You could query the message's Descriptor to find out the field number and
index of each field, and then use one of those (probably the index).
const Descriptor* descriptor = message.GetDescriptor()
int foo_index = descriptor-FindFieldByName(foo)-index();
On Mon, Feb 23, 2009 at 7:42 PM, Tim timbla...@gmail.com wrote:
OK, thanks. Just to clarify, I don't want access to _has_bits_, but
just to the definition of which bit position corresponds to which
field in the message. I.e., I want the compiler to do this:
#define ATTR1_BIT 1
...
_has_bit(ATTR1_BIT);
instead of this:
_has_bit(1);
Then my application can use the ATTR1_BIT definitions to implement it
own tracking of message field characteristics.
Does that change anything?
Tim
On Feb 23, 7:18 pm, Kenton Varda ken...@google.com wrote:
Hi Tim,
On Mon, Feb 23, 2009 at 7:01 PM, timbla...@gmail.com wrote:
In my application, I have a need to track characteristics of message
fields on a field-by-field basis, e.g. has this field changed. This is
very much like what is already done in libprotobuf code for tracking
whether a field has been set yet. Looking under the hood, I found the
_has_bits_, a simple bitfield tracking mechanism, and thought I could
reuse this for tracking other characteristics my app is interested in.
So far, though, it looks like the bit numbers are hard-coded in the
_set_bit/_clear_bit/has_bit method calls. Is there any plan to modify
the compiler to define these field bits as constants or at least
#defines in the generated c++ header file?
_has_bits_ is an internal (private) implementation detail. We don't plan
to
make it publicly-accessible.
Aside from this general question, is there another simple way you can
think of to track what fields have changed? I couldn't find anything
in the API that allowed diff'ing two instances of the same message
class. (I also couldn't find any equality operators, so had to define
that myself; please advise if this was unnecessary.)
It's not included in the base library, but you could write code to do
this
based on reflection.
Thanks,
Tim
--~--~-~--~~~---~--~~
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
-~--~~~~--~~--~--~---
