Package org.apache.lucene.codecs

# Class MultiLevelSkipListReader

java.lang.Object
org.apache.lucene.codecs.MultiLevelSkipListReader

All Implemented Interfaces:
  `Closeable`, `AutoCloseable`

public abstract class MultiLevelSkipListReader extends Object implements Closeable
This abstract class reads skip lists with multiple levels.

See `MultiLevelSkipListWriter` for the information about the encoding of the multi level skip lists.

Subclasses must implement the abstract method `readSkipData(int, IndexInput)` which defines the actual format of the skip data.

WARNING: This API is experimental and might change in incompatible ways in the next release.

## Field Summary

Fields
Modifier and Type
Field
Description
`protected int`
`maxNumberOfSkipLevels`
the maximum number of skip levels possible for this index
`protected int`
`numberOfSkipLevels`
number of levels in this skip list
`protected int[]`
`skipDoc`
Doc id of current skip entry per level.

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval)`
Creates a `MultiLevelSkipListReader`, where `skipInterval` and `skipMultiplier` are the same.
`protected`
`MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier)`
Creates a `MultiLevelSkipListReader`.

## Method Summary

Modifier and Type
Method
Description
`void`
`close()`
`int`
`getDoc()`
Returns the id of the doc to which the last call of `skipTo(int)` has skipped.
`void`
`init(long skipPointer, int df)`
Initializes the reader, for reuse on a new term.
`protected long`
`readChildPointer(IndexInput skipStream)`
read the child pointer written via `MultiLevelSkipListWriter.writeChildPointer(long, DataOutput)`.
`protected long`
`readLevelLength(IndexInput skipStream)`
read the length of the current level written via `MultiLevelSkipListWriter.writeLevelLength(long, IndexOutput)`.
`protected abstract int`
`readSkipData(int level, IndexInput skipStream)`
Subclasses must implement the actual skip data encoding in this method.
`protected void`
`seekChild(int level)`
Seeks the skip entry on the given level
`protected void`
`setLastSkipData(int level)`
Copies the values of the last read skip entry on this level
`int`
`skipTo(int target)`
Skips entries to the first beyond the current whose document number is greater than or equal to target.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Field Details

### maxNumberOfSkipLevels

protected int maxNumberOfSkipLevels
the maximum number of skip levels possible for this index

### numberOfSkipLevels

protected int numberOfSkipLevels
number of levels in this skip list

### skipDoc

protected int[] skipDoc
Doc id of current skip entry per level.

## Constructor Details

### MultiLevelSkipListReader

protected MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier)
Creates a `MultiLevelSkipListReader`.

### MultiLevelSkipListReader

protected MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval)
Creates a `MultiLevelSkipListReader`, where `skipInterval` and `skipMultiplier` are the same.

## Method Details

### getDoc

public int getDoc()
Returns the id of the doc to which the last call of `skipTo(int)` has skipped.

### skipTo

public int skipTo(int target) throws IOException
Skips entries to the first beyond the current whose document number is greater than or equal to target. Returns the current doc count.

Throws:
  `IOException`

### seekChild

protected void seekChild(int level) throws IOException
Seeks the skip entry on the given level

Throws:
  `IOException`

### close

public void close() throws IOException

Specified by:
  `close` in interface `AutoCloseable`
Specified by:
  `close` in interface `Closeable`
Throws:
  `IOException`

### init

public void init(long skipPointer, int df) throws IOException
Initializes the reader, for reuse on a new term.

Throws:
  `IOException`

### readSkipData

protected abstract int readSkipData(int level, IndexInput skipStream) throws IOException
Subclasses must implement the actual skip data encoding in this method.

Parameters:
  `level` - the level skip data shall be read from
  `skipStream` - the skip stream to read from
Throws:
  `IOException`

### readLevelLength

protected long readLevelLength(IndexInput skipStream) throws IOException
read the length of the current level written via `MultiLevelSkipListWriter.writeLevelLength(long, IndexOutput)`.

Parameters:
  `skipStream` - the IndexInput the length shall be read from
Returns:
  level length
Throws:
  `IOException`

### readChildPointer

protected long readChildPointer(IndexInput skipStream) throws IOException
read the child pointer written via `MultiLevelSkipListWriter.writeChildPointer(long, DataOutput)`.

Parameters:
  `skipStream` - the IndexInput the child pointer shall be read from
Returns:
  child pointer
Throws:
  `IOException`

### setLastSkipData

protected void setLastSkipData(int level)
Copies the values of the last read skip entry on this level