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"""
Common global constants and instances
"""

import errno
import multiprocessing
import os

import pqos_api # pylint: disable=cyclic-import
import config # pylint: disable=cyclic-import
import stats # pylint: disable=cyclic-import


CONFIG_FILENAME = "appqos.conf"
CAT_CAP = "cat"
MBA_CAP = "mba"
SSTBF_CAP = "sstbf"
POWER_CAP = "power"

RATE_LIMIT = 10 # rate limit of configuration changes in HZ

MANAGER = multiprocessing.Manager()
CONFIG_STORE = config.ConfigStore()
STATS_STORE = stats.StatsStore()
PQOS_API = pqos_api.PqosApi()


def check_link(path, flags):
    """
    A custom opener for "open" function.
    Rises PermissionError if path points to a link

    Parameters:
        path: path to file
        flags: flags for "os.open" function
    Returns:
        an open file descriptor
    """
    if os.path.islink(path):
        raise PermissionError(errno.EPERM, os.strerror(errno.EPERM) + ". Is a link.", path)
    return os.open(path, flags)