Any way to access fstat.st_blocks from Java (UnixFileAttributesView)

[Uwe Schindler]

Hi,

 

sorry for the late response. To actually fix my problem I had to go and use a native solution by using the JNR-POSIX package by Charles Nutter (@headius) from Maven (see  <https://github.com/jnr/jnr-posix> https://github.com/jnr/jnr-posix). I don’t like the complexity of that setup (you need like 8 additional jar files), but at least it works for now. JNA would have been another solution, but I did not want to create the st_stat structs and all syscalls needed to get from a NIO Path to that value.

 

The question is how to propose a change request like this, because getting the size a file *occupies* on disk is a useful information. Adding this should bring no backwards breaks or any need to change public APIs, as the “unix” view is not exposed as a public API, its just accessible using the lookup by string key. So adding two other key-value pairs should be easy. What do you think?

 

Maybe I can create a patch to add this, but what’s the way to go? This may be a first try to submit something as a “new contributor”, because I have signed the CLA already.

 

This change is not Lucene related (was a problem in my daily work), but we have some other ideas for more complex patches in Lucene, so this could be a start.

 

Uwe

 

-----

Uwe Schindler

uschindler at apache.org 

ASF Member, Apache Lucene PMC / Committer

Bremen, Germany

https://lucene.apache.org/

 

From: Brian Burkhalter <brian.burkhalter at oracle.com> 
Sent: Friday, June 28, 2019 5:45 PM
To: Alan Bateman <Alan.Bateman at oracle.com>
Cc: Uwe Schindler <uschindler at apache.org>; nio-dev <nio-dev at openjdk.java.net>
Subject: Re: Any way to access fstat.st_blocks from Java (UnixFileAttributesView)

 

 

On Jun 28, 2019, at 7:18 AM, Alan Bateman <Alan.Bateman at oracle.com <mailto:Alan.Bateman at oracle.com> > wrote:

 

Any hints to get the file size on disk from Java that uses the st_blocks and st_blksize behind the scenes?

There isn't anything at this time. You are right that the "unix" view could expose a "blocks" attribute. The block size is already exposed by FileStore::getBlockSize - the motivation for that was sizing and aligning buffers for use with direct I/O.

 

Maybe an enhancement should be filed?

 

Brian

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/nio-dev/attachments/20190703/26511a96/attachment-0001.html>