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map::slippy::cache(n) Mapping utilities map::slippy::cache(n) 





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.






API



  
::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.

  






METHODS



  

  
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.

  

  
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.

  

  
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.

  







  
[1]

  
The string set, the tile, and the image.

  
[2]

  
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.

  










REFERENCES



  
[1]

  
http://wiki.openstreetmap.org/wiki/Main_Page








KEYWORDS


cache, filesystem, location, map, slippy, tile, zoom







  

    0.2
    tcllib