ceph/src/rocksdb/java/src/main/java/org/rocksdb/LRUCache.java

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 // This source code is licensed under the BSD-style license found in the
   3 // LICENSE file in the root directory of this source tree. An additional grant
   4 // of patent rights can be found in the PATENTS file in the same directory.
   5
   6 package org.rocksdb;
   7
   8 /**
   9  * Least Recently Used Cache
  10  */
  11 public class LRUCache extends Cache {
  12
  13   /**
  14    * Create a new cache with a fixed size capacity
  15    *
  16    * @param capacity The fixed size capacity of the cache
  17    */
  18   public LRUCache(final long capacity) {
  19     this(capacity, -1, false, 0.0);
  20   }
  21
  22   /**
  23    * Create a new cache with a fixed size capacity. The cache is sharded
  24    * to 2^numShardBits shards, by hash of the key. The total capacity
  25    * is divided and evenly assigned to each shard.
  26    * numShardBits = -1 means it is automatically determined: every shard
  27    * will be at least 512KB and number of shard bits will not exceed 6.
  28    *
  29    * @param capacity The fixed size capacity of the cache
  30    * @param numShardBits The cache is sharded to 2^numShardBits shards,
  31    *     by hash of the key
  32    */
  33   public LRUCache(final long capacity, final int numShardBits) {
  34     super(newLRUCache(capacity, numShardBits, false,0.0));
  35   }
  36
  37   /**
  38    * Create a new cache with a fixed size capacity. The cache is sharded
  39    * to 2^numShardBits shards, by hash of the key. The total capacity
  40    * is divided and evenly assigned to each shard. If strictCapacityLimit
  41    * is set, insert to the cache will fail when cache is full.
  42    * numShardBits = -1 means it is automatically determined: every shard
  43    * will be at least 512KB and number of shard bits will not exceed 6.
  44    *
  45    * @param capacity The fixed size capacity of the cache
  46    * @param numShardBits The cache is sharded to 2^numShardBits shards,
  47    *     by hash of the key
  48    * @param strictCapacityLimit insert to the cache will fail when cache is full
  49    */
  50   public LRUCache(final long capacity, final int numShardBits,
  51                   final boolean strictCapacityLimit) {
  52     super(newLRUCache(capacity, numShardBits, strictCapacityLimit,0.0));
  53   }
  54
  55   /**
  56    * Create a new cache with a fixed size capacity. The cache is sharded
  57    * to 2^numShardBits shards, by hash of the key. The total capacity
  58    * is divided and evenly assigned to each shard. If strictCapacityLimit
  59    * is set, insert to the cache will fail when cache is full. User can also
  60    * set percentage of the cache reserves for high priority entries via
  61    * highPriPoolRatio.
  62    * numShardBits = -1 means it is automatically determined: every shard
  63    * will be at least 512KB and number of shard bits will not exceed 6.
  64    *
  65    * @param capacity The fixed size capacity of the cache
  66    * @param numShardBits The cache is sharded to 2^numShardBits shards,
  67    *     by hash of the key
  68    * @param strictCapacityLimit insert to the cache will fail when cache is full
  69    * @param highPriPoolRatio percentage of the cache reserves for high priority
  70    *     entries
  71    */
  72   public LRUCache(final long capacity, final int numShardBits,
  73       final boolean strictCapacityLimit, final double highPriPoolRatio) {
  74     super(newLRUCache(capacity, numShardBits, strictCapacityLimit,
  75         highPriPoolRatio));
  76   }
  77
  78   private native static long newLRUCache(final long capacity,
  79       final int numShardBits, final boolean strictCapacityLimit,
  80       final double highPriPoolRatio);
  81   @Override protected final native void disposeInternal(final long handle);
  82 }