zooui.tilesystem.tilestore.tilecache module

Thread-safe Least Recently Used (LRU) cache for storing tiles.

class zooui.tilesystem.tilestore.tilecache.TileCache(maxsize=256, maxage=60)

Bases: object

Constructor:

TileCache(maxsize, maxage)

Parameters :

maxsize : int maxage : int

TileCache(maxsize, maxage) –> None

TileCache objects are used for caching tiles in memory.

Tiles can be accessed in much the same way as dict objects: tilecache[tile_id] holds the tile identified by the given tile_id.

Constructor:

TileCache(maxsize, maxage)

Parameters :

maxsize : int maxage : int

TileCache(maxsize, maxage) –> None

Create a new TileCache object.

The maximum number of tiles to store is set by maxsize. There will be no limit if maxsize <= 0.

The maximum age of the tiles (in seconds) allowed before they are discarded is set by maxage. There will be no limit if maxage <= 0.

None tiles and (0,0,0) tiles do not count towards the number of stored tiles and will therefore not be automatically discarded.

shutdown()

Signal the periodic clean thread to stop and wait for it.

insert(tile_id, tile, maxaccesses=0)

Method :

TileCache.insert(tile_id, tile, maxaccesses)

Parameters :

tile_id : Tuple[str, int, int, int] tile : Any maxaccesses : int

TileCache.insert(tile_id, tile, maxaccesses) –> None

Insert the tile with the given tile_id into the cache.

If maxaccesses <= 0, then the behaviour is the same as tilecache[tile_id]=tile. Otherwise the tile is set to expire after it has been accessed maxaccesses times.

__mortal(tile_id, tile)

Method :

__mortal(tile_id, tile)

Parameters :

tile_id : Tuple[str, int, int, int] tile : Any

__mortal(tile_id, tile) –> bool

Returns a bool indicating whether the given tile is mortal.

The tile will never be removed from the cache if it is immortal.

None tiles and (0,0,0) tiles are the only ones considered immortal.

__periodic_clean()

Method :

__periodic_clean()

Parameters :

None

__periodic_clean() –> infinite loop

Periodically remove old tiles based on maxage.

__clean()

Method :

__clean()

Parameters :

None

__clean() –> None

Remove the least recently used tiles based on maxsize.

purge()

Method :

TileCache.purge()

Parameters :

None

TileCache.purge() –> None

Purge all tiles from the cache.