DecayingHashSet (I2P Anonymous Network - Java Documentation

java.lang.Object
- net.i2p.router.util.DecayingBloomFilter
- - net.i2p.router.util.DecayingHashSet

```
public class DecayingHashSet
extends DecayingBloomFilter
```
Double buffered hash set. Since DecayingBloomFilter was instantiated 4 times for a total memory usage of 8MB, it seemed like we could do a lot better, given these usage stats on a class L router: ./router/java/src/net/i2p/router/tunnel/BuildMessageProcessor.java: 32 bytes, peak 10 entries in 1m (320 peak entries seen on fast router) ./router/java/src/net/i2p/router/transport/udp/InboundMessageFragments.java: 4 bytes, peak 150 entries in 10s (1600 peak entries seen on fast router) ./router/java/src/net/i2p/router/MessageValidator.java: 8 bytes, peak 1K entries in 2m (36K peak entries seen on fast router) ./router/java/src/net/i2p/router/tunnel/BloomFilterIVValidator.java: 16 bytes, peak 15K entries in 10m If the ArrayWrapper object in the HashSet is 50 bytes, and BloomSHA1(23, 11) is 1MB, then for less than 20K entries this is smaller. And this uses space proportional to traffic, so it doesn't penalize small routers with a fixed 8MB. So let's try it for the first 2 or 3, for now. Also, DBF is synchronized, and uses SimpleTimer. Here we use a read/write lock, with synchronization only when switching double buffers, and we use SimpleTimer2. Yes, we could stare at stats all day, and try to calculate an acceptable false-positive rate for each of the above uses, then estimate the DBF size required to meet that rate for a given usage. Or even start adjusting the Bloom filter m and k values on a per-DBF basis. But it's a whole lot easier to implement something with a zero false positive rate, and uses less memory for almost all bandwidth classes. This has a strictly zero false positive rate for <= 8 byte keys. For larger keys, it is 1 / (2**64) ~= 5E-20, which is better than DBF for any entry count greater than about 14K. DBF has a zero false negative rate over the period 2 * durationMs. And a 100% false negative rate beyond that period. This has the same properties. This performs about twice as fast as DBF in the test below.

作成者:

zzz

フィールドの概要
- クラスから継承されたフィールド net.i2p.router.util.DecayingBloomFilter
  _context, _currentDuplicates, _decayEvent, _durationMs, _entryBytes, _keepDecaying, _log, _name, _reorganizeLock

コンストラクタの概要

コンストラクタ
コンストラクタ	説明
`DecayingHashSet(I2PAppContext context, int durationMs, int entryBytes)`	Create a double-buffered hash set that will decay its entries over time.
`DecayingHashSet(I2PAppContext context, int durationMs, int entryBytes, java.lang.String name)`

メソッドの概要

すべてのメソッドインスタンス・メソッド concreteメソッド
修飾子とタイプ	メソッド	説明
`boolean`	`add(byte[] entry, int off, int len)`
`boolean`	`add(long entry)`
`void`	`clear()`
`protected void`	`decay()`
`double`	`getFalsePositiveRate()`	pointless, only used for logging elsewhere
`int`	`getInsertedCount()`	unsynchronized but only used for logging elsewhere
`boolean`	`isKnown(long entry)`
`void`	`stopDecaying()`	super doesn't call clear, but neither do the users, so it seems like we should here

クラスから継承されたメソッド net.i2p.router.util.DecayingBloomFilter
add, getCurrentDuplicateCount, getReadLock, getWriteLock, releaseReadLock, releaseWriteLock

クラスから継承されたメソッド java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- コンストラクタの詳細
  - DecayingHashSet
```
public DecayingHashSet(I2PAppContext context,
                       int durationMs,
                       int entryBytes)
```
    Create a double-buffered hash set that will decay its entries over time.
    
    パラメータ:
    
    durationMs - entries last for at least this long, but no more than twice this long
    
    entryBytes - how large are the entries to be added? 1 to 32 bytes
  - DecayingHashSet
```
public DecayingHashSet(I2PAppContext context,
                       int durationMs,
                       int entryBytes,
                       java.lang.String name)
```
    パラメータ:
    
    name - just for logging / debugging / stats
- メソッドの詳細
  - getInsertedCount
```
public int getInsertedCount()
```
    unsynchronized but only used for logging elsewhere
    
    オーバーライド:
    
    getInsertedCount クラス内 DecayingBloomFilter
  - getFalsePositiveRate
```
public double getFalsePositiveRate()
```
    pointless, only used for logging elsewhere
    
    オーバーライド:
    
    getFalsePositiveRate クラス内 DecayingBloomFilter
  - add
```
public boolean add(byte[] entry,
                   int off,
                   int len)
```
    オーバーライド:
    
    add クラス内 DecayingBloomFilter
    
    戻り値:
    
    true if the entry added is a duplicate
  - add
```
public boolean add(long entry)
```
    オーバーライド:
    
    add クラス内 DecayingBloomFilter
    
    戻り値:
    
    true if the entry added is a duplicate. the number of low order bits used is determined by the entryBytes parameter used on creation of the filter.
  - isKnown
```
public boolean isKnown(long entry)
```
    オーバーライド:
    
    isKnown クラス内 DecayingBloomFilter
    
    戻り値:
    
    true if the entry is already known. this does NOT add the entry however.
  - clear
```
public void clear()
```
    オーバーライド:
    
    clear クラス内 DecayingBloomFilter
  - stopDecaying
```
public void stopDecaying()
```
    super doesn't call clear, but neither do the users, so it seems like we should here
    
    オーバーライド:
    
    stopDecaying クラス内 DecayingBloomFilter
  - decay
```
protected void decay()
```
    オーバーライド:
    
    decay クラス内 DecayingBloomFilter

クラス DecayingHashSet

フィールドの概要

クラスから継承されたフィールド net.i2p.router.util.DecayingBloomFilter

コンストラクタの概要

メソッドの概要

クラスから継承されたメソッド net.i2p.router.util.DecayingBloomFilter

クラスから継承されたメソッド java.lang.Object

コンストラクタの詳細

DecayingHashSet

DecayingHashSet

メソッドの詳細

getInsertedCount

getFalsePositiveRate

add

add

isKnown

clear

stopDecaying

decay