 2 [B B _ _ _ A A B B]
// 3 [B B _ _ _ A A A A]
// . . D .
//
unsafe {
self.copy(src + dst_pre_wrap_len, 0, len - dst_pre_wrap_len);
self.copy(src, dst, dst_pre_wrap_len);
}
}
(false, true, false) => {
// dst before src, src wraps, dst doesn't wrap
//
// . . S .
// 1 [C C _ _ _ A A B B]
// 2 [C C _ _ _ B B B B]
// 3 [C C _ _ _ B B C C]
// D . . .
//
unsafe {
self.copy(src, dst, src_pre_wrap_len);
self.copy(0, dst + src_pre_wrap_len, len - src_pre_wrap_len);
}
}
(true, true, false) => {
// src before dst, src wraps, dst doesn't wrap
//
// . . S .
// 1 [A A B B _ _ _ C C]
// 2 [A A A A _ _ _ C C]
// 3 [C C A A _ _ _ C C]
// D . . .
//
unsafe {
self.copy(0, dst + src_pre_wrap_len, len - src_pre_wrap_len);
self.copy(src, dst, src_pre_wrap_len);
}
}
(false, true, true) => {
// dst before src, src wraps, dst wraps
//
// . . . S .
// 1 [A B C D _ E F G H]
// 2 [A B C D _ E G H H]
// 3 [A B C D _ E G H A]
// 4 [B C C D _ E G H A]
// . . D . .
//
debug_assert!(dst_pre_wrap_len > src_pre_wrap_len);
let delta = dst_pre_wrap_len - src_pre_wrap_len;
unsafe {
self.copy(src, dst, src_pre_wrap_len);
self.copy(0, dst + src_pre_wrap_len, delta);
self.copy(delta, 0, len - dst_pre_wrap_len);
}
}
(true, true, true) => {
// src before dst, src wraps, dst wraps
//
// . . S . .
// 1 [A B C D _ E F G H]
// 2 [A A B D _ E F G H]
// 3 [H A B D _ E F G H]
// 4 [H A B D _ E F F G]
// . . . D .
//
debug_assert!(src_pre_wrap_len > dst_pre_wrap_len);
let delta = src_pre_wrap_len - dst_pre_wrap_len;
unsafe {
self.copy(0, delta, len - src_pre_wrap_len);
self.copy(self.capacity() - delta, 0, delta);
self.copy(src, dst, dst_pre_wrap_len);
}
}
}
}
/// Copies all values from `src` to `dst`, wrapping around if needed.
/// Assumes capacity is sufficient.
#[inline]
unsafe fn copy_slice(&mut self, dst: usize, src: &[T]) {
debug_assert!(src.len() <= self.capacity());
let head_room = self.capacity() - dst;
if src.len() <= head_room {
unsafe {
ptr::copy_nonoverlapping(src.as_ptr(), self.ptr().add(dst), src.len());
}
} else {
let (left, right) = src.split_at(head_room);
unsafe {
ptr::copy_nonoverlapping(left.as_ptr(), self.ptr().add(dst), left.len());
ptr::copy_nonoverlapping(right.as_ptr(), self.ptr(), right.len());
}
}
}
/// Writes all values from `iter` to `dst`.
///
/// # Safety
///
/// Assumes no wrapping around happens.
/// Assumes capacity is sufficient.
#[inline]
unsafe fn write_iter(
&mut self,
dst: usize,
iter: impl Iterator<Item = T>,
written: &mut usize,
) {
iter.enumerate().for_each(|(i, element)| unsafe {
self.buffer_write(dst + i, element);
*written += 1;
});
}
/// Writes all values from `iter` to `dst`, wrapping
/// at the end of the buffer and returns the number
/// of written values.
///
/// # Safety
///
/// Assumes that `iter` yields at most `len` items.
/// Assumes capacity is sufficient.
unsafe fn write_iter_wrapping(
&mut self,
dst: usize,
mut iter: impl Iterator<Item = T>,
len: usize,
) -> usize {
struct Guard<'a, T, A: Allocator> {
deque: &'a mut VecDeque<T, A>,
written: usize,
}
impl<'a, T, A: Allocator> Drop for Guard<'a, T, A> {
fn drop(&mut self) {
self.deque.len += self.written;
}
}
let head_room = self.capacity() - dst;
let mut guard = Guard { deque: self, written: 0 };
if head_room >= len {
unsafe { guard.deque.write_iter(dst, iter, &mut guard.written) };
} else {
unsafe {
guard.deque.write_iter(
dst,
ByRefSized(&mut iter).take(head_room),
&mut guard.written,
);
guard.deque.write_iter(0, iter, &mut guard.written)
};
}
guard.written
}
/// Frobs the head and tail sections around to handle the fact that we
/// just reallocated. Unsafe because it trusts old_capacity.
#[inline]
unsafe fn handle_capacity_increase(&mut self, old_capacity: usize) {
let new_capacity = self.capacity();
debug_assert!(new_capacity >= old_capacity);
// Move the shortest contiguous section of the ring buffer
//
// H := head
// L := last element (`self.to_physical_idx(self.len - 1)`)
//
// H L
// [o o o o o o o . ]
// H L
// A [o o o o o o o . . . . . . . . . ]
// L H
// [o o o o o o o o ]
// H L
// B [. . . o o o o o o o o . . . . . ]
// L H
// [o o o o o o o o ]
// L H
// C [o o o o o o . . . . . . . . o o ]
// can't use is_contiguous() because the capacity is already updated.
if self.head <= old_capacity - self.len {
// A
// Nop
} else {
let head_len = old_capacity - self.head;
let tail_len = self.len - head_len;
if head_len > tail_len && new_capacity - old_capacity >= tail_len {
// B
unsafe {
self.copy_nonoverlapping(0, old_capacity, tail_len);
}
} else {
// C
let new_head = new_capacity - head_len;
unsafe {
// can't use copy_nonoverlapping here, because if e.g. head_len = 2
// and new_capacity = old_capacity + 1, then the heads overlap.
self.copy(self.head, new_head, head_len);
}
self.head = new_head;
}
}
debug_assert!(self.head < self.capacity() || self.capacity() == 0);
}
}
impl<T> VecDeque<T> {
/// Creates an empty deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<u32> = VecDeque::new();
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_stable(feature = "const_vec_deque_new", since = "1.68.0")]
#[must_use]
pub const fn new() -> VecDeque<T> {
// FIXME: This should just be `VecDeque::new_in(Global)` once that hits stable.
VecDeque { head: 0, len: 0, buf: RawVec::NEW }
}
/// Creates an empty deque with space for at least `capacity` elements.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<u32> = VecDeque::with_capacity(10);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[must_use]
pub fn with_capacity(capacity: usize) -> VecDeque<T> {
Self::with_capacity_in(capacity, Global)
}
}
impl<T, A: Allocator> VecDeque<T, A> {
/// Creates an empty deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<u32> = VecDeque::new();
/// ```
#[inline]
#[unstable(feature = "allocator_api", issue = "32838")]
pub const fn new_in(alloc: A) -> VecDeque<T, A> {
VecDeque { head: 0, len: 0, buf: RawVec::new_in(alloc) }
}
/// Creates an empty deque with space for at least `capacity` elements.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<u32> = VecDeque::with_capacity(10);
/// ```
#[unstable(feature = "allocator_api", issue = "32838")]
pub fn with_capacity_in(capacity: usize, alloc: A) -> VecDeque<T, A> {
VecDeque { head: 0, len: 0, buf: RawVec::with_capacity_in(capacity, alloc) }
}
/// Creates a `VecDeque` from a raw allocation, when the initialized
/// part of that allocation forms a *contiguous* subslice thereof.
///
/// For use by `vec::IntoIter::into_vecdeque`
///
/// # Safety
///
/// All the usual requirements on the allocated memory like in
/// `Vec::from_raw_parts_in`, but takes a *range* of elements that are
/// initialized rather than only supporting `0..len`. Requires that
/// `initialized.start` ≤ `initialized.end` ≤ `capacity`.
#[inline]
pub(crate) unsafe fn from_contiguous_raw_parts_in(
ptr: *mut T,
initialized: Range<usize>,
capacity: usize,
alloc: A,
) -> Self {
debug_assert!(initialized.start <= initialized.end);
debug_assert!(initialized.end <= capacity);
// SAFETY: Our safety precondition guarantees the range length won't wrap,
// and that the allocation is valid for use in `RawVec`.
unsafe {
VecDeque {
head: initialized.start,
len: initialized.end.unchecked_sub(initialized.start),
buf: RawVec::from_raw_parts_in(ptr, capacity, alloc),
}
}
}
/// Provides a reference to the element at the given index.
///
/// Element at index 0 is the front of the queue.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(3);
/// buf.push_back(4);
/// buf.push_back(5);
/// buf.push_back(6);
/// assert_eq!(buf.get(1), Some(&4));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get(&self, index: usize) -> Option<&T> {
if index < self.len {
let idx = self.to_physical_idx(index);
unsafe { Some(&*self.ptr().add(idx)) }
} else {
None
}
}
/// Provides a mutable reference to the element at the given index.
///
/// Element at index 0 is the front of the queue.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(3);
/// buf.push_back(4);
/// buf.push_back(5);
/// buf.push_back(6);
/// assert_eq!(buf[1], 4);
/// if let Some(elem) = buf.get_mut(1) {
/// *elem = 7;
/// }
/// assert_eq!(buf[1], 7);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_mut(&mut self, index: usize) -> Option<&mut T> {
if index < self.len {
let idx = self.to_physical_idx(index);
unsafe { Some(&mut *self.ptr().add(idx)) }
} else {
None
}
}
/// Swaps elements at indices `i` and `j`.
///
/// `i` and `j` may be equal.
///
/// Element at index 0 is the front of the queue.
///
/// # Panics
///
/// Panics if either index is out of bounds.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(3);
/// buf.push_back(4);
/// buf.push_back(5);
/// assert_eq!(buf, [3, 4, 5]);
/// buf.swap(0, 2);
/// assert_eq!(buf, [5, 4, 3]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn swap(&mut self, i: usize, j: usize) {
assert!(i < self.len());
assert!(j < self.len());
let ri = self.to_physical_idx(i);
let rj = self.to_physical_idx(j);
unsafe { ptr::swap(self.ptr().add(ri), self.ptr().add(rj)) }
}
/// Returns the number of elements the deque can hold without
/// reallocating.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let buf: VecDeque<i32> = VecDeque::with_capacity(10);
/// assert!(buf.capacity() >= 10);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn capacity(&self) -> usize {
if T::IS_ZST { usize::MAX } else { self.buf.capacity() }
}
/// Reserves the minimum capacity for at least `additional` more elements to be inserted in the
/// given deque. Does nothing if the capacity is already sufficient.
///
/// Note that the allocator may give the collection more space than it requests. Therefore
/// capacity can not be relied upon to be precisely minimal. Prefer [`reserve`] if future
/// insertions are expected.
///
/// # Panics
///
/// Panics if the new capacity overflows `usize`.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<i32> = [1].into();
/// buf.reserve_exact(10);
/// assert!(buf.capacity() >= 11);
/// ```
///
/// [`reserve`]: VecDeque::reserve
#[stable(feature = "rust1", since = "1.0.0")]
pub fn reserve_exact(&mut self, additional: usize) {
let new_cap = self.len.checked_add(additional).expect("capacity overflow");
let old_cap = self.capacity();
if new_cap > old_cap {
self.buf.reserve_exact(self.len, additional);
unsafe {
self.handle_capacity_increase(old_cap);
}
}
}
/// Reserves capacity for at least `additional` more elements to be inserted in the given
/// deque. The collection may reserve more space to speculatively avoid frequent reallocations.
///
/// # Panics
///
/// Panics if the new capacity overflows `usize`.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<i32> = [1].into();
/// buf.reserve(10);
/// assert!(buf.capacity() >= 11);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn reserve(&mut self, additional: usize) {
let new_cap = self.len.checked_add(additional).expect("capacity overflow");
let old_cap = self.capacity();
if new_cap > old_cap {
// we don't need to reserve_exact(), as the size doesn't have
// to be a power of 2.
self.buf.reserve(self.len, additional);
unsafe {
self.handle_capacity_increase(old_cap);
}
}
}
/// Tries to reserve the minimum capacity for at least `additional` more elements to
/// be inserted in the given deque. After calling `try_reserve_exact`,
/// capacity will be greater than or equal to `self.len() + additional` if
/// it returns `Ok(())`. Does nothing if the capacity is already sufficient.
///
/// Note that the allocator may give the collection more space than it
/// requests. Therefore, capacity can not be relied upon to be precisely
/// minimal. Prefer [`try_reserve`] if future insertions are expected.
///
/// [`try_reserve`]: VecDeque::try_reserve
///
/// # Errors
///
/// If the capacity overflows `usize`, or the allocator reports a failure, then an error
/// is returned.
///
/// # Examples
///
/// ```
/// use std::collections::TryReserveError;
/// use std::collections::VecDeque;
///
/// fn process_data(data: &[u32]) -> Result<VecDeque<u32>, TryReserveError> {
/// let mut output = VecDeque::new();
///
/// // Pre-reserve the memory, exiting if we can't
/// output.try_reserve_exact(data.len())?;
///
/// // Now we know this can't OOM(Out-Of-Memory) in the middle of our complex work
/// output.extend(data.iter().map(|&val| {
/// val * 2 + 5 // very complicated
/// }));
///
/// Ok(output)
/// }
/// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
/// ```
#[stable(feature = "try_reserve", since = "1.57.0")]
pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
let new_cap =
self.len.checked_add(additional).ok_or(TryReserveErrorKind::CapacityOverflow)?;
let old_cap = self.capacity();
if new_cap > old_cap {
self.buf.try_reserve_exact(self.len, additional)?;
unsafe {
self.handle_capacity_increase(old_cap);
}
}
Ok(())
}
/// Tries to reserve capacity for at least `additional` more elements to be inserted
/// in the given deque. The collection may reserve more space to speculatively avoid
/// frequent reallocations. After calling `try_reserve`, capacity will be
/// greater than or equal to `self.len() + additional` if it returns
/// `Ok(())`. Does nothing if capacity is already sufficient. This method
/// preserves the contents even if an error occurs.
///
/// # Errors
///
/// If the capacity overflows `usize`, or the allocator reports a failure, then an error
/// is returned.
///
/// # Examples
///
/// ```
/// use std::collections::TryReserveError;
/// use std::collections::VecDeque;
///
/// fn process_data(data: &[u32]) -> Result<VecDeque<u32>, TryReserveError> {
/// let mut output = VecDeque::new();
///
/// // Pre-reserve the memory, exiting if we can't
/// output.try_reserve(data.len())?;
///
/// // Now we know this can't OOM in the middle of our complex work
/// output.extend(data.iter().map(|&val| {
/// val * 2 + 5 // very complicated
/// }));
///
/// Ok(output)
/// }
/// # process_data(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
/// ```
#[stable(feature = "try_reserve", since = "1.57.0")]
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
let new_cap =
self.len.checked_add(additional).ok_or(TryReserveErrorKind::CapacityOverflow)?;
let old_cap = self.capacity();
if new_cap > old_cap {
self.buf.try_reserve(self.len, additional)?;
unsafe {
self.handle_capacity_increase(old_cap);
}
}
Ok(())
}
/// Shrinks the capacity of the deque as much as possible.
///
/// It will drop down as close as possible to the length but the allocator may still inform the
/// deque that there is space for a few more elements.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::with_capacity(15);
/// buf.extend(0..4);
/// assert_eq!(buf.capacity(), 15);
/// buf.shrink_to_fit();
/// assert!(buf.capacity() >= 4);
/// ```
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn shrink_to_fit(&mut self) {
self.shrink_to(0);
}
/// Shrinks the capacity of the deque with a lower bound.
///
/// The capacity will remain at least as large as both the length
/// and the supplied value.
///
/// If the current capacity is less than the lower limit, this is a no-op.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::with_capacity(15);
/// buf.extend(0..4);
/// assert_eq!(buf.capacity(), 15);
/// buf.shrink_to(6);
/// assert!(buf.capacity() >= 6);
/// buf.shrink_to(0);
/// assert!(buf.capacity() >= 4);
/// ```
#[stable(feature = "shrink_to", since = "1.56.0")]
pub fn shrink_to(&mut self, min_capacity: usize) {
let target_cap = min_capacity.max(self.len);
// never shrink ZSTs
if T::IS_ZST || self.capacity() <= target_cap {
return;
}
// There are three cases of interest:
// All elements are out of desired bounds
// Elements are contiguous, and tail is out of desired bounds
// Elements are discontiguous
//
// At all other times, element positions are unaffected.
// `head` and `len` are at most `isize::MAX` and `target_cap < self.capacity()`, so nothing can
// overflow.
let tail_outside = (target_cap + 1..=self.capacity()).contains(&(self.head + self.len));
if self.len == 0 {
self.head = 0;
} else if self.head >= target_cap && tail_outside {
// Head and tail are both out of bounds, so copy all of them to the front.
//
// H := head
// L := last element
// H L
// [. . . . . . . . o o o o o o o . ]
// H L
// [o o o o o o o . ]
unsafe {
// nonoverlapping because `self.head >= target_cap >= self.len`.
self.copy_nonoverlapping(self.head, 0, self.len);
}
self.head = 0;
} else if self.head < target_cap && tail_outside {
// Head is in bounds, tail is out of bounds.
// Copy the overflowing part to the beginning of the
// buffer. This won't overlap because `target_cap >= self.len`.
//
// H := head
// L := last element
// H L
// [. . . o o o o o o o . . . . . . ]
// L H
// [o o . o o o o o ]
let len = self.head + self.len - target_cap;
unsafe {
self.copy_nonoverlapping(target_cap, 0, len);
}
} else if !self.is_contiguous() {
// The head slice is at least partially out of bounds, tail is in bounds.
// Copy the head backwards so it lines up with the target capacity.
// This won't overlap because `target_cap >= self.len`.
//
// H := head
// L := last element
// L H
// [o o o o o . . . . . . . . . o o ]
// L H
// [o o o o o . o o ]
let head_len = self.capacity() - self.head;
let new_head = target_cap - head_len;
unsafe {
// can't use `copy_nonoverlapping()` here because the new and old
// regions for the head might overlap.
self.copy(self.head, new_head, head_len);
}
self.head = new_head;
}
self.buf.shrink_to_fit(target_cap);
debug_assert!(self.head < self.capacity() || self.capacity() == 0);
debug_assert!(self.len <= self.capacity());
}
/// Shortens the deque, keeping the first `len` elements and dropping
/// the rest.
///
/// If `len` is greater or equal to the deque's current length, this has
/// no effect.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(5);
/// buf.push_back(10);
/// buf.push_back(15);
/// assert_eq!(buf, [5, 10, 15]);
/// buf.truncate(1);
/// assert_eq!(buf, [5]);
/// ```
#[stable(feature = "deque_extras", since = "1.16.0")]
pub fn truncate(&mut self, len: usize) {
/// Runs the destructor for all items in the slice when it gets dropped (normally or
/// during unwinding).
struct Dropper<'a, T>(&'a mut [T]);
impl<'a, T> Drop for Dropper<'a, T> {
fn drop(&mut self) {
unsafe {
ptr::drop_in_place(self.0);
}
}
}
// Safe because:
//
// * Any slice passed to `drop_in_place` is valid; the second case has
// `len <= front.len()` and returning on `len > self.len()` ensures
// `begin <= back.len()` in the first case
// * The head of the VecDeque is moved before calling `drop_in_place`,
// so no value is dropped twice if `drop_in_place` panics
unsafe {
if len >= self.len {
return;
}
let (front, back) = self.as_mut_slices();
if len > front.len() {
let begin = len - front.len();
let drop_back = back.get_unchecked_mut(begin..) as *mut _;
self.len = len;
ptr::drop_in_place(drop_back);
} else {
let drop_back = back as *mut _;
let drop_front = front.get_unchecked_mut(len..) as *mut _;
self.len = len;
// Make sure the second half is dropped even when a destructor
// in the first one panics.
let _back_dropper = Dropper(&mut *drop_back);
ptr::drop_in_place(drop_front);
}
}
}
/// Returns a reference to the underlying allocator.
#[unstable(feature = "allocator_api", issue = "32838")]
#[inline]
pub fn allocator(&self) -> &A {
self.buf.allocator()
}
/// Returns a front-to-back iterator.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(5);
/// buf.push_back(3);
/// buf.push_back(4);
/// let b: &[_] = &[&5, &3, &4];
/// let c: Vec<&i32> = buf.iter().collect();
/// assert_eq!(&c[..], b);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter(&self) -> Iter<'_, T> {
let (a, b) = self.as_slices();
Iter::new(a.iter(), b.iter())
}
/// Returns a front-to-back iterator that returns mutable references.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(5);
/// buf.push_back(3);
/// buf.push_back(4);
/// for num in buf.iter_mut() {
/// *num = *num - 2;
/// }
/// let b: &[_] = &[&mut 3, &mut 1, &mut 2];
/// assert_eq!(&buf.iter_mut().collect::<Vec<&mut i32>>()[..], b);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
let (a, b) = self.as_mut_slices();
IterMut::new(a.iter_mut(), b.iter_mut())
}
/// Returns a pair of slices which contain, in order, the contents of the
/// deque.
///
/// If [`make_contiguous`] was previously called, all elements of the
/// deque will be in the first slice and the second slice will be empty.
///
/// [`make_contiguous`]: VecDeque::make_contiguous
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque = VecDeque::new();
///
/// deque.push_back(0);
/// deque.push_back(1);
/// deque.push_back(2);
///
/// assert_eq!(deque.as_slices(), (&[0, 1, 2][..], &[][..]));
///
/// deque.push_front(10);
/// deque.push_front(9);
///
/// assert_eq!(deque.as_slices(), (&[9, 10][..], &[0, 1, 2][..]));
/// ```
#[inline]
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn as_slices(&self) -> (&[T], &[T]) {
let (a_range, b_range) = self.slice_ranges(.., self.len);
// SAFETY: `slice_ranges` always returns valid ranges into
// the physical buffer.
unsafe { (&*self.buffer_range(a_range), &*self.buffer_range(b_range)) }
}
/// Returns a pair of slices which contain, in order, the contents of the
/// deque.
///
/// If [`make_contiguous`] was previously called, all elements of the
/// deque will be in the first slice and the second slice will be empty.
///
/// [`make_contiguous`]: VecDeque::make_contiguous
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque = VecDeque::new();
///
/// deque.push_back(0);
/// deque.push_back(1);
///
/// deque.push_front(10);
/// deque.push_front(9);
///
/// deque.as_mut_slices().0[0] = 42;
/// deque.as_mut_slices().1[0] = 24;
/// assert_eq!(deque.as_slices(), (&[42, 10][..], &[24, 1][..]));
/// ```
#[inline]
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn as_mut_slices(&mut self) -> (&mut [T], &mut [T]) {
let (a_range, b_range) = self.slice_ranges(.., self.len);
// SAFETY: `slice_ranges` always returns valid ranges into
// the physical buffer.
unsafe { (&mut *self.buffer_range(a_range), &mut *self.buffer_range(b_range)) }
}
/// Returns the number of elements in the deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque = VecDeque::new();
/// assert_eq!(deque.len(), 0);
/// deque.push_back(1);
/// assert_eq!(deque.len(), 1);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn len(&self) -> usize {
self.len
}
/// Returns `true` if the deque is empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque = VecDeque::new();
/// assert!(deque.is_empty());
/// deque.push_front(1);
/// assert!(!deque.is_empty());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn is_empty(&self) -> bool {
self.len == 0
}
/// Given a range into the logical buffer of the deque, this function
/// return two ranges into the physical buffer that correspond to
/// the given range. The `len` parameter should usually just be `self.len`;
/// the reason it's passed explicitly is that if the deque is wrapped in
/// a `Drain`, then `self.len` is not actually the length of the deque.
///
/// # Safety
///
/// This function is always safe to call. For the resulting ranges to be valid
/// ranges into the physical buffer, the caller must ensure that the result of
/// calling `slice::range(range, ..len)` represents a valid range into the
/// logical buffer, and that all elements in that range are initialized.
fn slice_ranges<R>(&self, range: R, len: usize) -> (Range<usize>, Range<usize>)
where
R: RangeBounds<usize>,
{
let Range { start, end } = slice::range(range, ..len);
let len = end - start;
if len == 0 {
(0..0, 0..0)
} else {
// `slice::range` guarantees that `start <= end <= len`.
// because `len != 0`, we know that `start < end`, so `start < len`
// and the indexing is valid.
let wrapped_start = self.to_physical_idx(start);
// this subtraction can never overflow because `wrapped_start` is
// at most `self.capacity()` (and if `self.capacity != 0`, then `wrapped_start` is strictly less
// than `self.capacity`).
let head_len = self.capacity() - wrapped_start;
if head_len >= len {
// we know that `len + wrapped_start <= self.capacity <= usize::MAX`, so this addition can't overflow
(wrapped_start..wrapped_start + len, 0..0)
} else {
// can't overflow because of the if condition
let tail_len = len - head_len;
(wrapped_start..self.capacity(), 0..tail_len)
}
}
}
/// Creates an iterator that covers the specified range in the deque.
///
/// # Panics
///
/// Panics if the starting point is greater than the end point or if
/// the end point is greater than the length of the deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<_> = [1, 2, 3].into();
/// let range = deque.range(2..).copied().collect::<VecDeque<_>>();
/// assert_eq!(range, [3]);
///
/// // A full range covers all contents
/// let all = deque.range(..);
/// assert_eq!(all.len(), 3);
/// ```
#[inline]
#[stable(feature = "deque_range", since = "1.51.0")]
pub fn range<R>(&self, range: R) -> Iter<'_, T>
where
R: RangeBounds<usize>,
{
let (a_range, b_range) = self.slice_ranges(range, self.len);
// SAFETY: The ranges returned by `slice_ranges`
// are valid ranges into the physical buffer, so
// it's ok to pass them to `buffer_range` and
// dereference the result.
let a = unsafe { &*self.buffer_range(a_range) };
let b = unsafe { &*self.buffer_range(b_range) };
Iter::new(a.iter(), b.iter())
}
/// Creates an iterator that covers the specified mutable range in the deque.
///
/// # Panics
///
/// Panics if the starting point is greater than the end point or if
/// the end point is greater than the length of the deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque: VecDeque<_> = [1, 2, 3].into();
/// for v in deque.range_mut(2..) {
/// *v *= 2;
/// }
/// assert_eq!(deque, [1, 2, 6]);
///
/// // A full range covers all contents
/// for v in deque.range_mut(..) {
/// *v *= 2;
/// }
/// assert_eq!(deque, [2, 4, 12]);
/// ```
#[inline]
#[stable(feature = "deque_range", since = "1.51.0")]
pub fn range_mut<R>(&mut self, range: R) -> IterMut<'_, T>
where
R: RangeBounds<usize>,
{
let (a_range, b_range) = self.slice_ranges(range, self.len);
// SAFETY: The ranges returned by `slice_ranges`
// are valid ranges into the physical buffer, so
// it's ok to pass them to `buffer_range` and
// dereference the result.
let a = unsafe { &mut *self.buffer_range(a_range) };
let b = unsafe { &mut *self.buffer_range(b_range) };
IterMut::new(a.iter_mut(), b.iter_mut())
}
/// Removes the specified range from the deque in bulk, returning all
/// removed elements as an iterator. If the iterator is dropped before
/// being fully consumed, it drops the remaining removed elements.
///
/// The returned iterator keeps a mutable borrow on the queue to optimize
/// its implementation.
///
///
/// # Panics
///
/// Panics if the starting point is greater than the end point or if
/// the end point is greater than the length of the deque.
///
/// # Leaking
///
/// If the returned iterator goes out of scope without being dropped (due to
/// [`mem::forget`], for example), the deque may have lost and leaked
/// elements arbitrarily, including elements outside the range.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque: VecDeque<_> = [1, 2, 3].into();
/// let drained = deque.drain(2..).collect::<VecDeque<_>>();
/// assert_eq!(drained, [3]);
/// assert_eq!(deque, [1, 2]);
///
/// // A full range clears all contents, like `clear()` does
/// deque.drain(..);
/// assert!(deque.is_empty());
/// ```
#[inline]
#[stable(feature = "drain", since = "1.6.0")]
pub fn drain<R>(&mut self, range: R) -> Drain<'_, T, A>
where
R: RangeBounds<usize>,
{
// Memory safety
//
// When the Drain is first created, the source deque is shortened to
// make sure no uninitialized or moved-from elements are accessible at
// all if the Drain's destructor never gets to run.
//
// Drain will ptr::read out the values to remove.
// When finished, the remaining data will be copied back to cover the hole,
// and the head/tail values will be restored correctly.
//
let Range { start, end } = slice::range(range, ..self.len);
let drain_start = start;
let drain_len = end - start;
// The deque's elements are parted into three segments:
// * 0 -> drain_start
// * drain_start -> drain_start+drain_len
// * drain_start+drain_len -> self.len
//
// H = self.head; T = self.head+self.len; t = drain_start+drain_len; h = drain_head
//
// We store drain_start as self.len, and drain_len and self.len as
// drain_len and orig_len respectively on the Drain. This also
// truncates the effective array such that if the Drain is leaked, we
// have forgotten about the potentially moved values after the start of
// the drain.
//
// H h t T
// [. . . o o x x o o . . .]
//
// "forget" about the values after the start of the drain until after
// the drain is complete and the Drain destructor is run.
unsafe { Drain::new(self, drain_start, drain_len) }
}
/// Clears the deque, removing all values.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque = VecDeque::new();
/// deque.push_back(1);
/// deque.clear();
/// assert!(deque.is_empty());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn clear(&mut self) {
self.truncate(0);
// Not strictly necessary, but leaves things in a more consistent/predictable state.
self.head = 0;
}
/// Returns `true` if the deque contains an element equal to the
/// given value.
///
/// This operation is *O*(*n*).
///
/// Note that if you have a sorted `VecDeque`, [`binary_search`] may be faster.
///
/// [`binary_search`]: VecDeque::binary_search
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque: VecDeque<u32> = VecDeque::new();
///
/// deque.push_back(0);
/// deque.push_back(1);
///
/// assert_eq!(deque.contains(&1), true);
/// assert_eq!(deque.contains(&10), false);
/// ```
#[stable(feature = "vec_deque_contains", since = "1.12.0")]
pub fn contains(&self, x: &T) -> bool
where
T: PartialEq<T>,
{
let (a, b) = self.as_slices();
a.contains(x) || b.contains(x)
}
/// Provides a reference to the front element, or `None` if the deque is
/// empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// assert_eq!(d.front(), None);
///
/// d.push_back(1);
/// d.push_back(2);
/// assert_eq!(d.front(), Some(&1));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn front(&self) -> Option<&T> {
self.get(0)
}
/// Provides a mutable reference to the front element, or `None` if the
/// deque is empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// assert_eq!(d.front_mut(), None);
///
/// d.push_back(1);
/// d.push_back(2);
/// match d.front_mut() {
/// Some(x) => *x = 9,
/// None => (),
/// }
/// assert_eq!(d.front(), Some(&9));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn front_mut(&mut self) -> Option<&mut T> {
self.get_mut(0)
}
/// Provides a reference to the back element, or `None` if the deque is
/// empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// assert_eq!(d.back(), None);
///
/// d.push_back(1);
/// d.push_back(2);
/// assert_eq!(d.back(), Some(&2));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back(&self) -> Option<&T> {
self.get(self.len.wrapping_sub(1))
}
/// Provides a mutable reference to the back element, or `None` if the
/// deque is empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// assert_eq!(d.back(), None);
///
/// d.push_back(1);
/// d.push_back(2);
/// match d.back_mut() {
/// Some(x) => *x = 9,
/// None => (),
/// }
/// assert_eq!(d.back(), Some(&9));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back_mut(&mut self) -> Option<&mut T> {
self.get_mut(self.len.wrapping_sub(1))
}
/// Removes the first element and returns it, or `None` if the deque is
/// empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// d.push_back(1);
/// d.push_back(2);
///
/// assert_eq!(d.pop_front(), Some(1));
/// assert_eq!(d.pop_front(), Some(2));
/// assert_eq!(d.pop_front(), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop_front(&mut self) -> Option<T> {
if self.is_empty() {
None
} else {
let old_head = self.head;
self.head = self.to_physical_idx(1);
self.len -= 1;
Some(unsafe { self.buffer_read(old_head) })
}
}
/// Removes the last element from the deque and returns it, or `None` if
/// it is empty.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// assert_eq!(buf.pop_back(), None);
/// buf.push_back(1);
/// buf.push_back(3);
/// assert_eq!(buf.pop_back(), Some(3));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop_back(&mut self) -> Option<T> {
if self.is_empty() {
None
} else {
self.len -= 1;
Some(unsafe { self.buffer_read(self.to_physical_idx(self.len)) })
}
}
/// Prepends an element to the deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut d = VecDeque::new();
/// d.push_front(1);
/// d.push_front(2);
/// assert_eq!(d.front(), Some(&2));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push_front(&mut self, value: T) {
if self.is_full() {
self.grow();
}
self.head = self.wrap_sub(self.head, 1);
self.len += 1;
unsafe {
self.buffer_write(self.head, value);
}
}
/// Appends an element to the back of the deque.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(1);
/// buf.push_back(3);
/// assert_eq!(3, *buf.back().unwrap());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push_back(&mut self, value: T) {
if self.is_full() {
self.grow();
}
unsafe { self.buffer_write(self.to_physical_idx(self.len), value) }
self.len += 1;
}
#[inline]
fn is_contiguous(&self) -> bool {
// Do the calculation like this to avoid overflowing if len + head > usize::MAX
self.head <= self.capacity() - self.len
}
/// Removes an element from anywhere in the deque and returns it,
/// replacing it with the first element.
///
/// This does not preserve ordering, but is *O*(1).
///
/// Returns `None` if `index` is out of bounds.
///
/// Element at index 0 is the front of the queue.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// assert_eq!(buf.swap_remove_front(0), None);
/// buf.push_back(1);
/// buf.push_back(2);
/// buf.push_back(3);
/// assert_eq!(buf, [1, 2, 3]);
///
/// assert_eq!(buf.swap_remove_front(2), Some(3));
/// assert_eq!(buf, [2, 1]);
/// ```
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn swap_remove_front(&mut self, index: usize) -> Option<T> {
let length = self.len;
if index < length && index != 0 {
self.swap(index, 0);
} else if index >= length {
return None;
}
self.pop_front()
}
/// Removes an element from anywhere in the deque and returns it,
/// replacing it with the last element.
///
/// This does not preserve ordering, but is *O*(1).
///
/// Returns `None` if `index` is out of bounds.
///
/// Element at index 0 is the front of the queue.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// assert_eq!(buf.swap_remove_back(0), None);
/// buf.push_back(1);
/// buf.push_back(2);
/// buf.push_back(3);
/// assert_eq!(buf, [1, 2, 3]);
///
/// assert_eq!(buf.swap_remove_back(0), Some(1));
/// assert_eq!(buf, [3, 2]);
/// ```
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn swap_remove_back(&mut self, index: usize) -> Option<T> {
let length = self.len;
if length > 0 && index < length - 1 {
self.swap(index, length - 1);
} else if index >= length {
return None;
}
self.pop_back()
}
/// Inserts an element at `index` within the deque, shifting all elements
/// with indices greater than or equal to `index` towards the back.
///
/// Element at index 0 is the front of the queue.
///
/// # Panics
///
/// Panics if `index` is greater than deque's length
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut vec_deque = VecDeque::new();
/// vec_deque.push_back('a');
/// vec_deque.push_back('b');
/// vec_deque.push_back('c');
/// assert_eq!(vec_deque, &['a', 'b', 'c']);
///
/// vec_deque.insert(1, 'd');
/// assert_eq!(vec_deque, &['a', 'd', 'b', 'c']);
/// ```
#[stable(feature = "deque_extras_15", since = "1.5.0")]
pub fn insert(&mut self, index: usize, value: T) {
assert!(index <= self.len(), "index out of bounds");
if self.is_full() {
self.grow();
}
let k = self.len - index;
if k < index {
// `index + 1` can't overflow, because if index was usize::MAX, then either the
// assert would've failed, or the deque would've tried to grow past usize::MAX
// and panicked.
unsafe {
// see `remove()` for explanation why this wrap_copy() call is safe.
self.wrap_copy(self.to_physical_idx(index), self.to_physical_idx(index + 1), k);
self.buffer_write(self.to_physical_idx(index), value);
self.len += 1;
}
} else {
let old_head = self.head;
self.head = self.wrap_sub(self.head, 1);
unsafe {
self.wrap_copy(old_head, self.head, index);
self.buffer_write(self.to_physical_idx(index), value);
self.len += 1;
}
}
}
/// Removes and returns the element at `index` from the deque.
/// Whichever end is closer to the removal point will be moved to make
/// room, and all the affected elements will be moved to new positions.
/// Returns `None` if `index` is out of bounds.
///
/// Element at index 0 is the front of the queue.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(1);
/// buf.push_back(2);
/// buf.push_back(3);
/// assert_eq!(buf, [1, 2, 3]);
///
/// assert_eq!(buf.remove(1), Some(2));
/// assert_eq!(buf, [1, 3]);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn remove(&mut self, index: usize) -> Option<T> {
if self.len <= index {
return None;
}
let wrapped_idx = self.to_physical_idx(index);
let elem = unsafe { Some(self.buffer_read(wrapped_idx)) };
let k = self.len - index - 1;
// safety: due to the nature of the if-condition, whichever wrap_copy gets called,
// its length argument will be at most `self.len / 2`, so there can't be more than
// one overlapping area.
if k < index {
unsafe { self.wrap_copy(self.wrap_add(wrapped_idx, 1), wrapped_idx, k) };
self.len -= 1;
} else {
let old_head = self.head;
self.head = self.to_physical_idx(1);
unsafe { self.wrap_copy(old_head, self.head, index) };
self.len -= 1;
}
elem
}
/// Splits the deque into two at the given index.
///
/// Returns a newly allocated `VecDeque`. `self` contains elements `[0, at)`,
/// and the returned deque contains elements `[at, len)`.
///
/// Note that the capacity of `self` does not change.
///
/// Element at index 0 is the front of the queue.
///
/// # Panics
///
/// Panics if `at > len`.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<_> = [1, 2, 3].into();
/// let buf2 = buf.split_off(1);
/// assert_eq!(buf, [1]);
/// assert_eq!(buf2, [2, 3]);
/// ```
#[inline]
#[must_use = "use `.truncate()` if you don't need the other half"]
#[stable(feature = "split_off", since = "1.4.0")]
pub fn split_off(&mut self, at: usize) -> Self
where
A: Clone,
{
let len = self.len;
assert!(at <= len, "`at` out of bounds");
let other_len = len - at;
let mut other = VecDeque::with_capacity_in(other_len, self.allocator().clone());
unsafe {
let (first_half, second_half) = self.as_slices();
let first_len = first_half.len();
let second_len = second_half.len();
if at < first_len {
// `at` lies in the first half.
let amount_in_first = first_len - at;
ptr::copy_nonoverlapping(first_half.as_ptr().add(at), other.ptr(), amount_in_first);
// just take all of the second half.
ptr::copy_nonoverlapping(
second_half.as_ptr(),
other.ptr().add(amount_in_first),
second_len,
);
} else {
// `at` lies in the second half, need to factor in the elements we skipped
// in the first half.
let offset = at - first_len;
let amount_in_second = second_len - offset;
ptr::copy_nonoverlapping(
second_half.as_ptr().add(offset),
other.ptr(),
amount_in_second,
);
}
}
// Cleanup where the ends of the buffers are
self.len = at;
other.len = other_len;
other
}
/// Moves all the elements of `other` into `self`, leaving `other` empty.
///
/// # Panics
///
/// Panics if the new number of elements in self overflows a `usize`.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<_> = [1, 2].into();
/// let mut buf2: VecDeque<_> = [3, 4].into();
/// buf.append(&mut buf2);
/// assert_eq!(buf, [1, 2, 3, 4]);
/// assert_eq!(buf2, []);
/// ```
#[inline]
#[stable(feature = "append", since = "1.4.0")]
pub fn append(&mut self, other: &mut Self) {
if T::IS_ZST {
self.len = self.len.checked_add(other.len).expect("capacity overflow");
other.len = 0;
other.head = 0;
return;
}
self.reserve(other.len);
unsafe {
let (left, right) = other.as_slices();
self.copy_slice(self.to_physical_idx(self.len), left);
// no overflow, because self.capacity() >= old_cap + left.len() >= self.len + left.len()
self.copy_slice(self.to_physical_idx(self.len + left.len()), right);
}
// SAFETY: Update pointers after copying to avoid leaving doppelganger
// in case of panics.
self.len += other.len;
// Now that we own its values, forget everything in `other`.
other.len = 0;
other.head = 0;
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` for which `f(&e)` returns false.
/// This method operates in place, visiting each element exactly once in the
/// original order, and preserves the order of the retained elements.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.extend(1..5);
/// buf.retain(|&x| x % 2 == 0);
/// assert_eq!(buf, [2, 4]);
/// ```
///
/// Because the elements are visited exactly once in the original order,
/// external state may be used to decide which elements to keep.
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.extend(1..6);
///
/// let keep = [false, true, true, false, true];
/// let mut iter = keep.iter();
/// buf.retain(|_| *iter.next().unwrap());
/// assert_eq!(buf, [2, 3, 5]);
/// ```
#[stable(feature = "vec_deque_retain", since = "1.4.0")]
pub fn retain<F>(&mut self, mut f: F)
where
F: FnMut(&T) -> bool,
{
self.retain_mut(|elem| f(elem));
}
/// Retains only the elements specified by the predicate.
///
/// In other words, remove all elements `e` for which `f(&e)` returns false.
/// This method operates in place, visiting each element exactly once in the
/// original order, and preserves the order of the retained elements.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.extend(1..5);
/// buf.retain_mut(|x| if *x % 2 == 0 {
/// *x += 1;
/// true
/// } else {
/// false
/// });
/// assert_eq!(buf, [3, 5]);
/// ```
#[stable(feature = "vec_retain_mut", since = "1.61.0")]
pub fn retain_mut<F>(&mut self, mut f: F)
where
F: FnMut(&mut T) -> bool,
{
let len = self.len;
let mut idx = 0;
let mut cur = 0;
// Stage 1: All values are retained.
while cur < len {
if !f(&mut self[cur]) {
cur += 1;
break;
}
cur += 1;
idx += 1;
}
// Stage 2: Swap retained value into current idx.
while cur < len {
if !f(&mut self[cur]) {
cur += 1;
continue;
}
self.swap(idx, cur);
cur += 1;
idx += 1;
}
// Stage 3: Truncate all values after idx.
if cur != idx {
self.truncate(idx);
}
}
// Double the buffer size. This method is inline(never), so we expect it to only
// be called in cold paths.
// This may panic or abort
#[inline(never)]
fn grow(&mut self) {
// Extend or possibly remove this assertion when valid use-cases for growing the
// buffer without it being full emerge
debug_assert!(self.is_full());
let old_cap = self.capacity();
self.buf.reserve_for_push(old_cap);
unsafe {
self.handle_capacity_increase(old_cap);
}
debug_assert!(!self.is_full());
}
/// Modifies the deque in-place so that `len()` is equal to `new_len`,
/// either by removing excess elements from the back or by appending
/// elements generated by calling `generator` to the back.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(5);
/// buf.push_back(10);
/// buf.push_back(15);
/// assert_eq!(buf, [5, 10, 15]);
///
/// buf.resize_with(5, Default::default);
/// assert_eq!(buf, [5, 10, 15, 0, 0]);
///
/// buf.resize_with(2, || unreachable!());
/// assert_eq!(buf, [5, 10]);
///
/// let mut state = 100;
/// buf.resize_with(5, || { state += 1; state });
/// assert_eq!(buf, [5, 10, 101, 102, 103]);
/// ```
#[stable(feature = "vec_resize_with", since = "1.33.0")]
pub fn resize_with(&mut self, new_len: usize, generator: impl FnMut() -> T) {
let len = self.len;
if new_len > len {
self.extend(repeat_with(generator).take(new_len - len))
} else {
self.truncate(new_len);
}
}
/// Rearranges the internal storage of this deque so it is one contiguous
/// slice, which is then returned.
///
/// This method does not allocate and does not change the order of the
/// inserted elements. As it returns a mutable slice, this can be used to
/// sort a deque.
///
/// Once the internal storage is contiguous, the [`as_slices`] and
/// [`as_mut_slices`] methods will return the entire contents of the
/// deque in a single slice.
///
/// [`as_slices`]: VecDeque::as_slices
/// [`as_mut_slices`]: VecDeque::as_mut_slices
///
/// # Examples
///
/// Sorting the content of a deque.
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::with_capacity(15);
///
/// buf.push_back(2);
/// buf.push_back(1);
/// buf.push_front(3);
///
/// // sorting the deque
/// buf.make_contiguous().sort();
/// assert_eq!(buf.as_slices(), (&[1, 2, 3] as &[_], &[] as &[_]));
///
/// // sorting it in reverse order
/// buf.make_contiguous().sort_by(|a, b| b.cmp(a));
/// assert_eq!(buf.as_slices(), (&[3, 2, 1] as &[_], &[] as &[_]));
/// ```
///
/// Getting immutable access to the contiguous slice.
///
/// ```rust
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
///
/// buf.push_back(2);
/// buf.push_back(1);
/// buf.push_front(3);
///
/// buf.make_contiguous();
/// if let (slice, &[]) = buf.as_slices() {
/// // we can now be sure that `slice` contains all elements of the deque,
/// // while still having immutable access to `buf`.
/// assert_eq!(buf.len(), slice.len());
/// assert_eq!(slice, &[3, 2, 1] as &[_]);
/// }
/// ```
#[stable(feature = "deque_make_contiguous", since = "1.48.0")]
pub fn make_contiguous(&mut self) -> &mut [T] {
if T::IS_ZST {
self.head = 0;
}
if self.is_contiguous() {
unsafe { return slice::from_raw_parts_mut(self.ptr().add(self.head), self.len) }
}
let &mut Self { head, len, .. } = self;
let ptr = self.ptr();
let cap = self.capacity();
let free = cap - len;
let head_len = cap - head;
let tail = len - head_len;
let tail_len = tail;
if free >= head_len {
// there is enough free space to copy the head in one go,
// this means that we first shift the tail backwards, and then
// copy the head to the correct position.
//
// from: DEFGH....ABC
// to: ABCDEFGH....
unsafe {
self.copy(0, head_len, tail_len);
// ...DEFGH.ABC
self.copy_nonoverlapping(head, 0, head_len);
// ABCDEFGH....
}
self.head = 0;
} else if free >= tail_len {
// there is enough free space to copy the tail in one go,
// this means that we first shift the head forwards, and then
// copy the tail to the correct position.
//
// from: FGH....ABCDE
// to: ...ABCDEFGH.
unsafe {
self.copy(head, tail, head_len);
// FGHABCDE....
self.copy_nonoverlapping(0, tail + head_len, tail_len);
// ...ABCDEFGH.
}
self.head = tail;
} else {
// `free` is smaller than both `head_len` and `tail_len`.
// the general algorithm for this first moves the slices
// right next to each other and then uses `slice::rotate`
// to rotate them into place:
//
// initially: HIJK..ABCDEFG
// step 1: ..HIJKABCDEFG
// step 2: ..ABCDEFGHIJK
//
// or:
//
// initially: FGHIJK..ABCDE
// step 1: FGHIJKABCDE..
// step 2: ABCDEFGHIJK..
// pick the shorter of the 2 slices to reduce the amount
// of memory that needs to be moved around.
if head_len > tail_len {
// tail is shorter, so:
// 1. copy tail forwards
// 2. rotate used part of the buffer
// 3. update head to point to the new beginning (which is just `free`)
unsafe {
// if there is no free space in the buffer, then the slices are already
// right next to each other and we don't need to move any memory.
if free != 0 {
// because we only move the tail forward as much as there's free space
// behind it, we don't overwrite any elements of the head slice, and
// the slices end up right next to each other.
self.copy(0, free, tail_len);
}
// We just copied the tail right next to the head slice,
// so all of the elements in the range are initialized
let slice = &mut *self.buffer_range(free..self.capacity());
// because the deque wasn't contiguous, we know that `tail_len < self.len == slice.len()`,
// so this will never panic.
slice.rotate_left(tail_len);
// the used part of the buffer now is `free..self.capacity()`, so set
// `head` to the beginning of that range.
self.head = free;
}
} else {
// head is shorter so:
// 1. copy head backwards
// 2. rotate used part of the buffer
// 3. update head to point to the new beginning (which is the beginning of the buffer)
unsafe {
// if there is no free space in the buffer, then the slices are already
// right next to each other and we don't need to move any memory.
if free != 0 {
// copy the head slice to lie right behind the tail slice.
self.copy(self.head, tail_len, head_len);
}
// because we copied the head slice so that both slices lie right
// next to each other, all the elements in the range are initialized.
let slice = &mut *self.buffer_range(0..self.len);
// because the deque wasn't contiguous, we know that `head_len < self.len == slice.len()`
// so this will never panic.
slice.rotate_right(head_len);
// the used part of the buffer now is `0..self.len`, so set
// `head` to the beginning of that range.
self.head = 0;
}
}
}
unsafe { slice::from_raw_parts_mut(ptr.add(self.head), self.len) }
}
/// Rotates the double-ended queue `n` places to the left.
///
/// Equivalently,
/// - Rotates item `n` into the first position.
/// - Pops the first `n` items and pushes them to the end.
/// - Rotates `len() - n` places to the right.
///
/// # Panics
///
/// If `n` is greater than `len()`. Note that `n == len()`
/// does _not_ panic and is a no-op rotation.
///
/// # Complexity
///
/// Takes `*O*(min(n, len() - n))` time and no extra space.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<_> = (0..10).collect();
///
/// buf.rotate_left(3);
/// assert_eq!(buf, [3, 4, 5, 6, 7, 8, 9, 0, 1, 2]);
///
/// for i in 1..10 {
/// assert_eq!(i * 3 % 10, buf[0]);
/// buf.rotate_left(3);
/// }
/// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
/// ```
#[stable(feature = "vecdeque_rotate", since = "1.36.0")]
pub fn rotate_left(&mut self, n: usize) {
assert!(n <= self.len());
let k = self.len - n;
if n <= k {
unsafe { self.rotate_left_inner(n) }
} else {
unsafe { self.rotate_right_inner(k) }
}
}
/// Rotates the double-ended queue `n` places to the right.
///
/// Equivalently,
/// - Rotates the first item into position `n`.
/// - Pops the last `n` items and pushes them to the front.
/// - Rotates `len() - n` places to the left.
///
/// # Panics
///
/// If `n` is greater than `len()`. Note that `n == len()`
/// does _not_ panic and is a no-op rotation.
///
/// # Complexity
///
/// Takes `*O*(min(n, len() - n))` time and no extra space.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf: VecDeque<_> = (0..10).collect();
///
/// buf.rotate_right(3);
/// assert_eq!(buf, [7, 8, 9, 0, 1, 2, 3, 4, 5, 6]);
///
/// for i in 1..10 {
/// assert_eq!(0, buf[i * 3 % 10]);
/// buf.rotate_right(3);
/// }
/// assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
/// ```
#[stable(feature = "vecdeque_rotate", since = "1.36.0")]
pub fn rotate_right(&mut self, n: usize) {
assert!(n <= self.len());
let k = self.len - n;
if n <= k {
unsafe { self.rotate_right_inner(n) }
} else {
unsafe { self.rotate_left_inner(k) }
}
}
// SAFETY: the following two methods require that the rotation amount
// be less than half the length of the deque.
//
// `wrap_copy` requires that `min(x, capacity() - x) + copy_len <= capacity()`,
// but then `min` is never more than half the capacity, regardless of x,
// so it's sound to call here because we're calling with something
// less than half the length, which is never above half the capacity.
unsafe fn rotate_left_inner(&mut self, mid: usize) {
debug_assert!(mid * 2 <= self.len());
unsafe {
self.wrap_copy(self.head, self.to_physical_idx(self.len), mid);
}
self.head = self.to_physical_idx(mid);
}
unsafe fn rotate_right_inner(&mut self, k: usize) {
debug_assert!(k * 2 <= self.len());
self.head = self.wrap_sub(self.head, k);
unsafe {
self.wrap_copy(self.to_physical_idx(self.len), self.head, k);
}
}
/// Binary searches this `VecDeque` for a given element.
/// If the `VecDeque` is not sorted, the returned result is unspecified and
/// meaningless.
///
/// If the value is found then [`Result::Ok`] is returned, containing the
/// index of the matching element. If there are multiple matches, then any
/// one of the matches could be returned. If the value is not found then
/// [`Result::Err`] is returned, containing the index where a matching
/// element could be inserted while maintaining sorted order.
///
/// See also [`binary_search_by`], [`binary_search_by_key`], and [`partition_point`].
///
/// [`binary_search_by`]: VecDeque::binary_search_by
/// [`binary_search_by_key`]: VecDeque::binary_search_by_key
/// [`partition_point`]: VecDeque::partition_point
///
/// # Examples
///
/// Looks up a series of four elements. The first is found, with a
/// uniquely determined position; the second and third are not
/// found; the fourth could match any position in `[1, 4]`.
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<_> = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
///
/// assert_eq!(deque.binary_search(&13), Ok(9));
/// assert_eq!(deque.binary_search(&4), Err(7));
/// assert_eq!(deque.binary_search(&100), Err(13));
/// let r = deque.binary_search(&1);
/// assert!(matches!(r, Ok(1..=4)));
/// ```
///
/// If you want to insert an item to a sorted deque, while maintaining
/// sort order, consider using [`partition_point`]:
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque: VecDeque<_> = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
/// let num = 42;
/// let idx = deque.partition_point(|&x| x < num);
/// // The above is equivalent to `let idx = deque.binary_search(&num).unwrap_or_else(|x| x);`
/// deque.insert(idx, num);
/// assert_eq!(deque, &[0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
/// ```
#[stable(feature = "vecdeque_binary_search", since = "1.54.0")]
#[inline]
pub fn binary_search(&self, x: &T) -> Result<usize, usize>
where
T: Ord,
{
self.binary_search_by(|e| e.cmp(x))
}
/// Binary searches this `VecDeque` with a comparator function.
///
/// The comparator function should return an order code that indicates
/// whether its argument is `Less`, `Equal` or `Greater` the desired
/// target.
/// If the `VecDeque` is not sorted or if the comparator function does not
/// implement an order consistent with the sort order of the underlying
/// `VecDeque`, the returned result is unspecified and meaningless.
///
/// If the value is found then [`Result::Ok`] is returned, containing the
/// index of the matching element. If there are multiple matches, then any
/// one of the matches could be returned. If the value is not found then
/// [`Result::Err`] is returned, containing the index where a matching
/// element could be inserted while maintaining sorted order.
///
/// See also [`binary_search`], [`binary_search_by_key`], and [`partition_point`].
///
/// [`binary_search`]: VecDeque::binary_search
/// [`binary_search_by_key`]: VecDeque::binary_search_by_key
/// [`partition_point`]: VecDeque::partition_point
///
/// # Examples
///
/// Looks up a series of four elements. The first is found, with a
/// uniquely determined position; the second and third are not
/// found; the fourth could match any position in `[1, 4]`.
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<_> = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
///
/// assert_eq!(deque.binary_search_by(|x| x.cmp(&13)), Ok(9));
/// assert_eq!(deque.binary_search_by(|x| x.cmp(&4)), Err(7));
/// assert_eq!(deque.binary_search_by(|x| x.cmp(&100)), Err(13));
/// let r = deque.binary_search_by(|x| x.cmp(&1));
/// assert!(matches!(r, Ok(1..=4)));
/// ```
#[stable(feature = "vecdeque_binary_search", since = "1.54.0")]
pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
where
F: FnMut(&'a T) -> Ordering,
{
let (front, back) = self.as_slices();
let cmp_back = back.first().map(|elem| f(elem));
if let Some(Ordering::Equal) = cmp_back {
Ok(front.len())
} else if let Some(Ordering::Less) = cmp_back {
back.binary_search_by(f).map(|idx| idx + front.len()).map_err(|idx| idx + front.len())
} else {
front.binary_search_by(f)
}
}
/// Binary searches this `VecDeque` with a key extraction function.
///
/// Assumes that the deque is sorted by the key, for instance with
/// [`make_contiguous().sort_by_key()`] using the same key extraction function.
/// If the deque is not sorted by the key, the returned result is
/// unspecified and meaningless.
///
/// If the value is found then [`Result::Ok`] is returned, containing the
/// index of the matching element. If there are multiple matches, then any
/// one of the matches could be returned. If the value is not found then
/// [`Result::Err`] is returned, containing the index where a matching
/// element could be inserted while maintaining sorted order.
///
/// See also [`binary_search`], [`binary_search_by`], and [`partition_point`].
///
/// [`make_contiguous().sort_by_key()`]: VecDeque::make_contiguous
/// [`binary_search`]: VecDeque::binary_search
/// [`binary_search_by`]: VecDeque::binary_search_by
/// [`partition_point`]: VecDeque::partition_point
///
/// # Examples
///
/// Looks up a series of four elements in a slice of pairs sorted by
/// their second elements. The first is found, with a uniquely
/// determined position; the second and third are not found; the
/// fourth could match any position in `[1, 4]`.
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<_> = [(0, 0), (2, 1), (4, 1), (5, 1),
/// (3, 1), (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
/// (1, 21), (2, 34), (4, 55)].into();
///
/// assert_eq!(deque.binary_search_by_key(&13, |&(a, b)| b), Ok(9));
/// assert_eq!(deque.binary_search_by_key(&4, |&(a, b)| b), Err(7));
/// assert_eq!(deque.binary_search_by_key(&100, |&(a, b)| b), Err(13));
/// let r = deque.binary_search_by_key(&1, |&(a, b)| b);
/// assert!(matches!(r, Ok(1..=4)));
/// ```
#[stable(feature = "vecdeque_binary_search", since = "1.54.0")]
#[inline]
pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
where
F: FnMut(&'a T) -> B,
B: Ord,
{
self.binary_search_by(|k| f(k).cmp(b))
}
/// Returns the index of the partition point according to the given predicate
/// (the index of the first element of the second partition).
///
/// The deque is assumed to be partitioned according to the given predicate.
/// This means that all elements for which the predicate returns true are at the start of the deque
/// and all elements for which the predicate returns false are at the end.
/// For example, `[7, 15, 3, 5, 4, 12, 6]` is partitioned under the predicate `x % 2 != 0`
/// (all odd numbers are at the start, all even at the end).
///
/// If the deque is not partitioned, the returned result is unspecified and meaningless,
/// as this method performs a kind of binary search.
///
/// See also [`binary_search`], [`binary_search_by`], and [`binary_search_by_key`].
///
/// [`binary_search`]: VecDeque::binary_search
/// [`binary_search_by`]: VecDeque::binary_search_by
/// [`binary_search_by_key`]: VecDeque::binary_search_by_key
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let deque: VecDeque<_> = [1, 2, 3, 3, 5, 6, 7].into();
/// let i = deque.partition_point(|&x| x < 5);
///
/// assert_eq!(i, 4);
/// assert!(deque.iter().take(i).all(|&x| x < 5));
/// assert!(deque.iter().skip(i).all(|&x| !(x < 5)));
/// ```
///
/// If you want to insert an item to a sorted deque, while maintaining
/// sort order:
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut deque: VecDeque<_> = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
/// let num = 42;
/// let idx = deque.partition_point(|&x| x < num);
/// deque.insert(idx, num);
/// assert_eq!(deque, &[0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
/// ```
#[stable(feature = "vecdeque_binary_search", since = "1.54.0")]
pub fn partition_point<P>(&self, mut pred: P) -> usize
where
P: FnMut(&T) -> bool,
{
let (front, back) = self.as_slices();
if let Some(true) = back.first().map(|v| pred(v)) {
back.partition_point(pred) + front.len()
} else {
front.partition_point(pred)
}
}
}
impl<T: Clone, A: Allocator> VecDeque<T, A> {
/// Modifies the deque in-place so that `len()` is equal to new_len,
/// either by removing excess elements from the back or by appending clones of `value`
/// to the back.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// let mut buf = VecDeque::new();
/// buf.push_back(5);
/// buf.push_back(10);
/// buf.push_back(15);
/// assert_eq!(buf, [5, 10, 15]);
///
/// buf.resize(2, 0);
/// assert_eq!(buf, [5, 10]);
///
/// buf.resize(5, 20);
/// assert_eq!(buf, [5, 10, 20, 20, 20]);
/// ```
#[stable(feature = "deque_extras", since = "1.16.0")]
pub fn resize(&mut self, new_len: usize, value: T) {
if new_len > self.len() {
let extra = new_len - self.len();
self.extend(repeat_n(value, extra))
} else {
self.truncate(new_len);
}
}
}
/// Returns the index in the underlying buffer for a given logical element index.
#[inline]
fn wrap_index(logical_index: usize, capacity: usize) -> usize {
debug_assert!(
(logical_index == 0 && capacity == 0)
|| logical_index < capacity
|| (logical_index - capacity) < capacity
);
if logical_index >= capacity { logical_index - capacity } else { logical_index }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: PartialEq, A: Allocator> PartialEq for VecDeque<T, A> {
fn eq(&self, other: &Self) -> bool {
if self.len != other.len() {
return false;
}
let (sa, sb) = self.as_slices();
let (oa, ob) = other.as_slices();
if sa.len() == oa.len() {
sa == oa && sb == ob
} else if sa.len() < oa.len() {
// Always divisible in three sections, for example:
// self: [a b c|d e f]
// other: [0 1 2 3|4 5]
// front = 3, mid = 1,
// [a b c] == [0 1 2] && [d] == [3] && [e f] == [4 5]
let front = sa.len();
let mid = oa.len() - front;
let (oa_front, oa_mid) = oa.split_at(front);
let (sb_mid, sb_back) = sb.split_at(mid);
debug_assert_eq!(sa.len(), oa_front.len());
debug_assert_eq!(sb_mid.len(), oa_mid.len());
debug_assert_eq!(sb_back.len(), ob.len());
sa == oa_front && sb_mid == oa_mid && sb_back == ob
} else {
let front = oa.len();
let mid = sa.len() - front;
let (sa_front, sa_mid) = sa.split_at(front);
let (ob_mid, ob_back) = ob.split_at(mid);
debug_assert_eq!(sa_front.len(), oa.len());
debug_assert_eq!(sa_mid.len(), ob_mid.len());
debug_assert_eq!(sb.len(), ob_back.len());
sa_front == oa && sa_mid == ob_mid && sb == ob_back
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Eq, A: Allocator> Eq for VecDeque<T, A> {}
__impl_slice_eq1! { [] VecDeque<T, A>, Vec<U, A>, }
__impl_slice_eq1! { [] VecDeque<T, A>, &[U], }
__impl_slice_eq1! { [] VecDeque<T, A>, &mut [U], }
__impl_slice_eq1! { [const N: usize] VecDeque<T, A>, [U; N], }
__impl_slice_eq1! { [const N: usize] VecDeque<T, A>, &[U; N], }
__impl_slice_eq1! { [const N: usize] VecDeque<T, A>, &mut [U; N], }
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: PartialOrd, A: Allocator> PartialOrd for VecDeque<T, A> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
self.iter().partial_cmp(other.iter())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord, A: Allocator> Ord for VecDeque<T, A> {
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
self.iter().cmp(other.iter())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: Hash, A: Allocator> Hash for VecDeque<T, A> {
fn hash<H: Hasher>(&self, state: &mut H) {
state.write_length_prefix(self.len);
// It's not possible to use Hash::hash_slice on slices
// returned by as_slices method as their length can vary
// in otherwise identical deques.
//
// Hasher only guarantees equivalence for the exact same
// set of calls to its methods.
self.iter().for_each(|elem| elem.hash(state));
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> Index<usize> for VecDeque<T, A> {
type Output = T;
#[inline]
fn index(&self, index: usize) -> &T {
self.get(index).expect("Out of bounds access")
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> IndexMut<usize> for VecDeque<T, A> {
#[inline]
fn index_mut(&mut self, index: usize) -> &mut T {
self.get_mut(index).expect("Out of bounds access")
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> FromIterator<T> for VecDeque<T> {
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> VecDeque<T> {
SpecFromIter::spec_from_iter(iter.into_iter())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> IntoIterator for VecDeque<T, A> {
type Item = T;
type IntoIter = IntoIter<T, A>;
/// Consumes the deque into a front-to-back iterator yielding elements by
/// value.
fn into_iter(self) -> IntoIter<T, A> {
IntoIter::new(self)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, A: Allocator> IntoIterator for &'a VecDeque<T, A> {
type Item = &'a T;
type IntoIter = Iter<'a, T>;
fn into_iter(self) -> Iter<'a, T> {
self.iter()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T, A: Allocator> IntoIterator for &'a mut VecDeque<T, A> {
type Item = &'a mut T;
type IntoIter = IterMut<'a, T>;
fn into_iter(self) -> IterMut<'a, T> {
self.iter_mut()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
<Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter());
}
#[inline]
fn extend_one(&mut self, elem: T) {
self.push_back(elem);
}
#[inline]
fn extend_reserve(&mut self, additional: usize) {
self.reserve(additional);
}
}
#[stable(feature = "extend_ref", since = "1.2.0")]
impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
self.spec_extend(iter.into_iter());
}
#[inline]
fn extend_one(&mut self, &elem: &'a T) {
self.push_back(elem);
}
#[inline]
fn extend_reserve(&mut self, additional: usize) {
self.reserve(additional);
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for VecDeque<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.iter()).finish()
}
}
#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")]
impl<T, A: Allocator> From<Vec<T, A>> for VecDeque<T, A> {
/// Turn a [`Vec<T>`] into a [`VecDeque<T>`].
///
/// [`Vec<T>`]: crate::vec::Vec
/// [`VecDeque<T>`]: crate::collections::VecDeque
///
/// This conversion is guaranteed to run in *O*(1) time
/// and to not re-allocate the `Vec`'s buffer or allocate
/// any additional memory.
#[inline]
fn from(other: Vec<T, A>) -> Self {
let (ptr, len, cap, alloc) = other.into_raw_parts_with_alloc();
Self { head: 0, len, buf: unsafe { RawVec::from_raw_parts_in(ptr, cap, alloc) } }
}
}
#[stable(feature = "vecdeque_vec_conversions", since = "1.10.0")]
impl<T, A: Allocator> From<VecDeque<T, A>> for Vec<T, A> {
/// Turn a [`VecDeque<T>`] into a [`Vec<T>`].
///
/// [`Vec<T>`]: crate::vec::Vec
/// [`VecDeque<T>`]: crate::collections::VecDeque
///
/// This never needs to re-allocate, but does need to do *O*(*n*) data movement if
/// the circular buffer doesn't happen to be at the beginning of the allocation.
///
/// # Examples
///
/// ```
/// use std::collections::VecDeque;
///
/// // This one is *O*(1).
/// let deque: VecDeque<_> = (1..5).collect();
/// let ptr = deque.as_slices().0.as_ptr();
/// let vec = Vec::from(deque);
/// assert_eq!(vec, [1, 2, 3, 4]);
/// assert_eq!(vec.as_ptr(), ptr);
///
/// // This one needs data rearranging.
/// let mut deque: VecDeque<_> = (1..5).collect();
/// deque.push_front(9);
/// deque.push_front(8);
/// let ptr = deque.as_slices().1.as_ptr();
/// let vec = Vec::from(deque);
/// assert_eq!(vec, [8, 9, 1, 2, 3, 4]);
/// assert_eq!(vec.as_ptr(), ptr);
/// ```
fn from(mut other: VecDeque<T, A>) -> Self {
other.make_contiguous();
unsafe {
let other = ManuallyDrop::new(other);
let buf = other.buf.ptr();
let len = other.len();
let cap = other.capacity();
let alloc = ptr::read(other.allocator());
if other.head != 0 {
ptr::copy(buf.add(other.head), buf, len);
}
Vec::from_raw_parts_in(buf, len, cap, alloc)
}
}
}
#[stable(feature = "std_collections_from_array", since = "1.56.0")]
impl<T, const N: usize> From<[T; N]> for VecDeque<T> {
/// Converts a `[T; N]` into a `VecDeque<T>`.
///
/// ```
/// use std::collections::VecDeque;
///
/// let deq1 = VecDeque::from([1, 2, 3, 4]);
/// let deq2: VecDeque<_> = [1, 2, 3, 4].into();
/// assert_eq!(deq1, deq2);
/// ```
fn from(arr: [T; N]) -> Self {
let mut deq = VecDeque::with_capacity(N);
let arr = ManuallyDrop::new(arr);
if !<T>::IS_ZST {
// SAFETY: VecDeque::with_capacity ensures that there is enough capacity.
unsafe {
ptr::copy_nonoverlapping(arr.as_ptr(), deq.ptr(), N);
}
}
deq.head = 0;
deq.len = N;
deq
}
}