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

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and 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(IndexOutput 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(IndexOutput 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)`

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