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#!/usr/bin/env -S python3 -u
# Note that running python with the `-u` flag is required on Windows,
# in order to ensure that stdin and stdout are opened in binary, rather
# than text, mode.
import sys
import json
import struct
import subprocess
import os
import logging
# Read a message from stdin and decode it.
def getMessage():
rawLength = sys.stdin.buffer.read(4)
if len(rawLength) == 0:
sys.exit(0)
messageLength = struct.unpack('@I', rawLength)[0]
message = sys.stdin.buffer.read(messageLength).decode('utf-8')
return json.loads(message)
# Encode a message for transmission,
# given its content.
def encodeMessage(messageContent):
# https://docs.python.org/3/library/json.html#basic-usage
# To get the most compact JSON representation, you should specify
# (',', ':') to eliminate whitespace.
# We want the most compact representation because the browser rejects # messages that exceed 1 MB.
encodedContent = json.dumps(messageContent, separators=(',', ':')).encode('utf-8')
encodedLength = struct.pack('@I', len(encodedContent))
return {'length': encodedLength, 'content': encodedContent}
# Send an encoded message to stdout
def sendMessage(encodedMessage):
sys.stdout.buffer.write(encodedMessage['length'])
sys.stdout.buffer.write(encodedMessage['content'])
sys.stdout.buffer.flush()
counter = 0
logging.basicConfig(filename="/tmp/librejs.log",
filemode='a',
format='%(asctime)s.%(msecs)d %(name)s %(levelname)s %(message)s',
datefmt='%H:%M:%S',
level=logging.DEBUG)
while True:
receivedMessage = getMessage()
devnull = open(os.devnull, 'w')
counter += 1
logging.info(f'[{counter}] {receivedMessage}')
sendMessage(encodeMessage(f'Logged message No. {counter}'))
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