1 // (C) Copyright David Abrahams 2002.
2 // (C) Copyright Jeremy Siek    2002.
3 // (C) Copyright Thomas Witt    2002.
4 // Distributed under the Boost Software License, Version 1.0. (See
5 // accompanying file LICENSE_1_0.txt or copy at
6 // http://www.boost.org/LICENSE_1_0.txt)
7 #ifndef BOOST_FILTER_ITERATOR_23022003THW_HPP
8 #define BOOST_FILTER_ITERATOR_23022003THW_HPP
9 
10 #include <boost/iterator.hpp>
11 #include <boost/iterator/iterator_adaptor.hpp>
12 #include <boost/iterator/iterator_categories.hpp>
13 
14 #include <boost/type_traits/is_class.hpp>
15 #include <boost/static_assert.hpp>
16 
17 namespace boost {
18 namespace iterators {
19 
20   template <class Predicate, class Iterator>
21   class filter_iterator;
22 
23   namespace detail
24   {
25     template <class Predicate, class Iterator>
26     struct filter_iterator_base
27     {
28         typedef iterator_adaptor<
29             filter_iterator<Predicate, Iterator>
30           , Iterator
31           , use_default
32           , typename mpl::if_<
33                 is_convertible<
34                     typename iterator_traversal<Iterator>::type
35                   , random_access_traversal_tag
36                 >
37               , bidirectional_traversal_tag
38               , use_default
39             >::type
40         > type;
41     };
42   }
43 
44   template <class Predicate, class Iterator>
45   class filter_iterator
46     : public detail::filter_iterator_base<Predicate, Iterator>::type
47   {
48       typedef typename detail::filter_iterator_base<
49           Predicate, Iterator
50       >::type super_t;
51 
52       friend class iterator_core_access;
53 
54    public:
filter_iterator()55       filter_iterator() { }
56 
filter_iterator(Predicate f,Iterator x,Iterator end_=Iterator ())57       filter_iterator(Predicate f, Iterator x, Iterator end_ = Iterator())
58           : super_t(x), m_predicate(f), m_end(end_)
59       {
60           satisfy_predicate();
61       }
62 
filter_iterator(Iterator x,Iterator end_=Iterator ())63       filter_iterator(Iterator x, Iterator end_ = Iterator())
64         : super_t(x), m_predicate(), m_end(end_)
65       {
66         // Pro8 is a little too aggressive about instantiating the
67         // body of this function.
68 #if !BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3003))
69           // Don't allow use of this constructor if Predicate is a
70           // function pointer type, since it will be 0.
71           BOOST_STATIC_ASSERT(is_class<Predicate>::value);
72 #endif
73           satisfy_predicate();
74       }
75 
76       template<class OtherIterator>
filter_iterator(filter_iterator<Predicate,OtherIterator> const & t,typename enable_if_convertible<OtherIterator,Iterator>::type * =0)77       filter_iterator(
78           filter_iterator<Predicate, OtherIterator> const& t
79           , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0
80           )
81           : super_t(t.base()), m_predicate(t.predicate()), m_end(t.end()) {}
82 
predicate() const83       Predicate predicate() const { return m_predicate; }
84 
end() const85       Iterator end() const { return m_end; }
86 
87    private:
increment()88       void increment()
89       {
90           ++(this->base_reference());
91           satisfy_predicate();
92       }
93 
decrement()94       void decrement()
95       {
96         while(!this->m_predicate(*--(this->base_reference()))){};
97       }
98 
satisfy_predicate()99       void satisfy_predicate()
100       {
101           while (this->base() != this->m_end && !this->m_predicate(*this->base()))
102               ++(this->base_reference());
103       }
104 
105       // Probably should be the initial base class so it can be
106       // optimized away via EBO if it is an empty class.
107       Predicate m_predicate;
108       Iterator m_end;
109   };
110 
111   template <class Predicate, class Iterator>
112   inline filter_iterator<Predicate,Iterator>
make_filter_iterator(Predicate f,Iterator x,Iterator end=Iterator ())113   make_filter_iterator(Predicate f, Iterator x, Iterator end = Iterator())
114   {
115       return filter_iterator<Predicate,Iterator>(f,x,end);
116   }
117 
118   template <class Predicate, class Iterator>
119   inline filter_iterator<Predicate,Iterator>
make_filter_iterator(typename iterators::enable_if<is_class<Predicate>,Iterator>::type x,Iterator end=Iterator ())120   make_filter_iterator(
121       typename iterators::enable_if<
122           is_class<Predicate>
123         , Iterator
124       >::type x
125     , Iterator end = Iterator())
126   {
127       return filter_iterator<Predicate,Iterator>(x,end);
128   }
129 
130 } // namespace iterators
131 
132 using iterators::filter_iterator;
133 using iterators::make_filter_iterator;
134 
135 } // namespace boost
136 
137 #endif // BOOST_FILTER_ITERATOR_23022003THW_HPP
138