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#!/usr/bin/env python3
#
# Copyright (c) 2019 Jon Turney
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
#
# utility functions
#
import filecmp
import logging
import os
import subprocess
from contextlib import contextmanager
#
# touch a file
#
def touch(fn, times=None):
try:
with open(fn, 'a'): # ensure fn exists
os.utime(fn, times)
except PermissionError:
logging.error("couldn't update mtime for %s" % (fn))
#
# ensure a directory exists
#
# for some versions of python, os.makedirs() can still raise FileExistsError
# even when exists_ok=True, if the directory mode is not as expected.
#
def makedirs(name):
try:
os.makedirs(name, exist_ok=True)
except FileExistsError:
pass
#
# remove any empty subdirectories below a given depth
#
def rmemptysubdirs(path, depth=3):
for (dirpath, _subdirs, _files) in os.walk(path, topdown=False, followlinks=True):
# don't do anything while above the given depth
if len(os.path.relpath(dirpath, path).split(os.sep)) < depth:
continue
# check whether the directory is now empty after processing any
# subdirectories, and if so, remove it
if len(os.listdir(dirpath)) == 0:
logging.debug('rmdir %s' % dirpath)
os.rmdir(dirpath)
#
# a wrapper for open() which:
#
# - atomically changes the file contents (atomic)
# - only touches the mtime if the file contents have changed (move-if-changed)
#
@contextmanager
def open_amifc(filepath, mode='w', cb=None):
tmppath = filepath + '~'
while os.path.isfile(tmppath):
tmppath += '~'
try:
with open(tmppath, mode) as file:
logging.debug('writing %s for move-if-changed' % (tmppath))
yield file
changed = not os.path.exists(filepath) or not filecmp.cmp(tmppath, filepath, shallow=False)
if changed:
logging.info("writing %s" % (filepath))
os.rename(tmppath, filepath)
else:
logging.debug("unchanged %s" % (filepath))
finally:
try:
os.remove(tmppath)
except OSError:
pass
# notify callback if file was changed or not
if cb:
cb(changed)
#
# run a subprocess, logging it's output
#
# N.B. because we use shell=True, args should be a string to be supplied to 'sh
# -c', not a list.
#
def system(args):
logging.debug(args)
try:
output = subprocess.check_output(args, shell=True,
stdin=subprocess.DEVNULL,
stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as e:
for l in e.output.decode().splitlines():
logging.warning(l)
logging.warning('%s exited %d' % (args.split()[0], e.returncode))
else:
for l in output.decode().splitlines():
logging.info(l)
#
# This provides a simple wrapper around a function which takes a pathname as
# it's only parameter. The result is cached as long as the mtime of the
# pathname is unchanged.
#
def mtime_cache(user_function):
sentinel = object() # unique object used to signal cache misses
cache = {}
def wrapper(key):
# make sure path is absolute
key = os.path.abspath(key)
(result, mtime) = cache.get(key, (sentinel, 0))
new_mtime = os.path.getmtime(key)
# cache hit
if result is not sentinel:
# cache valid
if new_mtime == mtime:
return result
else:
logging.debug('%s cache invalidated by mtime change' % key)
# cache miss
result = user_function(key)
cache[key] = (result, new_mtime)
return result
return wrapper
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