Encode as grpc request

packGrpc.py

# * provide a message to be grpc encoded: `python packGrpc.py $FILE`
# * grpc compression will not be enabled
# * output: $FILE.pac is a one-message grpc frame

# opposite of https://gist.github.com/fynngodau/bba7b2d11a17d01f8439979f3cfe4fb9

import struct
import sys

assert len(sys.argv) == 2

with open(sys.argv[1], "rb") as file:
    decoded_message = file.read()

msg_is_compressed = False
length = len(decoded_message)

data = struct.pack("!?i", msg_is_compressed, length) + struct.pack("!%is" % length, decoded_message)

with open(sys.argv[1] + ".pac", "wb") as out_file:
    out_file.write(data)