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"""The function mimetools.choose_boundary() from Python 2.7, which seems to
have disappeared in Python 3 (although email.generator._make_boundary() might
work as a replacement?).
Tweaked to use lock from threading rather than thread.
"""
import os
from threading import Lock
_counter_lock = Lock()
_counter = 0
def _get_next_counter():
global _counter
with _counter_lock:
_counter += 1
return _counter
_prefix = None
def choose_boundary():
"""Return a string usable as a multipart boundary.
The string chosen is unique within a single program run, and
incorporates the user id (if available), process id (if available),
and current time. So it's very unlikely the returned string appears
in message text, but there's no guarantee.
The boundary contains dots so you have to quote it in the header."""
global _prefix
import time
if _prefix is None:
import socket
try:
hostid = socket.gethostbyname(socket.gethostname())
except socket.gaierror:
hostid = '127.0.0.1'
try:
uid = repr(os.getuid())
except AttributeError:
uid = '1'
try:
pid = repr(os.getpid())
except AttributeError:
pid = '1'
_prefix = hostid + '.' + uid + '.' + pid
return "%s.%.3f.%d" % (_prefix, time.time(), _get_next_counter())
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