Viewing file:  atomic_helper.py (2.45 KB) -rw-r--r--
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# This file is part of cloud-init. See LICENSE file for license information.
import json
import logging
import os
import stat
import tempfile
from base64 import b64decode, b64encode
_DEF_PERMS = 0o644
LOG = logging.getLogger(__name__)
def b64d(source):
# Base64 decode some data, accepting bytes or unicode/str, and returning
# str/unicode if the result is utf-8 compatible, otherwise returning bytes.
decoded = b64decode(source)
try:
return decoded.decode("utf-8")
except UnicodeDecodeError:
return decoded
def b64e(source):
# Base64 encode some data, accepting bytes or unicode/str, and returning
# str/unicode if the result is utf-8 compatible, otherwise returning bytes.
if not isinstance(source, bytes):
source = source.encode("utf-8")
return b64encode(source).decode("utf-8")
def write_file(
filename, content, mode=_DEF_PERMS, omode="wb", preserve_mode=False
):
# open filename in mode 'omode', write content, set permissions to 'mode'
if preserve_mode:
try:
file_stat = os.stat(filename)
mode = stat.S_IMODE(file_stat.st_mode)
except OSError:
pass
tf = None
try:
tf = tempfile.NamedTemporaryFile(
dir=os.path.dirname(filename), delete=False, mode=omode
)
LOG.debug(
"Atomically writing to file %s (via temporary file %s) - %s: [%o]"
" %d bytes/chars",
filename,
tf.name,
omode,
mode,
len(content),
)
tf.write(content)
tf.close()
os.chmod(tf.name, mode)
os.rename(tf.name, filename)
except Exception as e:
if tf is not None:
os.unlink(tf.name)
raise e
def json_serialize_default(_obj):
"""Handler for types which aren't json serializable."""
try:
return "ci-b64:{0}".format(b64e(_obj))
except AttributeError:
return "Warning: redacted unserializable type {0}".format(type(_obj))
def json_dumps(data):
"""Return data in nicely formatted json."""
return json.dumps(
data,
indent=1,
sort_keys=True,
separators=(",", ": "),
default=json_serialize_default,
)
def write_json(filename, data, mode=_DEF_PERMS):
# dump json representation of data to file filename.
return write_file(
filename,
json_dumps(data) + "\n",
omode="w",
mode=mode,
)
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