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

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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

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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
       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 con-
	      taining 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

map									0.2						     map::slippy::cache(n)