sdsl/include/sdsl/sorted_stack_support.hpp

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/* sdsl - succinct data structures library
    Copyright (C) 2009 Simon Gog

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see http://www.gnu.org/licenses/ .
*/
#ifndef INCLUDED_SDSL_SORTED_STACK_SUPPORT
#define INCLUDED_SDSL_SORTED_STACK_SUPPORT

#include "int_vector.hpp"
#include "bitmagic.hpp"
#include <vector>

namespace sdsl
{


class sorted_stack_support
{
    public:
        typedef int_vector<64>::size_type size_type;
    private:
        size_type m_n;   // Size of the supported vector.
        size_type m_cnt; // Counter for the indices on the stack.
        size_type m_top; // Topmost index of the stack.
        int_vector<64> m_stack; // Memory for the stack.

        inline size_type block_nr(size_type x) {
            return x/63;
        }; // TODO: maybe we can speed this up with bit hacks
        inline size_type block_pos(size_type x) {
            return x%63;
        }; // TODO: maybe we can speed this up with bit hacks
    public:

        sorted_stack_support(size_type n);

        sorted_stack_support(const sorted_stack_support& sis);
        ~sorted_stack_support() {};

        bool empty() const {
            return 0==m_cnt;
        };

        const size_type top() const;

        void pop();

        void push(size_type x);

        size_type size()const {
            return m_cnt;
        };

        size_type serialize(std::ostream& out)const;
        void load(std::istream& in);


        sorted_stack_support& operator=(const sorted_stack_support& sis);


        bool operator==(const sorted_stack_support& sis)const;

        bool operator!=(const sorted_stack_support& sis)const;

};

inline sorted_stack_support::sorted_stack_support(size_type n):m_n(n), m_cnt(0), m_top(0), m_stack()
{
    m_stack = int_vector<64>(block_nr(m_n+1)+1, 0);
    m_stack[0] = 1;
}

inline sorted_stack_support::sorted_stack_support(const sorted_stack_support& sis):m_n(sis.m_n), m_cnt(sis.m_cnt), m_top(sis.m_top), m_stack()
{
    m_stack = sis.m_stack;
}

inline sorted_stack_support& sorted_stack_support::operator=(const sorted_stack_support& sis)
{
    if (this != &sis) {
        m_n                     = sis.m_n;
        m_cnt           = sis.m_cnt;
        m_top           = sis.m_top;
        m_stack         = sis.m_stack;
    }
    return *this;
}

inline bool sorted_stack_support::operator==(const sorted_stack_support& sis)const
{
    return m_n == sis.m_n and m_cnt == sis.m_cnt and m_top == sis.m_top and m_stack == sis.m_stack;
}

inline bool sorted_stack_support::operator!=(const sorted_stack_support& sis)const
{
    return !(*this==sis);
}

inline const sorted_stack_support::size_type sorted_stack_support::top()const
{
    return m_top-1;
}

inline void sorted_stack_support::push(size_type x)
{
    x += 1;
    ++m_cnt;    //< increment counter
    size_type bn = block_nr(x);
    m_stack[bn] ^= (1ULL << block_pos(x));
    if (bn > 0 and m_stack[bn-1] == 0) {
        m_stack[bn-1] = 0x8000000000000000ULL | m_top;
    }
    m_top = x;
}

inline void sorted_stack_support::pop()
{
    if (!empty()) {
        --m_cnt; //< decrement counter
        size_type bn = block_nr(m_top);
        uint64_t w = m_stack[ bn ];
        assert((w>>63) == 0);    // highest bit is not set, as the block contains no pointer
        w ^= (1ULL << block_pos(m_top));
        m_stack[ bn ] = w;
        if (w>0) {
            m_top = bn*63 + bit_magic::l1BP(w);
        } else { // w==0 and cnt>0
            assert(bn > 0);
            w = m_stack[ bn-1 ];
            if ((w>>63) == 0) { // highest bit is not set => the block contains no pointer
                assert(w>0);
                m_top = (bn-1)*63 + bit_magic::l1BP(w);
            } else { // block contains pointers
                m_stack[bn-1] = 0;
                m_top = w&0x7FFFFFFFFFFFFFFFULL;
            }
        }
    }
}

inline sorted_stack_support::size_type sorted_stack_support::serialize(std::ostream& out)const
{
    size_type written_bytes = 0;
    written_bytes += util::write_member(m_n, out);
    written_bytes += util::write_member(m_top, out);
    written_bytes += util::write_member(m_cnt, out);
    written_bytes += m_stack.serialize(out);
    return written_bytes;
}

inline void sorted_stack_support::load(std::istream& in)
{
    util::read_member(m_n, in);
    util::read_member(m_top, in);
    util::read_member(m_cnt, in);
    m_stack.load(in);
}

}// end namespace sdsl

#endif // end file