Personal Computer World 2009 February/PCWFEB09.iso/Software/Linux/Kubuntu 8.10/kubuntu-8.10-desktop-i386.iso/casper/filesystem.squashfs/usr/lib/python2.5/mailbox.pyc

Python Compiled Bytecode | 2008-10-29 | 75KB | 2,593 lines

# Source Generated with Decompyle++
# File: in.pyc (Python 2.5)

'''Read/write support for Maildir, mbox, MH, Babyl, and MMDF mailboxes.'''
import sys
import os
import time
import calendar
import socket
import errno
import copy
import email
import email.Message as email
import email.Generator as email
import rfc822
import StringIO

try:
    if sys.platform == 'os2emx':
        raise ImportError

    import fcntl
except ImportError:
    fcntl = None

__all__ = [
    'Mailbox',
    'Maildir',
    'mbox',
    'MH',
    'Babyl',
    'MMDF',
    'Message',
    'MaildirMessage',
    'mboxMessage',
    'MHMessage',
    'BabylMessage',
    'MMDFMessage',
    'UnixMailbox',
    'PortableUnixMailbox',
    'MmdfMailbox',
    'MHMailbox',
    'BabylMailbox']

class Mailbox:
    '''A group of messages in a particular place.'''

    def __init__(self, path, factory = None, create = True):
        '''Initialize a Mailbox instance.'''
        self._path = os.path.abspath(os.path.expanduser(path))
        self._factory = factory


    def add(self, message):
        '''Add message and return assigned key.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def remove(self, key):
        """Remove the keyed message; raise KeyError if it doesn't exist."""
        raise NotImplementedError('Method must be implemented by subclass')


    def __delitem__(self, key):
        self.remove(key)


    def discard(self, key):
        '''If the keyed message exists, remove it.'''

        try:
            self.remove(key)
        except KeyError:
            pass



    def __setitem__(self, key, message):
        """Replace the keyed message; raise KeyError if it doesn't exist."""
        raise NotImplementedError('Method must be implemented by subclass')


    def get(self, key, default = None):
        """Return the keyed message, or default if it doesn't exist."""

        try:
            return self.__getitem__(key)
        except KeyError:
            return default



    def __getitem__(self, key):
        """Return the keyed message; raise KeyError if it doesn't exist."""
        if not self._factory:
            return self.get_message(key)
        else:
            return self._factory(self.get_file(key))


    def get_message(self, key):
        '''Return a Message representation or raise a KeyError.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def get_string(self, key):
        '''Return a string representation or raise a KeyError.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def get_file(self, key):
        '''Return a file-like representation or raise a KeyError.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def iterkeys(self):
        '''Return an iterator over keys.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def keys(self):
        '''Return a list of keys.'''
        return list(self.iterkeys())


    def itervalues(self):
        '''Return an iterator over all messages.'''
        for key in self.iterkeys():

            try:
                value = self[key]
            except KeyError:
                continue

            yield value



    def __iter__(self):
        return self.itervalues()


    def values(self):
        '''Return a list of messages. Memory intensive.'''
        return list(self.itervalues())


    def iteritems(self):
        '''Return an iterator over (key, message) tuples.'''
        for key in self.iterkeys():

            try:
                value = self[key]
            except KeyError:
                continue

            yield (key, value)



    def items(self):
        '''Return a list of (key, message) tuples. Memory intensive.'''
        return list(self.iteritems())


    def has_key(self, key):
        '''Return True if the keyed message exists, False otherwise.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def __contains__(self, key):
        return self.has_key(key)


    def __len__(self):
        '''Return a count of messages in the mailbox.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def clear(self):
        '''Delete all messages.'''
        for key in self.iterkeys():
            self.discard(key)



    def pop(self, key, default = None):
        '''Delete the keyed message and return it, or default.'''

        try:
            result = self[key]
        except KeyError:
            return default

        self.discard(key)
        return result


    def popitem(self):
        '''Delete an arbitrary (key, message) pair and return it.'''
        for key in self.iterkeys():
            return (key, self.pop(key))
        else:
            raise KeyError('No messages in mailbox')


    def update(self, arg = None):
        '''Change the messages that correspond to certain keys.'''
        if hasattr(arg, 'iteritems'):
            source = arg.iteritems()
        elif hasattr(arg, 'items'):
            source = arg.items()
        else:
            source = arg
        bad_key = False
        for key, message in source:

            try:
                self[key] = message
            continue
            except KeyError:
                bad_key = True
                continue



        if bad_key:
            raise KeyError('No message with key(s)')



    def flush(self):
        '''Write any pending changes to the disk.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def lock(self):
        '''Lock the mailbox.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def unlock(self):
        '''Unlock the mailbox if it is locked.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def close(self):
        '''Flush and close the mailbox.'''
        raise NotImplementedError('Method must be implemented by subclass')


    def _dump_message(self, message, target, mangle_from_ = False):
        '''Dump message contents to target file.'''
        if isinstance(message, email.Message.Message):
            buffer = StringIO.StringIO()
            gen = email.Generator.Generator(buffer, mangle_from_, 0)
            gen.flatten(message)
            buffer.seek(0)
            target.write(buffer.read().replace('\n', os.linesep))
        elif isinstance(message, str):
            if mangle_from_:
                message = message.replace('\nFrom ', '\n>From ')

            message = message.replace('\n', os.linesep)
            target.write(message)
        elif hasattr(message, 'read'):
            while True:
                line = message.readline()
                if line == '':
                    break

                if mangle_from_ and line.startswith('From '):
                    line = '>From ' + line[5:]

                line = line.replace('\n', os.linesep)
                target.write(line)
        else:
            raise TypeError('Invalid message type: %s' % type(message))



class Maildir(Mailbox):
    '''A qmail-style Maildir mailbox.'''
    colon = ':'

    def __init__(self, dirname, factory = rfc822.Message, create = True):
        '''Initialize a Maildir instance.'''
        Mailbox.__init__(self, dirname, factory, create)
        if not os.path.exists(self._path):
            if create:
                os.mkdir(self._path, 448)
                os.mkdir(os.path.join(self._path, 'tmp'), 448)
                os.mkdir(os.path.join(self._path, 'new'), 448)
                os.mkdir(os.path.join(self._path, 'cur'), 448)
            else:
                raise NoSuchMailboxError(self._path)

        self._toc = { }


    def add(self, message):
        '''Add message and return assigned key.'''
        tmp_file = self._create_tmp()

        try:
            self._dump_message(message, tmp_file)
        finally:
            _sync_close(tmp_file)

        if isinstance(message, MaildirMessage):
            subdir = message.get_subdir()
            suffix = self.colon + message.get_info()
            if suffix == self.colon:
                suffix = ''

        else:
            subdir = 'new'
            suffix = ''
        uniq = os.path.basename(tmp_file.name).split(self.colon)[0]
        dest = os.path.join(self._path, subdir, uniq + suffix)

        try:
            if hasattr(os, 'link'):
                os.link(tmp_file.name, dest)
                os.remove(tmp_file.name)
            else:
                os.rename(tmp_file.name, dest)
        except OSError:
            e = None
            os.remove(tmp_file.name)
            if e.errno == errno.EEXIST:
                raise ExternalClashError('Name clash with existing message: %s' % dest)
            else:
                raise
        except:
            e.errno == errno.EEXIST

        if isinstance(message, MaildirMessage):
            os.utime(dest, (os.path.getatime(dest), message.get_date()))

        return uniq


    def remove(self, key):
        """Remove the keyed message; raise KeyError if it doesn't exist."""
        os.remove(os.path.join(self._path, self._lookup(key)))


    def discard(self, key):
        '''If the keyed message exists, remove it.'''

        try:
            self.remove(key)
        except KeyError:
            pass
        except OSError:
            e = None
            if e.errno != errno.ENOENT:
                raise

        except:
            e.errno != errno.ENOENT



    def __setitem__(self, key, message):
        """Replace the keyed message; raise KeyError if it doesn't exist."""
        old_subpath = self._lookup(key)
        temp_key = self.add(message)
        temp_subpath = self._lookup(temp_key)
        if isinstance(message, MaildirMessage):
            dominant_subpath = temp_subpath
        else:
            dominant_subpath = old_subpath
        subdir = os.path.dirname(dominant_subpath)
        if self.colon in dominant_subpath:
            suffix = self.colon + dominant_subpath.split(self.colon)[-1]
        else:
            suffix = ''
        self.discard(key)
        new_path = os.path.join(self._path, subdir, key + suffix)
        os.rename(os.path.join(self._path, temp_subpath), new_path)
        if isinstance(message, MaildirMessage):
            os.utime(new_path, (os.path.getatime(new_path), message.get_date()))



    def get_message(self, key):
        '''Return a Message representation or raise a KeyError.'''
        subpath = self._lookup(key)
        f = open(os.path.join(self._path, subpath), 'r')

        try:
            if self._factory:
                msg = self._factory(f)
            else:
                msg = MaildirMessage(f)
        finally:
            f.close()

        (subdir, name) = os.path.split(subpath)
        msg.set_subdir(subdir)
        if self.colon in name:
            msg.set_info(name.split(self.colon)[-1])

        msg.set_date(os.path.getmtime(os.path.join(self._path, subpath)))
        return msg


    def get_string(self, key):
        '''Return a string representation or raise a KeyError.'''
        f = open(os.path.join(self._path, self._lookup(key)), 'r')

        try:
            return f.read()
        finally:
            f.close()



    def get_file(self, key):
        '''Return a file-like representation or raise a KeyError.'''
        f = open(os.path.join(self._path, self._lookup(key)), 'rb')
        return _ProxyFile(f)


    def iterkeys(self):
        '''Return an iterator over keys.'''
        self._refresh()
        for key in self._toc:

            try:
                self._lookup(key)
            except KeyError:
                continue

            yield key



    def has_key(self, key):
        '''Return True if the keyed message exists, False otherwise.'''
        self._refresh()
        return key in self._toc


    def __len__(self):
        '''Return a count of messages in the mailbox.'''
        self._refresh()
        return len(self._toc)


    def flush(self):
        '''Write any pending changes to disk.'''
        pass


    def lock(self):
        '''Lock the mailbox.'''
        pass


    def unlock(self):
        '''Unlock the mailbox if it is locked.'''
        pass


    def close(self):
        '''Flush and close the mailbox.'''
        pass


    def list_folders(self):
        '''Return a list of folder names.'''
        result = []
        for entry in os.listdir(self._path):
            if len(entry) > 1 and entry[0] == '.' and os.path.isdir(os.path.join(self._path, entry)):
                result.append(entry[1:])
                continue

        return result


    def get_folder(self, folder):
        '''Return a Maildir instance for the named folder.'''
        return Maildir(os.path.join(self._path, '.' + folder), factory = self._factory, create = False)


    def add_folder(self, folder):
        '''Create a folder and return a Maildir instance representing it.'''
        path = os.path.join(self._path, '.' + folder)
        result = Maildir(path, factory = self._factory)
        maildirfolder_path = os.path.join(path, 'maildirfolder')
        if not os.path.exists(maildirfolder_path):
            os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY))

        return result


    def remove_folder(self, folder):
        '''Delete the named folder, which must be empty.'''
        path = os.path.join(self._path, '.' + folder)
        for entry in os.listdir(os.path.join(path, 'new')) + os.listdir(os.path.join(path, 'cur')):
            if len(entry) < 1 or entry[0] != '.':
                raise NotEmptyError('Folder contains message(s): %s' % folder)
                continue

        for entry in os.listdir(path):
            if entry != 'new' and entry != 'cur' and entry != 'tmp' and os.path.isdir(os.path.join(path, entry)):
                raise NotEmptyError("Folder contains subdirectory '%s': %s" % (folder, entry))
                continue

        for root, dirs, files in os.walk(path, topdown = False):
            for entry in files:
                os.remove(os.path.join(root, entry))

            for entry in dirs:
                os.rmdir(os.path.join(root, entry))


        os.rmdir(path)


    def clean(self):
        '''Delete old files in "tmp".'''
        now = time.time()
        for entry in os.listdir(os.path.join(self._path, 'tmp')):
            path = os.path.join(self._path, 'tmp', entry)
            if now - os.path.getatime(path) > 129600:
                os.remove(path)
                continue


    _count = 1

    def _create_tmp(self):
        '''Create a file in the tmp subdirectory and open and return it.'''
        now = time.time()
        hostname = socket.gethostname()
        if '/' in hostname:
            hostname = hostname.replace('/', '\\057')

        if ':' in hostname:
            hostname = hostname.replace(':', '\\072')

        uniq = '%s.M%sP%sQ%s.%s' % (int(now), int((now % 1) * 1e+06), os.getpid(), Maildir._count, hostname)
        path = os.path.join(self._path, 'tmp', uniq)

        try:
            os.stat(path)
        except OSError:
            e = None
            if e.errno == errno.ENOENT:
                Maildir._count += 1

                try:
                    return _create_carefully(path)
                except OSError:
                    Maildir
                    e = Maildir
                    if e.errno != errno.EEXIST:
                        raise

                except:
                    e.errno != errno.EEXIST


            Maildir<EXCEPTION MATCH>OSError
            raise
        except:
            Maildir

        raise ExternalClashError('Name clash prevented file creation: %s' % path)


    def _refresh(self):
        '''Update table of contents mapping.'''
        self._toc = { }
        for subdir in ('new', 'cur'):
            subdir_path = os.path.join(self._path, subdir)
            for entry in os.listdir(subdir_path):
                p = os.path.join(subdir_path, entry)
                if os.path.isdir(p):
                    continue

                uniq = entry.split(self.colon)[0]
                self._toc[uniq] = os.path.join(subdir, entry)




    def _lookup(self, key):
        '''Use TOC to return subpath for given key, or raise a KeyError.'''

        try:
            if os.path.exists(os.path.join(self._path, self._toc[key])):
                return self._toc[key]
        except KeyError:
            pass

        self._refresh()

        try:
            return self._toc[key]
        except KeyError:
            raise KeyError('No message with key: %s' % key)



    def next(self):
        '''Return the next message in a one-time iteration.'''
        if not hasattr(self, '_onetime_keys'):
            self._onetime_keys = self.iterkeys()

        while True:

            try:
                return self[self._onetime_keys.next()]
            continue
            except StopIteration:
                return None
                continue
                except KeyError:
                    continue
                    continue

                None<EXCEPTION MATCH>KeyError
            return None




class _singlefileMailbox(Mailbox):
    '''A single-file mailbox.'''

    def __init__(self, path, factory = None, create = True):
        '''Initialize a single-file mailbox.'''
        Mailbox.__init__(self, path, factory, create)

        try:
            f = open(self._path, 'rb+')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                if create:
                    f = open(self._path, 'wb+')
                else:
                    raise NoSuchMailboxError(self._path)
            elif e.errno == errno.EACCES:
                f = open(self._path, 'rb')
            else:
                raise
        except:
            e.errno == errno.ENOENT

        self._file = f
        self._toc = None
        self._next_key = 0
        self._pending = False
        self._locked = False


    def add(self, message):
        '''Add message and return assigned key.'''
        self._lookup()
        self._toc[self._next_key] = self._append_message(message)
        self._next_key += 1
        self._pending = True
        return self._next_key - 1


    def remove(self, key):
        """Remove the keyed message; raise KeyError if it doesn't exist."""
        self._lookup(key)
        del self._toc[key]
        self._pending = True


    def __setitem__(self, key, message):
        """Replace the keyed message; raise KeyError if it doesn't exist."""
        self._lookup(key)
        self._toc[key] = self._append_message(message)
        self._pending = True


    def iterkeys(self):
        '''Return an iterator over keys.'''
        self._lookup()
        for key in self._toc.keys():
            yield key



    def has_key(self, key):
        '''Return True if the keyed message exists, False otherwise.'''
        self._lookup()
        return key in self._toc


    def __len__(self):
        '''Return a count of messages in the mailbox.'''
        self._lookup()
        return len(self._toc)


    def lock(self):
        '''Lock the mailbox.'''
        if not self._locked:
            _lock_file(self._file)
            self._locked = True



    def unlock(self):
        '''Unlock the mailbox if it is locked.'''
        if self._locked:
            _unlock_file(self._file)
            self._locked = False



    def flush(self):
        '''Write any pending changes to disk.'''
        if not self._pending:
            return None

        self._lookup()
        new_file = _create_temporary(self._path)

        try:
            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)
        except:
            new_file.close()
            os.remove(new_file.name)
            raise

        _sync_close(new_file)
        self._file.close()

        try:
            os.rename(new_file.name, self._path)
        except OSError:
            e = None
            if (e.errno == errno.EEXIST or os.name == 'os2') and e.errno == errno.EACCES:
                os.remove(self._path)
                os.rename(new_file.name, self._path)
            else:
                raise
        except:
            e.errno == errno.EACCES

        self._file = open(self._path, 'rb+')
        self._toc = new_toc
        self._pending = False
        if self._locked:
            _lock_file(self._file, dotlock = False)



    def _pre_mailbox_hook(self, f):
        '''Called before writing the mailbox to file f.'''
        pass


    def _pre_message_hook(self, f):
        '''Called before writing each message to file f.'''
        pass


    def _post_message_hook(self, f):
        '''Called after writing each message to file f.'''
        pass


    def close(self):
        '''Flush and close the mailbox.'''
        self.flush()
        if self._locked:
            self.unlock()

        self._file.close()


    def _lookup(self, key = None):
        '''Return (start, stop) or raise KeyError.'''
        if self._toc is None:
            self._generate_toc()

        if key is not None:

            try:
                return self._toc[key]
            except KeyError:
                raise KeyError('No message with key: %s' % key)
            except:
                None<EXCEPTION MATCH>KeyError


        None<EXCEPTION MATCH>KeyError


    def _append_message(self, message):
        '''Append message to mailbox and return (start, stop) offsets.'''
        self._file.seek(0, 2)
        self._pre_message_hook(self._file)
        offsets = self._install_message(message)
        self._post_message_hook(self._file)
        self._file.flush()
        return offsets



class _mboxMMDF(_singlefileMailbox):
    '''An mbox or MMDF mailbox.'''
    _mangle_from_ = True

    def get_message(self, key):
        '''Return a Message representation or raise a KeyError.'''
        (start, stop) = self._lookup(key)
        self._file.seek(start)
        from_line = self._file.readline().replace(os.linesep, '')
        string = self._file.read(stop - self._file.tell())
        msg = self._message_factory(string.replace(os.linesep, '\n'))
        msg.set_from(from_line[5:])
        return msg


    def get_string(self, key, from_ = False):
        '''Return a string representation or raise a KeyError.'''
        (start, stop) = self._lookup(key)
        self._file.seek(start)
        if not from_:
            self._file.readline()

        string = self._file.read(stop - self._file.tell())
        return string.replace(os.linesep, '\n')


    def get_file(self, key, from_ = False):
        '''Return a file-like representation or raise a KeyError.'''
        (start, stop) = self._lookup(key)
        self._file.seek(start)
        if not from_:
            self._file.readline()

        return _PartialFile(self._file, self._file.tell(), stop)


    def _install_message(self, message):
        '''Format a message and blindly write to self._file.'''
        from_line = None
        if isinstance(message, str) and message.startswith('From '):
            newline = message.find('\n')
            if newline != -1:
                from_line = message[:newline]
                message = message[newline + 1:]
            else:
                from_line = message
                message = ''
        elif isinstance(message, _mboxMMDFMessage):
            from_line = 'From ' + message.get_from()
        elif isinstance(message, email.Message.Message):
            from_line = message.get_unixfrom()

        if from_line is None:
            from_line = 'From MAILER-DAEMON %s' % time.asctime(time.gmtime())

        start = self._file.tell()
        self._file.write(from_line + os.linesep)
        self._dump_message(message, self._file, self._mangle_from_)
        stop = self._file.tell()
        return (start, stop)



class mbox(_mboxMMDF):
    '''A classic mbox mailbox.'''
    _mangle_from_ = True

    def __init__(self, path, factory = None, create = True):
        '''Initialize an mbox mailbox.'''
        self._message_factory = mboxMessage
        _mboxMMDF.__init__(self, path, factory, create)


    def _pre_message_hook(self, f):
        '''Called before writing each message to file f.'''
        if f.tell() != 0:
            f.write(os.linesep)



    def _generate_toc(self):
        '''Generate key-to-(start, stop) table of contents.'''
        starts = []
        stops = []
        self._file.seek(0)
        while True:
            line_pos = self._file.tell()
            line = self._file.readline()
            if line.startswith('From '):
                if len(stops) < len(starts):
                    stops.append(line_pos - len(os.linesep))

                starts.append(line_pos)
                continue
            if line == '':
                stops.append(line_pos)
                break
                continue
        self._toc = dict(enumerate(zip(starts, stops)))
        self._next_key = len(self._toc)



class MMDF(_mboxMMDF):
    '''An MMDF mailbox.'''

    def __init__(self, path, factory = None, create = True):
        '''Initialize an MMDF mailbox.'''
        self._message_factory = MMDFMessage
        _mboxMMDF.__init__(self, path, factory, create)


    def _pre_message_hook(self, f):
        '''Called before writing each message to file f.'''
        f.write('\x01\x01\x01\x01' + os.linesep)


    def _post_message_hook(self, f):
        '''Called after writing each message to file f.'''
        f.write(os.linesep + '\x01\x01\x01\x01' + os.linesep)


    def _generate_toc(self):
        '''Generate key-to-(start, stop) table of contents.'''
        starts = []
        stops = []
        self._file.seek(0)
        next_pos = 0
        while True:
            line_pos = next_pos
            line = self._file.readline()
            next_pos = self._file.tell()
            if line.startswith('\x01\x01\x01\x01' + os.linesep):
                starts.append(next_pos)
                while True:
                    line_pos = next_pos
                    line = self._file.readline()
                    next_pos = self._file.tell()
                    if line == '\x01\x01\x01\x01' + os.linesep:
                        stops.append(line_pos - len(os.linesep))
                        break
                        continue
                    if line == '':
                        stops.append(line_pos)
                        break
                        continue
                continue
            if line == '':
                break
                continue
        self._toc = dict(enumerate(zip(starts, stops)))
        self._next_key = len(self._toc)



class MH(Mailbox):
    '''An MH mailbox.'''

    def __init__(self, path, factory = None, create = True):
        '''Initialize an MH instance.'''
        Mailbox.__init__(self, path, factory, create)
        if not os.path.exists(self._path):
            if create:
                os.mkdir(self._path, 448)
                os.close(os.open(os.path.join(self._path, '.mh_sequences'), os.O_CREAT | os.O_EXCL | os.O_WRONLY, 384))
            else:
                raise NoSuchMailboxError(self._path)

        self._locked = False


    def add(self, message):
        '''Add message and return assigned key.'''
        keys = self.keys()
        if len(keys) == 0:
            new_key = 1
        else:
            new_key = max(keys) + 1
        new_path = os.path.join(self._path, str(new_key))
        f = _create_carefully(new_path)

        try:
            if self._locked:
                _lock_file(f)


            try:
                self._dump_message(message, f)
                if isinstance(message, MHMessage):
                    self._dump_sequences(message, new_key)
            finally:
                if self._locked:
                    _unlock_file(f)


        finally:
            _sync_close(f)

        return new_key


    def remove(self, key):
        """Remove the keyed message; raise KeyError if it doesn't exist."""
        path = os.path.join(self._path, str(key))

        try:
            f = open(path, 'rb+')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                raise KeyError('No message with key: %s' % key)
            else:
                raise
        except:
            e.errno == errno.ENOENT


        try:
            if self._locked:
                _lock_file(f)


            try:
                f.close()
                os.remove(os.path.join(self._path, str(key)))
            finally:
                if self._locked:
                    _unlock_file(f)


        finally:
            f.close()



    def __setitem__(self, key, message):
        """Replace the keyed message; raise KeyError if it doesn't exist."""
        path = os.path.join(self._path, str(key))

        try:
            f = open(path, 'rb+')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                raise KeyError('No message with key: %s' % key)
            else:
                raise
        except:
            e.errno == errno.ENOENT


        try:
            if self._locked:
                _lock_file(f)


            try:
                os.close(os.open(path, os.O_WRONLY | os.O_TRUNC))
                self._dump_message(message, f)
                if isinstance(message, MHMessage):
                    self._dump_sequences(message, key)
            finally:
                if self._locked:
                    _unlock_file(f)


        finally:
            _sync_close(f)



    def get_message(self, key):
        '''Return a Message representation or raise a KeyError.'''

        try:
            if self._locked:
                f = open(os.path.join(self._path, str(key)), 'r+')
            else:
                f = open(os.path.join(self._path, str(key)), 'r')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                raise KeyError('No message with key: %s' % key)
            else:
                raise
        except:
            e.errno == errno.ENOENT


        try:
            if self._locked:
                _lock_file(f)


            try:
                msg = MHMessage(f)
            finally:
                if self._locked:
                    _unlock_file(f)


        finally:
            f.close()

        for name, key_list in self.get_sequences():
            if key in key_list:
                msg.add_sequence(name)
                continue

        return msg


    def get_string(self, key):
        '''Return a string representation or raise a KeyError.'''

        try:
            if self._locked:
                f = open(os.path.join(self._path, str(key)), 'r+')
            else:
                f = open(os.path.join(self._path, str(key)), 'r')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                raise KeyError('No message with key: %s' % key)
            else:
                raise
        except:
            e.errno == errno.ENOENT


        try:
            if self._locked:
                _lock_file(f)


            try:
                return f.read()
            finally:
                if self._locked:
                    _unlock_file(f)


        finally:
            f.close()



    def get_file(self, key):
        '''Return a file-like representation or raise a KeyError.'''

        try:
            f = open(os.path.join(self._path, str(key)), 'rb')
        except IOError:
            e = None
            if e.errno == errno.ENOENT:
                raise KeyError('No message with key: %s' % key)
            else:
                raise
        except:
            e.errno == errno.ENOENT

        return _ProxyFile(f)


    def iterkeys(self):
        '''Return an iterator over keys.'''
        return iter(sorted((lambda .0: for entry in .0:
if entry.isdigit():
int(entry)continue)(os.listdir(self._path))))


    def has_key(self, key):
        '''Return True if the keyed message exists, False otherwise.'''
        return os.path.exists(os.path.join(self._path, str(key)))


    def __len__(self):
        '''Return a count of messages in the mailbox.'''
        return len(list(self.iterkeys()))


    def lock(self):
        '''Lock the mailbox.'''
        if not self._locked:
            self._file = open(os.path.join(self._path, '.mh_sequences'), 'rb+')
            _lock_file(self._file)
            self._locked = True



    def unlock(self):
        '''Unlock the mailbox if it is locked.'''
        if self._locked:
            _unlock_file(self._file)
            _sync_close(self._file)
            del self._file
            self._locked = False



    def flush(self):
        '''Write any pending changes to the disk.'''
        pass


    def close(self):
        '''Flush and close the mailbox.'''
        if self._locked:
            self.unlock()



    def list_folders(self):
        '''Return a list of folder names.'''
        result = []
        for entry in os.listdir(self._path):
            if os.path.isdir(os.path.join(self._path, entry)):
                result.append(entry)
                continue

        return result


    def get_folder(self, folder):
        '''Return an MH instance for the named folder.'''
        return MH(os.path.join(self._path, folder), factory = self._factory, create = False)


    def add_folder(self, folder):
        '''Create a folder and return an MH instance representing it.'''
        return MH(os.path.join(self._path, folder), factory = self._factory)


    def remove_folder(self, folder):
        '''Delete the named folder, which must be empty.'''
        path = os.path.join(self._path, folder)
        entries = os.listdir(path)
        if entries == [
            '.mh_sequences']:
            os.remove(os.path.join(path, '.mh_sequences'))
        elif entries == []:
            pass
        else:
            raise NotEmptyError('Folder not empty: %s' % self._path)
        os.rmdir(path)


    def get_sequences(self):
        '''Return a name-to-key-list dictionary to define each sequence.'''
        results = { }
        f = open(os.path.join(self._path, '.mh_sequences'), 'r')

        try:
            all_keys = set(self.keys())
            for line in f:

                try:
                    (name, contents) = line.split(':')
                    keys = set()
                    for spec in contents.split():
                        if spec.isdigit():
                            keys.add(int(spec))
                            continue
                        (start, stop) = (lambda .0: for x in .0:
int(x))(spec.split('-'))
                        keys.update(range(start, stop + 1))

                    results[name] = _[1]
                    if len(results[name]) == 0:
                        del results[name]
                continue
                except ValueError:
                    raise FormatError('Invalid sequence specification: %s' % line.rstrip())
                    continue


        finally:
            f.close()

        return results


    def set_sequences(self, sequences):
        '''Set sequences using the given name-to-key-list dictionary.'''
        f = open(os.path.join(self._path, '.mh_sequences'), 'r+')

        try:
            os.close(os.open(f.name, os.O_WRONLY | os.O_TRUNC))
            for name, keys in sequences.iteritems():
                if len(keys) == 0:
                    continue

                f.write('%s:' % name)
                prev = None
                completing = False
                for key in sorted(set(keys)):
                    if key - 1 == prev:
                        if not completing:
                            completing = True
                            f.write('-')

                    elif completing:
                        completing = False
                        f.write('%s %s' % (prev, key))
                    else:
                        f.write(' %s' % key)
                    prev = key

                if completing:
                    f.write(str(prev) + '\n')
                    continue
                f.write('\n')
        finally:
            _sync_close(f)



    def pack(self):
        '''Re-name messages to eliminate numbering gaps. Invalidates keys.'''
        sequences = self.get_sequences()
        prev = 0
        changes = []
        for key in self.iterkeys():
            if key - 1 != prev:
                changes.append((key, prev + 1))
                if hasattr(os, 'link'):
                    os.link(os.path.join(self._path, str(key)), os.path.join(self._path, str(prev + 1)))
                    os.unlink(os.path.join(self._path, str(key)))
                else:
                    os.rename(os.path.join(self._path, str(key)), os.path.join(self._path, str(prev + 1)))

            prev += 1

        self._next_key = prev + 1
        if len(changes) == 0:
            return None

        for name, key_list in sequences.items():
            for old, new in changes:
                if old in key_list:
                    key_list[key_list.index(old)] = new
                    continue


        self.set_sequences(sequences)


    def _dump_sequences(self, message, key):
        '''Inspect a new MHMessage and update sequences appropriately.'''
        pending_sequences = message.get_sequences()
        all_sequences = self.get_sequences()
        for name, key_list in all_sequences.iteritems():
            if name in pending_sequences:
                key_list.append(key)
                continue
            if key in key_list:
                del key_list[key_list.index(key)]
                continue

        for sequence in pending_sequences:
            if sequence not in all_sequences:
                all_sequences[sequence] = [
                    key]
                continue

        self.set_sequences(all_sequences)



class Babyl(_singlefileMailbox):
    '''An Rmail-style Babyl mailbox.'''
    _special_labels = frozenset(('unseen', 'deleted', 'filed', 'answered', 'forwarded', 'edited', 'resent'))

    def __init__(self, path, factory = None, create = True):
        '''Initialize a Babyl mailbox.'''
        _singlefileMailbox.__init__(self, path, factory, create)
        self._labels = { }


    def add(self, message):
        '''Add message and return assigned key.'''
        key = _singlefileMailbox.add(self, message)
        if isinstance(message, BabylMessage):
            self._labels[key] = message.get_labels()

        return key


    def remove(self, key):
        """Remove the keyed message; raise KeyError if it doesn't exist."""
        _singlefileMailbox.remove(self, key)
        if key in self._labels:
            del self._labels[key]



    def __setitem__(self, key, message):
        """Replace the keyed message; raise KeyError if it doesn't exist."""
        _singlefileMailbox.__setitem__(self, key, message)
        if isinstance(message, BabylMessage):
            self._labels[key] = message.get_labels()



    def get_message(self, key):
        '''Return a Message representation or raise a KeyError.'''
        (start, stop) = self._lookup(key)
        self._file.seek(start)
        self._file.readline()
        original_headers = StringIO.StringIO()
        while True:
            line = self._file.readline()
            if line == '*** EOOH ***' + os.linesep or line == '':
                break

            original_headers.write(line.replace(os.linesep, '\n'))
        visible_headers = StringIO.StringIO()
        while True:
            line = self._file.readline()
            if line == os.linesep or line == '':
                break

            visible_headers.write(line.replace(os.linesep, '\n'))
        body = self._file.read(stop - self._file.tell()).replace(os.linesep, '\n')
        msg = BabylMessage(original_headers.getvalue() + body)
        msg.set_visible(visible_headers.getvalue())
        if key in self._labels:
            msg.set_labels(self._labels[key])

        return msg


    def get_string(self, key):
        '''Return a string representation or raise a KeyError.'''
        (start, stop) = self._lookup(key)
        self._file.seek(start)
        self._file.readline()
        original_headers = StringIO.StringIO()
        while True:
            line = self._file.readline()
            if line == '*** EOOH ***' + os.linesep or line == '':
                break

            original_headers.write(line.replace(os.linesep, '\n'))
        while True:
            line = self._file.readline()
            if line == os.linesep or line == '':
                break
                continue
        return original_headers.getvalue() + self._file.read(stop - self._file.tell()).replace(os.linesep, '\n')


    def get_file(self, key):
        '''Return a file-like representation or raise a KeyError.'''
        return StringIO.StringIO(self.get_string(key).replace('\n', os.linesep))


    def get_labels(self):
        '''Return a list of user-defined labels in the mailbox.'''
        self._lookup()
        labels = set()
        for label_list in self._labels.values():
            labels.update(label_list)

        labels.difference_update(self._special_labels)
        return list(labels)


    def _generate_toc(self):
        '''Generate key-to-(start, stop) table of contents.'''
        starts = []
        stops = []
        self._file.seek(0)
        next_pos = 0
        label_lists = []
        while True:
            line_pos = next_pos
            line = self._file.readline()
            next_pos = self._file.tell()
            if line == '\x1f\x0c' + os.linesep:
                if len(stops) < len(starts):
                    stops.append(line_pos - len(os.linesep))

                starts.append(next_pos)
                labels = _[1]
                label_lists.append(labels)
                continue
            []
            if line == '\x1f' or line == '\x1f' + os.linesep:
                if len(stops) < len(starts):
                    stops.append(line_pos - len(os.linesep))

            len(stops) < len(starts)
            if line == '':
                stops.append(line_pos - len(os.linesep))
                break
                continue
            []
        self._toc = dict(enumerate(zip(starts, stops)))
        self._labels = dict(enumerate(label_lists))
        self._next_key = len(self._toc)


    def _pre_mailbox_hook(self, f):
        '''Called before writing the mailbox to file f.'''
        f.write('BABYL OPTIONS:%sVersion: 5%sLabels:%s%s\x1f' % (os.linesep, os.linesep, ','.join(self.get_labels()), os.linesep))


    def _pre_message_hook(self, f):
        '''Called before writing each message to file f.'''
        f.write('\x0c' + os.linesep)


    def _post_message_hook(self, f):
        '''Called after writing each message to file f.'''
        f.write(os.linesep + '\x1f')


    def _install_message(self, message):
        '''Write message contents and return (start, stop).'''
        start = self._file.tell()
        if isinstance(message, BabylMessage):
            special_labels = []
            labels = []
            for label in message.get_labels():
                if label in self._special_labels:
                    special_labels.append(label)
                    continue
                labels.append(label)

            self._file.write('1')
            for label in special_labels:
                self._file.write(', ' + label)

            self._file.write(',,')
            for label in labels:
                self._file.write(' ' + label + ',')

            self._file.write(os.linesep)
        else:
            self._file.write('1,,' + os.linesep)
        if isinstance(message, email.Message.Message):
            orig_buffer = StringIO.StringIO()
            orig_generator = email.Generator.Generator(orig_buffer, False, 0)
            orig_generator.flatten(message)
            orig_buffer.seek(0)
            while True:
                line = orig_buffer.readline()
                self._file.write(line.replace('\n', os.linesep))
                if line == '\n' or line == '':
                    break
                    continue
            self._file.write('*** EOOH ***' + os.linesep)
            if isinstance(message, BabylMessage):
                vis_buffer = StringIO.StringIO()
                vis_generator = email.Generator.Generator(vis_buffer, False, 0)
                vis_generator.flatten(message.get_visible())
                while True:
                    line = vis_buffer.readline()
                    self._file.write(line.replace('\n', os.linesep))
                    if line == '\n' or line == '':
                        break
                        continue
            else:
                orig_buffer.seek(0)
                while True:
                    line = orig_buffer.readline()
                    self._file.write(line.replace('\n', os.linesep))
                    if line == '\n' or line == '':
                        break
                        continue
            while True:
                buffer = orig_buffer.read(4096)
                if buffer == '':
                    break

                self._file.write(buffer.replace('\n', os.linesep))
        elif isinstance(message, str):
            body_start = message.find('\n\n') + 2
            if body_start - 2 != -1:
                self._file.write(message[:body_start].replace('\n', os.linesep))
                self._file.write('*** EOOH ***' + os.linesep)
                self._file.write(message[:body_start].replace('\n', os.linesep))
                self._file.write(message[body_start:].replace('\n', os.linesep))
            else:
                self._file.write('*** EOOH ***' + os.linesep + os.linesep)
                self._file.write(message.replace('\n', os.linesep))
        elif hasattr(message, 'readline'):
            original_pos = message.tell()
            first_pass = True
            while True:
                line = message.readline()
                self._file.write(line.replace('\n', os.linesep))
                if line == '\n' or line == '':
                    self._file.write('*** EOOH ***' + os.linesep)
                    if first_pass:
                        first_pass = False
                        message.seek(original_pos)
                    else:
                        break
                first_pass
            while True:
                buffer = message.read(4096)
                if buffer == '':
                    break

                self._file.write(buffer.replace('\n', os.linesep))
        else:
            raise TypeError('Invalid message type: %s' % type(message))
        stop = self._file.tell()
        return (start, stop)



class Message(email.Message.Message):
    '''Message with mailbox-format-specific properties.'''

    def __init__(self, message = None):
        '''Initialize a Message instance.'''
        if isinstance(message, email.Message.Message):
            self._become_message(copy.deepcopy(message))
            if isinstance(message, Message):
                message._explain_to(self)

        elif isinstance(message, str):
            self._become_message(email.message_from_string(message))
        elif hasattr(message, 'read'):
            self._become_message(email.message_from_file(message))
        elif message is None:
            email.Message.Message.__init__(self)
        else:
            raise TypeError('Invalid message type: %s' % type(message))


    def _become_message(self, message):
        '''Assume the non-format-specific state of message.'''
        for name in ('_headers', '_unixfrom', '_payload', '_charset', 'preamble', 'epilogue', 'defects', '_default_type'):
            self.__dict__[name] = message.__dict__[name]



    def _explain_to(self, message):
        '''Copy format-specific state to message insofar as possible.'''
        if isinstance(message, Message):
            return None
        else:
            raise TypeError('Cannot convert to specified type')



class MaildirMessage(Message):
    '''Message with Maildir-specific properties.'''

    def __init__(self, message = None):
        '''Initialize a MaildirMessage instance.'''
        self._subdir = 'new'
        self._info = ''
        self._date = time.time()
        Message.__init__(self, message)


    def get_subdir(self):
        """Return 'new' or 'cur'."""
        return self._subdir


    def set_subdir(self, subdir):
        """Set subdir to 'new' or 'cur'."""
        if subdir == 'new' or subdir == 'cur':
            self._subdir = subdir
        else:
            raise ValueError("subdir must be 'new' or 'cur': %s" % subdir)


    def get_flags(self):
        '''Return as a string the flags that are set.'''
        if self._info.startswith('2,'):
            return self._info[2:]
        else:
            return ''


    def set_flags(self, flags):
        '''Set the given flags and unset all others.'''
        self._info = '2,' + ''.join(sorted(flags))


    def add_flag(self, flag):
        '''Set the given flag(s) without changing others.'''
        self.set_flags(''.join(set(self.get_flags()) | set(flag)))


    def remove_flag(self, flag):
        '''Unset the given string flag(s) without changing others.'''
        if self.get_flags() != '':
            self.set_flags(''.join(set(self.get_flags()) - set(flag)))



    def get_date(self):
        '''Return delivery date of message, in seconds since the epoch.'''
        return self._date


    def set_date(self, date):
        '''Set delivery date of message, in seconds since the epoch.'''

        try:
            self._date = float(date)
        except ValueError:
            raise TypeError("can't convert to float: %s" % date)



    def get_info(self):
        '''Get the message\'s "info" as a string.'''
        return self._info


    def set_info(self, info):
        '''Set the message\'s "info" string.'''
        if isinstance(info, str):
            self._info = info
        else:
            raise TypeError('info must be a string: %s' % type(info))


    def _explain_to(self, message):
        '''Copy Maildir-specific state to message insofar as possible.'''
        if isinstance(message, MaildirMessage):
            message.set_flags(self.get_flags())
            message.set_subdir(self.get_subdir())
            message.set_date(self.get_date())
        elif isinstance(message, _mboxMMDFMessage):
            flags = set(self.get_flags())
            if 'S' in flags:
                message.add_flag('R')

            if self.get_subdir() == 'cur':
                message.add_flag('O')

            if 'T' in flags:
                message.add_flag('D')

            if 'F' in flags:
                message.add_flag('F')

            if 'R' in flags:
                message.add_flag('A')

            message.set_from('MAILER-DAEMON', time.gmtime(self.get_date()))
        elif isinstance(message, MHMessage):
            flags = set(self.get_flags())
            if 'S' not in flags:
                message.add_sequence('unseen')

            if 'R' in flags:
                message.add_sequence('replied')

            if 'F' in flags:
                message.add_sequence('flagged')

        elif isinstance(message, BabylMessage):
            flags = set(self.get_flags())
            if 'S' not in flags:
                message.add_label('unseen')

            if 'T' in flags:
                message.add_label('deleted')

            if 'R' in flags:
                message.add_label('answered')

            if 'P' in flags:
                message.add_label('forwarded')

        elif isinstance(message, Message):
            pass
        else:
            raise TypeError('Cannot convert to specified type: %s' % type(message))



class _mboxMMDFMessage(Message):
    '''Message with mbox- or MMDF-specific properties.'''

    def __init__(self, message = None):
        '''Initialize an mboxMMDFMessage instance.'''
        self.set_from('MAILER-DAEMON', True)
        if isinstance(message, email.Message.Message):
            unixfrom = message.get_unixfrom()
            if unixfrom is not None and unixfrom.startswith('From '):
                self.set_from(unixfrom[5:])


        Message.__init__(self, message)


    def get_from(self):
        '''Return contents of "From " line.'''
        return self._from


    def set_from(self, from_, time_ = None):
        '''Set "From " line, formatting and appending time_ if specified.'''
        if time_ is not None:
            if time_ is True:
                time_ = time.gmtime()

            from_ += ' ' + time.asctime(time_)

        self._from = from_


    def get_flags(self):
        '''Return as a string the flags that are set.'''
        return self.get('Status', '') + self.get('X-Status', '')


    def set_flags(self, flags):
        '''Set the given flags and unset all others.'''
        flags = set(flags)
        (status_flags, xstatus_flags) = ('', '')
        for flag in ('R', 'O'):
            if flag in flags:
                status_flags += flag
                flags.remove(flag)
                continue

        for flag in ('D', 'F', 'A'):
            if flag in flags:
                xstatus_flags += flag
                flags.remove(flag)
                continue

        xstatus_flags += ''.join(sorted(flags))

        try:
            self.replace_header('Status', status_flags)
        except KeyError:
            self.add_header('Status', status_flags)


        try:
            self.replace_header('X-Status', xstatus_flags)
        except KeyError:
            self.add_header('X-Status', xstatus_flags)



    def add_flag(self, flag):
        '''Set the given flag(s) without changing others.'''
        self.set_flags(''.join(set(self.get_flags()) | set(flag)))


    def remove_flag(self, flag):
        '''Unset the given string flag(s) without changing others.'''
        if 'Status' in self or 'X-Status' in self:
            self.set_flags(''.join(set(self.get_flags()) - set(flag)))



    def _explain_to(self, message):
        '''Copy mbox- or MMDF-specific state to message insofar as possible.'''
        if isinstance(message, MaildirMessage):
            flags = set(self.get_flags())
            if 'O' in flags:
                message.set_subdir('cur')

            if 'F' in flags:
                message.add_flag('F')

            if 'A' in flags:
                message.add_flag('R')

            if 'R' in flags:
                message.add_flag('S')

            if 'D' in flags:
                message.add_flag('T')

            del message['status']
            del message['x-status']
            maybe_date = ' '.join(self.get_from().split()[-5:])

            try:
                message.set_date(calendar.timegm(time.strptime(maybe_date, '%a %b %d %H:%M:%S %Y')))
            except (ValueError, OverflowError):
                pass
            except:
                None<EXCEPTION MATCH>(ValueError, OverflowError)


        None<EXCEPTION MATCH>(ValueError, OverflowError)
        if isinstance(message, _mboxMMDFMessage):
            message.set_flags(self.get_flags())
            message.set_from(self.get_from())
        elif isinstance(message, MHMessage):
            flags = set(self.get_flags())
            if 'R' not in flags:
                message.add_sequence('unseen')

            if 'A' in flags:
                message.add_sequence('replied')

            if 'F' in flags:
                message.add_sequence('flagged')

            del message['status']
            del message['x-status']
        elif isinstance(message, BabylMessage):
            flags = set(self.get_flags())
            if 'R' not in flags:
                message.add_label('unseen')

            if 'D' in flags:
                message.add_label('deleted')

            if 'A' in flags:
                message.add_label('answered')

            del message['status']
            del message['x-status']
        elif isinstance(message, Message):
            pass
        else:
            raise TypeError('Cannot convert to specified type: %s' % type(message))



class mboxMessage(_mboxMMDFMessage):
    '''Message with mbox-specific properties.'''
    pass


class MHMessage(Message):
    '''Message with MH-specific properties.'''

    def __init__(self, message = None):
        '''Initialize an MHMessage instance.'''
        self._sequences = []
        Message.__init__(self, message)


    def get_sequences(self):
        '''Return a list of sequences that include the message.'''
        return self._sequences[:]


    def set_sequences(self, sequences):
        '''Set the list of sequences that include the message.'''
        self._sequences = list(sequences)


    def add_sequence(self, sequence):
        '''Add sequence to list of sequences including the message.'''
        if isinstance(sequence, str):
            if sequence not in self._sequences:
                self._sequences.append(sequence)

        else:
            raise TypeError('sequence must be a string: %s' % type(sequence))


    def remove_sequence(self, sequence):
        '''Remove sequence from the list of sequences including the message.'''

        try:
            self._sequences.remove(sequence)
        except ValueError:
            pass



    def _explain_to(self, message):
        '''Copy MH-specific state to message insofar as possible.'''
        if isinstance(message, MaildirMessage):
            sequences = set(self.get_sequences())
            if 'unseen' in sequences:
                message.set_subdir('cur')
            else:
                message.set_subdir('cur')
                message.add_flag('S')
            if 'flagged' in sequences:
                message.add_flag('F')

            if 'replied' in sequences:
                message.add_flag('R')

        elif isinstance(message, _mboxMMDFMessage):
            sequences = set(self.get_sequences())
            if 'unseen' not in sequences:
                message.add_flag('RO')
            else:
                message.add_flag('O')
            if 'flagged' in sequences:
                message.add_flag('F')

            if 'replied' in sequences:
                message.add_flag('A')

        elif isinstance(message, MHMessage):
            for sequence in self.get_sequences():
                message.add_sequence(sequence)

        elif isinstance(message, BabylMessage):
            sequences = set(self.get_sequences())
            if 'unseen' in sequences:
                message.add_label('unseen')

            if 'replied' in sequences:
                message.add_label('answered')

        elif isinstance(message, Message):
            pass
        else:
            raise TypeError('Cannot convert to specified type: %s' % type(message))



class BabylMessage(Message):
    '''Message with Babyl-specific properties.'''

    def __init__(self, message = None):
        '''Initialize an BabylMessage instance.'''
        self._labels = []
        self._visible = Message()
        Message.__init__(self, message)


    def get_labels(self):
        '''Return a list of labels on the message.'''
        return self._labels[:]


    def set_labels(self, labels):
        '''Set the list of labels on the message.'''
        self._labels = list(labels)


    def add_label(self, label):
        '''Add label to list of labels on the message.'''
        if isinstance(label, str):
            if label not in self._labels:
                self._labels.append(label)

        else:
            raise TypeError('label must be a string: %s' % type(label))


    def remove_label(self, label):
        '''Remove label from the list of labels on the message.'''

        try:
            self._labels.remove(label)
        except ValueError:
            pass



    def get_visible(self):
        '''Return a Message representation of visible headers.'''
        return Message(self._visible)


    def set_visible(self, visible):
        '''Set the Message representation of visible headers.'''
        self._visible = Message(visible)


    def update_visible(self):
        '''Update and/or sensibly generate a set of visible headers.'''
        for header in self._visible.keys():
            if header in self:
                self._visible.replace_header(header, self[header])
                continue
            del self._visible[header]

        for header in ('Date', 'From', 'Reply-To', 'To', 'CC', 'Subject'):
            if header in self and header not in self._visible:
                self._visible[header] = self[header]
                continue



    def _explain_to(self, message):
        '''Copy Babyl-specific state to message insofar as possible.'''
        if isinstance(message, MaildirMessage):
            labels = set(self.get_labels())
            if 'unseen' in labels:
                message.set_subdir('cur')
            else:
                message.set_subdir('cur')
                message.add_flag('S')
            if 'forwarded' in labels or 'resent' in labels:
                message.add_flag('P')

            if 'answered' in labels:
                message.add_flag('R')

            if 'deleted' in labels:
                message.add_flag('T')

        elif isinstance(message, _mboxMMDFMessage):
            labels = set(self.get_labels())
            if 'unseen' not in labels:
                message.add_flag('RO')
            else:
                message.add_flag('O')
            if 'deleted' in labels:
                message.add_flag('D')

            if 'answered' in labels:
                message.add_flag('A')

        elif isinstance(message, MHMessage):
            labels = set(self.get_labels())
            if 'unseen' in labels:
                message.add_sequence('unseen')

            if 'answered' in labels:
                message.add_sequence('replied')

        elif isinstance(message, BabylMessage):
            message.set_visible(self.get_visible())
            for label in self.get_labels():
                message.add_label(label)

        elif isinstance(message, Message):
            pass
        else:
            raise TypeError('Cannot convert to specified type: %s' % type(message))



class MMDFMessage(_mboxMMDFMessage):
    '''Message with MMDF-specific properties.'''
    pass


class _ProxyFile:
    '''A read-only wrapper of a file.'''

    def __init__(self, f, pos = None):
        '''Initialize a _ProxyFile.'''
        self._file = f
        if pos is None:
            self._pos = f.tell()
        else:
            self._pos = pos


    def read(self, size = None):
        '''Read bytes.'''
        return self._read(size, self._file.read)


    def readline(self, size = None):
        '''Read a line.'''
        return self._read(size, self._file.readline)


    def readlines(self, sizehint = None):
        '''Read multiple lines.'''
        result = []
        for line in self:
            result.append(line)
            if sizehint is not None:
                sizehint -= len(line)
                if sizehint <= 0:
                    break

            sizehint <= 0

        return result


    def __iter__(self):
        '''Iterate over lines.'''
        return iter(self.readline, '')


    def tell(self):
        '''Return the position.'''
        return self._pos


    def seek(self, offset, whence = 0):
        '''Change position.'''
        if whence == 1:
            self._file.seek(self._pos)

        self._file.seek(offset, whence)
        self._pos = self._file.tell()


    def close(self):
        '''Close the file.'''
        del self._file


    def _read(self, size, read_method):
        '''Read size bytes using read_method.'''
        if size is None:
            size = -1

        self._file.seek(self._pos)
        result = read_method(size)
        self._pos = self._file.tell()
        return result



class _PartialFile(_ProxyFile):
    '''A read-only wrapper of part of a file.'''

    def __init__(self, f, start = None, stop = None):
        '''Initialize a _PartialFile.'''
        _ProxyFile.__init__(self, f, start)
        self._start = start
        self._stop = stop


    def tell(self):
        '''Return the position with respect to start.'''
        return _ProxyFile.tell(self) - self._start


    def seek(self, offset, whence = 0):
        '''Change position, possibly with respect to start or stop.'''
        if whence == 0:
            self._pos = self._start
            whence = 1
        elif whence == 2:
            self._pos = self._stop
            whence = 1

        _ProxyFile.seek(self, offset, whence)


    def _read(self, size, read_method):
        '''Read size bytes using read_method, honoring start and stop.'''
        remaining = self._stop - self._pos
        if remaining <= 0:
            return ''

        if size is None and size < 0 or size > remaining:
            size = remaining

        return _ProxyFile._read(self, size, read_method)



def _lock_file(f, dotlock = True):
    '''Lock file f using lockf and dot locking.'''
    dotlock_done = False

    try:
        if fcntl:

            try:
                fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
            except IOError:
                e = None
                if e.errno in (errno.EAGAIN, errno.EACCES):
                    raise ExternalClashError('lockf: lock unavailable: %s' % f.name)
                else:
                    raise
            except:
                e.errno in (errno.EAGAIN, errno.EACCES)


        None<EXCEPTION MATCH>IOError
        if dotlock:

            try:
                pre_lock = _create_temporary(f.name + '.lock')
                pre_lock.close()
            except IOError:
                e = None
                if e.errno == errno.EACCES:
                    return None
                else:
                    raise
            except:
                e.errno == errno.EACCES


            try:
                if hasattr(os, 'link'):
                    os.link(pre_lock.name, f.name + '.lock')
                    dotlock_done = True
                    os.unlink(pre_lock.name)
                else:
                    os.rename(pre_lock.name, f.name + '.lock')
                    dotlock_done = True
            except OSError:
                e = None
                if (e.errno == errno.EEXIST or os.name == 'os2') and e.errno == errno.EACCES:
                    os.remove(pre_lock.name)
                    raise ExternalClashError('dot lock unavailable: %s' % f.name)
                else:
                    raise
            except:
                e.errno == errno.EACCES


        None<EXCEPTION MATCH>OSError
    except:
        if fcntl:
            fcntl.lockf(f, fcntl.LOCK_UN)

        if dotlock_done:
            os.remove(f.name + '.lock')

        raise



def _unlock_file(f):
    '''Unlock file f using lockf and dot locking.'''
    if fcntl:
        fcntl.lockf(f, fcntl.LOCK_UN)

    if os.path.exists(f.name + '.lock'):
        os.remove(f.name + '.lock')



def _create_carefully(path):
    """Create a file if it doesn't exist and open for reading and writing."""
    fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR)

    try:
        return open(path, 'rb+')
    finally:
        os.close(fd)



def _create_temporary(path):
    '''Create a temp file based on path and open for reading and writing.'''
    return _create_carefully('%s.%s.%s.%s' % (path, int(time.time()), socket.gethostname(), os.getpid()))


def _sync_flush(f):
    '''Ensure changes to file f are physically on disk.'''
    f.flush()
    if hasattr(os, 'fsync'):
        os.fsync(f.fileno())



def _sync_close(f):
    '''Close file f, ensuring all changes are physically on disk.'''
    _sync_flush(f)
    f.close()


class _Mailbox:

    def __init__(self, fp, factory = rfc822.Message):
        self.fp = fp
        self.seekp = 0
        self.factory = factory


    def __iter__(self):
        return iter(self.next, None)


    def next(self):
        while None:

            try:
                self._search_start()
            except EOFError:
                self.seekp = self.fp.tell()
                return None

            start = self.fp.tell()
            self._search_end()
            self.seekp = stop = self.fp.tell()
            if start != stop:
                break
                continue
            continue
            return self.factory(_PartialFile(self.fp, start, stop))



class UnixMailbox(_Mailbox):

    def _search_start(self):
        while None:
            pos = self.fp.tell()
            line = self.fp.readline()
            if not line:
                raise EOFError

            if line[:5] == 'From ' and self._isrealfromline(line):
                self.fp.seek(pos)
                return None
                continue
            continue
            return None


    def _search_end(self):
        self.fp.readline()
        while None:
            pos = self.fp.tell()
            line = self.fp.readline()
            if not line:
                return None

            if line[:5] == 'From ' and self._isrealfromline(line):
                self.fp.seek(pos)
                return None
                continue
            continue
            return None

    _fromlinepattern = 'From \\s*[^\\s]+\\s+\\w\\w\\w\\s+\\w\\w\\w\\s+\\d?\\d\\s+\\d?\\d:\\d\\d(:\\d\\d)?(\\s+[^\\s]+)?\\s+\\d\\d\\d\\d\\s*[^\\s]*\\s*$'
    _regexp = None

    def _strict_isrealfromline(self, line):
        if not self._regexp:
            import re as re
            self._regexp = re.compile(self._fromlinepattern)

        return self._regexp.match(line)


    def _portable_isrealfromline(self, line):
        return True

    _isrealfromline = _strict_isrealfromline


class PortableUnixMailbox(UnixMailbox):
    _isrealfromline = UnixMailbox._portable_isrealfromline


class MmdfMailbox(_Mailbox):

    def _search_start(self):
        while None:
            line = self.fp.readline()
            if not line:
                raise EOFError

            if line[:5] == '\x01\x01\x01\x01\n':
                return None
                continue
            continue
            return None


    def _search_end(self):
        while None:
            pos = self.fp.tell()
            line = self.fp.readline()
            if not line:
                return None

            if line == '\x01\x01\x01\x01\n':
                self.fp.seek(pos)
                return None
                continue
            continue
            return None



class MHMailbox:

    def __init__(self, dirname, factory = rfc822.Message):
        import re
        pat = re.compile('^[1-9][0-9]*$')
        self.dirname = dirname
        list = os.listdir(self.dirname)
        list = filter(pat.match, list)
        list = map(long, list)
        list.sort()
        self.boxes = map(str, list)
        self.boxes.reverse()
        self.factory = factory


    def __iter__(self):
        return iter(self.next, None)


    def next(self):
        if not self.boxes:
            return None

        fn = self.boxes.pop()
        fp = open(os.path.join(self.dirname, fn))
        msg = self.factory(fp)

        try:
            msg._mh_msgno = fn
        except (AttributeError, TypeError):
            pass

        return msg



class BabylMailbox(_Mailbox):

    def _search_start(self):
        while None:
            line = self.fp.readline()
            if not line:
                raise EOFError

            if line == '*** EOOH ***\n':
                return None
                continue
            continue
            return None


    def _search_end(self):
        while None:
            pos = self.fp.tell()
            line = self.fp.readline()
            if not line:
                return None

            if line == '\x1f\x0c\n' or line == '\x1f':
                self.fp.seek(pos)
                return None
                continue
            continue
            return None



class Error(Exception):
    '''Raised for module-specific errors.'''
    pass


class NoSuchMailboxError(Error):
    """The specified mailbox does not exist and won't be created."""
    pass


class NotEmptyError(Error):
    '''The specified mailbox is not empty and deletion was requested.'''
    pass


class ExternalClashError(Error):
    '''Another process caused an action to fail.'''
    pass


class FormatError(Error):
    '''A file appears to have an invalid format.'''
    pass