RFR 8193842: Refactor InputStream-to-OutputStream copy into a utility method

[Alan Bateman]

On 22/12/2017 21:51, Brian Burkhalter wrote:
> https://bugs.openjdk.java.net/browse/JDK-8194133
> http://cr.openjdk.java.net/~bpb/8194133/webrev.00/
>
> Add jdk.internal.io.IOSupport with copy() methods for InputStream-to-OutputStream copying and modify some classes to use these new methods.
>
> One thing that I noticed when looking at this is that in the fix for https://bugs.openjdk.java.net/browse/JDK-8193842, the Files.copy() method had a loop like
>
> while ((n = read(…)) > 0)
>
> whereas InputStream.transferTo() had
>
> while((n = read(…)) >= 0)
>
> which is to say that Files.copy() would terminate if there were an empty read() but transferTo() would not. The patch for 8193842 therefore possibly introduced a subtle behavioral change which no one noticed.
>
read(byte[]) is blocking so it should only return 0 if called with a 
0-length array. So not clear to me that Files.copy methods needs to use 
this.

For JrtPath then the code is specific to the jimage -> jimage case. I 
think that can be left along too or just replaced with a better 
implementation for jrtfs.

-Alan.