Package com.google.cloud

Interface ReadChannel

All Superinterfaces:
AutoCloseable, Channel, Closeable, ReadableByteChannel, Restorable<ReadChannel>
public interface ReadChannel extends ReadableByteChannel, Closeable, Restorable<ReadChannel>
A channel for reading data from a Google Cloud object.

Implementations of this class may buffer data internally to reduce remote calls. This interface implements Restorable to allow saving the reader's state to continue reading afterwards.

  • Method Summary

    Modifier and Type
    Method
    Description
    RestorableState<ReadChannel>
    capture()
    Captures the read channel state so that it can be saved and restored afterwards.
    void
    close()
    Overridden to remove IOException.
    default long
    limit()
    The currently defined limit for this channel.
    default ReadChannel
    limit(long limit)
    Limit the maximum number of bytes to be read from the objects content, counting from the beginning of the object, which will be available to read from this channel.
    void
    seek(long position)
    Set the offset to read from.
    void
    setChunkSize(int chunkSize)
    Sets the minimum size that will be read by a single RPC.

    Methods inherited from interface java.nio.channels.Channel

    isOpen

    Methods inherited from interface java.nio.channels.ReadableByteChannel

    read

  • Method Details

    • close

      void close()
      Overridden to remove IOException.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Channel
      Specified by:
      close in interface Closeable
      See Also:

    • seek

      void seek(long position) throws IOException
      Set the offset to read from.
      Throws:
      IOException

    • setChunkSize

      void setChunkSize(int chunkSize)
      Sets the minimum size that will be read by a single RPC. Read data will be locally buffered until consumed.

    • capture

      RestorableState<ReadChannel> capture()
      Captures the read channel state so that it can be saved and restored afterwards.
      Specified by:
      capture in interface Restorable<ReadChannel>
      Returns:
      a RestorableState object that contains the read channel state and can restore it afterwards.

    • limit

      default ReadChannel limit(long limit)
      Limit the maximum number of bytes to be read from the objects content, counting from the beginning of the object, which will be available to read from this channel. If the limit is larger than the actual size of the content this will have no material impact.

      If used in conjunction with seek(long) the total number of returned bytes from this channel will be reduced by the number of bytes specified to seek.

      The value provided as limit will define a left-closed, right-open interval along with either 0 or any value provided to seek(long), i.e. [seek(long), limit(long)).

      An example to help illustrate the relationship

      Imagine some data [A, B, C, D, E, F, G, H, I, J], 10 bytes total.
      1. limit(5) would produce [A, B, C, D, E]
      2. seek(8) would produce [I, J]
      3. seek(2) limit(5) would produce [C, D, E]
      4. seek(3) limit(3) would produce []

      NOTE:Implementers are not required to return a new instance from this method, however they are allowed to. Users of this method should always use the instance returned from this method.

      Default Implementation:By default, this method will simply return this.

      Parameters:
      limit - the maximum number of bytes to limit this channel to
      Returns:
      The instance of channel which will respect the limit.
      Throws:
      UnsupportedOperationException - If the this instances does not support limiting
      Since:
      2.4.0

    • limit

      default long limit()
      The currently defined limit for this channel. Initial value is Long.MAX_VALUE
      Returns:
      the current limit for this channel
      Throws:
      UnsupportedOperationException - If the this instances does not support limiting
      Since:
      2.4.0