On 22 December 2016 at 14:50,  <song1...@hotmail.com> wrote:
> Thanks for the reply.
>
> My question here is: I use protobuffer to store a bytes data, how can I
> retrieve it back?

Symmetric to the SerializeToArray(), use ParseFromArray() or
ParseFromString() to parse a serialized version of a protocol buffer
back.

> In my previous example, just offset 2 from the protobuffer
> data? However, the size field may vary, right?

That code does not make any sense in the real world: you are starting
with a protocol buffer, then serialize the resulting string in a new
protocol buffer. I suspect that was only for testing something ?

>
> On Thursday, December 22, 2016 at 2:13:14 PM UTC-8, Adam Cozzette wrote:
>>
>> It looks like you are building up a protocol buffer containing a
>> serialized protocol buffer, which itself contains a serialized protocol
>> buffer, which in turn contains a serialized protocol buffer, etc. Each level
>> of nesting requires an additional two bytes: one byte for the tag number and
>> a second byte for the length of the byte string that follows.
>>
>> For example, the first time you serialize it you need six bytes:
>> [ tag (one byte) ] [ size = 4 (one byte) ] [ ... 4 bytes of data ]
>>
>> Then the second serialization looks like this (8 bytes total):
>>
>> [ tag (one byte) ] [ size = 6 (one byte) ] [ ... the six bytes from above
>> ]
>>
>> See here for more information about the wire format.
>>
>> On Thu, Dec 22, 2016 at 1:52 PM, <song...@hotmail.com> wrote:
>>>
>>> I defined a simple bytes message below
>>> message MfStream {
>>>   bytes message=1;
>>> }
>>>
>>> and run a test below, in which I use for a loop to keep
>>> serialize/deserialize the bytes message.
>>>
>>> char buf[1024];
>>> int tmp = 1;
>>> MfStream testMsg;
>>> testMsg.set_message(&tmp, sizeof(tmp));
>>> for (int i=0; i<5; i++) {
>>>     int size = testMsg.ByteSize();
>>>     testMsg.SerializeToArray(buf, sizeof(buf));
>>>     cout << "i=" << i << ", size=" << size << endl;
>>>     testMsg.set_message(buf, size);
>>> }
>>>
>>>
>>> The results below shows that the message size keeps increasing by 2 every
>>> loop. Why? How should I serialize/deserialize bytes data?
>>>
>>> i=0, size=6
>>> i=1, size=8
>>> i=2, size=10
>>> i=3, size=12
>>> i=4, size=14
>>>
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>>
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