RFR: 8279283 - BufferedInputStream should override transferTo [v7]

[Markus KARG]

On Tue, 6 Sep 2022 12:32:46 GMT, Markus KARG <duke at openjdk.org> wrote:

>> BIS dates from JDK 1.0 and it's not hard to find examples that extend it. The HexPrinter test reminds us that it has been possible for 25+ years to override the read methods and snoop on all bytes that are read. Adding an override of the transferTo method that bypasses the read methods might break these subclasses. So I think Daniel is right that we have to be cautious.
>> 
>> So I think the feedback that you have now is that bypassing the buffer is problematic when using mark, when there are buffered bytes, or when BIS has been extended. It may be that the starting point is something very conservative like this:
>> 
>> 
>>     @Override
>>     public long transferTo(OutputStream out) throws IOException {
>>         if (getClass() == BufferedInputStream.class
>>                 && ((count - pos) <= 0) && (markpos == -1)) {
>>             return getInIfOpen().transferTo(out);
>>         } else {
>>             return super.transferTo(out);
>>         }
>>     }
>> 
>> 
>> There is also the issue of locking and async close to look into.
>
> Thank you for your decision about this issue, so instead of fixing the existing bugs I will implement as you outlined.
> 
> BTW, locking and rebasing is on the way.

Rebased and fixed locking, using your proposed code now.

@AlanBateman  Async close leaves BIS in an invalid state. The JavaDocs say ` The behavior for the case where the inputand/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output streamspecific, and therefore not specified.`. So there is seems to be no *essential* need to do something *particular* in that case (the caller cannot further use the BIS, just like after an IOE: `It is strongly recommended that both streams be promptly closed if an I/O error occurs.` -- which is what *I personally, as a user of BIS* would do after async close), but if you *want* that we reach a particular outcome, then just tell me what outcome you envision.

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PR: https://git.openjdk.org/jdk/pull/6935