## org.apache.lucene.codecs.lucene40
Class Lucene40LiveDocsFormat

    java.lang.Object
      org.apache.lucene.codecs.LiveDocsFormat
          org.apache.lucene.codecs.lucene40.Lucene40LiveDocsFormat

    public class Lucene40LiveDocsFormat

extends LiveDocsFormat

Lucene 4.0 Live Documents Format.

The .del file is optional, and only exists when a segment contains deletions.

Although per-segment, this file is maintained exterior to compound segment files.

Deletions (.del) --> Format,Header,ByteCount,BitCount, Bits | DGaps (depending on Format)

- Format,ByteSize,BitCount --> `Uint32`
- Bits --> <`Byte`> ByteCount
- DGaps --> <DGap,NonOnesByte> NonzeroBytesCount
- DGap --> `VInt`
- NonOnesByte --> `Byte`
- Header --> `CodecHeader`

Format is 1: indicates cleared DGaps.

ByteCount indicates the number of bytes in Bits. It is typically (SegSize/8)+1.

BitCount indicates the number of bits that are currently set in Bits.

Bits contains one bit for each document indexed. When the bit corresponding to a document number is cleared, that document is marked as deleted. Bit ordering is from least to most significant. Thus, if Bits contains two bytes, 0x00 and 0x02, then document 9 is marked as alive (not deleted).

DGaps represents sparse bit-vectors more efficiently than Bits. It is made of DGaps on indexes of nonOnes bytes in Bits, and the nonOnes bytes themselves. The number of nonOnes bytes in Bits (NonOnesBytesCount) is not stored.

For example, if there are 8000 bits and only bits 10,12,32 are cleared, DGaps would be used:

(VInt) 1 , (byte) 20 , (VInt) 3 , (Byte) 1

Constructor Summary
`Lucene40LiveDocsFormat()` Sole constructor.

Method Summary
`void` `files(SegmentInfoPerCommit info, Collection<String> files)` Records all files in use by this `SegmentInfoPerCommit` into the files argument.
`MutableBits` `newLiveDocs(Bits existing)` Creates a new mutablebits of the same bits set and size of existing.
`MutableBits` `newLiveDocs(int size)` Creates a new MutableBits, with all bits set, for the specified size.
`Bits` `readLiveDocs(Directory dir, SegmentInfoPerCommit info, IOContext context)` Read live docs bits.
`void` `writeLiveDocs(MutableBits bits, Directory dir, SegmentInfoPerCommit info, int newDelCount, IOContext context)` Persist live docs bits.

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

Constructor Detail

### Lucene40LiveDocsFormat

    public Lucene40LiveDocsFormat()

  Sole constructor.

Method Detail

### newLiveDocs

    public MutableBits newLiveDocs(int size)
                            throws IOException

  Description copied from class: `LiveDocsFormat`
  Creates a new MutableBits, with all bits set, for the specified size.

  Specified by:
    `newLiveDocs` in class `LiveDocsFormat`
  Throws:
    `IOException`

### newLiveDocs

    public MutableBits newLiveDocs(Bits existing)
                            throws IOException

  Description copied from class: `LiveDocsFormat`
  Creates a new mutablebits of the same bits set and size of existing.

  Specified by:
    `newLiveDocs` in class `LiveDocsFormat`
  Throws:
    `IOException`

### readLiveDocs

    public Bits readLiveDocs(Directory dir,
                             SegmentInfoPerCommit info,
                             IOContext context)
                      throws IOException

  Description copied from class: `LiveDocsFormat`
  Read live docs bits.

  Specified by:
    `readLiveDocs` in class `LiveDocsFormat`
  Throws:
    `IOException`

### writeLiveDocs

    public void writeLiveDocs(MutableBits bits,
                              Directory dir,
                              SegmentInfoPerCommit info,
                              int newDelCount,
                              IOContext context)
                       throws IOException

  Description copied from class: `LiveDocsFormat`
  Persist live docs bits. Use `SegmentInfoPerCommit.getNextDelGen()` to determine the generation of the deletes file you should write to.

  Specified by:
    `writeLiveDocs` in class `LiveDocsFormat`
  Throws:
    `IOException`

### files

    public void files(SegmentInfoPerCommit info,
                      Collection<String> files)
               throws IOException

  Description copied from class: `LiveDocsFormat`
  Records all files in use by this `SegmentInfoPerCommit` into the files argument.

  Specified by:
    `files` in class `LiveDocsFormat`
  Throws:
    `IOException`

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