NAME¶map::slippy::cache - Management of a tile cache in the local filesystem
SYNOPSIS¶package require Tcl 8.4
package require Tk 8.4
package require img::png
package require map::slippy
package require map::slippy::cache ?0.2?
::map::slippy::cache cacheName cachedir provider
cacheName valid tile ?msgvar?
cacheName exists tile
cacheName get tile donecmd
DESCRIPTION¶This package provides a class for managing a cache of tiles for slippy-based maps in the local filesystem.
- ::map::slippy::cache cacheName cachedir provider
- Creates the cache cacheName and configures it with both the path to
the directory contaiing the locally cached tiles (cachedir), and
the command prefix from which it will pull tiles asked for and not yet
known to the cache itself (provider).
The result of the command is cacheName.
- cacheName valid tile ?msgvar?
- This method checks the validity of a the given tile identifier. This is a convenience wrapper to ::map::slippy tile valid and has the same interface.
- cacheName exists tile
- This methods tests whether the cache contains the specified tile or not. The result is a boolean value, true if the tile is known, and false otherwise. The tile is identified by a list containing three elements, zoom level, row, and column number, in this order.
- cacheName get tile donecmd
- This is the main method of the cache, retrieving the image for the
specified tile from the cache. The tile identifier is a list
containing three elements, the zoom level, row, and column number of the
tile, in this order.
The command refix donecmd will be invoked when the cache either knows the image for the tile or that no image will forthcoming. It will be invoked with either 2 or 3 arguments, i.e.
- The string set, the tile, and the image.
- The string unset, and the tile.
- These two possibilities are used to either signal the image for the
tile, or that the tile has no image defined for it.
When the cache has no information about the tile it will invoke the provider command prefix specified during its construction, adding three arguments: The string get, the tile, and a callback into the cache. The latter will be invoked by the provider to either transfer the image to the cache, or signal that the tile has no image.
When multiple requests for the same tile are made only one request will be issued to the provider.
KEYWORDS¶cache, filesystem, location, map, slippy, tile, zoom