Is the intention of the C++ CodedStreams that they are "cheap" and so
I should use one per message? Or should I reuse one if I have a large
sequence of messages to read/write? For writing, I've been using a
single CodedOutputStream, something like:
CodedOutputStream out(...)
for (message in long sequence) {
out.WriteVarint32((int32_t) message.ByteSize());
message.SerializeToCodedStream(&out);
}
This works fine. However, doing the same on input does not work,
because I run into the total byte limit. In Java, I call
resetSizeCounter() to avoid this problem. Is there a reason a similar
function does not exist for the C++ side? I'm working around this by
moving the CodedInputStream inside my loop, which is fine, but seems
sub-optimal. At the very least, since I have lots of small messages,
this means my ZeroCopyInputStream's methods get called many times.
Related question: If I am writing length-prefixed values, what is the
"best" way to do this? I think there are 3 approaches:
1. out.WriteVarint32(msg.ByteSize()); msg.SerializeToCodedStream(&out);
This approach will choose between the "ToArray" and "regular" versions
of the Serialize method, as appropriate. However, it computes the
ByteSize twice.
2. out.WriteVarint32(msg.ByteSize());
msg.SerializeWithCachedSizes(&out);
This computes the ByteSize once, but never uses the "fast path"
ToArray method.
3. Some custom code that calls ByteSize once, then chooses between the
"fast" and "slow" methods, as appropriate. Is there actually any
significant difference in performance between SerializeWithCachedSizes
and SerializeWithCachedSizesToArray, so it would be worth me actually
doing this?
Thanks,
Evan
--
Evan Jones
http://evanjones.ca/
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