RFR [8020669] java.nio.file.Files.readAllBytes() does not read any data when Files.size() is 0

roger riggs roger.riggs at oracle.com
Fri Jul 19 18:06:59 UTC 2013

Hi Ivan,

I think this change takes too big a hit for the cases where the size is 

No real file system can be wrong about the size of a file so this is a 
only for special file systems. If the problem is with size reporting zero
then maybe using the incremental read only for size == would be a better 

At least you could pass the size to the constructor for BAOS and avoid
the thrashing for every re-size; but still it will allocate and create 
an extra copy
of the every time.

$.02, Roger

On 7/19/2013 1:15 PM, Ivan Gerasimov wrote:
> Hello everybody!
> Would you please review a fix for the problem with 
> j.n.f.Files.readAllBytes() function?
> The current implementation relies on FileChannel.size() to preallocate 
> a buffer for the whole file's content.
> However, some special filesystems can report a wrong size.
> An example is procfs under Linux, which reports many files under /proc 
> to be zero sized.
> Thus it is proposed not to rely on the size() and instead continuously 
> read until EOF.
> The downside is reallocation and copying file content between buffers.
> But taking into account that the doc says: "It is not intended for 
> reading in large files." it should not be a big problem.
> http://bugs.sun.com/view_bug.do?bug_id=8020669
> http://cr.openjdk.java.net/~igerasim/8020669/0/webrev/
> The fix is for JDK8. If it is approved, it can be applied to JDK7 as 
> well.
> Sincerely yours,
> Ivan Gerasimov

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