--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.9/site-packages/boltons/mboxutils.py	Mon Mar 22 18:12:50 2021 +0000
@@ -0,0 +1,121 @@
+# -*- coding: utf-8 -*-
+"""Useful utilities for working with the `mbox`_-formatted
+mailboxes. Credit to Mark Williams for these.
+
+.. _mbox: https://en.wikipedia.org/wiki/Mbox
+"""
+
+import mailbox
+import tempfile
+
+
+DEFAULT_MAXMEM = 4 * 1024 * 1024  # 4MB
+
+
+class mbox_readonlydir(mailbox.mbox):
+    """A subclass of :class:`mailbox.mbox` suitable for use with mboxs
+    insides a read-only mail directory, e.g., ``/var/mail``. Otherwise
+    the API is exactly the same as the built-in mbox.
+
+    Deletes messages via truncation, in the manner of `Heirloom mailx`_.
+
+    Args:
+        path (str): Path to the mbox file.
+        factory (type): Message type (defaults to :class:`rfc822.Message`)
+        create (bool): Create mailbox if it does not exist. (defaults
+                       to ``True``)
+        maxmem (int): Specifies, in bytes, the largest sized mailbox
+                      to attempt to copy into memory. Larger mailboxes
+                      will be copied incrementally which is more
+                      hazardous. (defaults to 4MB)
+
+    .. note::
+
+       Because this truncates and rewrites parts of the mbox file,
+       this class can corrupt your mailbox.  Only use this if you know
+       the built-in :class:`mailbox.mbox` does not work for your use
+       case.
+
+    .. _Heirloom mailx: http://heirloom.sourceforge.net/mailx.html
+    """
+    def __init__(self, path, factory=None, create=True, maxmem=1024 * 1024):
+        mailbox.mbox.__init__(self, path, factory, create)
+        self.maxmem = maxmem
+
+    def flush(self):
+        """Write any pending changes to disk. This is called on mailbox
+        close and is usually not called explicitly.
+
+        .. note::
+
+           This deletes messages via truncation. Interruptions may
+           corrupt your mailbox.
+        """
+
+        # Appending and basic assertions are the same as in mailbox.mbox.flush.
+        if not self._pending:
+            if self._pending_sync:
+                # Messages have only been added, so syncing the file
+                # is enough.
+                mailbox._sync_flush(self._file)
+                self._pending_sync = False
+            return
+
+        # In order to be writing anything out at all, self._toc must
+        # already have been generated (and presumably has been modified
+        # by adding or deleting an item).
+        assert self._toc is not None
+
+        # Check length of self._file; if it's changed, some other process
+        # has modified the mailbox since we scanned it.
+        self._file.seek(0, 2)
+        cur_len = self._file.tell()
+        if cur_len != self._file_length:
+            raise mailbox.ExternalClashError('Size of mailbox file changed '
+                                             '(expected %i, found %i)' %
+                                             (self._file_length, cur_len))
+
+        self._file.seek(0)
+
+        # Truncation logic begins here.  Mostly the same except we
+        # can use tempfile because we're not doing rename(2).
+        with tempfile.TemporaryFile() as new_file:
+            new_toc = {}
+            self._pre_mailbox_hook(new_file)
+            for key in sorted(self._toc.keys()):
+                start, stop = self._toc[key]
+                self._file.seek(start)
+                self._pre_message_hook(new_file)
+                new_start = new_file.tell()
+                while True:
+                    buffer = self._file.read(min(4096,
+                                                 stop - self._file.tell()))
+                    if buffer == '':
+                        break
+                    new_file.write(buffer)
+                new_toc[key] = (new_start, new_file.tell())
+                self._post_message_hook(new_file)
+            self._file_length = new_file.tell()
+
+            self._file.seek(0)
+            new_file.seek(0)
+
+            # Copy back our messages
+            if self._file_length <= self.maxmem:
+                self._file.write(new_file.read())
+            else:
+                while True:
+                    buffer = new_file.read(4096)
+                    if not buffer:
+                        break
+                    self._file.write(buffer)
+
+            # Delete the rest.
+            self._file.truncate()
+
+        # Same wrap up.
+        self._toc = new_toc
+        self._pending = False
+        self._pending_sync = False
+        if self._locked:
+            mailbox._lock_file(self._file, dotlock=False)