src/collision_grid_iterator.h

   1 #ifndef __COLLISION_GRID_ITERATOR_H__
   2 #define __COLLISION_GRID_ITERATOR_H__
   3
   4 #include "math/rectangle.h"
   5
   6 using namespace SuperTux;
   7
   8 class CollisionGrid;
   9
  10 class CollisionGridIterator
  11 {
  12 public:
  13   CollisionGridIterator(CollisionGrid& newgrid, const Rectangle& bbox)
  14     : grid(newgrid)
  15   {
  16     start_x = int(bbox.p1.x / grid.cell_width) - 2;
  17     if(start_x < 0)
  18       start_x = 0;
  19     x = start_x;
  20
  21     y = int(bbox.p1.y / grid.cell_height) - 2;
  22     if(y < 0)
  23       y = 0;
  24
  25     end_x = int(bbox.p2.x / grid.cell_width) + 2;
  26     if(end_x > (int) grid.cells_x)
  27       end_x = grid.cells_x;
  28
  29     end_y = int(bbox.p2.y / grid.cell_height) + 2;
  30     if(end_y > (int) grid.cells_y)
  31       end_y = grid.cells_y;
  32
  33     if(start_x >= end_x) {
  34       printf("bad region.\n");
  35       y = 0;
  36       end_y = 0;
  37       return;
  38     }
  39
  40     timestamp = grid.iterator_timestamp++;
  41     entry = 0;
  42   }
  43
  44   MovingObject* next()
  45   {
  46     CollisionGrid::ObjectWrapper* wrapper = next_wrapper();
  47     if(wrapper == 0)
  48       return 0;
  49
  50     return wrapper->object;
  51   }
  52
  53 private:
  54   friend class CollisionGrid;
  55
  56   CollisionGrid::ObjectWrapper* next_wrapper()
  57   {
  58     CollisionGrid::ObjectWrapper* wrapper;
  59
  60     do {
  61       while(entry == 0) {
  62         if(y >= end_y)
  63           return 0;
  64
  65         entry = grid.grid[y*grid.cells_x + x];
  66         x++;
  67         if(x >= end_x) {
  68           x = start_x;
  69           y++;
  70         }
  71       }
  72
  73       wrapper = entry->object_wrapper;
  74       entry = entry->next;
  75     } while(wrapper->timestamp == timestamp);
  76
  77     wrapper->timestamp = timestamp;
  78
  79     return wrapper;
  80   }
  81
  82   CollisionGrid& grid;
  83   CollisionGrid::GridEntry* entry;
  84   int x, y;
  85   int start_x, end_x, end_y;
  86   int timestamp;
  87 };
  88
  89 #endif
  90