* UPB_STOP -> UPB_BREAK, better represents breaking
out of a parsing loop.
* UPB_STATUS_OK -> UPB_OK, for all status codes, more
concise at no readability cost (perhaps an improvement).
1. the start and end callbacks can now return
a upb_flow_t and set a status message.
2. clarified some semantics around passing an
error status back from the callbacks.
Unfortunately my previous detailed commit message was
lost somehow by git or vi. Will have to explain in more
detail at a later date the rationale for this change.
The build will be broken until I port the old decoder
to this new interface.
This should make it both easier to use and easier to
optimize, in exchange for a small amount of generality.
In practice, any remotely normal case is still very
natural.
The cost is that a upb_msg will now always have an overhead
of 2*sizeof(void*). This is comparable to proto2 overhead.
The benefit is that upb_msg is now self-describing, and
read-only algorithms can now operate on a upb_msg regardless
of the memory-management scheme.
Also, upb_array and upb_string now know inherently if they
own their associated memory, and upb_array has a generic
pointer for memory management purposes like upb_msg does.
There is significant refactoring here, as well as some more trivial
name changes. upb_msg has become upb_msgdef, to reflect the fact
that a upb_msg is not *itself* a message, it describes a message.
There are other renamings, such as upb_parse_state -> upb_stream_parser.
More significantly, the upb_msg class and parser have been refactored
to reflect my recent realization about how memory management should
work. upb_msg now has no memory management, and a memory mangement
scheme (that works beautifully with multiple language runtimes) will
be layered on top of it.
This iteration has the new, read-only upb_msg. upb_mm_msg (a
memory-managed message class) will come in the next change.
Joshua Haberman