org.apache.lucene.store

## Class ByteBuffersDataOutput

- java.lang.Object
- - org.apache.lucene.store.DataOutput
  - - org.apache.lucene.store.ByteBuffersDataOutput

- All Implemented Interfaces:
    Accountable

      public final class ByteBuffersDataOutput
      extends DataOutput
      implements Accountable

  A `DataOutput` storing data in a list of `ByteBuffer`s.

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `ByteBuffersDataOutput.ByteBufferRecycler` An implementation of a `ByteBuffer` allocation and recycling policy.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static IntFunction<ByteBuffer>` | `ALLOCATE_BB_ON_HEAP`
    `static int` | `DEFAULT_MAX_BITS_PER_BLOCK`
    `static int` | `DEFAULT_MIN_BITS_PER_BLOCK`
    `static Consumer<ByteBuffer>` | `NO_REUSE` A singleton instance of "no-reuse" buffer strategy.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ByteBuffersDataOutput()`
    `ByteBuffersDataOutput(int minBitsPerBlock, int maxBitsPerBlock, IntFunction<ByteBuffer> blockAllocate, Consumer<ByteBuffer> blockReuse)`
    `ByteBuffersDataOutput(long expectedSize)`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `copyTo(DataOutput output)` Copy the current content of this object into another `DataOutput`.
    `static ByteBuffersDataOutput` | `newResettableInstance()`
    `long` | `ramBytesUsed()` Return the memory usage of this object in bytes.
    `void` | `reset()` This method resets this object to a clean (zero-size) state and publishes any currently allocated buffers for reuse to the reuse strategy provided in the constructor.
    `long` | `size()`
    `byte[]` | `toArrayCopy()` Return a contiguous array with the current content written to the output.
    `ArrayList<ByteBuffer>` | `toBufferList()` Return a list of read-only view of `ByteBuffer` blocks over the current content written to the output.
    `ByteBuffersDataInput` | `toDataInput()` Return a `ByteBuffersDataInput` for the set of current buffers (`toBufferList()`).
    `String` | `toString()`
    `ArrayList<ByteBuffer>` | `toWriteableBufferList()` Returns a list of writeable blocks over the (source) content buffers.
    `void` | `writeByte(byte b)` Writes a single byte.
    `void` | `writeBytes(byte[] b)`
    `void` | `writeBytes(byte[] b, int length)` Writes an array of bytes.
    `void` | `writeBytes(byte[] src, int offset, int length)` Writes an array of bytes.
    `void` | `writeBytes(ByteBuffer buffer)`
    `void` | `writeInt(int v)` Writes an int as four bytes.
    `void` | `writeLong(long v)` Writes a long as eight bytes.
    `void` | `writeMapOfStrings(Map<String,String> map)` Writes a String map.
    `void` | `writeSetOfStrings(Set<String> set)` Writes a String set.
    `void` | `writeShort(short v)` Writes a short as two bytes.
    `void` | `writeString(String v)` Writes a string.

    - ### Methods inherited from class org.apache.lucene.store.DataOutput

      `copyBytes, writeVInt, writeVLong, writeZInt, writeZLong`

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

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

    - ### Methods inherited from interface org.apache.lucene.util.Accountable

      `getChildResources`

- - ### Field Detail

    - #### ALLOCATE_BB_ON_HEAP

          public static final IntFunction<ByteBuffer> ALLOCATE_BB_ON_HEAP

    - #### NO_REUSE

          public static final Consumer<ByteBuffer> NO_REUSE

      A singleton instance of "no-reuse" buffer strategy.

    - #### DEFAULT_MIN_BITS_PER_BLOCK

          public static final int DEFAULT_MIN_BITS_PER_BLOCK

      See Also:
        Constant Field Values

    - #### DEFAULT_MAX_BITS_PER_BLOCK

          public static final int DEFAULT_MAX_BITS_PER_BLOCK

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### ByteBuffersDataOutput

          public ByteBuffersDataOutput(long expectedSize)

    - #### ByteBuffersDataOutput

          public ByteBuffersDataOutput()

    - #### ByteBuffersDataOutput

          public ByteBuffersDataOutput(int minBitsPerBlock,
                                       int maxBitsPerBlock,
                                       IntFunction<ByteBuffer> blockAllocate,
                                       Consumer<ByteBuffer> blockReuse)

  - ### Method Detail

    - #### writeByte

          public void writeByte(byte b)

      Description copied from class: `DataOutput`
      Writes a single byte.

      The most primitive data type is an eight-bit byte. Files are accessed as sequences of bytes. All other data types are defined as sequences of bytes, so file formats are byte-order independent.

      Specified by:
        `writeByte` in class `DataOutput`
      See Also:
        `DataInput.readByte()`

    - #### writeBytes

          public void writeBytes(byte[] src,
                                 int offset,
                                 int length)

      Description copied from class: `DataOutput`
      Writes an array of bytes.
      Specified by:
        `writeBytes` in class `DataOutput`
      Parameters:
        `src` - the bytes to write
        `offset` - the offset in the byte array
        `length` - the number of bytes to write
      See Also:
        `DataInput.readBytes(byte[],int,int)`

    - #### writeBytes

          public void writeBytes(byte[] b,
                                 int length)

      Description copied from class: `DataOutput`
      Writes an array of bytes.
      Overrides:
        `writeBytes` in class `DataOutput`
      Parameters:
        `b` - the bytes to write
        `length` - the number of bytes to write
      See Also:
        `DataInput.readBytes(byte[],int,int)`

    - #### writeBytes

          public void writeBytes(byte[] b)

    - #### writeBytes

          public void writeBytes(ByteBuffer buffer)

    - #### toBufferList

          public ArrayList<ByteBuffer> toBufferList()

      Return a list of read-only view of `ByteBuffer` blocks over the current content written to the output.

    - #### toWriteableBufferList

          public ArrayList<ByteBuffer> toWriteableBufferList()

      Returns a list of writeable blocks over the (source) content buffers. This method returns the raw content of source buffers that may change over the lifetime of this object (blocks can be recycled or discarded, for example). Most applications should favor calling `toBufferList()` which returns a read-only view over the content of the source buffers. The difference between `toBufferList()` and `toWriteableBufferList()` is that read-only view of source buffers will always return `false` from `ByteBuffer.hasArray()` (which sometimes may be required to avoid double copying).

    - #### toDataInput

          public ByteBuffersDataInput toDataInput()

      Return a `ByteBuffersDataInput` for the set of current buffers (`toBufferList()`).

    - #### toArrayCopy

          public byte[] toArrayCopy()

      Return a contiguous array with the current content written to the output. The returned array is always a copy (can be mutated).

    - #### copyTo

          public void copyTo(DataOutput output)
                      throws IOException

      Copy the current content of this object into another `DataOutput`.
      Throws:
        `IOException`

    - #### size

          public long size()

      Returns:
        The number of bytes written to this output so far.

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

    - #### writeShort

          public void writeShort(short v)

      Description copied from class: `DataOutput`
      Writes a short as two bytes.
      Overrides:
        `writeShort` in class `DataOutput`
      See Also:
        `DataInput.readShort()`

    - #### writeInt

          public void writeInt(int v)

      Description copied from class: `DataOutput`
      Writes an int as four bytes.

      32-bit unsigned integer written as four bytes, high-order bytes first.

      Overrides:
        `writeInt` in class `DataOutput`
      See Also:
        `DataInput.readInt()`

    - #### writeLong

          public void writeLong(long v)

      Description copied from class: `DataOutput`
      Writes a long as eight bytes.

      64-bit unsigned integer written as eight bytes, high-order bytes first.

      Overrides:
        `writeLong` in class `DataOutput`
      See Also:
        `DataInput.readLong()`

    - #### writeString

          public void writeString(String v)

      Description copied from class: `DataOutput`
      Writes a string.

      Writes strings as UTF-8 encoded bytes. First the length, in bytes, is written as a `VInt`, followed by the bytes.

      Overrides:
        `writeString` in class `DataOutput`
      See Also:
        `DataInput.readString()`

    - #### writeMapOfStrings

          public void writeMapOfStrings(Map<String,String> map)

      Description copied from class: `DataOutput`
      Writes a String map.

      First the size is written as an `vInt`, followed by each key-value pair written as two consecutive `String`s.

      Overrides:
        `writeMapOfStrings` in class `DataOutput`
      Parameters:
        `map` - Input map.

    - #### writeSetOfStrings

          public void writeSetOfStrings(Set<String> set)

      Description copied from class: `DataOutput`
      Writes a String set.

      First the size is written as an `vInt`, followed by each value written as a `String`.

      Overrides:
        `writeSetOfStrings` in class `DataOutput`
      Parameters:
        `set` - Input set.

    - #### ramBytesUsed

          public long ramBytesUsed()

      Description copied from interface: `Accountable`
      Return the memory usage of this object in bytes. Negative values are illegal.
      Specified by:
        `ramBytesUsed` in interface `Accountable`

    - #### reset

          public void reset()

      This method resets this object to a clean (zero-size) state and publishes any currently allocated buffers for reuse to the reuse strategy provided in the constructor. Sharing byte buffers for reads and writes is dangerous and will very likely lead to hard-to-debug issues, use with great care.

    - #### newResettableInstance

          public static ByteBuffersDataOutput newResettableInstance()

      Returns:
        Returns a new `ByteBuffersDataOutput` with the `reset()` capability.

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