util.py

#!/usr/bin/python3

#PyVCDS Util script. used to load config files and do per-module logging,

import json
import io
import threading
import inspect
import os

class Config:
  def __init__(self, path):
    self.lock = threading.Lock()
    self.path = None
    if not path:
      self.backing = None
    else:
      if not os.path.exists(path):
        fd = open(path,"w")
        fd.write("{}")
        fd.close()
      self.open(path)
  def __getitem__(self, idx):
    if not idx in self.backing:
      self.backing[idx] = {}
    return self.backing[idx]
  def __setitem__(self, idx, item):
    with self.lock: #ensures config writes are always consistent among threads
      self.backing[idx] = item
      self.flush()
  def open(self,fname):
    self.path = fname #no need to flush, since we do that on every config update
    with self.lock:
      fd = open(fname,"r")
      self.backing = json.loads(fd.read())
      fd.close()
  def flush(self): #NOTE: do *NOT* add a call to 'self.lock' due to deadlocking with `__setitem__`
    fd = open(self.path, "w")
    fd.write(json.dumps(self.backing,indent=4))
    fd.close()


home = os.environ["HOME"]
assert home, "No home directory? cannot run on windows."
cfgpath = home  + "/.pyvcds/config.json"
if not os.path.exists(home + "/.pyvcds"):
  os.mkdir(home + "/.pyvcds")
config = Config(cfgpath)

levels = [
"FATAL", #0
"CRITICAL", #1
"ERROR", #2
"WARNING", #3
"INFO", #4
"DEBUG", #5
"TRACE" #6
]

def log(level, *args):
  global config
  modname = inspect.getmodule(inspect.stack()[1][0]).__name__ #get the calling stack frame, dereference it to the method, then get the module from it.
  if not modname in config["log"]:
    config["log"][modname] = 4 #initialize the module's log level config to "INFO"
    config.flush() #need to manually flush here, since sub-module configs don't trigger our __setitem__ call.
  if level <= config["log"][modname]:
    if modname == "__main__": #don't include __main__ for module tracing.
      print("[{}]".format(levels[level]),*args)
    else:
      print("[{}] [{}]".format(levels[level],modname),*args)