api: Add C support (#549)

api/c/.gitignore

@@ -0,0 +1,2 @@
+/src/
+/proto/

api/c/Makefile

@@ -0,0 +1,34 @@
+.PHONY: all pre-build
+
+PROTOC := protoc-c
+PROTOC_ARGS := -I=proto -I=proto/chirpstack-api --c_out=./src
+
+GOOGLE_PROTOBUF_REQUIREMENTS =
+GOOGLE_PROTOBUF_REQUIREMENTS += timestamp.proto
+GOOGLE_PROTOBUF_REQUIREMENTS += duration.proto
+GOOGLE_PROTOBUF_REQUIREMENTS += struct.proto
+GOOGLE_PROTOBUF_REQUIREMENTS += empty.proto
+GOOGLE_PROTOBUF_REQUIREMENTS += descriptor.proto
+GOOGLE_PROTOBUF_OUTPUT = $(patsubst %.proto, src/google/protobuf/%.pb-c.h, $(GOOGLE_PROTOBUF_REQUIREMENTS))
+
+all: pre-build $(GOOGLE_PROTOBUF_OUTPUT) build
+
+pre-build:
+	rm -rf proto src
+	mkdir -p proto/chirpstack-api
+	mkdir -p proto/google/protobuf
+	cp -r ../proto/* proto/chirpstack-api/
+	mv proto/chirpstack-api/google/api proto/google/api
+	mkdir -p src
+	sed -i \
+		-r 's/(\s+bytes std)(in|out|err)(\s+=.*)/\1_\2\3/' \
+		proto/chirpstack-api/gw/gw.proto
+
+src/google/protobuf/%.pb-c.h: /protobuf/src/google/protobuf/%.proto
+	cp $< proto/google/protobuf/
+
+build:
+	find proto \
+		-name '*.proto' \
+		-type f \
+		-exec $(PROTOC) $(PROTOC_ARGS) {} \;