A PluginFrontend instance provides a platform-dependent way for protoc to communicate with a JVM based ProtocCodeGenerator.

protoc is able to launch plugins. Plugins are executables that take a serialized CodeGenerationRequest via stdin and serialize a CodeGenerationRequest to stdout. The idea in PluginFrontend is to create a minimal plugin that wires its stdin/stdout to this JVM.

The two-way communication always goes as follows:

1. protoc writes a request to the stdin of a plugin 2. plugin writes the data to the channel 3. this JVM reads it, interprets it as CodeGenerationRequest and process it. 4. this JVM writes a CodeGenerationResponse to the channel 5. this JVM closes the channel. 6. the plugin reads the data and writes it to standard out. 7. protoc handles the CodeGenerationResponse (creates Scala sources)