Package org.apache.hadoop.fs

Interface ByteBufferPositionedReadable

All Known Implementing Classes:
FSDataInputStream, HdfsDataInputStream
@Public @Evolving public interface ByteBufferPositionedReadable
Implementers of this interface provide a positioned read API that writes to a ByteBuffer rather than a byte[].
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    read(long position, ByteBuffer buf)
    Reads up to buf.remaining() bytes into buf from a given position in the file and returns the number of bytes read.
    void
    readFully(long position, ByteBuffer buf)
    Reads buf.remaining() bytes into buf from a given position in the file or until the end of the data was reached before the read operation completed.

  • Method Details

    • read

      int read(long position, ByteBuffer buf) throws IOException
      Reads up to buf.remaining() bytes into buf from a given position in the file and returns the number of bytes read. Callers should use buf.limit(...) to control the size of the desired read and buf.position(...) to control the offset into the buffer the data should be written to.

      After a successful call, buf.position() will be advanced by the number of bytes read and buf.limit() will be unchanged.

      In the case of an exception, the state of the buffer (the contents of the buffer, the buf.position(), the buf.limit(), etc.) is undefined, and callers should be prepared to recover from this eventuality.

      Callers should use StreamCapabilities.hasCapability(String) with StreamCapabilities.PREADBYTEBUFFER to check if the underlying stream supports this interface, otherwise they might get a UnsupportedOperationException.

      Implementations should treat 0-length requests as legitimate, and must not signal an error upon their receipt.

      This does not change the current offset of a file, and is thread-safe.

      Parameters:
      position - position within file
      buf - the ByteBuffer to receive the results of the read operation.
      Returns:
      the number of bytes read, possibly zero, or -1 if reached end-of-stream
      Throws:
      IOException - if there is some error performing the read

    • readFully

      void readFully(long position, ByteBuffer buf) throws IOException
      Reads buf.remaining() bytes into buf from a given position in the file or until the end of the data was reached before the read operation completed. Callers should use buf.limit(...) to control the size of the desired read and buf.position(...) to control the offset into the buffer the data should be written to.

      This operation provides similar semantics to read(long, ByteBuffer), the difference is that this method is guaranteed to read data until the ByteBuffer is full, or until the end of the data stream is reached.

      Parameters:
      position - position within file
      buf - the ByteBuffer to receive the results of the read operation.
      Throws:
      IOException - if there is some error performing the read
      EOFException - the end of the data was reached before the read operation completed
      See Also: