boost/boost/spirit/home/support/iterators/line_pos_iterator.hpp

/*==============================================================================
    Copyright (c) 2001-2011 Joel de Guzman
    Copyright (c) 2010      Bryce Lelbach

    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)
==============================================================================*/

#if !defined(BOOST_SPIRIT_SUPPORT_LINE_POS_ITERATOR)
#define BOOST_SPIRIT_SUPPORT_LINE_POS_ITERATOR

#include <boost/iterator/iterator_adaptor.hpp>
#include <boost/range/iterator_range.hpp>

namespace boost { namespace spirit
{
    //[line_pos_iterator_class
    /*`The `line_pos_iterator` is a lightweight line position iterator.
       This iterator adapter only stores the current line number, nothing else.
       Unlike __classic__'s `position_iterator`, it does not store the
       column number and does not need an end iterator. The current column can
       be computed, if needed. */
    //`[heading Class Reference]
    template <class Iterator>
    class line_pos_iterator : public boost::iterator_adaptor<
        line_pos_iterator<Iterator>  // Derived
      , Iterator                     // Base
      , boost::use_default           // Value
      , boost::forward_traversal_tag // CategoryOrTraversal
    > {
    public:
        line_pos_iterator();

        explicit line_pos_iterator(Iterator);

        std::size_t position() const;

    private:
        friend class boost::iterator_core_access;

        void increment();

        std::size_t line; // The line position.
        typename std::iterator_traits<Iterator>::value_type prev;
    };
    //]

    template <class Iterator>
    line_pos_iterator<Iterator>::line_pos_iterator() :
        line_pos_iterator::iterator_adaptor_(), line(1), prev(0) { }

    template <class Iterator>
    line_pos_iterator<Iterator>::line_pos_iterator(Iterator base) :
        line_pos_iterator::iterator_adaptor_(base), line(1), prev(0) { }

    template <class Iterator>
    std::size_t line_pos_iterator<Iterator>::position() const
    {
        return line;
    }
 
    template<class Iterator>
    void line_pos_iterator<Iterator>::increment()
    {
        typename std::iterator_traits<Iterator>::reference
          ref = *(this->base());
      
        switch (ref) {
          case '\r':
            if (prev != '\n')
              ++line;
            break;
          case '\n':
            if (prev != '\r')
              ++line;
            break;
          default:
            break;
        }
      
        prev = ref;
        ++this->base_reference();
    }

    //[line_pos_iterator_utilities
    //`[heading get_line]
    template <class Iterator>
    inline std::size_t get_line(Iterator);
    /*`Get the line position. Returns -1 if Iterator is not a
       `line_pos_iterator`. */

    //`[heading get_line_start]
    template <class Iterator>
    inline Iterator get_line_start(Iterator lower_bound, Iterator current); 
    /*`Get an iterator to the beginning of the line. Applicable to any
       iterator. */

    //`[heading get_current_line]
    template <class Iterator>
    inline iterator_range<Iterator>
    get_current_line(Iterator lower_bound, Iterator current,
                     Iterator upper_bound); 
    /*`Get an `iterator_range` containing the current line. Applicable to any
       iterator. */ 

    //`[heading get_column]
    template <class Iterator>
    inline std::size_t get_column(Iterator lower_bound, Iterator current,
                                  std::size_t tabs = 4); 
    /*`Get the current column. Applicable to any iterator. */ 
    //]

    template <class Iterator>
    inline std::size_t get_line(Iterator)
    {
        return -1;
    }
    
    template <class Iterator>
    inline std::size_t get_line(line_pos_iterator<Iterator> i)
    {
        return i.position();
    }
    
    template <class Iterator>
    inline Iterator get_line_start(Iterator lower_bound, Iterator current)
    {
        Iterator latest = lower_bound;
      
        for (Iterator i = lower_bound; i != current; ++i) {
          switch (*i) {
            case '\r':
            case '\n':
              latest = i;
          }
        }
      
        return latest;
    }
    
    template <class Iterator>
    inline iterator_range<Iterator>
    get_current_line(Iterator lower_bound,
                     Iterator current,
                     Iterator upper_bound)
    {
        Iterator first = get_line_start(lower_bound, current);
        Iterator last = get_line_start(current, upper_bound);
      
        if (last == current)
          last = upper_bound;
      
        return iterator_range<Iterator>(first, last);
    }
    
    template <class Iterator>
    inline std::size_t get_column(Iterator lower_bound,
                                  Iterator current,
                                  std::size_t tabs)
    {
        std::size_t column = 1;
        Iterator first = get_line_start(lower_bound, current);
      
        for (Iterator i = first; i != current; ++i) {
          switch (*i) {
            case '\t':
              column += tabs - (column - 1) % tabs;
              break;
            default:
              ++column;
          }
        }
      
        return column;
    }

}}

#endif // BOOST_SPIRIT_SUPPORT_LINE_POS_ITERATOR