dynproto

This is a fork of github.com/golang/protobuf to add schema parsing & marshaling/unmarshaling of blobs from dynamically parsed schemas.

Use this to parse protos when schemas aren't available at compile-time.

Example:

// careful: this is paraphrased from test suite. Never tested as-is.

schema, _ := proto.ParseSchema("syntax = \"proto3\"; message Hello {int32 a = 1; string b = 3;}")
dyn := proto.DynStruct(&schema)

val := reflect.New(dyn[0]) // dyn[0] i.e. the 0th message in the schema
val.Elem().FieldByName("A").SetInt(10)
val.Elem().FieldByName("B").SetString("ten")

buf := proto.Buffer{}
buf.Marshal(val.Interface())
val2 := reflect.New(dyn[0])
buf.Unmarshal(val2.Interface())

if val2.Elem().FieldByName("A").Int() != 10 || val.Elem().FieldByName("B").String() != "ten" {
	log.Panicf("%v\n", val2)
}

Changes from upstream:

• use cgo to wrap schema parsing from libprotobuf.
• added DynProto function which returns a reflect.Type (a dynamic struct)
• Buffer.Marshal / Unmarshal takes interface{} instead of proto.Message
• proto package copies parts of protoc-gen-go/generator.go.

Status & concerns:

• working and non-working features:
  • scalars
  • strings
  • nested protos
  • repeated fields
  • enums
  • maps
  • including other proto files
• I don't know how to test this project under all build constraints (appengine / JS). I assume it fails for the JS target because of cgo.
• cgo piece (schemaparser.go) needs review from someone who understands cgo to check for memory leaks
• haven't done any performance testing. Should be way slower than generated marshal/unmarshal functions.
• security: I don't know if the schema parsing & ser/des code were written with user-provided input in mind. You should pay for a security audit before pointing this at the internet.

Future work:

• I'm evaluating this for use in a larger project. If that moves forward, I plan to clean up this fork and ask the maintainers to merge back my changes.
• Don't expect this repo to stay functional or up-to-date. If your organization wants to use these features, you should take over the project.