ceph/src/boost/libs/gil/example/interleaved_ptr.hpp

   1 //
   2 // Copyright 2005-2007 Adobe Systems Incorporated
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 #ifndef BOOST_GIL_EXAMPLE_INTERLEAVED_PTR_HPP
   9 #define BOOST_GIL_EXAMPLE_INTERLEAVED_PTR_HPP
  10
  11 #include <boost/gil.hpp>
  12 #include <boost/mp11.hpp>
  13
  14 #include <type_traits>
  15
  16 #include "interleaved_ref.hpp"
  17
  18 // Example on how to create a pixel iterator
  19
  20 namespace boost { namespace gil {
  21
  22 // A model of an interleaved pixel iterator. Contains an iterator to the first channel of the current pixel
  23 //
  24 // Models:
  25 //     MutablePixelIteratorConcept
  26 //        PixelIteratorConcept
  27 //           boost_concepts::RandomAccessTraversalConcept
  28 //           PixelBasedConcept
  29 //     HomogeneousPixelBasedConcept
  30 //        PixelBasedConcept
  31 //     ByteAdvanceableConcept
  32 //     HasDynamicXStepTypeConcept
  33
  34 template <typename ChannelPtr,  // Models Channel Iterator (examples: unsigned char* or const unsigned char*)
  35           typename Layout>      // A layout (includes the color space and channel ordering)
  36 struct interleaved_ptr : boost::iterator_facade
  37     <
  38         interleaved_ptr<ChannelPtr, Layout>,
  39         pixel<typename std::iterator_traits<ChannelPtr>::value_type, Layout>,
  40         boost::random_access_traversal_tag,
  41         interleaved_ref<typename std::iterator_traits<ChannelPtr>::reference, Layout> const
  42     >
  43 {
  44 private:
  45     using parent_t = boost::iterator_facade
  46         <
  47             interleaved_ptr<ChannelPtr, Layout>,
  48             pixel<typename std::iterator_traits<ChannelPtr>::value_type, Layout>,
  49             boost::random_access_traversal_tag,
  50             interleaved_ref
  51             <
  52                 typename std::iterator_traits<ChannelPtr>::reference,
  53                 Layout
  54             > const
  55         >;
  56
  57     using channel_t = typename std::iterator_traits<ChannelPtr>::value_type;
  58
  59 public:
  60     using reference = typename parent_t::reference;
  61     using difference_type = typename parent_t::difference_type;
  62
  63     interleaved_ptr() {}
  64     interleaved_ptr(const interleaved_ptr& ptr) : _channels(ptr._channels) {}
  65     template <typename CP> interleaved_ptr(const interleaved_ptr<CP,Layout>& ptr) : _channels(ptr._channels) {}
  66
  67     interleaved_ptr(const ChannelPtr& channels) : _channels(channels) {}
  68
  69     // Construct from a pointer to the reference type. Not required by concepts but important
  70     interleaved_ptr(reference* pix) : _channels(&((*pix)[0])) {}
  71     interleaved_ptr& operator=(reference* pix) { _channels=&((*pix)[0]); return *this; }
  72
  73     /// For some reason operator[] provided by boost::iterator_facade returns a custom class that is convertible to reference
  74     /// We require our own reference because it is registered in iterator_traits
  75     reference operator[](difference_type d) const { return memunit_advanced_ref(*this,d*sizeof(channel_t));}
  76
  77     // Put this for every iterator whose reference is a proxy type
  78     reference operator->()                  const { return **this; }
  79
  80     // Channels accessor (not required by any concept)
  81     const ChannelPtr& channels()            const { return _channels; }
  82           ChannelPtr& channels()                  { return _channels; }
  83
  84     // Not required by concepts but useful
  85     static const std::size_t num_channels = mp11::mp_size<typename Layout::color_space_t>::value;
  86 private:
  87     ChannelPtr _channels;
  88     friend class boost::iterator_core_access;
  89     template <typename CP, typename L> friend struct interleaved_ptr;
  90
  91     void increment()            { _channels+=num_channels; }
  92     void decrement()            { _channels-=num_channels; }
  93     void advance(std::ptrdiff_t d)   { _channels+=num_channels*d; }
  94
  95     std::ptrdiff_t distance_to(const interleaved_ptr& it) const { return (it._channels-_channels)/num_channels; }
  96     bool equal(const interleaved_ptr& it) const { return _channels==it._channels; }
  97
  98     reference dereference() const { return reference(_channels); }
  99 };
 100
 101 /////////////////////////////
 102 //  PixelIteratorConcept
 103 /////////////////////////////
 104
 105 // To get from the channel pointer a channel pointer to const, we have to go through the channel traits, which take a model of channel
 106 // So we can get a model of channel from the channel pointer via iterator_traits. Notice that we take the iterator_traits::reference and not
 107 // iterator_traits::value_type. This is because sometimes multiple reference and pointer types share the same value type. An example of this is
 108 // GIL's planar reference and iterator ("planar_pixel_reference" and "planar_pixel_iterator") which share the class "pixel" as the value_type. The
 109 // class "pixel" is also the value type for interleaved pixel references. Here we are dealing with channels, not pixels, but the principles still apply.
 110 template <typename ChannelPtr, typename Layout>
 111 struct const_iterator_type<interleaved_ptr<ChannelPtr,Layout>> {
 112 private:
 113     using channel_ref_t = typename std::iterator_traits<ChannelPtr>::reference;
 114     using channel_const_ptr_t = typename channel_traits<channel_ref_t>::const_pointer;
 115 public:
 116     using type = interleaved_ptr<channel_const_ptr_t, Layout>;
 117 };
 118
 119 template <typename ChannelPtr, typename Layout>
 120 struct iterator_is_mutable<interleaved_ptr<ChannelPtr,Layout>> : std::true_type {};
 121 template <typename Channel, typename Layout>
 122 struct iterator_is_mutable<interleaved_ptr<const Channel*,Layout>> : std::false_type {};
 123
 124 template <typename ChannelPtr, typename Layout>
 125 struct is_iterator_adaptor<interleaved_ptr<ChannelPtr,Layout>> : std::false_type {};
 126
 127 /////////////////////////////
 128 //  PixelBasedConcept
 129 /////////////////////////////
 130
 131 template <typename ChannelPtr, typename Layout>
 132 struct color_space_type<interleaved_ptr<ChannelPtr,Layout>>
 133 {
 134     using type = typename Layout::color_space_t;
 135 };
 136
 137 template <typename ChannelPtr, typename Layout>
 138 struct channel_mapping_type<interleaved_ptr<ChannelPtr,Layout>>
 139 {
 140     using type = typename Layout::channel_mapping_t;
 141 };
 142
 143 template <typename ChannelPtr, typename Layout>
 144 struct is_planar<interleaved_ptr<ChannelPtr,Layout>> : std::false_type {};
 145
 146 /////////////////////////////
 147 //  HomogeneousPixelBasedConcept
 148 /////////////////////////////
 149
 150 template <typename ChannelPtr, typename Layout>
 151 struct channel_type<interleaved_ptr<ChannelPtr, Layout>>
 152 {
 153     using type = typename std::iterator_traits<ChannelPtr>::value_type;
 154 };
 155
 156 /////////////////////////////
 157 //  ByteAdvanceableConcept
 158 /////////////////////////////
 159
 160 template <typename ChannelPtr, typename Layout>
 161 inline std::ptrdiff_t memunit_step(const interleaved_ptr<ChannelPtr,Layout>&) {
 162     return sizeof(typename std::iterator_traits<ChannelPtr>::value_type)*   // size of each channel in bytes
 163            interleaved_ptr<ChannelPtr,Layout>::num_channels;                // times the number of channels
 164 }
 165
 166 template <typename ChannelPtr, typename Layout>
 167 inline std::ptrdiff_t memunit_distance(const interleaved_ptr<ChannelPtr,Layout>& p1, const interleaved_ptr<ChannelPtr,Layout>& p2) {
 168     return memunit_distance(p1.channels(),p2.channels());
 169 }
 170
 171 template <typename ChannelPtr, typename Layout>
 172 inline void memunit_advance(interleaved_ptr<ChannelPtr,Layout>& p, std::ptrdiff_t diff) {
 173     memunit_advance(p.channels(), diff);
 174 }
 175
 176 template <typename ChannelPtr, typename Layout>
 177 inline interleaved_ptr<ChannelPtr,Layout> memunit_advanced(const interleaved_ptr<ChannelPtr,Layout>& p, std::ptrdiff_t diff) {
 178     interleaved_ptr<ChannelPtr,Layout> ret=p;
 179     memunit_advance(ret, diff);
 180     return ret;
 181 }
 182
 183 template <typename ChannelPtr, typename Layout>
 184 inline typename interleaved_ptr<ChannelPtr,Layout>::reference memunit_advanced_ref(const interleaved_ptr<ChannelPtr,Layout>& p, std::ptrdiff_t diff) {
 185     interleaved_ptr<ChannelPtr,Layout> ret=p;
 186     memunit_advance(ret, diff);
 187     return *ret;
 188 }
 189
 190 /////////////////////////////
 191 //  HasDynamicXStepTypeConcept
 192 /////////////////////////////
 193
 194 template <typename ChannelPtr, typename Layout>
 195 struct dynamic_x_step_type<interleaved_ptr<ChannelPtr, Layout>>
 196 {
 197     using type = memory_based_step_iterator<interleaved_ptr<ChannelPtr, Layout>>;
 198 };
 199 } }  // namespace boost::gil
 200
 201 #endif