Package org.apache.lucene.util.packed

Class DirectWriter

java.lang.Object

org.apache.lucene.util.packed.DirectWriter

public final class DirectWriter
extends Object

Class for writing packed integers to be directly read from Directory. Integers can be read on-the-fly via DirectReader.

Unlike PackedInts, it optimizes for read i/o operations and supports > 2B values. Example usage:

   int bitsPerValue = DirectWriter.bitsRequired(100); // values up to and including 100
   IndexOutput output = dir.createOutput("packed", IOContext.DEFAULT);
   DirectWriter writer = DirectWriter.getInstance(output, numberOfValues, bitsPerValue);
   for (int i = 0; i < numberOfValues; i++) {
     writer.add(value);
   }
   writer.finish();
   output.close();
 

See Also:

DirectReader

Method Summary

Modifier and Type	Method	Description
void	add(long l)	Adds a value to this writer
static int	bitsRequired(long maxValue)	Returns how many bits are required to hold values up to and including maxValue
void	finish()	finishes writing
static DirectWriter	getInstance(DataOutput output, long numValues, int bitsPerValue)	Returns an instance suitable for encoding numValues using bitsPerValue
static int	unsignedBitsRequired(long maxValue)	Returns how many bits are required to hold values up to and including maxValue, interpreted as an unsigned value.

Methods inherited from class java.lang.Object

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

Method Detail

add

public void add(long l)
         throws IOException

Adds a value to this writer

Throws:

IOException

finish

public void finish()
            throws IOException

finishes writing

Throws:

IOException

getInstance

public static DirectWriter getInstance(DataOutput output,
                                       long numValues,
                                       int bitsPerValue)

Returns an instance suitable for encoding numValues using bitsPerValue

bitsRequired

public static int bitsRequired(long maxValue)

Returns how many bits are required to hold values up to and including maxValue

Parameters:

maxValue - the maximum value that should be representable.

Returns:

the amount of bits needed to represent values from 0 to maxValue.

See Also:

PackedInts.bitsRequired(long)

unsignedBitsRequired

public static int unsignedBitsRequired(long maxValue)

Returns how many bits are required to hold values up to and including maxValue, interpreted as an unsigned value.

Parameters:

maxValue - the maximum value that should be representable.

Returns:

the amount of bits needed to represent values from 0 to maxValue.

See Also:

PackedInts.unsignedBitsRequired(long)