metadata_reader.py

import re
import base64
import math
import threading
import argparse

metadata = {}
lock = threading.Lock()

def update_metadata(type, code, length, data):
  global metadata
  if code == "mdst" and length == 0:
    lock.acquire()
    metadata = {}
  if code == "mden" and length == 0:
    lock.release()
    print(metadata)
  if type == "core":
    if code == "asal":
      metadata["album"] = data
    if code == "asar":
      metadata["artist"] = data
    if code == "minm":
      metadata["title"] = data


xml_pattern = re.compile("<type>(.*)<\/type><code>(.*)<\/code><length>(\d*)<\/length>(?:<data encoding=\"(.*)\">(.*)<\/data>){0,1}")

def parse_metadata(xml):
  m = xml_pattern.match(xml)
  type = m.group(1)
  type = bytes.fromhex(type).decode('ascii')
  code = m.group(2)
  code = bytes.fromhex(code).decode('ascii')
  length = int(m.group(3))
  encoding = m.group(4)
  data = m.group(5)
  if encoding == "base64":
    data = base64.b64decode(data)
  update_metadata(type, code, length, data)

def read_fifo(path):
  fifo = open(path, "r")
  info_tag_pattern = re.compile("<type>(.*)<\/type><code>(.*)<\/code><length>(\d*)<\/length>")
  line_group = next(fifo).rstrip('\r\n')
  while True:
    line = next(fifo).rstrip('\r\n')
    info_tag = info_tag_pattern.match(line)
    if not info_tag:
      line_group += line
    else:
      parse_metadata(line_group)
      line_group = line
  fifo.close()

if __name__ == "__main__":
  parser = argparse.ArgumentParser(description='Process metadata from shairport-sync.')
  parser.add_argument('fifo', metavar='f', type=str, help='path of the metadata fifo file')
  args = parser.parse_args()
  read_fifo(args.fifo)