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#ifndef EXPIRE_TILES_H
#define EXPIRE_TILES_H
#include <memory>
#include <unordered_set>
#include "osmtypes.hpp"
class reprojection;
class table_t;
class tile;
namespace ewkb {
class parser_t;
}
/**
* \brief Simple struct for the x and y index of a tile ID.
*/
struct xy_coord_t
{
uint32_t x;
uint32_t y;
xy_coord_t() : x(0), y(0) {}
};
/**
* Implementation of the output of the tile expiry list to a file.
*/
class tile_output_t
{
FILE *outfile;
uint32_t outcount = 0;
public:
tile_output_t(const char *filename);
~tile_output_t();
/**
* Output dirty tile.
*
* \param x x index
* \param y y index
* \param zoom zoom level of the tile
*/
void output_dirty_tile(uint32_t x, uint32_t y, uint32_t zoom);
};
struct expire_tiles
{
expire_tiles(uint32_t maxzoom, double maxbbox,
const std::shared_ptr<reprojection> &projection);
int from_bbox(double min_lon, double min_lat, double max_lon, double max_lat);
void from_wkb(const char* wkb, osmid_t osm_id);
int from_db(table_t* table, osmid_t osm_id);
/**
* Write the list of expired tiles to a file.
*
* You will probably use tile_output_t as template argument for production code
* and another class which does not write to a file for unit tests.
*
* \param filename name of the file
* \param minzoom minimum zoom level
*/
void output_and_destroy(const char *filename, uint32_t minzoom);
/**
* Output expired tiles on all requested zoom levels.
*
* \tparam TILE_WRITER class which implements the method
* output_dirty_tile(uint32_t x, uint32_t y, uint32_t zoom) which usually writes the tile ID to a file
* (production code) or does something else (usually unit tests)
*
* \param minzoom minimum zoom level
*/
template <class TILE_WRITER>
void output_and_destroy(TILE_WRITER &output_writer, uint32_t minzoom)
{
assert(minzoom <= maxzoom);
// build a sorted vector of all expired tiles
std::vector<uint64_t> tiles_maxzoom(m_dirty_tiles.begin(),
m_dirty_tiles.end());
std::sort(tiles_maxzoom.begin(), tiles_maxzoom.end());
/* Loop over all requested zoom levels (from maximum down to the minimum zoom level).
* Tile IDs of the tiles enclosing this tile at lower zoom levels are calculated using
* bit shifts.
*
* last_quadkey is initialized with a value which is not expected to exist
* (larger than largest possible quadkey). */
uint64_t last_quadkey = 1ULL << (2 * maxzoom);
for (std::vector<uint64_t>::const_iterator it = tiles_maxzoom.cbegin();
it != tiles_maxzoom.cend(); ++it) {
for (uint32_t dz = 0; dz <= maxzoom - minzoom; dz++) {
// scale down to the current zoom level
uint64_t qt_current = *it >> (dz * 2);
/* If dz > 0, there are propably multiple elements whose quadkey
* is equal because they are all sub-tiles of the same tile at the current
* zoom level. We skip all of them after we have written the first sibling.
*/
if (qt_current == last_quadkey >> (dz * 2)) {
continue;
}
xy_coord_t xy = quadkey_to_xy(qt_current, maxzoom - dz);
output_writer.output_dirty_tile(xy.x, xy.y, maxzoom - dz);
}
last_quadkey = *it;
}
}
/**
* merge the list of expired tiles in the other object into this
* object, destroying the list in the other object.
*/
void merge_and_destroy(expire_tiles &other);
/**
* Helper method to convert a tile ID (x and y) into a quadkey
* using bitshifts.
*
* Quadkeys are interleaved this way: YXYX…
*
* \param x x index
* \param y y index
* \param zoom zoom level
* \returns quadtree ID as integer
*/
static uint64_t xy_to_quadkey(uint32_t x, uint32_t y, uint32_t zoom);
/**
* Convert a quadkey into a tile ID (x and y) using bitshifts.
*
* Quadkeys coordinates are interleaved this way: YXYX…
*
* \param quadkey the quadkey to be converted
* \param zoom zoom level
*/
static xy_coord_t quadkey_to_xy(uint64_t quadkey, uint32_t zoom);
private:
/**
* Expire a single tile.
*
* \param x x index of the tile to be expired.
* \param y y index of the tile to be expired.
*/
void expire_tile(uint32_t x, uint32_t y);
int normalise_tile_x_coord(int x);
void from_line(double lon_a, double lat_a, double lon_b, double lat_b);
void from_wkb_point(ewkb::parser_t *wkb);
void from_wkb_line(ewkb::parser_t *wkb);
void from_wkb_polygon(ewkb::parser_t *wkb, osmid_t osm_id);
double tile_width;
double max_bbox;
int map_width;
uint32_t maxzoom;
std::shared_ptr<reprojection> projection;
/**
* x coordinate of the tile which has been added as last tile to the unordered set
*/
uint32_t last_tile_x;
/**
* y coordinate of the tile which has been added as last tile to the unordered set
*/
uint32_t last_tile_y;
/**
* manages which tiles have been marked as empty
*
* This set stores the IDs of the tiles at the maximum zoom level. We don't
* store the IDs of the expired tiles of lower zoom levels. They are calculated
* on the fly at the end.
*
* Tile IDs are converted into so-called quadkeys as used by Bing Maps.
* https://msdn.microsoft.com/en-us/library/bb259689.aspx
* A quadkey is generated by interleaving the x and y index in following order:
* YXYX...
*
* Example:
* x = 3 = 0b011, y = 5 = 0b101
* results in the quadkey 0b100111.
*
* Bing Maps itself uses the quadkeys as a base-4 number converted to a string.
* We interpret this IDs as simple 64-bit integers due to performance reasons.
*/
std::unordered_set<uint64_t> m_dirty_tiles;
};
#endif
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