RequestTable

java.lang.Object
- org.jgroups.util.RequestTable<T>

```
public class RequestTable<T>
extends java.lang.Object
```
Table for storing requests associated with monotonically increasing sequence numbers (seqnos).
Used for example in RequestCorrelator. Grows and shrinks when needed. Addition is always at the end, yielding monotonically increasing seqnos. Removal is done by nulling the element(s) between low and high and advancing the low pointer whenever possible.
See JGRP-1982 for details.

Since:

3.6.7

Author:

Bela Ban

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static interface RequestTable.Visitor<T>

Nested Classes
Modifier and Type	Class and Description
`static interface`	`RequestTable.Visitor<T>`

Field Summary

Fields
Modifier and Type	Field and Description
`protected T[]`	`buffer`
`protected long`	`high`
`protected java.util.concurrent.locks.Lock`	`lock`
`protected long`	`low`
`protected int`	`num_removes`
`protected int`	`removes_till_compaction`

Constructor Summary

Constructors
Constructor and Description

RequestTable(int capacity)

RequestTable(int capacity, long low, long high)

Constructors
Constructor and Description
`RequestTable(int capacity)`
`RequestTable(int capacity, long low, long high)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected boolean`	`_compact()` Shrinks the array to half of its current size if the current number of elements fit into half of the capacity.
`protected boolean`	`_contiguousSpaceAvailable(int space_needed)` Check if we have at least space_needed contiguous free slots available in range [low+1 ..
`protected void`	`_copy(int new_cap)` Copies elements from old into new array
`protected void`	`_grow(long new_capacity)`
`long`	`add(T element)` Adds a new element and returns the sequence number at which it was inserted.
`protected void`	`advanceLow()`
`int`	`capacity()`
`RequestTable<T>`	`clear()` Removes all elements, compacts the buffer and sets low=high=0
`RequestTable<T>`	`clear(long mark)`
`boolean`	`compact()` Shrinks the underlying array to half its size _if_ the new array can hold all of the existing elements.
`boolean`	`contiguousSpaceAvailable()` Checks if there is at least buffer.length/2 contiguous space in range [low+1 ..
`java.lang.String`	`dumpContents()`
`RequestTable<T>`	`forEach(RequestTable.Visitor<T> visitor)`
`RequestTable<T>`	`forEachNonBlocking(RequestTable.Visitor<T> visitor)` Non-blocking alternative to `forEach(Visitor)`: iteration is performed on the array that exists at the time of this call.
`T`	`get(long seqno)`
`RequestTable<T>`	`grow(int new_capacity)` Grows the array to at least new_capacity.
`long`	`high()`
`protected int`	`highestContiguousSpaceAvailable()`
`int`	`index(long seqno)`
`protected static int`	`index(long seqno, int length)`
`long`	`low()`
`T`	`remove(long seqno)` Removes the element at the index matching seqno.
`int`	`removesTillCompaction()`
`RequestTable<T>`	`removesTillCompaction(int rems)`
`int`	`size()` Returns the number of non-null elements in range [low ..
`java.lang.String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - buffer
```
protected T[] buffer
```
  - low
```
protected long low
```
  - high
```
protected long high
```
  - removes_till_compaction
```
protected int removes_till_compaction
```
  - num_removes
```
protected int num_removes
```
  - lock
```
protected final java.util.concurrent.locks.Lock lock
```
- Constructor Detail
  - RequestTable
```
public RequestTable(int capacity)
```
  - RequestTable
```
public RequestTable(int capacity,
                    long low,
                    long high)
```
- Method Detail
  - low
```
public long low()
```
  - high
```
public long high()
```
  - capacity
```
public int capacity()
```
  - index
```
public int index(long seqno)
```
  - removesTillCompaction
```
public int removesTillCompaction()
```
  - removesTillCompaction
```
public RequestTable<T> removesTillCompaction(int rems)
```
  - add
```
public long add(T element)
```
    Adds a new element and returns the sequence number at which it was inserted. Advances the high pointer and grows the buffer if needed.
    
    Parameters:
    
    element - the element to be added. Must not be null or an exception will be thrown
    
    Returns:
    
    the seqno at which element was added
  - get
```
public T get(long seqno)
```
  - remove
```
public T remove(long seqno)
```
    Removes the element at the index matching seqno. If seqno == low, tries to advance low until a non-null element is encountered, up to high
    
    Parameters:
    
    seqno -
    
    Returns:
  - clear
```
public RequestTable<T> clear()
```
    Removes all elements, compacts the buffer and sets low=high=0
  - clear
```
public RequestTable<T> clear(long mark)
```
  - forEach
```
public RequestTable<T> forEach(RequestTable.Visitor<T> visitor)
```
  - forEachNonBlocking
```
public RequestTable<T> forEachNonBlocking(RequestTable.Visitor<T> visitor)
```
    Non-blocking alternative to forEach(Visitor): iteration is performed on the array that exists at the time of this call. Changes to the underlying array will not be reflected in the iteration.
    
    Parameters:
    
    visitor - the RequestTable.Visitor.
  - grow
```
public RequestTable<T> grow(int new_capacity)
```
    Grows the array to at least new_capacity. This method is mainly used for testing and is not typically called directly, but indirectly when adding elements and the underlying array has no space left.
    
    Parameters:
    
    new_capacity - the new capacity of the underlying array. Will be rounded up to the nearest power of 2 value. A value smaller than the current capacity is ignored.
  - compact
```
public boolean compact()
```
    Shrinks the underlying array to half its size _if_ the new array can hold all of the existing elements.
    
    Returns:
    
    true if the compaction succeeded, or false if it failed (e.g. not enough space)
  - contiguousSpaceAvailable
```
public boolean contiguousSpaceAvailable()
```
    Checks if there is at least buffer.length/2 contiguous space in range [low+1 .. high-1] available
  - size
```
public int size()
```
    Returns the number of non-null elements in range [low .. high-1]
    
    Returns:
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - _grow
```
protected void _grow(long new_capacity)
```
  - _compact
```
protected boolean _compact()
```
    Shrinks the array to half of its current size if the current number of elements fit into half of the capacity.
    
    Returns:
    
    true if the compaction succeeded, else false (e.g. when the current elements would not fit)
  - dumpContents
```
public java.lang.String dumpContents()
```
  - _copy
```
protected void _copy(int new_cap)
```
    Copies elements from old into new array
  - _contiguousSpaceAvailable
```
protected boolean _contiguousSpaceAvailable(int space_needed)
```
    Check if we have at least space_needed contiguous free slots available in range [low+1 .. high-1]
    
    Parameters:
    
    space_needed - the number of contiguous free slots required to do compaction, usually half of the current buffer size
    
    Returns:
    
    true if a contiguous space was found, false otherwise
  - highestContiguousSpaceAvailable
```
protected int highestContiguousSpaceAvailable()
```
  - advanceLow
```
protected void advanceLow()
```
  - index
```
protected static int index(long seqno,
                           int length)
```

Class RequestTable<T>

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

buffer

low

high

removes_till_compaction

num_removes

lock

Constructor Detail

RequestTable

RequestTable

Method Detail

low

high

capacity

index

removesTillCompaction

removesTillCompaction

add

get

remove

clear

clear

forEach

forEachNonBlocking

grow

compact

contiguousSpaceAvailable

size

toString

_grow

_compact

dumpContents

_copy

_contiguousSpaceAvailable

highestContiguousSpaceAvailable

advanceLow

index