Review JDK-8010837 - TEST_BUG: java/io/FileInputStream/LargeFileAvailable.java fails intermittently

[Alan Bateman]

On 26/03/2013 19:29, Dan Xu wrote:
> Hi All,
>
> In the old JVM function, os::available, it could return negative 
> values because lseek() allows the file offset to be set beyond the end 
> of a file. In the previous change of removing jvm functions, I wasn't 
> aware of that and regardnegative values as invalid and return 0, which 
> causes this test failed if it handles negative values. This 
> fixaddressedthis problem and added a new testcase to ensure the 
> correctbehaviour when available() encounters negative values.
>
> Webrev: http://cr.openjdk.java.net/~dxu/8010837/webrev/
>
> Thanks,
>
> -Dan
I see this has already been pushed but I think it requires further 
discussion. I think it would be surprising if available() returned 
anything other than 0 for this case. You can't read a negative number of 
bytes, and with a normal InputStream then a negative skip is a no-op. So 
minimally we will need a spec clarification to make it clear how 
available() should behave when the file position is beyond the current 
file size. I just checked Channels.newInputStream and it does return 0 
for this case. I also checked the FileInputStream.skip method and it 
seems to differ from its spec in that it allows a negative skip if the 
resulting file position is >= 0. I'll create bugs for these issues 
(assuming there aren't existing bugs on these topics area).

-Alan.