On Thu, Jun 20, 2013 at 2:13 AM, Sébastien Muscat <seb.mus...@gmail.com>wrote:
> Hi,
>
> I've got an encoding question about the following proto :
>
> message Property {
> required string key = 1;
> optional string value = 2;
> }
>
> message SysDate {
> required uint64 sec = 1;
> required uint32 usec = 2;
> }
>
> message BuiltInTest {
> required uint32 bit = 1;
> required uint32 bit_status = 2;
> required SysDate date = 3 ;
> optional Property bit_properties = 16 ;
> required string infos = 17;
> }
>
> then, I receive the following message
>
> 08 02 10 01 1A 08 08 EB 80 10 10 83 90 0A
> 82 01 10 0A A5 6B 65 79 12 07 76 61 6C 75 65
> 8A 01 05 69 6E 66 6F 73
>
> If I decode the first line, it's ok I got the value for bit, bit_status
> and date
> For the second line it's also ok, I got the values for bit_properties
> (with key attribute = "key" and value attribute = "value")
> And for the last line, I understand that byte 8A means wire type 2 and tag
> 17, byte 05 means a length of 5 but I don't understand the byte 01 ? what
> does it mean ?
>
The most significant bit of "8A" simply means there are more bytes coming
along which combined together represent a varint value, and the most
significant bit of "01" suggests this is the last byte of the varint. So
you combine the two to decode the varint value:
8A 01 ==> (1)000 1010 (0)000 0001 == remove the most significant bit and
swap the position for it's little endian ==> 000 0001 000 1010 ==> wire
type 2, tag 17
See the varint encoding:
https://developers.google.com/protocol-buffers/docs/encoding
>
> Thanks for your help
>
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