You can decode the protocol buffer with just wire type + tag number, but you won't know the original types without a proto definition. Everything would be treated as an unknown field. You could access these by iterating through the UnknownFieldSet, but again, you can't recover the original types.
On Sat, Nov 14, 2009 at 1:10 PM, rahul prasad <rahu...@gmail.com> wrote: > Hi Marc, > > Thanks for the clarification. If the actual .proto was there, i would not > have posted that question [?] at the first place. Anyways, to decode a > protocol buffer, is it not enough to have just the wire type + tag number > combination? (except of course, handling of the sub-messages-ness and other > ambiguities you mentioned below have to be done manually though) > > Regards, > Rahul Prasad > > > > On Sat, Nov 14, 2009 at 3:57 PM, Marc Gravell <marc.grav...@gmail.com>wrote: > >> If you treat it as a string (UTF8), you are likely to get garbage. If you >> treat it as a byte[], then you just get a BLOB - you don't lose anything, >> but you might not be showing some more detail that you could show. >> >> You could, however, check for likely-sub-message-ness - i.e. after getting >> the length, you could try decoding the next few bytes as a variant, and do >> the shift trick; see if it looks likely to be a sub-message etc; you could >> try to validate the entire "string", see if it makes sense. Note that you >> don't have to store any of the data - just follow the rules for each >> wire-format until something doesn't look right or you've checked the string. >> >> Easiest, though, is to have the .proto available ;-p >> >> Marc >> >> 2009/11/14 rahul prasad <rahu...@gmail.com> >> >>> Hi, >>> >>> As seen from the below wire types table from protobuf documentation, if i >>> try to extract a value from a protobuf that is of type 2, it could either be >>> a string, byte array or a embedded message etc, If I cast the value as bytes >>> or string on the decoding side, while on the encoding side it was actually >>> an embedded message, what would this result in? Will I be able to retrieve >>> the actual value, someway or the other doing it this way? >>> >>> The available wire types are as follows: >>> Type Meaning Used For 0 Varint int32, int64, uint32, uint64, sint32, >>> sint64, bool, enum 1 64-bit fixed64, sfixed64, double 2 >>> Length-delimitedstring, bytes, embedded messages, packed repeated >>> fields3Start groupgroups (deprecated)4End groupgroups >>> (deprecated)532-bitfixed32, sfixed32, float >>> Regards, >>> Rahul Prasad >>> >>> >>> >>> >> >> >> -- >> Regards, >> >> Marc >> > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To post to this group, send email to protobuf@googlegroups.com To unsubscribe from this group, send email to protobuf+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/protobuf?hl=en -~----------~----~----~----~------~----~------~--~---
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