# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import os
import glob
import re

# Matching a string of length m in an NFA of size n is O(mn^2), but the
# performance also depends largely on the implementation. It appears to be fast
# enough according to the tests.
#
# The performance bottleneck of this script is readelf. Unless this becomes
# slower than readelf, don't waste time here.
def is_whitelisted(list_name, pattern):
    """chech whether the given pattern is specified in the whitelist.

    Args:
        list_name: name of the whitelist
        pattern: the target string
    Returns:
        True if matched otherwise False
    """
    return pattern and whitelists[list_name].match(pattern)

def prepare_whitelist(patterns):
    """Join and compile the re patterns.

    Args:
        patterns: regex patterns.
    Return:
        A compiled re object
    """
    return re.compile('|'.join(patterns))

def load_whitelists(dirname):
    """Load whitelists under dirname.

    A whitelist ends with .whitelist.

    Args:
        dirname: path to the dir.
    Returns:
        A dictionary of 'filename' -> whitelist matcher.
    """
    wlist = {}
    for fn in glob.glob(os.path.join(dirname, '*.whitelist')):
        key = os.path.splitext(os.path.basename(fn))[0]
        with open(fn, 'r') as f:
            patterns = f.read().splitlines()
            patterns = [l for l in patterns if l != '']
            patterns = [l for l in patterns if l[0] != '#']
        wlist[key] = prepare_whitelist(patterns)
    return wlist


whitelists = load_whitelists(os.path.dirname(__file__))