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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5191) revisit zero-copy API in FSDataInputStream to make it more intuitive
Date Thu, 12 Sep 2013 14:50:52 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13765494#comment-13765494

Colin Patrick McCabe commented on HDFS-5191:

The current proposal looks like this:
 * Read from the current location at least 1 and up to maxLength bytes. In most situations,
the returned
 * buffer will contain maxLength bytes unless either:
 *  * the read crosses a block boundary and zero copy is being used
 *  * the stream has fewer than maxLength bytes left
 * The returned buffer will either be one that was created by the factory or a MappedByteBuffer.
public ByteBuffer read(ByteBufferFactory factory, int maxLength) throws IOException;

 * Release a buffer that was returned from readByteBuffer. If the method was created by the
 * it will be returned to the factory.
public void releaseByteBuffer(ByteBufferFactory factory, ByteBuffer buffer);

 * Allow application to manage how ByteBuffers are created for fallback buffers. Only buffers
created by
 * the factory will be released to it.
public interface ByteBufferFactory {
  ByteBuffer createBuffer(int capacity);
  void releaseBuffer(ByteBuffer buffer);
> revisit zero-copy API in FSDataInputStream to make it more intuitive
> --------------------------------------------------------------------
>                 Key: HDFS-5191
>                 URL: https://issues.apache.org/jira/browse/HDFS-5191
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client, libhdfs
>    Affects Versions: HDFS-4949
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
> As per the discussion on HDFS-4953, we should revisit the zero-copy API to make it more
intuitive for new users.

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