RFR: 8257234 : Add gz option to SA jmap to write a gzipped heap dump [v19]

[Lin Zang]

On Wed, 10 Feb 2021 01:53:38 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> Lin Zang has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   refine code in test.
>
> src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 1504:
> 
>> 1502:             segmentBuffer[segmentWritten++] = (byte)(v >>>  8);
>> 1503:             segmentBuffer[segmentWritten++] = (byte)(v >>>  0);
>> 1504:         }
> 
> I'm not familiar to hprof format, but I guess we need to write them with big endian.
> Can we use `ByteBuffer::putInt` and `ByteBuffer::order` at here? I guess it makes ease to maintenance.

Hi @YaSuenag, 
I found there is also similar code in the original implement, in function fillInHeapRecordLength(). 
` fos.write((dumpLen >>> 24) & 0xFF);`
`  fos.write((dumpLen >>> 16) & 0xFF);`
` fos.write((dumpLen >>> 8) & 0xFF);`       
`  fos.write((dumpLen >>> 0) & 0xFF);`

Do you think it is ok to also change these codes? If my understanding is correct, the fileOutputStream does not have the process of big/little endian. 

Thanks,
Lin

-------------

PR: https://git.openjdk.java.net/jdk/pull/1712