CodingInputStream/OutputStream have all that. readInt32/etc. There's no strict advantage... but presumably you're using protobuf to make your life easier, and this will make your life easier. (With a string, you have to include the length, etc. And if the header ever changes and you want to have back/forward compat, it can be convenient.)
On Sat, Jul 7, 2018 at 4:03 PM, John Lilley <[email protected]> wrote: > Does protobuf include utility methods for direct ser/deser on varint, > string, etc? > Thanks > john > > On Sat, Jul 7, 2018 at 2:02 PM John Lilley <[email protected]> wrote: >> >> Thanks! >> Given that, is there any advantage to a "header message" as opposed to >> just hand-serializing everything in the header? >> >> >> On Sat, Jul 7, 2018 at 12:45 PM Ilia Mirkin <[email protected]> wrote: >>> >>> You need explicit lengths. Usually this is done as <header length >>> varint><header><body>. And the header contains the body length in it. >>> In Java, there's a CodedInputStream/OutputStream which makes it easy >>> to consume fixed lengths (push/popLimit) as well as raw varints (as >>> for the initial header length). Other languages have similar >>> abstractions. >>> >>> On Sat, Jul 7, 2018 at 2:26 PM, John Lilley <[email protected]> wrote: >>> > I am posting protobuf messages to a message broker, and in order to >>> > identify >>> > them, I prefix the message bytes with the serialized result of a >>> > "header" >>> > message: >>> > >>> > message Header { >>> > int version = 1; >>> > string message_type = 2; >>> > } >>> > >>> > It is easy, to concatenate the header+actual message bytes and post the >>> > resulting block to a queue. But how do I take these apart on the >>> > receiving >>> > end? Suppose I get a byte-buffer consisting of: >>> > >>> > --------------- >>> > | header | >>> > --------------- >>> > | body | >>> > --------------- >>> > >>> > Is it OK to throw this oversized buffer at the Header deserialization? >>> > Will >>> > the extra bytes hurt anything? >>> > >>> > Then, once I extract the Header message, how do I know where the body >>> > begins? I could turn around and ask the Header object "how big would >>> > you be >>> > if serialized?". Is that reliable? Is there a better way? >>> > >>> > Thanks >>> > john >>> > >>> > -- >>> > You received this message because you are subscribed to the Google >>> > Groups >>> > "Protocol Buffers" group. >>> > To unsubscribe from this group and stop receiving emails from it, send >>> > an >>> > email to [email protected]. >>> > To post to this group, send email to [email protected]. >>> > Visit this group at https://groups.google.com/group/protobuf. >>> > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Protocol Buffers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/protobuf. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/protobuf. For more options, visit https://groups.google.com/d/optout.
