org.ka2ddo.yaac.osm

Class OsmSegmenter.OpenRandomAccessFileCache

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<java.lang.String,MultiBufferedRandomAccessFile>

org.ka2ddo.yaac.osm.OsmSegmenter.OpenRandomAccessFileCache

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map<java.lang.String,MultiBufferedRandomAccessFile>

Enclosing class:

OsmSegmenter

protected static class OsmSegmenter.OpenRandomAccessFileCache
extends java.util.LinkedHashMap<java.lang.String,MultiBufferedRandomAccessFile>

LIFO cache for random access files, so as to minimize file opens and reloads while not exceeding the maximum number of open file descriptors.

Author:

Andrew Pavlin, KA2DDO

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	OpenRandomAccessFileCache(java.io.PrintStream out) Create a cache for opened random access files.

Method Summary

Modifier and Type	Method and Description
int	getHoldingLimit() Get the current maximum number of open file allowed in the cache.
void	reduceHoldingLimit(int reserve) Reduces the holding limit to 'reserve' less than the map size.
protected boolean	removeEldestEntry(java.util.Map.Entry<java.lang.String,MultiBufferedRandomAccessFile> eldest) Returns true if this map should remove its eldest entry.

Methods inherited from class java.util.LinkedHashMap

clear, containsValue, entrySet, forEach, get, getOrDefault, keySet, replaceAll, values

Methods inherited from class java.util.HashMap

clone, compute, computeIfAbsent, computeIfPresent, containsKey, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, containsKey, equals, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size

Constructor Detail

OpenRandomAccessFileCache

protected OpenRandomAccessFileCache(java.io.PrintStream out)

Create a cache for opened random access files.

Parameters:

out - PrintStream to write debugging logging messages to

Method Detail

removeEldestEntry

protected boolean removeEldestEntry(java.util.Map.Entry<java.lang.String,MultiBufferedRandomAccessFile> eldest)

Returns true if this map should remove its eldest entry. This method is invoked by put and putAll after inserting a new entry into the map. It provides the implementor with the opportunity to remove the eldest entry each time a new one is added. This is useful if the map represents a cache: it allows the map to reduce memory consumption by deleting stale entries.

Overrides:

removeEldestEntry in class java.util.LinkedHashMap<java.lang.String,MultiBufferedRandomAccessFile>

Parameters:

eldest - The least recently accessed entry. This is the entry that will be removed it this method returns true. If the map was empty prior to the put or putAll invocation resulting in this invocation, this will be the entry that was just inserted; in other words, if the map contains a single entry, the eldest entry is also the newest.

Returns:

true if the eldest entry should be removed from the map; false if it should be retained.

reduceHoldingLimit

public void reduceHoldingLimit(int reserve)

Reduces the holding limit to 'reserve' less than the map size. Used to handle cases where the JVM's open file quota isn't big enough for as many files as the OsmSegmenter would like to access at the same time.

Parameters:

reserve - int quantity to lower the limit relative to the current size if an IOException occurs trying to open a new file to put in the cache

getHoldingLimit

public int getHoldingLimit()

Get the current maximum number of open file allowed in the cache.

Returns:

limit on cache size