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