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https://issues.apache.org/jira/browse/HDFS-12653?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Manoj Govindassamy updated HDFS-12653:
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Attachment: HDFS-12653.01.patch
Attached v01 patch to address the following
1. Implemented {{ReadOnlyList#toArray()}} and {{ReadOnlyList#subArray()}} to
return an array view of the backing list
2. TestReadOnly - unit tests to verify various contracts in ReadOnlyList.
ReadOnly#toArray() and ReadOnlyList#subArray() can be made use when getting
attributes from INodeAttributesProvider (HDFS-12652) and when working on the
children list for a snapshot. Will follow on these after completing this jira.
[~eddyxu], [~yzhangal], [~daryn], can you please take a look at the patch.
> Implement toArray() and subArray() for ReadOnlyList
> ---------------------------------------------------
>
> Key: HDFS-12653
> URL: https://issues.apache.org/jira/browse/HDFS-12653
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Manoj Govindassamy
> Assignee: Manoj Govindassamy
> Attachments: HDFS-12653.01.patch
>
>
> {{ReadOnlyList}} today gives an unmodifiable view of the backing List. This
> list supports following Util methods for easy construction of read only views
> of any given list.
> {noformat}
> public static <E> ReadOnlyList<E> asReadOnlyList(final List<E> list)
> public static <E> List<E> asList(final ReadOnlyList<E> list)
> {noformat}
> {{asList}} above additionally overrides {{Object[] toArray()}} of the
> {{java.util.List}} interface. Unlike the {{java.util.List}}, the above one
> returns an array of Objects referring to the backing list and avoid any
> copying of objects. Given that we have many usages of read only lists,
> 1. Lets have a light-weight / shared-view {{toArray()}} implementation for
> {{ReadOnlyList}} as well.
> 2. Additionally, similar to {{java.util.List#subList(fromIndex, toIndex)}},
> lets have {{ReadOnlyList#subArray(fromIndex, toIndex)}}
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