This is in preparation for making upb_def capable
of parsing binary descriptors directly.
We leave upb/descriptor/descriptor.upbdefs.* in
place for now, because upb/descriptor/reader.*
still depends on it.
Also removed a bit of cruft from the codegen.
1. For decoding, an unknownfields will be lazily created on message,
which contains bytes of unknown fields.
2. For encoding, if the unknownfields is present on message, all bytes
contained in it will be serialized.
Also includes an implementation of the conformance tests
to display what the API usage will be like.
There is still a lot to do, and things that are broken (oneofs,
repeated fields, etc), but it's a good start.
This involves:
- remove upb_msglayout -> upb_msgfactory dependency.
- remove upb_msglayout -> upb_msgdef dependency (in progress).
- make upb_msglayout use a representation that can be
statically initialized by generated code.
The goal here is that upb_msglayout becomes a kind of "descriptor
lite": it contains enough data to parser and serialize protobufs
and manipulate a upb_msg in memory, while being far smaller and
simpler than a full descriptor. It also does not include field
names, which can be a benefit for applications that do not want
to leak field names.
Generated code can then create a upb_msglayout, and do most things
without ever needing to construct full descriptors/defs if they
don't want to.
Bo Yang
Josh Haberman