On Jun 22, 2010, at 13:54 , sheila miguez wrote:
When I have a message to compress, I know the size of the byte array
stream buffer to allocate. Then call the writeTo on it. Is there
anything I should do other than this, given a message? writeTo should
be pretty performant, yes? In unit test, when measuring the speed that
takes, it is pretty good.


I don't quite understand what you are doing. Are you allocating a ByteArrayOutputStream, writing the message to it, then passing the byte[] from the ByteArrayOutputStream to some LZO library? You could just call message.toByteArray() if that is what you want, which will be faster.

I haven't tested this carefully, but my experience is that if you want the absolute best performance while using the Java API:

* If you are writing to an OutputStream, you want re-use a single CodedOutputStream. It has an internal buffer, and allocating this buffer multiple times seems to slow things down. You probably want this option if you are writing many messages. Its typically pretty easy to provide your own implementation of OutputStream if you need to pass data to something else (eg. LZO).

* If you have a byte[] array that is big enough, pass it in to CodedOutputStream.newInstance() to avoid an extra copy.

* If you just want a byte[] array that is the exact right size, just call message.toByteArray()


Does the LZO library have an OutputStream API? This would allow you to compress large protobuf messages as they are written out, rather than needing to serialize the entire thing to a byte[] array, then compress it. This could be "better," but as always you'll have to measure it.

Hope this helps,

Evan

--
Evan Jones
http://evanjones.ca/

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