dynamic_bitset.hpp 54.5 KB
Newer Older
xuebingbing's avatar
xuebingbing committed
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
// -----------------------------------------------------------
//
//   Copyright (c) 2001-2002 Chuck Allison and Jeremy Siek
//        Copyright (c) 2003-2006, 2008 Gennaro Prota
//             Copyright (c) 2014 Ahmed Charles
//
// Copyright (c) 2014 Glen Joseph Fernandes
// glenfe at live dot com
//
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
//
// -----------------------------------------------------------

#ifndef BOOST_DYNAMIC_BITSET_DYNAMIC_BITSET_HPP
#define BOOST_DYNAMIC_BITSET_DYNAMIC_BITSET_HPP

#include <assert.h>
#include <string>
#include <stdexcept>
#include <algorithm>
#include <vector>
#include <climits>      // for CHAR_BIT

#include "boost/dynamic_bitset/config.hpp"

#ifndef BOOST_NO_STD_LOCALE
#  include <locale>
#endif

#if defined(BOOST_OLD_IOSTREAMS)
#  include <iostream.h>
#  include <ctype.h> // for isspace
#else
#  include <istream>
#  include <ostream>
#endif

#include "boost/dynamic_bitset_fwd.hpp"
#include "boost/detail/dynamic_bitset.hpp"
#include "boost/detail/iterator.hpp" // used to implement append(Iter, Iter)
#include "boost/move/move.hpp"
#include "boost/limits.hpp"
#include "boost/pending/lowest_bit.hpp"
#include "boost/static_assert.hpp"
#include "boost/utility/addressof.hpp"
#include "boost/detail/no_exceptions_support.hpp"
#include "boost/throw_exception.hpp"


namespace boost {

template <typename Block, typename Allocator>
class dynamic_bitset
{
    // Portability note: member function templates are defined inside
    // this class definition to avoid problems with VC++. Similarly,
    // with the member functions of nested classes.
    //
    // [October 2008: the note above is mostly historical; new versions
    // of VC++ are likely able to digest a more drinking form of the
    // code; but changing it now is probably not worth the risks...]

    BOOST_STATIC_ASSERT((bool)detail::dynamic_bitset_impl::allowed_block_type<Block>::value);
    typedef std::vector<Block, Allocator> buffer_type;

public:
    typedef Block block_type;
    typedef Allocator allocator_type;
    typedef std::size_t size_type;
    typedef typename buffer_type::size_type block_width_type;

    BOOST_STATIC_CONSTANT(block_width_type, bits_per_block = (std::numeric_limits<Block>::digits));
    BOOST_STATIC_CONSTANT(size_type, npos = static_cast<size_type>(-1));


public:

    // A proxy class to simulate lvalues of bit type.
    //
    class reference
    {
        friend class dynamic_bitset<Block, Allocator>;


        // the one and only non-copy ctor
        reference(block_type & b, block_type pos)
            :m_block(b),
             m_mask( (assert(pos < bits_per_block),
                      block_type(1) << pos )
                   )
        { }

        void operator&(); // left undefined

    public:

        // copy constructor: compiler generated

        operator bool() const { return (m_block & m_mask) != 0; }
        bool operator~() const { return (m_block & m_mask) == 0; }

        reference& flip() { do_flip(); return *this; }

        reference& operator=(bool x)               { do_assign(x);   return *this; } // for b[i] = x
        reference& operator=(const reference& rhs) { do_assign(rhs); return *this; } // for b[i] = b[j]

        reference& operator|=(bool x) { if  (x) do_set();   return *this; }
        reference& operator&=(bool x) { if (!x) do_reset(); return *this; }
        reference& operator^=(bool x) { if  (x) do_flip();  return *this; }
        reference& operator-=(bool x) { if  (x) do_reset(); return *this; }

     private:
        block_type & m_block;
        const block_type m_mask;

        void do_set() { m_block |= m_mask; }
        void do_reset() { m_block &= ~m_mask; }
        void do_flip() { m_block ^= m_mask; }
        void do_assign(bool x) { x? do_set() : do_reset(); }
    };

    typedef bool const_reference;

    // constructors, etc.
    explicit
    dynamic_bitset(const Allocator& alloc = Allocator());

    explicit
    dynamic_bitset(size_type num_bits, unsigned long value = 0,
               const Allocator& alloc = Allocator());


    // WARNING: you should avoid using this constructor.
    //
    //  A conversion from string is, in most cases, formatting,
    //  and should be performed by using operator>>.
    //
    // NOTE:
    //  Leave the parentheses around std::basic_string<CharT, Traits, Alloc>::npos.
    //  g++ 3.2 requires them and probably the standard will - see core issue 325
    // NOTE 2:
    //  split into two constructors because of bugs in MSVC 6.0sp5 with STLport

    template <typename CharT, typename Traits, typename Alloc>
    dynamic_bitset(const std::basic_string<CharT, Traits, Alloc>& s,
        typename std::basic_string<CharT, Traits, Alloc>::size_type pos,
        typename std::basic_string<CharT, Traits, Alloc>::size_type n,
        size_type num_bits = npos,
        const Allocator& alloc = Allocator())

    :m_bits(alloc),
     m_num_bits(0)
    {
      init_from_string(s, pos, n, num_bits);
    }

    template <typename CharT, typename Traits, typename Alloc>
    explicit
    dynamic_bitset(const std::basic_string<CharT, Traits, Alloc>& s,
      typename std::basic_string<CharT, Traits, Alloc>::size_type pos = 0)

    :m_bits(Allocator()),
     m_num_bits(0)
    {
      init_from_string(s, pos, (std::basic_string<CharT, Traits, Alloc>::npos),
                       npos);
    }

    // The first bit in *first is the least significant bit, and the
    // last bit in the block just before *last is the most significant bit.
    template <typename BlockInputIterator>
    dynamic_bitset(BlockInputIterator first, BlockInputIterator last,
                   const Allocator& alloc = Allocator())

    :m_bits(alloc),
     m_num_bits(0)
    {
        using boost::detail::dynamic_bitset_impl::value_to_type;
        using boost::detail::dynamic_bitset_impl::is_numeric;

        const value_to_type<
            is_numeric<BlockInputIterator>::value> selector;

        dispatch_init(first, last, selector);
    }

    template <typename T>
    void dispatch_init(T num_bits, unsigned long value,
                       detail::dynamic_bitset_impl::value_to_type<true>)
    {
        init_from_unsigned_long(static_cast<size_type>(num_bits), value);
    }

    template <typename T>
    void dispatch_init(T first, T last,
                       detail::dynamic_bitset_impl::value_to_type<false>)
    {
        init_from_block_range(first, last);
    }

    template <typename BlockIter>
    void init_from_block_range(BlockIter first, BlockIter last)
    {
        assert(m_bits.size() == 0);
        m_bits.insert(m_bits.end(), first, last);
        m_num_bits = m_bits.size() * bits_per_block;
    }

    // copy constructor
    dynamic_bitset(const dynamic_bitset& b);

    ~dynamic_bitset();

    void swap(dynamic_bitset& b);
    dynamic_bitset& operator=(const dynamic_bitset& b);

#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
    dynamic_bitset(dynamic_bitset&& src);
    dynamic_bitset& operator=(dynamic_bitset&& src);
#endif // BOOST_NO_CXX11_RVALUE_REFERENCES

    allocator_type get_allocator() const;

    // size changing operations
    void resize(size_type num_bits, bool value = false);
    void clear();
    void push_back(bool bit);
    void append(Block block);

    template <typename BlockInputIterator>
    void m_append(BlockInputIterator first, BlockInputIterator last, std::input_iterator_tag)
    {
        std::vector<Block, Allocator> v(first, last);
        m_append(v.begin(), v.end(), std::random_access_iterator_tag());
    }
    template <typename BlockInputIterator>
    void m_append(BlockInputIterator first, BlockInputIterator last, std::forward_iterator_tag)
    {
        assert(first != last);
        block_width_type r = count_extra_bits();
        std::size_t d = boost::detail::distance(first, last);
        m_bits.reserve(num_blocks() + d);
        if (r == 0) {
            for( ; first != last; ++first)
                m_bits.push_back(*first); // could use vector<>::insert()
        }
        else {
            m_highest_block() |= (*first << r);
            do {
                Block b = *first >> (bits_per_block - r);
                ++first;
                m_bits.push_back(b | (first==last? 0 : *first << r));
            } while (first != last);
        }
        m_num_bits += bits_per_block * d;
    }
    template <typename BlockInputIterator>
    void append(BlockInputIterator first, BlockInputIterator last) // strong guarantee
    {
        if (first != last) {
            typename detail::iterator_traits<BlockInputIterator>::iterator_category cat;
            m_append(first, last, cat);
        }
    }


    // bitset operations
    dynamic_bitset& operator&=(const dynamic_bitset& b);
    dynamic_bitset& operator|=(const dynamic_bitset& b);
    dynamic_bitset& operator^=(const dynamic_bitset& b);
    dynamic_bitset& operator-=(const dynamic_bitset& b);
    dynamic_bitset& operator<<=(size_type n);
    dynamic_bitset& operator>>=(size_type n);
    dynamic_bitset operator<<(size_type n) const;
    dynamic_bitset operator>>(size_type n) const;

    // basic bit operations
    dynamic_bitset& set(size_type n, bool val = true);
    dynamic_bitset& set();
    dynamic_bitset& reset(size_type n);
    dynamic_bitset& reset();
    dynamic_bitset& flip(size_type n);
    dynamic_bitset& flip();
    bool test(size_type n) const;
    bool test_set(size_type n, bool val = true);
    bool all() const;
    bool any() const;
    bool none() const;
    dynamic_bitset operator~() const;
    size_type count() const BOOST_NOEXCEPT;

    // subscript
    reference operator[](size_type pos) {
        return reference(m_bits[block_index(pos)], bit_index(pos));
    }
    bool operator[](size_type pos) const { return test(pos); }

    unsigned long to_ulong() const;

    size_type size() const BOOST_NOEXCEPT;
    size_type num_blocks() const BOOST_NOEXCEPT;
    size_type max_size() const BOOST_NOEXCEPT;
    bool empty() const BOOST_NOEXCEPT;

    bool is_subset_of(const dynamic_bitset& a) const;
    bool is_proper_subset_of(const dynamic_bitset& a) const;
    bool intersects(const dynamic_bitset & a) const;

    // lookup
    size_type find_first() const;
    size_type find_next(size_type pos) const;


#if !defined BOOST_DYNAMIC_BITSET_DONT_USE_FRIENDS
    // lexicographical comparison
    template <typename B, typename A>
    friend bool operator==(const dynamic_bitset<B, A>& a,
                           const dynamic_bitset<B, A>& b);

    template <typename B, typename A>
    friend bool operator<(const dynamic_bitset<B, A>& a,
                          const dynamic_bitset<B, A>& b);


    template <typename B, typename A, typename BlockOutputIterator>
    friend void to_block_range(const dynamic_bitset<B, A>& b,
                               BlockOutputIterator result);

    template <typename BlockIterator, typename B, typename A>
    friend void from_block_range(BlockIterator first, BlockIterator last,
                                 dynamic_bitset<B, A>& result);


    template <typename CharT, typename Traits, typename B, typename A>
    friend std::basic_istream<CharT, Traits>& operator>>(std::basic_istream<CharT, Traits>& is,
                                                         dynamic_bitset<B, A>& b);

    template <typename B, typename A, typename stringT>
    friend void to_string_helper(const dynamic_bitset<B, A> & b, stringT & s, bool dump_all);


#endif


private:
    BOOST_STATIC_CONSTANT(block_width_type, ulong_width = std::numeric_limits<unsigned long>::digits);

    void m_zero_unused_bits();
    bool m_check_invariants() const;

    size_type m_do_find_from(size_type first_block) const;

    block_width_type count_extra_bits() const BOOST_NOEXCEPT { return bit_index(size()); }
    static size_type block_index(size_type pos) BOOST_NOEXCEPT { return pos / bits_per_block; }
    static block_width_type bit_index(size_type pos) BOOST_NOEXCEPT { return static_cast<block_width_type>(pos % bits_per_block); }
    static Block bit_mask(size_type pos) BOOST_NOEXCEPT { return Block(1) << bit_index(pos); }

    template <typename CharT, typename Traits, typename Alloc>
    void init_from_string(const std::basic_string<CharT, Traits, Alloc>& s,
        typename std::basic_string<CharT, Traits, Alloc>::size_type pos,
        typename std::basic_string<CharT, Traits, Alloc>::size_type n,
        size_type num_bits)
    {
        assert(pos <= s.size());

        typedef typename std::basic_string<CharT, Traits, Alloc> StrT;
        typedef typename StrT::traits_type Tr;

        const typename StrT::size_type rlen = (std::min)(n, s.size() - pos);
        const size_type sz = ( num_bits != npos? num_bits : rlen);
        m_bits.resize(calc_num_blocks(sz));
        m_num_bits = sz;


        BOOST_DYNAMIC_BITSET_CTYPE_FACET(CharT, fac, std::locale());
        const CharT one = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');

        const size_type m = num_bits < rlen ? num_bits : rlen;
        typename StrT::size_type i = 0;
        for( ; i < m; ++i) {

            const CharT c = s[(pos + m - 1) - i];

            assert( Tr::eq(c, one)
                    || Tr::eq(c, BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0')) );

            if (Tr::eq(c, one))
                set(i);

        }

    }

    void init_from_unsigned_long(size_type num_bits,
                                 unsigned long value/*,
                                 const Allocator& alloc*/)
    {

        assert(m_bits.size() == 0);

        m_bits.resize(calc_num_blocks(num_bits));
        m_num_bits = num_bits;

        typedef unsigned long num_type;
        typedef boost::detail::dynamic_bitset_impl
            ::shifter<num_type, bits_per_block, ulong_width> shifter;

        //if (num_bits == 0)
        //    return;

        // zero out all bits at pos >= num_bits, if any;
        // note that: num_bits == 0 implies value == 0
        if (num_bits < static_cast<size_type>(ulong_width)) {
            const num_type mask = (num_type(1) << num_bits) - 1;
            value &= mask;
        }

        typename buffer_type::iterator it = m_bits.begin();
        for( ; value; shifter::left_shift(value), ++it) {
            *it = static_cast<block_type>(value);
        }

    }



BOOST_DYNAMIC_BITSET_PRIVATE:

    bool m_unchecked_test(size_type pos) const;
    static size_type calc_num_blocks(size_type num_bits);

    Block&        m_highest_block();
    const Block&  m_highest_block() const;

    buffer_type m_bits;
    size_type   m_num_bits;


    class bit_appender;
    friend class bit_appender;
    class bit_appender {
      // helper for stream >>
      // Supplies to the lack of an efficient append at the less
      // significant end: bits are actually appended "at left" but
      // rearranged in the destructor. From the perspective of
      // client code everything works *as if* dynamic_bitset<> had
      // an append_at_right() function (eventually throwing the same
      // exceptions as push_back) except that the function is in fact
      // called bit_appender::do_append().
      //
      dynamic_bitset & bs;
      size_type n;
      Block mask;
      Block * current;

      // not implemented
      bit_appender(const bit_appender &);
      bit_appender & operator=(const bit_appender &);

    public:
        bit_appender(dynamic_bitset & r) : bs(r), n(0), mask(0), current(0) {}
        ~bit_appender() {
            // reverse the order of blocks, shift
            // if needed, and then resize
            //
            std::reverse(bs.m_bits.begin(), bs.m_bits.end());
            const block_width_type offs = bit_index(n);
            if (offs)
                bs >>= (bits_per_block - offs);
            bs.resize(n); // doesn't enlarge, so can't throw
            assert(bs.m_check_invariants());
        }
        inline void do_append(bool value) {

            if (mask == 0) {
                bs.append(Block(0));
                current = &bs.m_highest_block();
                mask = Block(1) << (bits_per_block - 1);
            }

            if(value)
                *current |= mask;

            mask /= 2;
            ++n;
        }
        size_type get_count() const { return n; }
    };

};

#if !defined BOOST_NO_INCLASS_MEMBER_INITIALIZATION

template <typename Block, typename Allocator>
const typename dynamic_bitset<Block, Allocator>::block_width_type
dynamic_bitset<Block, Allocator>::bits_per_block;

template <typename Block, typename Allocator>
const typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::npos;

template <typename Block, typename Allocator>
const typename dynamic_bitset<Block, Allocator>::block_width_type
dynamic_bitset<Block, Allocator>::ulong_width;

#endif

// Global Functions:

// comparison
template <typename Block, typename Allocator>
bool operator!=(const dynamic_bitset<Block, Allocator>& a,
                const dynamic_bitset<Block, Allocator>& b);

template <typename Block, typename Allocator>
bool operator<=(const dynamic_bitset<Block, Allocator>& a,
                const dynamic_bitset<Block, Allocator>& b);

template <typename Block, typename Allocator>
bool operator>(const dynamic_bitset<Block, Allocator>& a,
               const dynamic_bitset<Block, Allocator>& b);

template <typename Block, typename Allocator>
bool operator>=(const dynamic_bitset<Block, Allocator>& a,
                const dynamic_bitset<Block, Allocator>& b);

// stream operators
#ifdef BOOST_OLD_IOSTREAMS
template <typename Block, typename Allocator>
std::ostream& operator<<(std::ostream& os,
                         const dynamic_bitset<Block, Allocator>& b);

template <typename Block, typename Allocator>
std::istream& operator>>(std::istream& is, dynamic_bitset<Block,Allocator>& b);
#else
template <typename CharT, typename Traits, typename Block, typename Allocator>
std::basic_ostream<CharT, Traits>&
operator<<(std::basic_ostream<CharT, Traits>& os,
           const dynamic_bitset<Block, Allocator>& b);

template <typename CharT, typename Traits, typename Block, typename Allocator>
std::basic_istream<CharT, Traits>&
operator>>(std::basic_istream<CharT, Traits>& is,
           dynamic_bitset<Block, Allocator>& b);
#endif

// bitset operations
template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator&(const dynamic_bitset<Block, Allocator>& b1,
          const dynamic_bitset<Block, Allocator>& b2);

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator|(const dynamic_bitset<Block, Allocator>& b1,
          const dynamic_bitset<Block, Allocator>& b2);

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator^(const dynamic_bitset<Block, Allocator>& b1,
          const dynamic_bitset<Block, Allocator>& b2);

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator-(const dynamic_bitset<Block, Allocator>& b1,
          const dynamic_bitset<Block, Allocator>& b2);

// namespace scope swap
template<typename Block, typename Allocator>
void swap(dynamic_bitset<Block, Allocator>& b1,
          dynamic_bitset<Block, Allocator>& b2);


template <typename Block, typename Allocator, typename stringT>
void
to_string(const dynamic_bitset<Block, Allocator>& b, stringT & s);

template <typename Block, typename Allocator, typename BlockOutputIterator>
void
to_block_range(const dynamic_bitset<Block, Allocator>& b,
               BlockOutputIterator result);


template <typename BlockIterator, typename B, typename A>
inline void
from_block_range(BlockIterator first, BlockIterator last,
                 dynamic_bitset<B, A>& result)
{
    // PRE: distance(first, last) <= numblocks()
    std::copy (first, last, result.m_bits.begin());
}

//=============================================================================
// dynamic_bitset implementation


//-----------------------------------------------------------------------------
// constructors, etc.

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>::dynamic_bitset(const Allocator& alloc)
  : m_bits(alloc), m_num_bits(0)
{

}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>::
dynamic_bitset(size_type num_bits, unsigned long value, const Allocator& alloc)
    : m_bits(alloc),
      m_num_bits(0)
{
    init_from_unsigned_long(num_bits, value);
}

// copy constructor
template <typename Block, typename Allocator>
inline dynamic_bitset<Block, Allocator>::
dynamic_bitset(const dynamic_bitset& b)
  : m_bits(b.m_bits), m_num_bits(b.m_num_bits)
{

}

template <typename Block, typename Allocator>
inline dynamic_bitset<Block, Allocator>::
~dynamic_bitset()
{
    assert(m_check_invariants());
}

template <typename Block, typename Allocator>
inline void dynamic_bitset<Block, Allocator>::
swap(dynamic_bitset<Block, Allocator>& b) // no throw
{
    std::swap(m_bits, b.m_bits);
    std::swap(m_num_bits, b.m_num_bits);
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>& dynamic_bitset<Block, Allocator>::
operator=(const dynamic_bitset<Block, Allocator>& b)
{
    m_bits = b.m_bits;
    m_num_bits = b.m_num_bits;
    return *this;
}

#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES

template <typename Block, typename Allocator>
inline dynamic_bitset<Block, Allocator>::
dynamic_bitset(dynamic_bitset<Block, Allocator>&& b)
  : m_bits(boost::move(b.m_bits)), m_num_bits(boost::move(b.m_num_bits))
{
    // Required so that assert(m_check_invariants()); works.
    assert((b.m_bits = buffer_type()).empty());
    b.m_num_bits = 0;
}

template <typename Block, typename Allocator>
inline dynamic_bitset<Block, Allocator>& dynamic_bitset<Block, Allocator>::
operator=(dynamic_bitset<Block, Allocator>&& b)
{
    if (boost::addressof(b) == this) { return *this; }

    m_bits = boost::move(b.m_bits);
    m_num_bits = boost::move(b.m_num_bits);
    // Required so that assert(m_check_invariants()); works.
    assert((b.m_bits = buffer_type()).empty());
    b.m_num_bits = 0;
    return *this;
}

#endif // BOOST_NO_CXX11_RVALUE_REFERENCES

template <typename Block, typename Allocator>
inline typename dynamic_bitset<Block, Allocator>::allocator_type
dynamic_bitset<Block, Allocator>::get_allocator() const
{
    return m_bits.get_allocator();
}

//-----------------------------------------------------------------------------
// size changing operations

template <typename Block, typename Allocator>
void dynamic_bitset<Block, Allocator>::
resize(size_type num_bits, bool value) // strong guarantee
{

  const size_type old_num_blocks = num_blocks();
  const size_type required_blocks = calc_num_blocks(num_bits);

  const block_type v = value? ~Block(0) : Block(0);

  if (required_blocks != old_num_blocks) {
    m_bits.resize(required_blocks, v); // s.g. (copy)
  }


  // At this point:
  //
  //  - if the buffer was shrunk, we have nothing more to do,
  //    except a call to m_zero_unused_bits()
  //
  //  - if it was enlarged, all the (used) bits in the new blocks have
  //    the correct value, but we have not yet touched those bits, if
  //    any, that were 'unused bits' before enlarging: if value == true,
  //    they must be set.

  if (value && (num_bits > m_num_bits)) {

    const block_width_type extra_bits = count_extra_bits();
    if (extra_bits) {
        assert(old_num_blocks >= 1 && old_num_blocks <= m_bits.size());

        // Set them.
        m_bits[old_num_blocks - 1] |= (v << extra_bits);
    }

  }

  m_num_bits = num_bits;
  m_zero_unused_bits();

}

template <typename Block, typename Allocator>
void dynamic_bitset<Block, Allocator>::
clear() // no throw
{
  m_bits.clear();
  m_num_bits = 0;
}


template <typename Block, typename Allocator>
void dynamic_bitset<Block, Allocator>::
push_back(bool bit)
{
  const size_type sz = size();
  resize(sz + 1);
  set(sz, bit);
}

template <typename Block, typename Allocator>
void dynamic_bitset<Block, Allocator>::
append(Block value) // strong guarantee
{
    const block_width_type r = count_extra_bits();

    if (r == 0) {
        // the buffer is empty, or all blocks are filled
        m_bits.push_back(value);
    }
    else {
        m_bits.push_back(value >> (bits_per_block - r));
        m_bits[m_bits.size() - 2] |= (value << r); // m_bits.size() >= 2
    }

    m_num_bits += bits_per_block;
    assert(m_check_invariants());

}


//-----------------------------------------------------------------------------
// bitset operations
template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::operator&=(const dynamic_bitset& rhs)
{
    assert(size() == rhs.size());
    for (size_type i = 0; i < num_blocks(); ++i)
        m_bits[i] &= rhs.m_bits[i];
    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::operator|=(const dynamic_bitset& rhs)
{
    assert(size() == rhs.size());
    for (size_type i = 0; i < num_blocks(); ++i)
        m_bits[i] |= rhs.m_bits[i];
    //m_zero_unused_bits();
    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::operator^=(const dynamic_bitset& rhs)
{
    assert(size() == rhs.size());
    for (size_type i = 0; i < this->num_blocks(); ++i)
        m_bits[i] ^= rhs.m_bits[i];
    //m_zero_unused_bits();
    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::operator-=(const dynamic_bitset& rhs)
{
    assert(size() == rhs.size());
    for (size_type i = 0; i < num_blocks(); ++i)
        m_bits[i] &= ~rhs.m_bits[i];
    //m_zero_unused_bits();
    return *this;
}

//
// NOTE:
//  Note that the 'if (r != 0)' is crucial to avoid undefined
//  behavior when the left hand operand of >> isn't promoted to a
//  wider type (because rs would be too large).
//
template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::operator<<=(size_type n)
{
    if (n >= m_num_bits)
        return reset();
    //else
    if (n > 0) {

        size_type    const last = num_blocks() - 1;  // num_blocks() is >= 1
        size_type    const div  = n / bits_per_block; // div is <= last
        block_width_type const r = bit_index(n);
        block_type * const b    = &m_bits[0];

        if (r != 0) {

            block_width_type const rs = bits_per_block - r;

            for (size_type i = last-div; i>0; --i) {
                b[i+div] = (b[i] << r) | (b[i-1] >> rs);
            }
            b[div] = b[0] << r;

        }
        else {
            for (size_type i = last-div; i>0; --i) {
                b[i+div] = b[i];
            }
            b[div] = b[0];
        }

        // zero out div blocks at the less significant end
        std::fill_n(m_bits.begin(), div, static_cast<block_type>(0));

        // zero out any 1 bit that flowed into the unused part
        m_zero_unused_bits(); // thanks to Lester Gong

    }

    return *this;


}


//
// NOTE:
//  see the comments to operator <<=
//
template <typename B, typename A>
dynamic_bitset<B, A> & dynamic_bitset<B, A>::operator>>=(size_type n) {
    if (n >= m_num_bits) {
        return reset();
    }
    //else
    if (n>0) {

        size_type  const last  = num_blocks() - 1; // num_blocks() is >= 1
        size_type  const div   = n / bits_per_block;   // div is <= last
        block_width_type const r     = bit_index(n);
        block_type * const b   = &m_bits[0];


        if (r != 0) {

            block_width_type const ls = bits_per_block - r;

            for (size_type i = div; i < last; ++i) {
                b[i-div] = (b[i] >> r) | (b[i+1]  << ls);
            }
            // r bits go to zero
            b[last-div] = b[last] >> r;
        }

        else {
            for (size_type i = div; i <= last; ++i) {
                b[i-div] = b[i];
            }
            // note the '<=': the last iteration 'absorbs'
            // b[last-div] = b[last] >> 0;
        }



        // div blocks are zero filled at the most significant end
        std::fill_n(m_bits.begin() + (num_blocks()-div), div, static_cast<block_type>(0));
    }

    return *this;
}


template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
dynamic_bitset<Block, Allocator>::operator<<(size_type n) const
{
    dynamic_bitset r(*this);
    return r <<= n;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
dynamic_bitset<Block, Allocator>::operator>>(size_type n) const
{
    dynamic_bitset r(*this);
    return r >>= n;
}


//-----------------------------------------------------------------------------
// basic bit operations

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::set(size_type pos, bool val)
{
    assert(pos < m_num_bits);

    if (val)
        m_bits[block_index(pos)] |= bit_mask(pos);
    else
        reset(pos);

    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::set()
{
  std::fill(m_bits.begin(), m_bits.end(), ~Block(0));
  m_zero_unused_bits();
  return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::reset(size_type pos)
{
    assert(pos < m_num_bits);
#if defined __MWERKS__ && BOOST_WORKAROUND(__MWERKS__, <= 0x3003) // 8.x
    // CodeWarrior 8 generates incorrect code when the &=~ is compiled,
    // use the |^ variation instead.. <grafik>
    m_bits[block_index(pos)] |= bit_mask(pos);
    m_bits[block_index(pos)] ^= bit_mask(pos);
#else
    m_bits[block_index(pos)] &= ~bit_mask(pos);
#endif
    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::reset()
{
  std::fill(m_bits.begin(), m_bits.end(), Block(0));
  return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::flip(size_type pos)
{
    assert(pos < m_num_bits);
    m_bits[block_index(pos)] ^= bit_mask(pos);
    return *this;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>&
dynamic_bitset<Block, Allocator>::flip()
{
    for (size_type i = 0; i < num_blocks(); ++i)
        m_bits[i] = ~m_bits[i];
    m_zero_unused_bits();
    return *this;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::m_unchecked_test(size_type pos) const
{
    return (m_bits[block_index(pos)] & bit_mask(pos)) != 0;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::test(size_type pos) const
{
    assert(pos < m_num_bits);
    return m_unchecked_test(pos);
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::test_set(size_type pos, bool val)
{
    bool const b = test(pos);
    if (b != val) {
        set(pos, val);
    }
    return b;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::all() const
{
    if (empty()) {
        return true;
    }

    const block_width_type extra_bits = count_extra_bits();
    block_type const all_ones = ~static_cast<Block>(0);

    if (extra_bits == 0) {
        for (size_type i = 0, e = num_blocks(); i < e; ++i) {
            if (m_bits[i] != all_ones) {
                return false;
            }
        }
    } else {
        for (size_type i = 0, e = num_blocks() - 1; i < e; ++i) {
            if (m_bits[i] != all_ones) {
                return false;
            }
        }
        block_type const mask = ~(~static_cast<Block>(0) << extra_bits);
        if (m_highest_block() != mask) {
            return false;
        }
    }
    return true;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::any() const
{
    for (size_type i = 0; i < num_blocks(); ++i)
        if (m_bits[i])
            return true;
    return false;
}

template <typename Block, typename Allocator>
inline bool dynamic_bitset<Block, Allocator>::none() const
{
    return !any();
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
dynamic_bitset<Block, Allocator>::operator~() const
{
    dynamic_bitset b(*this);
    b.flip();
    return b;
}

template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::count() const BOOST_NOEXCEPT
{
    using detail::dynamic_bitset_impl::table_width;
    using detail::dynamic_bitset_impl::access_by_bytes;
    using detail::dynamic_bitset_impl::access_by_blocks;
    using detail::dynamic_bitset_impl::value_to_type;

#if BOOST_WORKAROUND(__GNUC__, == 4) && (__GNUC_MINOR__ == 3) && (__GNUC_PATCHLEVEL__ == 3)
    // NOTE: Explicit qualification of "bits_per_block"
    //       breaks compilation on gcc 4.3.3
    enum { no_padding = bits_per_block == CHAR_BIT * sizeof(Block) };
#else
    // NOTE: Explicitly qualifying "bits_per_block" to workaround
    //       regressions of gcc 3.4.x
    enum { no_padding =
        dynamic_bitset<Block, Allocator>::bits_per_block
        == CHAR_BIT * sizeof(Block) };
#endif

    enum { enough_table_width = table_width >= CHAR_BIT };

    enum { mode = (no_padding && enough_table_width)
                          ? access_by_bytes
                          : access_by_blocks };

    return do_count(m_bits.begin(), num_blocks(), Block(0),
                    static_cast<value_to_type<(bool)mode> *>(0));
}


//-----------------------------------------------------------------------------
// conversions


template <typename B, typename A, typename stringT>
void to_string_helper(const dynamic_bitset<B, A> & b, stringT & s,
                      bool dump_all)
{
    typedef typename stringT::traits_type Tr;
    typedef typename stringT::value_type  Ch;

    BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, std::locale());
    const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
    const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');

    // Note that this function may access (when
    // dump_all == true) bits beyond position size() - 1

    typedef typename dynamic_bitset<B, A>::size_type size_type;

    const size_type len = dump_all?
         dynamic_bitset<B, A>::bits_per_block * b.num_blocks():
         b.size();
    s.assign (len, zero);

    for (size_type i = 0; i < len; ++i) {
        if (b.m_unchecked_test(i))
            Tr::assign(s[len - 1 - i], one);

    }

}


// A comment similar to the one about the constructor from
// basic_string can be done here. Thanks to James Kanze for
// making me (Gennaro) realize this important separation of
// concerns issue, as well as many things about i18n.
//
template <typename Block, typename Allocator, typename stringT>
inline void
to_string(const dynamic_bitset<Block, Allocator>& b, stringT& s)
{
    to_string_helper(b, s, false);
}


// Differently from to_string this function dumps out
// every bit of the internal representation (may be
// useful for debugging purposes)
//
template <typename B, typename A, typename stringT>
inline void
dump_to_string(const dynamic_bitset<B, A>& b, stringT& s)
{
    to_string_helper(b, s, true /* =dump_all*/);
}

template <typename Block, typename Allocator, typename BlockOutputIterator>
inline void
to_block_range(const dynamic_bitset<Block, Allocator>& b,
               BlockOutputIterator result)
{
    // note how this copies *all* bits, including the
    // unused ones in the last block (which are zero)
    std::copy(b.m_bits.begin(), b.m_bits.end(), result);
}

template <typename Block, typename Allocator>
unsigned long dynamic_bitset<Block, Allocator>::
to_ulong() const
{

  if (m_num_bits == 0)
      return 0; // convention

  // Check for overflows. This may be a performance burden on very
  // large bitsets but is required by the specification, sorry
  if (find_next(ulong_width - 1) != npos)
    BOOST_THROW_EXCEPTION(std::overflow_error("boost::dynamic_bitset::to_ulong overflow"));


  // Ok, from now on we can be sure there's no "on" bit
  // beyond the "allowed" positions
  typedef unsigned long result_type;

  const size_type maximum_size =
            (std::min)(m_num_bits, static_cast<size_type>(ulong_width));

  const size_type last_block = block_index( maximum_size - 1 );

  assert((last_block * bits_per_block) < static_cast<size_type>(ulong_width));

  result_type result = 0;
  for (size_type i = 0; i <= last_block; ++i) {
    const size_type offset = i * bits_per_block;
    result |= (static_cast<result_type>(m_bits[i]) << offset);
  }

  return result;
}

template <typename Block, typename Allocator>
inline typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::size() const BOOST_NOEXCEPT
{
    return m_num_bits;
}

template <typename Block, typename Allocator>
inline typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::num_blocks() const BOOST_NOEXCEPT
{
    return m_bits.size();
}

template <typename Block, typename Allocator>
inline typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::max_size() const BOOST_NOEXCEPT
{
    // Semantics of vector<>::max_size() aren't very clear
    // (see lib issue 197) and many library implementations
    // simply return dummy values, _unrelated_ to the underlying
    // allocator.
    //
    // Given these problems, I was tempted to not provide this
    // function at all but the user could need it if he provides
    // his own allocator.
    //

    const size_type m = detail::dynamic_bitset_impl::
                        vector_max_size_workaround(m_bits);

    return m <= (size_type(-1)/bits_per_block) ?
        m * bits_per_block :
        size_type(-1);
}

template <typename Block, typename Allocator>
inline bool dynamic_bitset<Block, Allocator>::empty() const BOOST_NOEXCEPT
{
  return size() == 0;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::
is_subset_of(const dynamic_bitset<Block, Allocator>& a) const
{
    assert(size() == a.size());
    for (size_type i = 0; i < num_blocks(); ++i)
        if (m_bits[i] & ~a.m_bits[i])
            return false;
    return true;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::
is_proper_subset_of(const dynamic_bitset<Block, Allocator>& a) const
{
    assert(size() == a.size());
    assert(num_blocks() == a.num_blocks());

    bool proper = false;
    for (size_type i = 0; i < num_blocks(); ++i) {
        const Block & bt =   m_bits[i];
        const Block & ba = a.m_bits[i];

        if (bt & ~ba)
            return false; // not a subset at all
        if (ba & ~bt)
            proper = true;
    }
    return proper;
}

template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::intersects(const dynamic_bitset & b) const
{
    size_type common_blocks = num_blocks() < b.num_blocks()
                              ? num_blocks() : b.num_blocks();

    for(size_type i = 0; i < common_blocks; ++i) {
        if(m_bits[i] & b.m_bits[i])
            return true;
    }
    return false;
}

// --------------------------------
// lookup


// look for the first bit "on", starting
// from the block with index first_block
//
template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::m_do_find_from(size_type first_block) const
{
    size_type i = first_block;

    // skip null blocks
    while (i < num_blocks() && m_bits[i] == 0)
        ++i;

    if (i >= num_blocks())
        return npos; // not found

    return i * bits_per_block + static_cast<size_type>(boost::lowest_bit(m_bits[i]));

}


template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::find_first() const
{
    return m_do_find_from(0);
}


template <typename Block, typename Allocator>
typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::find_next(size_type pos) const
{

    const size_type sz = size();
    if (pos >= (sz-1) || sz == 0)
        return npos;

    ++pos;

    const size_type blk = block_index(pos);
    const block_width_type ind = bit_index(pos);

    // shift bits upto one immediately after current
    const Block fore = m_bits[blk] >> ind;

    return fore?
        pos + static_cast<size_type>(lowest_bit(fore))
        :
        m_do_find_from(blk + 1);

}



//-----------------------------------------------------------------------------
// comparison

template <typename Block, typename Allocator>
bool operator==(const dynamic_bitset<Block, Allocator>& a,
                const dynamic_bitset<Block, Allocator>& b)
{
    return (a.m_num_bits == b.m_num_bits)
           && (a.m_bits == b.m_bits);
}

template <typename Block, typename Allocator>
inline bool operator!=(const dynamic_bitset<Block, Allocator>& a,
                       const dynamic_bitset<Block, Allocator>& b)
{
    return !(a == b);
}

template <typename Block, typename Allocator>
bool operator<(const dynamic_bitset<Block, Allocator>& a,
               const dynamic_bitset<Block, Allocator>& b)
{
    assert(a.size() == b.size());
    typedef typename dynamic_bitset<Block, Allocator>::size_type size_type;

    //if (a.size() == 0)
    //  return false;

    // Since we are storing the most significant bit
    // at pos == size() - 1, we need to do the comparisons in reverse.
    //
    for (size_type ii = a.num_blocks(); ii > 0; --ii) {
      size_type i = ii-1;
      if (a.m_bits[i] < b.m_bits[i])
        return true;
      else if (a.m_bits[i] > b.m_bits[i])
        return false;
    }
    return false;
}

template <typename Block, typename Allocator>
inline bool operator<=(const dynamic_bitset<Block, Allocator>& a,
                       const dynamic_bitset<Block, Allocator>& b)
{
    return !(a > b);
}

template <typename Block, typename Allocator>
inline bool operator>(const dynamic_bitset<Block, Allocator>& a,
                      const dynamic_bitset<Block, Allocator>& b)
{
    return b < a;
}

template <typename Block, typename Allocator>
inline bool operator>=(const dynamic_bitset<Block, Allocator>& a,
                       const dynamic_bitset<Block, Allocator>& b)
{
    return !(a < b);
}

//-----------------------------------------------------------------------------
// stream operations

#ifdef BOOST_OLD_IOSTREAMS
template < typename Block, typename Alloc>
std::ostream&
operator<<(std::ostream& os, const dynamic_bitset<Block, Alloc>& b)
{
    // NOTE: since this is aimed at "classic" iostreams, exception
    // masks on the stream are not supported. The library that
    // ships with gcc 2.95 has an exceptions() member function but
    // nothing is actually implemented; not even the class ios::failure.

    using namespace std;

    const ios::iostate ok = ios::goodbit;
    ios::iostate err = ok;

    if (os.opfx()) {

        //try
        typedef typename dynamic_bitset<Block, Alloc>::size_type bitsetsize_type;

        const bitsetsize_type sz = b.size();
        std::streambuf * buf = os.rdbuf();
        size_t npad = os.width() <= 0  // careful: os.width() is signed (and can be < 0)
            || (bitsetsize_type) os.width() <= sz? 0 : os.width() - sz;

        const char fill_char = os.fill();
        const ios::fmtflags adjustfield = os.flags() & ios::adjustfield;

        // if needed fill at left; pad is decresed along the way
        if (adjustfield != ios::left) {
            for (; 0 < npad; --npad)
                if (fill_char != buf->sputc(fill_char)) {
                    err |= ios::failbit;
                    break;
                }
        }

        if (err == ok) {
            // output the bitset
            for (bitsetsize_type i = b.size(); 0 < i; --i) {
                const char dig = b.test(i-1)? '1' : '0';
                if (EOF == buf->sputc(dig)) {
                    err |= ios::failbit;
                    break;
                }
            }
        }

        if (err == ok) {
            // if needed fill at right
            for (; 0 < npad; --npad) {
                if (fill_char != buf->sputc(fill_char)) {
                    err |= ios::failbit;
                    break;
                }
            }
        }

        os.osfx();
        os.width(0);

    } // if opfx

    if(err != ok)
        os.setstate(err); // assume this does NOT throw
    return os;

}
#else

template <typename Ch, typename Tr, typename Block, typename Alloc>
std::basic_ostream<Ch, Tr>&
operator<<(std::basic_ostream<Ch, Tr>& os,
           const dynamic_bitset<Block, Alloc>& b)
{

    using namespace std;

    const ios_base::iostate ok = ios_base::goodbit;
    ios_base::iostate err = ok;

    typename basic_ostream<Ch, Tr>::sentry cerberos(os);
    if (cerberos) {

        BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, os.getloc());
        const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
        const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');

        BOOST_TRY {

            typedef typename dynamic_bitset<Block, Alloc>::size_type bitset_size_type;
            typedef basic_streambuf<Ch, Tr> buffer_type;

            buffer_type * buf = os.rdbuf();
            // careful: os.width() is signed (and can be < 0)
            const bitset_size_type width = (os.width() <= 0) ? 0 : static_cast<bitset_size_type>(os.width());
            streamsize npad = (width <= b.size()) ? 0 : width - b.size();

            const Ch fill_char = os.fill();
            const ios_base::fmtflags adjustfield = os.flags() & ios_base::adjustfield;

            // if needed fill at left; pad is decreased along the way
            if (adjustfield != ios_base::left) {
                for (; 0 < npad; --npad)
                    if (Tr::eq_int_type(Tr::eof(), buf->sputc(fill_char))) {
                          err |= ios_base::failbit;
                          break;
                    }
            }

            if (err == ok) {
                // output the bitset
                for (bitset_size_type i = b.size(); 0 < i; --i) {
                    typename buffer_type::int_type
                        ret = buf->sputc(b.test(i-1)? one : zero);
                    if (Tr::eq_int_type(Tr::eof(), ret)) {
                        err |= ios_base::failbit;
                        break;
                    }
                }
            }

            if (err == ok) {
                // if needed fill at right
                for (; 0 < npad; --npad) {
                    if (Tr::eq_int_type(Tr::eof(), buf->sputc(fill_char))) {
                        err |= ios_base::failbit;
                        break;
                    }
                }
            }


            os.width(0);

        } BOOST_CATCH (...) { // see std 27.6.1.1/4
            bool rethrow = false;
            BOOST_TRY { os.setstate(ios_base::failbit); } BOOST_CATCH (...) { rethrow = true; } BOOST_CATCH_END

            if (rethrow)
                BOOST_RETHROW;
        }
        BOOST_CATCH_END
    }

    if(err != ok)
        os.setstate(err); // may throw exception
    return os;

}
#endif


#ifdef BOOST_OLD_IOSTREAMS

    // A sentry-like class that calls isfx in its destructor.
    // "Necessary" because bit_appender::do_append may throw.
    class pseudo_sentry {
        std::istream & m_r;
        const bool m_ok;
    public:
        explicit pseudo_sentry(std::istream & r) : m_r(r), m_ok(r.ipfx(0)) { }
        ~pseudo_sentry() { m_r.isfx(); }
        operator bool() const { return m_ok; }
    };

template <typename Block, typename Alloc>
std::istream&
operator>>(std::istream& is, dynamic_bitset<Block, Alloc>& b)
{

// Extractor for classic IO streams (libstdc++ < 3.0)
// ----------------------------------------------------//
//  It's assumed that the stream buffer functions, and
//  the stream's setstate() _cannot_ throw.


    typedef dynamic_bitset<Block, Alloc> bitset_type;
    typedef typename bitset_type::size_type size_type;

    std::ios::iostate err = std::ios::goodbit;
    pseudo_sentry cerberos(is); // skips whitespaces
    if(cerberos) {

        b.clear();

        const std::streamsize w = is.width();
        const size_type limit = w > 0 && static_cast<size_type>(w) < b.max_size()
                                                         ? static_cast<size_type>(w) : b.max_size();
        typename bitset_type::bit_appender appender(b);
        std::streambuf * buf = is.rdbuf();
        for(int c = buf->sgetc(); appender.get_count() < limit; c = buf->snextc() ) {

            if (c == EOF) {
                err |= std::ios::eofbit;
                break;
            }
            else if (char(c) != '0' && char(c) != '1')
                break; // non digit character

            else {
                BOOST_TRY {
                    appender.do_append(char(c) == '1');
                }
                BOOST_CATCH(...) {
                    is.setstate(std::ios::failbit); // assume this can't throw
                    BOOST_RETHROW;
                }
                BOOST_CATCH_END
            }

        } // for
    }

    is.width(0);
    if (b.size() == 0)
        err |= std::ios::failbit;
    if (err != std::ios::goodbit)
        is.setstate (err); // may throw

    return is;
}

#else // BOOST_OLD_IOSTREAMS

template <typename Ch, typename Tr, typename Block, typename Alloc>
std::basic_istream<Ch, Tr>&
operator>>(std::basic_istream<Ch, Tr>& is, dynamic_bitset<Block, Alloc>& b)
{

    using namespace std;

    typedef dynamic_bitset<Block, Alloc> bitset_type;
    typedef typename bitset_type::size_type size_type;

    const streamsize w = is.width();
    const size_type limit = 0 < w && static_cast<size_type>(w) < b.max_size()?
                                         static_cast<size_type>(w) : b.max_size();

    ios_base::iostate err = ios_base::goodbit;
    typename basic_istream<Ch, Tr>::sentry cerberos(is); // skips whitespaces
    if(cerberos) {

        // in accordance with prop. resol. of lib DR 303 [last checked 4 Feb 2004]
        BOOST_DYNAMIC_BITSET_CTYPE_FACET(Ch, fac, is.getloc());
        const Ch zero = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '0');
        const Ch one  = BOOST_DYNAMIC_BITSET_WIDEN_CHAR(fac, '1');

        b.clear();
        BOOST_TRY {
            typename bitset_type::bit_appender appender(b);
            basic_streambuf <Ch, Tr> * buf = is.rdbuf();
            typename Tr::int_type c = buf->sgetc();
            for( ; appender.get_count() < limit; c = buf->snextc() ) {

                if (Tr::eq_int_type(Tr::eof(), c)) {
                    err |= ios_base::eofbit;
                    break;
                }
                else {
                    const Ch to_c = Tr::to_char_type(c);
                    const bool is_one = Tr::eq(to_c, one);

                    if (!is_one && !Tr::eq(to_c, zero))
                        break; // non digit character

                    appender.do_append(is_one);

                }

            } // for
        }
        BOOST_CATCH (...) {
            // catches from stream buf, or from vector:
            //
            // bits_stored bits have been extracted and stored, and
            // either no further character is extractable or we can't
            // append to the underlying vector (out of memory)

            bool rethrow = false;   // see std 27.6.1.1/4
            BOOST_TRY { is.setstate(ios_base::badbit); }
            BOOST_CATCH(...) { rethrow = true; }
            BOOST_CATCH_END

            if (rethrow)
                BOOST_RETHROW;

        }
        BOOST_CATCH_END
    }

    is.width(0);
    if (b.size() == 0 /*|| !cerberos*/)
        err |= ios_base::failbit;
    if (err != ios_base::goodbit)
        is.setstate (err); // may throw

    return is;

}


#endif


//-----------------------------------------------------------------------------
// bitset operations

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator&(const dynamic_bitset<Block, Allocator>& x,
          const dynamic_bitset<Block, Allocator>& y)
{
    dynamic_bitset<Block, Allocator> b(x);
    return b &= y;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator|(const dynamic_bitset<Block, Allocator>& x,
          const dynamic_bitset<Block, Allocator>& y)
{
    dynamic_bitset<Block, Allocator> b(x);
    return b |= y;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator^(const dynamic_bitset<Block, Allocator>& x,
          const dynamic_bitset<Block, Allocator>& y)
{
    dynamic_bitset<Block, Allocator> b(x);
    return b ^= y;
}

template <typename Block, typename Allocator>
dynamic_bitset<Block, Allocator>
operator-(const dynamic_bitset<Block, Allocator>& x,
          const dynamic_bitset<Block, Allocator>& y)
{
    dynamic_bitset<Block, Allocator> b(x);
    return b -= y;
}

//-----------------------------------------------------------------------------
// namespace scope swap

template<typename Block, typename Allocator>
inline void
swap(dynamic_bitset<Block, Allocator>& left,
     dynamic_bitset<Block, Allocator>& right) // no throw
{
    left.swap(right);
}


//-----------------------------------------------------------------------------
// private (on conforming compilers) member functions


template <typename Block, typename Allocator>
inline typename dynamic_bitset<Block, Allocator>::size_type
dynamic_bitset<Block, Allocator>::calc_num_blocks(size_type num_bits)
{
    return num_bits / bits_per_block
           + static_cast<size_type>( num_bits % bits_per_block != 0 );
}

// gives a reference to the highest block
//
template <typename Block, typename Allocator>
inline Block& dynamic_bitset<Block, Allocator>::m_highest_block()
{
    return const_cast<Block &>
           (static_cast<const dynamic_bitset *>(this)->m_highest_block());
}

// gives a const-reference to the highest block
//
template <typename Block, typename Allocator>
inline const Block& dynamic_bitset<Block, Allocator>::m_highest_block() const
{
    assert(size() > 0 && num_blocks() > 0);
    return m_bits.back();
}


// If size() is not a multiple of bits_per_block
// then not all the bits in the last block are used.
// This function resets the unused bits (convenient
// for the implementation of many member functions)
//
template <typename Block, typename Allocator>
inline void dynamic_bitset<Block, Allocator>::m_zero_unused_bits()
{
    assert (num_blocks() == calc_num_blocks(m_num_bits));

    // if != 0 this is the number of bits used in the last block
    const block_width_type extra_bits = count_extra_bits();

    if (extra_bits != 0)
        m_highest_block() &= ~(~static_cast<Block>(0) << extra_bits);

}

// check class invariants
template <typename Block, typename Allocator>
bool dynamic_bitset<Block, Allocator>::m_check_invariants() const
{
    const block_width_type extra_bits = count_extra_bits();
    if (extra_bits > 0) {
        block_type const mask = (~static_cast<Block>(0) << extra_bits);
        if ((m_highest_block() & mask) != 0)
            return false;
    }
    if (m_bits.size() > m_bits.capacity() || num_blocks() != calc_num_blocks(size()))
        return false;

    return true;

}


} // namespace boost


#undef BOOST_BITSET_CHAR

#endif // include guard