This mirrors the structure of C++ protobuf, which has an EpsCopyInputStream class.
This will lay the foundation for making EpsCopyInputStream capable of true streaming, by reading its input from a ZeroCopyInputStream. It also lets us test EpsCopyInputStream separately from the decoder: see the new unit test that fuzzes upb_EpsCopyInputStream.
After this CL is submitted, the two decoders (the normal decoder and the fast decoder) should no longer be accessing the members of upb_EpsCopyInputStream.
PiperOrigin-RevId: 494400285
This required some work to unify map entry messages with regular messages, with respect to presence. Before map entry fields could never have presence. Now they can have presence according to normal rules. Note that this only applies to times that the user constructs a map entry directly.
PiperOrigin-RevId: 490611656
Prior to this CL, there were several different code paths for reading/writing message data. Generated code, MiniTable accessors, and reflection all performed direct manipulation of the bits and bytes in a message, but they all had distinct implementations that did not share much of any code. This divergence meant that they could easily have different behavior, bugs could creep into one but not another, and we would need three different sets of tests to get full test coverage. This also made it very difficult to change the internal representation in any way, since it would require updating many places in the code.
With this CL, the three different APIs for accessing message data now all share a common set of functions. The common functions all take a `upb_MiniTableField` as the canonical description of a field's type and layout. The lowest-level functions are very branchy, as they must test for every possible variation in the field type (field vs oneof, hasbit vs no-hasbit, different field sizes, whether a nonzero default value exists, extension vs. regular field), however these functions are declared inline and designed to be very optimizable when values are known at compile time.
In generated accessors, for example, we can declare constant `upb_MiniTableField` instances so that all values can constant-propagate, and we can get fully specialized code even though we are calling a generic function. On the other hand, when we use the generic functions from reflection, we get runtime branches since values are not known at compile time. But even the function is written to still be as efficient as possible even when used from reflection. For example, we use memcpy() calls with constant length so that the compiler can optimize these into inline loads/stores without having to make an out-of-line call to memcpy().
In this way, this CL should be a benefit to both correctness and performance. It will also make it easier to change the message representation, for example to optimize the encoder by giving hasbits to all fields.
Note that we have not completely consolidated all access in this CL:
1. Some functions outside of get/set such as clear and hazzers are not yet unified.
2. The encoder and decoder still touch the message without going through the common functions. The encoder and decoder require a bit more specialized code to get good performance when reading/writing fields en masse.
PiperOrigin-RevId: 490016095
Remove circular dependencies that were bouncing back and forth between
msg_internal.h and mini_table/, including:
- splitting out each mini table subtype into its own header
- moving the non-reflection message code into message/
- moving the accessors from mini_table/ to message/
PiperOrigin-RevId: 489121042
- replace all instances of the deprecated iterator with the much nicer new one
- fix a bug which caused the new iterator to skip all values in the hash array
- fix a bug which caused the new iterator to skip the first value in the hash table
- delete the old iterator code
- also replace most uses of the deprecated string hash table iterator
PiperOrigin-RevId: 489093240
There are several other functions which might eventually end up here and ideally become unified across json/ and text/ and io/ so this is just a first step to create the new subdir and get rid of upb/internal/
PiperOrigin-RevId: 488954926
Move the map-related functions from msg_internal.h that are only used in generated code into map_gencode_util.h. Then move the rest of the map-related functions from msg_internal.h into map_internal.h.
PiperOrigin-RevId: 486299140
Eric Salo
Joshua Haberman
Mike Kruskal