libbase/GnashAlgorithm.h

   1 // GnashAlgorithm.h: useful templates and functors for generic algorithms
   2 //
   3 //   Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
   4 //
   5 // This program is free software; you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation; either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // This program is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with this program; if not, write to the Free Software
  17 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18 //
  19
  20 #ifndef GNASH_ALGORITHM_H
  21 #define GNASH_ALGORITHM_H
  22
  23 #include <algorithm>
  24 #include <boost/checked_delete.hpp>
  25 #include <boost/intrusive_ptr.hpp>
  26 #include <boost/shared_ptr.hpp>
  27 #include <boost/bind.hpp>
  28
  29 namespace gnash {
  30
  31 /// Retrieve the second element of a container with std::pairs.
  32 template<typename T>
  33 struct SecondElement
  34 {
  35     typedef typename T::second_type result_type;
  36
  37     const result_type& operator()(const T& pair) const {
  38         return pair.second;
  39     }
  40 };
  41
  42 /// Retrieve the first element of a container with std::pairs.
  43 template<typename T>
  44 struct FirstElement
  45 {
  46     typedef typename T::first_type result_type;
  47
  48     const result_type& operator()(const T& pair) const {
  49         return pair.first;
  50     }
  51 };
  52
  53 /// Return a pointer to a type
  54 template<typename T>
  55 struct CreatePointer
  56 {
  57     typedef T* result_type;
  58     result_type operator()(T& t) {
  59         return &t;
  60     }
  61 };
  62
  63 /// Erase elements from an associative container based on a predicate
  64 //
  65 /// This removes elements from a container such as a map if they fulfil a
  66 /// particular condition. Because keys of associative container are const,
  67 /// we can't do this using iterators, because we can't write to them.
  68 template<typename Container, typename Predicate>
  69 void EraseIf(Container& c, Predicate p)
  70 {
  71     typedef typename Container::iterator iterator;
  72
  73     for (iterator i = c.begin(), e = c.end(); i != e; ) {
  74         iterator stored = i++;
  75         if (p(*stored)) c.erase(stored);
  76     }
  77 }
  78
  79
  80 /// Get the size of an array without passing a pointer by mistake
  81 template<typename T, size_t N>
  82 size_t
  83 arraySize(T(&)[N])
  84 {
  85     return N;
  86 }
  87
  88
  89 /// Delete a pointer safely
  90 //
  91 /// Any depth of pointers-to-pointers (up to maximum template recursion) can
  92 /// be passed to this struct. The type of the pointee is deduced and passed
  93 /// to boost::checked_deleter, which ensures that the type is fully known
  94 /// at the point of deletion. It does not, of course, check that the pointer
  95 /// was allocated with new, so this isn't completely idiot-proof.
  96 template<typename T>
  97 struct CheckedDeleter
  98 {
  99 };
 100
 101 template<typename T>
 102 struct CheckedDeleter<T**>
 103 {
 104     /// Typedef for use in boost::bind.
 105     typedef typename CheckedDeleter<T*>::result_type result_type;
 106
 107     void operator()(T** p) const {
 108         CheckedDeleter<T*>()(*p);
 109     }
 110 };
 111
 112 template<typename T>
 113 struct CheckedDeleter<T*>
 114 {
 115     /// Typedef for use in boost::bind.
 116     typedef void result_type;
 117
 118     void operator()(T* p) const {
 119         boost::checked_delete<T>(p);
 120     }
 121 };
 122
 123
 124 /// Call a functor on the second element of each element in a range.
 125 //
 126 /// @tparam T           An iterator type satisfying the requirements of a
 127 ///                     forward iterator
 128 /// @tparam U           The type of the functor op.
 129 /// @param begin        The start of the range to call op on.
 130 /// @param end          The end of the range to call op on.
 131 /// @param op           The function to call on each second element.
 132 template<typename T, typename U>
 133 void
 134 foreachSecond(T begin, T end, U op)
 135 {
 136     typedef SecondElement<typename std::iterator_traits<T>::value_type> S;
 137     std::for_each(begin, end, boost::bind(op, boost::bind(S(), _1)));
 138 }
 139
 140 /// Safely call delete on each element in a range.
 141 //
 142 /// This checks that the type is fully known, but cannot check whether the
 143 /// pointer was allocated with new. Pointers allocated with new[] or any other
 144 /// allocation function should never be passed to this function.
 145 //
 146 /// @param begin        The start of the range to call delete on.
 147 /// @param end          The end of the range to call delete on.
 148 template<typename T>
 149 void
 150 deleteChecked(T begin, T end)
 151 {
 152     typedef typename std::iterator_traits<T>::value_type value_type;
 153     std::for_each(begin, end, CheckedDeleter<value_type>());
 154 }
 155
 156 } // namespace gnash
 157
 158 #endif
 159