RFR JDK-8164278: java.util.Base64.EncOutputStream/DecInputStream is slower than corresponding version in javax.mail package

Xueming Shen xueming.shen at oracle.com
Tue Feb 6 16:56:59 UTC 2018

On 2/6/18, 8:28 AM, Roger Riggs wrote:
> Hi Sherman,
> On 2/5/2018 9:00 PM, Xueming Shen wrote:
>> Hi,
>> Please help review the change for  JDK-8164278.
>> issue: https://bugs.openjdk.java.net/browse/JDK-8164278
>> webrev: http://cr.openjdk.java.net/~sherman/8164278/webrev
> Are the reentrant locks necessary?  concurrent reads from streams are 
> not usually
> synchronized so its the caller that need to synchronize.
> If locks are necessary, why no lock for the EncOutputStream buffer?
Thanks Roger,

I don't really care the "correctnesss" of the de/coding via the 
in/output stream
under concurrent access. As you said the caller should take the 
for that. In case of DecInputStream there is risk that the "pos" might 
be updated
out of the buffer boundary and trigger exception, if under concurrent 
It's not the case for EncOutputStream. But yes, let me see if I can get 
away with
this via local copy of the pos/cnt.

> 809: Can the buffer byte array be sized based on linemax?  The field 
> declaration should
>   be with the other fields at the top of the file.

sure possible with some calculation.
> 848: checkNewline compares == with linemax; that works when each byte 
> is counted separately
>  It seems like it would safer if it was ">=".


> 957: can sbBuf be shared with lbuf?

probably not. lbuf is for the bytes from underlying input stream. sbBuf 
is to
store/get the first byte of the decoded result.
>>     However, there is a side-effect of adding a buffering mechanism 
>> into DecInputStream. The
>>     current implementation read bytes from the underlying stream one 
>> by one, it never reads
>>     more bytes than it needs, which means it should/is supposed to 
>> just stop at the last byte
>>     that it needs to decode, when there is "=" present in the stream.
>>     With buffering, it's possible more bytes (after "=", which 
>> indicates "end of base64 stream") might
>>     be read/consumed in and buffered.  A concern? if this is indeed a 
>> concern, the only alternative
>>     might be to add a separate method to support this 
>> "faster-buffered-decoder"?
> How much buffering is needed to speed it up?  Can the mark/reset 
> functions of the underlying
> stream be used to backup the stream if it overshoots?
> If mark and reset are not supported then read 1 byte at a time.
will take a look at the mark/reset possibility. maybe I will put 
DecInputStream optimization to a
separate rfe.


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